Scanning Tunneling Microscope:

STM detects the flow of electrons through quantum tunneling between the tip and the sample, generating high-resolution images of surface topography with atomic-scale precision [41-42].

Principle of Scanning Tunneling Microscope:

The Scanning Tunneling Microscope (STM) functions based on quantum tunneling, a phenomenon in quantum mechanics where a particle can pass through a potential energy barrier despite lacking sufficient classical energy. In STM, a sharp conducting tip is positioned very close to the sample surface. By applying a small bias voltage between the tip and the sample, electrons can tunnel through the vacuum gap separating them.
a) Tip and Sample Interaction: The STM comprises a sharp metallic tip mounted on a piezoelectric scanner and a conductive sample. The tip is positioned within an extremely close distance, typically a few angstroms, from the sample surface.
b) Quantum Tunneling: When a small bias voltage (usually ranging from a few millivolts to a few volts) is applied between the tip and the sample in an STM, electrons have the ability to tunnel through the vacuum gap separating them. The likelihood of tunneling exponentially correlates with the width of this gap.
c) Current Measurement: A feedback loop is employed to sustain a constant current (typically ranging from a few picoamperes) by adjusting the tip-sample distance during scanning. Variations in the tunneling current are utilized to map the surface topography with atomic-scale resolution.
d) Topographic Imaging: As the tip moves across the sample surface, changes in the tunneling current occur because of variations in the distance between the tip and sample surface induced by surface features. These fluctuations are utilized to create a topographic image of the sample surface.
e) Atomic Resolution: Since the tunneling current is highly sensitive to the tip-sample distance, the STM can achieve atomic resolution by precisely controlling this distance. This allows researchers to visualize individual atoms and molecular structures on the sample surface.

Instrumentation of Scanning Tunneling Microscope:

a) Probe Tip: The heart of the STM is a sharp metallic probe tip, typically made of tungsten or platinum-iridium, with a radius of a few atoms. The tip is mounted on a flexible cantilever and brought into close proximity to the sample surface.
b) Piezoelectric Scanner: The sample stage is mounted on a piezoelectric scanner, which allows for precise control of the position of the sample relative to the probe tip. The scanner can move the sample in the x, y, and z directions with nanometer-scale precision, enabling raster scanning of the probe tip across the sample surface to generate high-resolution images.
c) Feedback Control System: A feedback control system is used to maintain a constant tunneling current between the probe tip and the sample surface during scanning. This feedback loop adjusts the vertical position of the probe tip by moving the piezoelectric scanner up or down to keep the tunneling current constant.
d) Electronics and Amplifiers: Electronics and amplifiers are used to measure the tunneling current between the probe tip and the sample surface. The tunneling current is typically in the range of picoamperes to Nano amperes and requires sensitive amplifiers to detect.
e) Voltage Source: A voltage source is used to apply a bias voltage between the probe tip and the sample surface, which controls the tunneling current. By adjusting the bias voltage, researchers can change the height of the tunneling barrier and thus the sensitivity of the STM to surface features.
f) Control and Data Acquisition System: A control and data acquisition system is used to operate the STM, control scanning parameters, and acquire data from the tunneling current measurements. This system typically includes software for image acquisition, processing, and analysis, as well as hardware components such as analog-to-digital converters (ADCs) and digital signal processors (DSPs).
g) Environmental Control: Some STM systems are equipped with environmental control features to minimize vibration, temperature fluctuations, and humidity changes that can affect imaging performance. This may include vibration isolation tables, temperature-controlled enclosures, and vacuum chambers (Figure 6).

Advantage of Scanning Tunneling Microscope:

a) Atomic Resolution: The STM provides atomic-scale resolution, allowing researchers to visualize individual atoms and molecules on surfaces. This level of detail is essential for studying surface structures, defects, and chemical bonding at the atomic level.
b) Versatility: STM can be used to study a wide range of materials, including metals, semiconductors, insulators, and biological samples. It is particularly well-suited for analyzing conducting or semiconducting surfaces due to its reliance on tunneling current.
c) Non-destructive Imaging: STM imaging is nondestructive, as it relies on the quantum mechanical tunneling of electrons rather than physical interaction with the sample surface. This allows researchers to image samples in their native state without altering their structure or properties.
d) High Sensitivity: STM is highly sensitive to changes in tip-sample distance, making it capable of detecting subtle variations in surface topography and electronic properties. This sensitivity enables the detection of atomic-scale features and surface defects with high precision.
e) Real-time Imaging: STM can provide real-time imaging of sample surfaces, allowing researchers to observe dynamic processes as they occur. This capability is particularly valuable for studying surface reactions, growth processes, and surface diffusion phenomena.
f) Manipulation and Nanolithography: STM can be used for precise manipulation of atoms and molecules on surfaces through a technique known as scanning tunneling spectroscopy. This enables researchers to create nanostructures, manipulate individual atoms, and study the properties of nanoscale devices.
g) Operational Flexibility: STM can operate in various environments, including ultra-high vacuum, ambient conditions, and liquid environments. This flexibility allows researchers to study samples under conditions relevant to specific applications, such as catalysis, corrosion, and biological processes. Quantitative Analysis: STM can provide quantitative measurements of surface properties, including surface roughness, height profiles, and electronic density of states. These measurements are valuable for characterizing material properties and understanding surface phenomena at the atomic scale.

Limitation of Scanning Tunneling Microscope:

a) Conducting Sample Requirement: STM requires the sample to be conductive or semi-conductive. Insulating samples cannot be imaged directly using STM unless they are coated with a conductive layer, which can alter their properties or introduce artifacts.
b) Sample Preparation: Sample preparation for STM can be challenging and time-consuming. Samples must be clean, flat, and stable to achieve high-quality imaging, and preparation techniques such as cleaving, annealing, or deposition may be required.
c) Limited Depth of Field: STM has a limited depth of field, meaning that only surface features within a narrow range of heights are in focus at any given time.
d) Tip Wear and Contamination: The STM tip can wear out or become contaminated over time, affecting imaging quality and resolution. Tip degradation can lead to imaging artifacts and require frequent tip replacement or cleaning, increasing experimental costs and downtime.
e) Vibration Sensitivity: STM is sensitive to mechanical vibrations, which can degrade imaging quality and resolution.
f) Limited Scanning Area: The scanning area of STM is relatively small compared to other microscopy techniques. Largearea imaging require stitching together multiple scans, which is time-consuming and introduce alignment errors.
g) Temperature Sensitivity: STM performance can be affected by temperature variations, particularly at cryogenic temperatures or in environments with temperature gradients. Temperature stabilization measures may be required for accurate and reproducible imaging.
h) Low Imaging Speed: STM imaging typically operates at relatively slow scan speeds compared to other microscopy techniques such as scanning electron microscopy (SEM) or atomic force microscopy (AFM). This limitation can be particularly significant when studying dynamic processes or large sample areas.

Scanning Near-field Optical Microscope (SNOM or NSOM): Principle of Scanning Near-field Optical Microscope:

The SNOM or NSOM operates on the principle of exploiting the near-field interaction between a sharp probe and a sample surface to achieve sub-diffraction-limited optical resolution. Unlike conventional optical microscopy, which is limited by the diffraction of light, SNOM utilizes the evanescent optical field that extends beyond the optical diffraction limit [43-46].

Sharp Probe Tip: SNOM employs a sharp probe tip, typically tapered to a nanometer-scale aperture, that is scanned across the sample surface. The probe tip acts as a nano-sized optical antenna, interacting with the near-field optical signals emanating from the sample.
a) Evanescent Near-field Interaction: When the probe tip is positioned close to the sample surface (within a distance on the order of the wavelength of light), it interacts with the evanescent optical field that extends beyond the surface. This interaction results in changes to the probe’s optical properties, such as transmission, reflection, or scattering.
b) Detection of Optical Signals: The optical signals modified by the near-field interaction are detected and analyzed to generate images or spectroscopic data. Various detection methods can be employed, including collection-mode SNOM (measuring transmitted or reflected light) or illuminationmode SNOM (illuminating the sample through the probe tip and detecting scattered light).
c) Scanning Probe Operation: The probe tip is scanned across the sample surface in a raster pattern using precise positioning mechanisms. By recording the optical signals at each position, a high-resolution optical image or map of the sample’s optical properties is generated.
d) Sub-diffraction-limited Resolution: The spatial resolution of SNOM is determined by the dimensions of the probe tip and its proximity to the sample surface, rather than the wavelength of light. This allows SNOM to achieve optical resolution beyond the diffraction limit, with lateral resolutions down to tens of nanometers or even below.

Instrumentation of Scanning Near Field Optical-Microscope:

a) Optical Fiber Probe: The heart of the SNOM is a tapered optical fiber probe, typically made of silica or other dielectric materials. The probe tip is tapered to a sharp point with dimensions on the order of the wavelength of light. The probe acts as both an illumination source and a near-field detector for optical signals.
b) Cantilever Assembly: The optical fiber probe is mounted on a flexible cantilever, similar to those used in Atomic Force Microscopy (AFM). The cantilever allows for precise positioning of the probe tip relative to the sample surface and enables scanning in the x, y, and z directions.
c) Piezoelectric Scanner: The sample stage is mounted on a piezoelectric scanner, which allows for precise control of the position of the sample relative to the probe tip. The scanner can move the sample in the x, y, and z directions with nanometer-scale precision, enabling raster scanning of the probe tip across the sample surface to generate high-resolution images.
d) Feedback Control System: A feedback control system is used to maintain a constant distance between the probe tip and the sample surface during scanning. This feedback loop adjusts the vertical position of the probe tip by moving the piezoelectric scanner up or down to keep the near-field interaction constant.
e) Optical Source: An optical source, typically a laser, is used to illuminate the sample surface through the optical fiber probe. The laser light is coupled into the probe and focused to a diffraction-limited spot at the probe tip, creating a highly localized optical field near the sample surface.
f) Optical Detection System: Light scattered or emitted from the sample surface is collected by the probe tip and guided back through the optical fiber to a detector. The detector measures the intensity, polarization, wavelength, or other optical properties of the collected light, providing information about the sample’s optical properties and surface features.
g) Control and Data Acquisition System: A control and data acquisition system is used to operate the SNOM, control scanning parameters, and acquire data from the detector. This system typically includes software for image acquisition, processing, and analysis, as well as hardware components such as analog-to-digital converters (ADCs) and digital signal processors (DSPs).
h) Environmental Control: Some SNOM systems are equipped with environmental control features to minimize vibration, temperature fluctuations, and humidity changes that can affect imaging performance. This may include vibration isolation tables, temperature-controlled enclosures, and vacuum chambers (Figure 7).

Figure 4 shows the distribution of socio-economic impacts on forest-dependent communities, including displacement, poverty increase, and loss of cultural heritage [34].

Advantage of Scanning Near Field Optical-Microscope:

a) Sub-diffraction-limited Resolution: SNOM can achieve optical resolution beyond the diffraction limit of light, allowing for imaging and spectroscopy at the nanometer scale. This enables researchers to study optical properties and structures with unprecedented detail.
b) Nanoscale Optical Imaging: SNOM provides highresolution optical imaging of nanoscale features, including surface plasmon polarities, photonic nanostructures, and biological samples.
c) Real-time Imaging: SNOM can provide real-time imaging of dynamic processes at the nanoscale, allowing researchers to observe rapid changes in optical properties or sample morphology as they occur.
d) Surface Sensitivity: SNOM is highly sensitive to changes in the local optical properties of the sample surface, such as refractive index variations, absorption, and fluorescence. This sensitivity enables the detection of subtle surface features and optical phenomena that may not be observable with conventional optical microscopy techniques.
e) Multimodal Imaging and Spectroscopy: SNOM can be combined with other imaging and spectroscopy techniques, such as atomic force microscopy (AFM), fluorescence microscopy, and Raman spectroscopy, to provide complementary information about sample properties.
f) Non-destructive Imaging: SNOM imaging is nondestructive, as it does not require staining or labeling of samples.
g) Versatility: SNOM can be used to study a wide range of materials and sample types, including semiconductors, metals, polymers, Nano photonics, plasmonics, Biosensing and biological samples.

Limitation of Scanning Near-field Optical Microscope:

a) Complex Probe Fabrication: SNOM probes require precise fabrication to produce sharp tips with nanometer-scale apertures. Fabrication methods such as electrochemical etching or focused ion beam milling can be time-consuming and may result in variability between probes, affecting imaging quality and reproducibility.
b) Limited Signal Collection Efficiency: SNOM typically collects only a small fraction of the total emitted or scattered light from the sample surface. This limited collection efficiency can result in low signal-to-noise ratios, especially for weakly emitting or scattering samples, making it challenging to obtain high-quality images or spectroscopic data.
c) Probe-sample Interaction: The interaction between the SNOM probe tip and the sample surface can influence the measured optical signals and introduce artifacts. Tip-sample interactions, such as tip-induced sample deformation or surface modification, may alter the sample’s optical properties and affect imaging accuracy.
d) Tip Wear and Degradation: SNOM probe tips can wear out or become contaminated during scanning, leading to changes in probe geometry and optical properties. Tip degradation can degrade imaging resolution and sensitivity, necessitating frequent probe replacement or cleaning.
e) Sample Preparation Requirements: SNOM imaging often requires samples to be flat, clean, and optically smooth to achieve high-quality results. Sample preparation techniques, such as surface polishing or coating, may alter the sample’s native properties or introduce artifacts that affect imaging accuracy.
f) Limited Imaging Speed: SNOM imaging typically operates at relatively slow scan speeds compared to other microscopy techniques. This limitation can be particularly significant for large-area imaging or time-resolved experiments, where long acquisition times may be required.
g) Environmental Sensitivity: SNOM performance can be sensitive to environmental conditions such as temperature, humidity, and vibrations. Maintaining stable experimental conditions is crucial for obtaining reproducible and reliable imaging results.

Scanning Electron Microscope (SEM) with a Field Emission Gun (FEG):

The Scanning Electron Microscope (SEM) with a Field Emission Gun (FEG) represents a significant advancement in electron microscopy technology. The development of FEG-SEM traces back to the mid-20th century when field emission electron sources were first proposed and studied [47-49].

Principle of Scanning Electron Microscope with Field Emission Gun:

a) Field Emission Electron Source: The FEG utilizes a sharp tungsten or other refractory metal tip with a nanometerscale apex. Applying a high electric field to the tip causes electrons to be emitted from its surface via the quantum mechanical tunneling phenomenon known as field emission.
b) Highly Focused Electron Beam: The emitted electrons form a highly collimated beam due to the small size of the emitter tip and the strong electric field. This focused electron beam is then accelerated and directed towards the sample surface.
c) Sample Interaction: When the electron beam interacts with the atoms in the sample, various phenomena occur, including elastic and inelastic scattering, secondary electron emission, backscattered electron emission, and X-ray emission. These interactions depend on the sample’s atomic number, density, and composition.
d) Detection of Signals: Various detectors within the SEM capture signals resulting from interactions between the electron beam and the sample. Secondary electrons, backscattered electrons, and X-rays are commonly detected and used for imaging or compositional analysis of the sample.
e) Scanning and Imaging: The electron beam scans across the sample surface in a raster pattern using electromagnetic or scanning coils. At each position, the detected signals are processed to generate an image of the sample surface. Precise control over beam position and intensity enables high-resolution imaging of sample morphology.
f) Resolution and Imaging Modes: FEG-SEM typically achieves sub-nanometer resolution, facilitating detailed imaging of surface features. Different imaging modes, such as secondary electron imaging, backscattered electron imaging, and energydispersive X-ray spectroscopy (EDS), provide complementary information on sample composition, topography, and material contrast (Figure 8).

Advantage of Scanning Electron Microscope with Field Emission Gun:/

a) Improved Resolution: FEG-SEM typically achieves higher resolution than conventional SEMs due to the smaller electron source size and higher beam brightness. This allows for the visualization of finer surface features and the imaging of nanoscale structures with sub-nanometer resolution.
b) Enhanced Beam Brightness: FEG-SEM produces a highly focused and intense electron beam with a small source size, resulting in increased beam brightness. This improved brightness enables sharper imaging, higher signal-to-noise ratios, and better sensitivity for detecting low-energy secondary electrons and X-rays.
c) Higher Spatial Resolution at Low Beam Energies: FEG-SEM can achieve high spatial resolution even at low beam energies, making it suitable for imaging sensitive or beamsensitive samples. This capability is particularly advantageous for studying biological specimens, polymers, and nanomaterials without causing sample damage or beam-induced artifacts.
d) Reduced Beam Damage: The high beam brightness and small probe size of FEG-SEM result in reduced beam damage to the sample compared to conventional SEMs. This allows for longer imaging times and repeated imaging of the same area without significant sample degradation, making FEG-SEM suitable for long-term studies and in-situ experiments.
e) Improved Depth of Field: FEG-SEM exhibits improved depth of field compared to conventional SEMs, allowing for clearer imaging of samples with uneven or rough surfaces. This enables the visualization of three-dimensional surface structures and topographies with greater clarity and detail.
f) Versatility in Imaging Modes: FEG-SEM offers versatile imaging modes, including secondary electron imaging, backscattered electron imaging, and compositional analysis using energy-dispersive X-ray spectroscopy (EDS). This flexibility allows researchers to obtain complementary information about sample morphology, composition, and material contrast in a single instrument.
g) Increased Stability and Reliability: FEG-SEM systems are often designed with advanced stability mechanisms and vacuum systems, resulting in improved instrument reliability and uptime. This ensures consistent performance and high-quality imaging over extended periods of operation.

Limitation of Scanning Electron Microscope with Field Emission Gun:

a) Complexity: FEG-SEM systems are more complex in design and operation compared to conventional SEMs. The integration of a field emission electron source requires sophisticated engineering and control systems, leading to increased complexity in instrument setup, maintenance, and troubleshooting.
b) High Vacuum Requirement: FEG-SEM systems operate under high vacuum conditions to maintain electron beam stability and minimize electron scattering. Achieving and maintaining high vacuum levels can be challenging and may require specialized vacuum pumps and stringent cleanliness protocols.
c) Beam Instability: Despite their improved beam brightness, FEG-SEM systems may still experience beam instability due to factors such as electronic noise, thermal fluctuations, or mechanical vibrations. Beam instability can result in image drift, reduced imaging resolution, and decreased data quality.
d) Sample Charging: FEG-SEM imaging can be susceptible to sample charging effects, particularly when imaging insulating materials or non-conductive samples. Sample charging can lead to image distortions, artifacts, and difficulties in obtaining accurate surface topography.
e) Beam-induced Damage: While FEG-SEM systems produce a highly focused electron beam, prolonged exposure to the beam can still cause sample damage, particularly for beamsensitive materials. Beam-induced heating, radiation damage, and surface contamination can affect sample integrity and introduce artifacts in imaging.
f) Limited Depth of Field: FEG-SEM imaging typically exhibits a limited depth of field, particularly at high magnifications and low beam energies. This can make it challenging to obtain clear images of samples with complex topographies or large height variations.

Scanning Kelvin Probe Microscope (SKPM):

The Scanning Kelvin Probe Microscope (SKPM) has its roots in the Kelvin probe technique, which was first developed in the 19^th century by Lord Kelvin to measure the work function of metals.

Principle of Scanning Kelvin Probe Microscope:

The Scanning Kelvin Probe Microscope (SKPM) measures the surface potential of a sample by scanning a conductive probe tip at a constant height above the sample surface, applying a small alternating current (AC) bias voltage in the process table.
Conductive Probe Tip: The SKPM probe tip is typically made of a conductive material such as metal-coated silicon or conducting diamond. It is brought into close proximity to the sample surface, maintaining a constant height during scanning.
a) Small AC Bias Voltage: A small AC bias voltage, typically in the millivolt range, is applied between the probe tip and the sample surface. This voltage creates an electric field between the probe and the sample, leading to charge redistribution on the sample surface.
b) Detection of Electrostatic Force: As the probe scans over the sample surface, fluctuations in the surface potential cause variations in the electrostatic force between the probe tip and the sample. These force changes are observed by monitoring the deflection of the probe or measuring the capacitance between the probe and the sample.
c) Feedback Control: A feedback loop is used to sustain a consistent force or capacitance between the probe tip and the sample surface by modifying the DC bias voltage applied to the probe. The amount of DC bias voltage needed to maintain this constancy is directly related to the surface potential of the sample at each location.
d) Surface Potential Mapping: By documenting the DC bias voltage at each position while the probe scans the sample surface, a surface potential map is created. This map offers insights into variations in surface charge distribution, work function, and electrical characteristics of the sample on a nanometer scale.

Instrumentation of Scanning Kelvin Probe Microscope:

a) Probe Tip Assembly: The key component of the SKPM is the probe tip assembly, which typically consists of a sharp metallic tip attached to a cantilever. The probe tip is made of a conductive material such as gold or platinum and is brought into close proximity to the sample surface during imaging.
b) Cantilever and Scanner: The probe tip assembly is mounted on a flexible cantilever, similar to those used in Atomic Force Microscopy (AFM). The cantilever allows for precise positioning of the probe tip relative to the sample surface and enables scanning in the x, y, and z directions. A piezoelectric scanner controls the movement of the sample stage to facilitate raster scanning of the probe tip across the sample surface.
c) Feedback Control System: A feedback control system is used to maintain a constant distance between the probe tip and the sample surface during scanning. This feedback loop adjusts the vertical position of the probe tip by moving the piezoelectric scanner up or down to keep the force between the tip and the sample constant.
d) Kelvin Probe: The Kelvin probe is used to measure the contact potential difference (CPD) between the probe tip and the sample surface. The Kelvin probe typically consists of a reference electrode and a sample electrode, with the CPD being proportional to the difference in work function between the two electrodes.
e) AC Biasing System: The SKPM applies an AC bias voltage between the probe tip and the sample surface to measure variations in surface potential.
f) Lock-In Amplifier: A lock-in amplifier is used to detect and measure the AC component of the current flowing between the probe tip and the sample surface. The lock-in amplifier synchronizes with the AC bias voltage to selectively measure the signal at the modulation frequency, providing a highly sensitive measurement of the CPD.
g) Control and Data Acquisition System: A control and data acquisition system is used to operate the SKPM, control scanning parameters, and acquire data from the lock-in amplifier. This system typically includes software for image acquisition, processing, and analysis, as well as hardware components such as analog-to-digital converters (ADCs) and digital signal processors (DSPs).
h) Environmental Control: Some SKPM systems are equipped with environmental control features to minimize vibration, temperature fluctuations, and humidity changes that can affect imaging performance. This may include vibration isolation tables, temperature-controlled enclosures, and vacuum chambers (Figure 9).

Advantage of Scanning Kelvin Probe Microscope:

a) Surface Potential Mapping: SKPM provides highresolution mapping of surface potential variations on a sample surface. This capability allows researchers to visualize and quantify surface charge distribution, work function differences, and electrical properties with nanometer-scale spatial resolution.
b) Non-destructive Measurement: SKPM measurements are non-destructive and non-invasive, as they do not require physical contact with the sample surface. This allows for the characterization of delicate or sensitive materials without altering their properties or inducing damage.
c) Quantitative Analysis: SKPM enables quantitative measurement of surface potential values, providing precise information about the electrical properties of materials. This quantitative analysis is valuable for studying charge transport mechanisms, surface reactivity, and device performance.
d) High Sensitivity: SKPM is highly sensitive to changes in surface potential, making it capable of detecting subtle variations in charge distribution and work function. This sensitivity allows for the detection of surface defects, dopant concentrations, and interface properties at the nanoscale.
e) Multi-modal Imaging: SKPM can be combined with other scanning probe microscopy techniques, such as atomic force microscopy (AFM), to provide complementary information about sample morphology, mechanical properties, and surface potential simultaneously. This multimodal imaging approach enhances the understanding of structure-property relationships in materials.
f) Versatility: SKPM can be applied to a wide range of materials, including semiconductors, metals, polymers, and biological samples.
g) In-situ and Operando Studies: SKPM can be used for in-situ and operando studies, allowing researchers to investigate dynamic processes, such as surface reactions, charge transfer, and device operation, in real-time. This capability is valuable for understanding the kinetics and mechanisms of surface phenomena [50-52].

Limitation of Kelvin Probe Microscope:

a) Surface Sensitivity: SKPM measurements are sensitive to surface contamination, roughness, and non-uniformities, which can affect the accuracy and reliability of surface potential mapping. Surface preparation and cleanliness are critical for obtaining meaningful results.
b) Sample Conductivity Requirement: SKPM requires samples to be at least semi-conductive or electrically grounded to obtain accurate surface potential measurements. Insulating samples may exhibit charge accumulation or surface charging effects, leading to inaccurate results or image artifacts.
c) Complexity of Interpretation: Interpreting SKPM data and extracting meaningful information about sample properties can be challenging, particularly for heterogeneous or complex materials. Calibration procedures, data analysis algorithms, and model assumptions may introduce uncertainties in surface potential measurements.
d) Limited Depth Sensitivity: SKPM is inherently a surface-sensitive technique, with limited depth penetration into the sample. It provides information about the surface potential but does not provide depth-resolved measurements of subsurface layers or buried interfaces.
e) Topography Coupling: Surface topography variations can affect SKPM measurements by modulating the probe-sample distance and influencing the electrostatic force between the probe tip and the sample. Proper compensation and correction methods are required to decouple surface potential from surface topography effects.
f) Tip-sample Interaction: SKPM measurements can be influenced by tip-sample interactions, such as tip-induced surface deformation or sample damage. Careful selection of probe tip materials, tip geometries, and imaging parameters is necessary to minimize tip-sample interactions and preserve sample integrity.
g) Environmental Sensitivity: SKPM performance may be sensitive to environmental conditions such as temperature, humidity, and atmospheric gases. Controlling environmental factors and maintaining stable experimental conditions are essential for reproducible and reliable measurements.

Scanning Capacitance Microscope:

Scanning Capacitance Microscopy (SCM) emerged in 1989 when David P. Pulfrey and colleagues combined atomic force microscopy (AFM) with capacitance sensing, pioneering a technique to map electrical properties at the nanoscale. Initially used to study semiconductor devices, SCM’s scope has expanded to materials science and failure analysis. In modern SCM instruments, a conductive tip scans the sample surface, measuring local capacitance variations induced by charges. These variations are then translated into high-resolution maps of carrier concentration, doping profiles, and electric field gradients [53- 55].

Principle of Scanning Capacitance Microscope:

a) Capacitance Sensing: When a conductive tip nears a semiconductor surface, it forms a capacitor with the underlying material. The capacitance of this setup is influenced by the dielectric properties of the material and the distance between the tip and the sample surface.
b) Variation in Capacitance: As the tip scans the sample surface, the local capacitance changes due to variations in the electrical properties of the underlying material. These variations can be caused by differences in carrier concentration, doping profiles, defects, or electric field gradients.
c) Detection and Imaging: The Scanning Capacitance Microscopy (SCM) detects these capacitance variations by applying a small AC voltage to the conductive tip and measuring the resulting AC current. By keeping a constant tip-sample distance, the SCM generates a topographic image of the sample surface while simultaneously mapping the local capacitance changes.
d) Data Analysis: The measured capacitance variations are processed to generate high-resolution maps of carrier concentration, doping profiles, and electric field gradients on the sample surface.

Instrumentation of Scanning Capacitance Microscope:

a) Probe Tip Assembly: The essential component of Scanning Capacitance Microscopy (SCM) is the probe tip assembly, typically consisting of a sharp metallic tip attached to a cantilever. This conductive tip, often made of materials like tungsten or platinum, is brought very close to the sample surface during imaging.
b) Cantilever and Scanner: Like other scanning probe microscopy techniques, the probe tip assembly in SCM is mounted on a flexible cantilever, enabling precise positioning of the tip relative to the sample surface. Movement of the sample stage is controlled by a piezoelectric scanner, facilitating raster scanning of the probe tip across the sample surface.
c) Feedback Control System: During scanning, a feedback control system is employed to keep a constant distance between the probe tip and the sample surface. This system adjusts the vertical position of the probe tip by moving the piezoelectric scanner up or down, ensuring the force between the tip and the sample remains consistent.
d) AC Biasing System: The SCM applies an AC bias voltage between the probe tip and the sample surface to measure variations in capacitance. The AC bias voltage typically has a frequency in the range of tens to hundreds of kilohertz, allowing for sensitive detection of changes in capacitance.
e) Capacitance Detection System: The SCM measures the capacitance between the probe tip and the sample surface using a capacitance detection system. This system typically includes a lock-in amplifier, which synchronizes with the AC bias voltage to selectively measure the signal at the modulation frequency, providing a highly sensitive measurement of capacitance.
f) Control and Data Acquisition System: A control and data acquisition system is used to operate the SCM, control scanning parameters, and acquire data from the capacitance detection system. This system typically includes software for image acquisition, processing, and analysis, as well as hardware components such as analog-to-digital converters (ADCs) and digital signal processors (DSPs).
g) Environmental Control: Some SCM systems are equipped with environmental control features to minimize vibration, temperature fluctuations, and humidity changes that can affect imaging performance. This may include vibration isolation tables, temperature-controlled enclosures, and vacuum chambers. Scanning Capacitance Microscope is diagrammatically shown in Figure 10.

Advantage of Scanning Capacitance Microscopy:

a) High Spatial Resolution: SCM provides nanometerscale resolution, allowing for the imaging and characterization of semiconductor devices and materials at the atomic or molecular level. This high spatial resolution is crucial for understanding the local variations in carrier concentration, doping profiles, and electric field gradients.
b) Non-destructive Characterization: SCM is a nondestructive technique that does not require sample preparation or alteration. It enables researchers and engineers to study semiconductor devices and materials without damaging them, making it suitable for both research and manufacturing applications.
c) Quantitative Analysis: Modern SCM systems are equipped with advanced data analysis software that enables quantitative analysis of SCM images. This software allows for the extraction of key parameters such as carrier concentration, doping profiles, and depletion widths from SCM data, providing valuable insights into the electrical properties of semiconductor materials.
d) Versatility: SCM can be used to study a wide range of semiconductor materials and devices, including transistors, diodes, integrated circuits, and thin films. It is applicable to various semiconductor materials such as silicon, gallium arsenide, and silicon carbide, making it a versatile tool in semiconductor research and manufacturing.
e) In-line Monitoring: SCM can be integrated with semiconductor manufacturing equipment for in-line monitoring of device properties during fabrication processes.

Limitations of Scanning Capacitance Microscope:

a) Surface Sensitivity: SCM is highly sensitive to the surface topography and cleanliness of the sample. Surface roughness and contamination can affect the accuracy and reliability of SCM measurements, potentially leading to artifacts in the obtained images.
b) Sample Preparation: Sample preparation for SCM can be time-consuming and challenging, especially for non-planar or heavily doped semiconductor structures. Achieving a flat and clean sample surface is essential for obtaining accurate SCM measurements.
c) Calibration Requirements: Proper calibration of SCM systems is crucial for obtaining quantitative measurements of carrier concentration and doping profiles. Calibration typically involves reference samples with known doping profiles, which may not always be readily available or representative of the sample being studied.
d) Limited Depth Sensitivity: SCM primarily probes the near-surface region of the sample, typically within a few nanometers of the surface. This limited depth sensitivity restricts the ability to characterize buried features or interfaces within semiconductor devices, such as buried junctions or interfaces between different materials.
e) Complex Data Analysis: Interpretation of SCM data can be complex, particularly for heterogeneous or multi-layered semiconductor structures. Extracting meaningful information from SCM images often requires advanced data analysis techniques and modeling to account for factors such as tip-sample interactions and material properties.

Scanning Thermal Microscopy:

Scanning Thermal Microscopy (SThM) emerged in the late 1980s, pioneered by researchers like Stephen Quake and Joseph Stroscio. SThM combines scanning probe microscopy (SPM) with a thermal probe to map variations in temperature at the nanoscale. Initially used to study thermal properties of materials, SThM’s scope has expanded to include heat dissipation in electronic devices, phase transitions, and thermal conductivity measurements [56-60].

Principle of Scanning Thermal Microscope:

a) Thermal Probe: The heart of the SThM is a tiny thermal probe, usually made of a material with high thermal sensitivity, such as a fine metal wire or a carbon nanotube. This probe serves as both a heater and a thermometer.
b) Thermal Exchange: When the thermal probe comes into contact with the sample surface, heat is exchanged between the probe and the sample due to their temperature differences. This heat exchange induces a change in the electrical resistance or another measurable property of the probe.
c) Temperature Mapping: As the SThM scans the sample surface, the thermal probe measures local temperature variations. By correlating these variations with the probe’s position, a temperature map of the sample surface is generated.
d) Feedback Control: To maintain a constant temperature at the probe’s tip, feedback control mechanisms are employed. These mechanisms adjust the probe’s heating power based on the detected temperature changes, ensuring accurate temperature measurements.
e) Imaging and Analysis: The temperature map obtained by the SThM is typically visualized as a thermal image overlaid with topographic information obtained simultaneously using other SPM techniques, such as atomic force microscopy (AFM).

Instrumentation of Scanning Thermal Microscope:

a) Probe Tip Assembly: The essential part of the SThM is the probe tip assembly, usually comprising a sharp metallic tip connected to a cantilever. This tip is crafted from a material with high thermal conductivity, such as silicon or diamond, and is positioned very close to the sample surface during imaging.
b) Cantilever and Scanner: Similar to other scanning probe microscopy techniques, the probe tip assembly is mounted on a flexible cantilever, enabling precise positioning of the tip relative to the sample surface. A piezoelectric scanner manages the movement of the sample stage, allowing for raster scanning of the probe tip across the sample surface.
c) Feedback Control System: A feedback control system is employed to maintain a constant distance between the probe tip and the sample surface during scanning. This system adjusts the vertical position of the probe tip by moving the piezoelectric scanner up or down, ensuring that the force between the tip and the sample remains consistent.
d) Thermal Measurement System: The SThM measures the temperature of the sample surface using a variety of techniques. It can use a thermocouple or resistance temperature detector (RTD) embedded in the probe tip to directly measure the local temperature or infrared radiation detection or frequencydependent thermal analysis to indirectly measure temperature variations.
e) Thermal Control System: Some SThM systems incorporate a thermal control system to regulate the temperature of the probe tip or the sample surface during imaging. This may involve heating or cooling elements integrated into the probe tip assembly or the sample stage, as well as temperature feedback loops to maintain a constant temperature.
f) Control and Data Acquisition System: A control and data acquisition system is used to operate the SThM, control scanning parameters, and acquire data from the thermal measurement system. This system typically includes software for image acquisition, processing, and analysis, as well as hardware components such as analog-to-digital converters (ADCs) and digital signal processors (DSPs) (Figure 11).

Advantage of Scanning Thermal Microscope:

a) High Spatial Resolution: SThM provides nanoscale spatial resolution, allowing for the imaging and characterization of temperature variations with high precision. This capability is crucial for studying thermal properties at the micro- and nanoscale, where conventional thermometry techniques often struggle.
b) Localized Temperature Measurement: SThM enables localized temperature measurements, allowing researchers to study temperature gradients, hotspots, and thermal fluctuations with exceptional sensitivity.
c) Multi-Modal Imaging: SThM can be integrated with other scanning probe microscopy (SPM) techniques, such as atomic force microscopy (AFM), allowing for simultaneous imaging of topography and temperature which provides comprehensive insights into the correlation between surface morphology and thermal properties.
d) Non-destructive Characterization: SThM is a nondestructive technique that does not require sample preparation or alteration.
e) Wide Range of Application: It is used to characterize thermal properties of electronic devices, study heat dissipation in nanomaterials, investigate thermal conductivity of materials, and map temperature distributions in biological samples.

Limitations of Scanning Thermal Microscope:

Complexity of Calibration: Calibrating an SThM system can be challenging due to the need to establish a reliable correlation between the probe’s thermal properties and the measured signals. Achieving accurate and reproducible temperature measurements requires careful calibration procedures, often involving reference samples with known thermal properties.
a) Tip-Sample Interaction: The interaction between the thermal probe and the sample surface can affect temperature measurements, leading to uncertainties in the obtained data. Factors such as tip-sample contact area, thermal conductivity of the sample, and thermal coupling between the probe and the sample can influence the measured temperature values.
b) Limited Depth Sensitivity: SThM primarily probes the near-surface region of the sample, typically within a few nanometers of the surface.
c) Environmental Sensitivity: SThM measurements can be sensitive to environmental conditions such as temperature fluctuations, humidity, and air flow.
d) Sample Compatibility: SThM measurements may be challenging for samples with complex geometries, rough surfaces, or non-flat topographies. Achieving good thermal contact between the probe and the sample surface is crucial for accurate temperature measurements, which may be difficult to achieve for certain sample types.
e) Limited Throughput: SThM measurements typically require scanning over the sample surface point by point, which can be time-consuming, especially for large-area measurements or high-resolution imaging.

Go to

• Review Article
• Abstract
• Electron Microscope
• X-Ray Microscope:
• Probe Microscopy
• Conclusion
• Acknowledgment
• References

Conclusion

In the recent past there has been rapid change in the characterization techniques for biological and nanomaterials. Also, the existing technique has advanced due to adaptation of new technology. Today, many researchers are engaged in the research and development of nanomaterials. These materials have found applications in veterinary medicine, health, and agriculture. Since nanomaterials are beyond the perception of the human eye, it is crucial to have accurate characterization techniques for analyzing materials at the nanoscale. Thus, keeping this in mind we have tried to focus on the recent development in some of the important characterization techniques required in nanotechnology, biotechnology, veterinary sciences, health and pharmaceutical sciences. In the last section we have discussed various applications of materials at nanoscale especially their uses in veterinary science and agriculture. Overall the manuscript would be highly beneficial for the researchers, students and industrial persons working in nanoscience and technology.

Go to

• Review Article
• Abstract
• Electron Microscope
• X-Ray Microscope:
• Probe Microscopy
• Conclusion
• Acknowledgment
• References

Acknowledgment

The authors pay sincere tribute to Late Ms. Deepika Rai Dhirendra Prasad who suddenly left this world and lived a very short span of life. The authors fondly remember her on this occasion and pray to Almighty God for the peace of her holy soul. Her sweet memories remain in the hearts of the authors, who are deeply grateful to her. The authors are also thankful to Shri Baldev Singh IAS, then Chief Executive Officer, Zilla Parishad, Kolhapur and to the supportive staffs of Veterinary Dispensary Grade 1, Navargaon, District Chandrapur Mr. Natthu Chikram and Mr. Kavadu Kadmi who maintained friendly and co-operation environment during the stay of authors.

Go to

• Review Article
• Abstract
• Electron Microscope
• X-Ray Microscope:
• Probe Microscopy
• Conclusion
• Acknowledgment
• References

References

1. Jariwala PH, Sonavane YA, Thakor PB, Gupta SK (2021) Strain dependent electronic transport of pristine Si and Ge nanowires. Computational Materials Science 188: 110181.
2. Shi J, Votruba AR, Farokhzad OC, R Langer (2010) Nanotechnology in drug delivery and tissue engineering: from discovery to applications. Nano Lett 10(9): 3223-3230.
3. Patil SS, Bhat TS, Teli AM, Beknalkar SA, Dhavale SB, et al. (2020) Hybrid solid state supercapacitors (HSSC’s) for high energy & power density: an overview. Engineered Science 12: 38-51.
4. Sai-Halasz GA, Wordeman MR, Kern DP, Rishton SA, Ganin E, et al. (1990) Experimental technology and performance of 0.1-μm-gate-length FETs operated at liquid nitrogen temperature. IBM J Research & Devlop 34(4): 452-465.
5. Patil SS, Patil PS (2023) Transition metal pyrophosphate (MxP2O7): a new arrival in hybrid supercapacitors. Chemical Engineering Journal 455: 140639.
6. Rothe H, Fautz R, Gerber E, Neumann L, Rettinger K, et al. (2011) Special aspects of cosmetic spray safety evaluations: Principles on inhalation risk assessment. Toxicology Letters 205(2): 97-104.
7. Mali SS, Patil JV, Rondiya SR, Dzade NY, Steele JA, et al. (2022) Terbium‐Doped and Dual‐Passivated γ‐CsPb (I1- x Brx) 3 Inorganic Perovskite Solar Cells with Improved Air Thermal Stability and High Efficiency. Adv Mater 34(29): 2203204.
8. Bhattacharjee K, Prasad BLV (2023) Surface functionalization of inorganic nanoparticles with ligands: a necessary step for their utility. Chemical Society Reviews 52(8): 2573-2595.
9. Nikam AV, Prasad BLV, Kulkarni AA (2018) Wet chemical synthesis of metal oxide nanoparticles: a review. Cryst Eng Comm 20(35): 5091-5107.
10. Gatoo MA, Naseem S, Arfat MS, Dar AM, Qasim K, et al. (2014) Physicochemical Properties of Nanomaterials: Implication in Associated Toxic Manifestations. Biomed Res Int.
11. Prasad SR, Teli SB, Ghosh J, Prasad NR, Shaikh VS, et al. (2021) A Review on Bio-inspired Synthesis of Silver Nanoparticles: Their Antimicrobial Efficacy and Toxicity. Engineered Science 16: 90-128.
12. Pharande PS, Mhaldar PM, Lohar TR, Ghotekar SK, Chhowala TN, et al. (2023) A selective heterogeneous cellulose supported Schiff base Cu (II) catalyst for Chan–Evans–Lam coupling. Research on Chemical Intermediates 49: 4541-4560.
13. Nazeruddin GM (2015) Int J of Nanomaterials and Nanostructures 1(1): 16-32.
14. Sharma K, Sharma DK, Kumar V (2020) Copper selenide films via screen printing and sintering technique for semiconductor device applications: Synthesis and characterization. Optik 206: 164376.
15. Gupta R, Xie H (2018) Nanoparticles in Daily Life: Applications, Toxicity and Regulations. J Environ Pathol Toxicol Oncol 37(3): 2018026009.
16. Altafhusen AG, Kale DP, Garadkar KM, Jagadale MB, Gophane AD, et al. (2020) Photocatalytic degradation of methyl orange by magnetically retrievable supported ionic liquid phase photocatalyst. ACS Omega 131-144.
17. Edwards PP, Thomas JM (2007) Gold in a metallic divided state--from Faraday to present-day nanoscience. Angew Chem Int Ed Engl 46(29): 5480-5486.
18. Karmankar, SmitaBadur (2022) NeuroQuantology 20(20): 2640.
19. Arvizo RR, Bhattacharya S, Kudgus R, Giri K, Bhattacharya R, et.al. (2012) Intrinsic Therapeutic Applications of Noble Metal Nanoparticles: Past, Present and Future. Chem Soc Rev 41(1): 2943-2970.
20. Prasad RD, Sarvalkar PD, Prasad N, Prasad RS, Prasad RB, et.al. (2024) Emerging Trends of Bioactive Nano-materials in Modern Veterinary Science and Animal Husbandry. ES Food & Agroforestry.
21. Mulvaney P, (1996) Materials Mix. Optical properties of metal clusters By U. Kreibig, M. Vollmer, Springer Series in Materials Science. Advanced Materials 8(8): 699.
22. Sarvalkar PD, Jamadar AS, Kakade SS, Magdum AB, Pawar PK, et al. (2024) Biogenic Synthesis of Co3 O4 nanoparticles from Aloe barbadensis extract: Anti-oxidant and antimicrobial activities, and photocatalytic degradation of azo dyes. Results in Engineering 22: 102094.
23. Zhao Y, Xie Z, Gu H, Zhu C, GU Z (2012) Bio-inspired variable structural color materials. Chem Soc Rev 41: 3297-3317.
24. Prasad SR, Kumbar VB, Prasad NR (2024) Applications of Nanotechnology in Textile: A Review. ES Food and Agroforestry 15: 1019.
25. Sarvalkar PD, Prasada NR, Kamble SS, Japtan AS, Thounaojam P, et al. (2023) Impact of Selective Nano-catalysts in Nitroarene Reduction Reactions. Nano Trends: A Journal Nanotechnology and its Applications 25(2).
26. Bhat TS, Mali SS, Sheikh AD, Tarwal NL, Korade SD, et al. (2018) ZnS passivated PbSe sensitized TiO2 nanorod arrays to suppress photocorrosion in photoelectrochemical solar cells. Mater Today Commun 16: 186-193.
27. Karvekar OS, Vadanagekar AS, Sarvalkar PD, Suryawanshi SS, Jadhav SM, et al. (2022) Bos Taurus urine Assisted Bio-active Cobalt Oxide Anchored ZnO. A Novel Nanoscale Approach. Sci Rep 12(1): 15584.
28. Kumbhar GS, Patil SV, Sarvalkar PD, Vadanagekar AS, Karvekar OS, et al. (2022) Synthesis of Ag/Rgo Nanocomposite using Bos Taurus indicus urine for niroarene reduction and biological activity. RSC Advances 12: 35598-35612.
29. Musale SP, Patil KR, Gavhane RJ, Dagade DH (2018) Density and speed-of-sound measurements for dilute binary mixtures of diethylammonium-based protic ionic liquids with water. Journal of Chemical & Engineering Data 6: 1859-1876.
30. Karvekar OS, Sarvalkar PD, Vadanagekar AS, Singhan RD, Jadhav SM, et al. Biogenic synthesis of silver anchored ZnO nanorods as nano catalyst for organic transformation reactions and dye degradation. Appl Nanosci 12(7): 2207-2226.
31. Pawar CA, Sharma AK, Prasad NR, Suryawanshi SS, Nazeruddin GM, et al. (2022) A comparative study on anti-microbial efficacies of biologically synthesized nano gold using Bos Taurus indicus urine with pharmaceutical drug sample. Current Research in Green and Sustainable 5: 100311.
32. Shaikh YI, Shaikh VS, Nazeruddin GM, Shekh Z, Gugale Gs, et al. (2022) A Green Chemistry Approach Towards Synthesis of Bis- coumarins catalyzed by different biocatalysts such as Dragon fruit, Kiwi Fruit juice and Butter Milk Separated by Grinding Stone Technique: A comparative study. ES Food and Agroforestry 7: 25-29.
33. Salvalkar PD, Barawkar SD, Karvekar OS, Patil PD, Prasad SR, et al. (2022) A review on multifunctional nanotechnological aspects in modern textile. The Journal of Textile Institute 114(3): 470-487.
34. Biradar AI, Sarvalkar PD, Teli SB, Pawar CA, Patil PS, et al. (2021) Photocatalytic degradation of dyes using one step synthesized silica nanoparticles. Materials Today Proceedings 43(4): 2832-2838.
35. Pawar CA, Sharma AK, Prasad NR, Suryawanshi SS, Yewale MA, et al. (2021) Murraya koenigii Assisted Synthesis of Bioactive Silver Nanomaterial. Macromolecular Symposia 400(1): 2100126.
36. Ramteke AA, Chougule PK, Prasad N, Vyawahare YK, Kulal SR, et al. (2021) Study on Acoustic Properties of Lead Oxide Nanoparticle in Different Solvent Mixtures at 305 K by Using Nanofluid Interfrometer. Macromolecular Symposia 400(1): 2100171.
37. Salvalkar PD, Mandhavkar RR, Nimbalkar MS, Sharma KK, Patil PS, et al. (2021) Bio- mimetic synthesis of catalytically active nano-silver using Bos tautus (A-2) urine. Scientific Reports 16934.
38. Padvi MN, Mohalkar AV, Prasad SR, Prasad NR (2021) A Critical Review on Design and Development of Gas Sensing Materials. Engineered Science 15: 20-37.
39. Prasad SR, Padvi MN, Suryawanshi SS, Shaikh YI, Chaudhary LS, et al. (2020) Bio-inspired synthesis of catalytically and biologically active palladium nanoparticles using Bos taurus urine. SN Applied Sciences 2:754.
40. GM Nazeruddin (2015) International Journal of Applied Nanotechnology 1(1-2).
41. Narwade B, Prasad N, Lokhande S, Madavi AB, Sahoo AK (2018) Extracellular Biosynthesis of Silver Nanoparticles Using Moringa Oleifera Leaves Extract and Its Anti-microbial Efficacy in Packaging Materials.
42. Jadhav P, Shinde S, Suryawanshi SS, Teli SB, Patil PS, et al. (2020) Green AgNPs Decorated ZnO Nanocomposite for Dye Degradation and Anti-microbial Applications. Engineered Science 12: 79-94.
43. Joshi SS, Sahoo AK, Prasad NR, Udachan IR (2018) Biosynthesis of Silver nanoparticles (AgNPs) By extract of Annona squasosa waste characterization and their anti-microbial activity. International journal of Research and Analytical Review (IJRAR) 5(4): 907-914.
44. PhD thesis C A Pawar, Submitted to SU Kolhapur (2023)
45. PhD thesis N R Prasad Submitted to SPPU, Pune, India.
46. Nazeruddin GM, Prasad NR, Prasad SR, Garadkar KM, Nayak AK (2014) In-vitro bio-fabrication of silver nanoparticles using Adhatoda vasica leaf extract and its antimicrobial activity. Physica e 61:56–61.
47. Deepak SP (2023) Thermo-Hydraulic Performance of Partially Blocked Metal-Foam Channels. Diss Virginia Polytechnic Institute and State University.
48. Issa B, Obaidat IM, Albiss BA, Haik Y (2013) Magnetic nanoparticles: surface effects and properties related to biomedicine applications. Int J Mol Sci 14(11): 21266-21305.
49. Selvamani V (2019) Stability Studies on Nanomaterials Used in Drugs. Characterization and Biology of Nanomaterials for Drug Delivery 425-444.
50. Li Y, Zhou B, Zheng G, Liu X, Li T, et al. (2018) Continuously prepared highly conductive and stretchable SWNT/MWNT synergistically composited electrospun thermoplastic polyurethane yarns for wearable sensing. Journal of Materials Chemistry C 6: 2258-2269.
51. Khot AC, Dongale TD, Park JH, Kesavan AV, Kim TG, et al. (2021) Ti3C2-based MXene oxide nanosheets for resistive memory and synaptic learning applications. ACS Appl Mater Interfaces 13(4): 5216-5227.
52. Dongale TD, Khot AC, Takaloo AV, Kim GT (2021) Facile synthesis of nickel cobaltite quasi-hexagonal nanosheets for multilevel resistive switching and synaptic learning applications. NPG Asia Materials 13: 16.
53. Raju PV, Bhat U, Reddy T, Mutnuri VM (2023) EDUCATIONAL DIAGNOSIS IN RURAL POOR COMMUNITY ON TUBERCULOSIS. Int J Acad Med Pharm 5(5): 1208-1211.
54. Jatkar CM, Patil JM, Kumbhar RR, Sabale S (2022) AN OVERVIEW ON ALKALINE TREATMENTS FOR MODIFICATION OF AGRO-WASTE AND ITS APPLICATIONS. International Journal of Education & Applied Sciences Research 9(2): 01-09.
55. Jatkar C, Dhabbe R, Garadhar K, Kupwade R, Shen J, et al. A sustainable approach for tailoring coir-fibre based bio-adsorbent and its composite for industrial applications. Biomass Conversion and Biorefinery.
56. Ong J (2022) Cryogenic Storage and Transport of Biological Products for Biobanking (Doctoral dissertation, Monash University).
57. Gupta RC, Varma DR (2020) Methyl isocyanate: The Bhopal gas. In Handbook of Toxicology of Chemical Warfare Agents (pp. 389-402). Academic Press.
58. Fuller R, Landrigan PJ, Balakrishnan K, Bathan G, Bose-O'Reilly S, et al. (2022) Pollution and health: a progress update. Lancet Planet Health 6(6): e535-e547.
59. Pyo S, Lee J, Bae K, Sim S, Kim J (2021). Recent progress in flexible tactile sensors for human‐interactive systems: from sensors to advanced applications. Advanced Materials 33(47): 2005902.
60. Xie P, Shi Z, Feng M, Sun K, Liu Y, et al. (2022) Recent advances in radio-frequency negative dielectric metamaterials by designing heterogeneous composites. Advanced Composites and Hybrid Materials 5: 679-695.