CHARACTERIZATION

X-Ray Diffraction (XRD)

The first characterization we perform for any synthesized material is its identification. To confirm the phase of our material, we conduct Rietveld refinement and compare it with existing literature. For XRD measurements, we collaborate with several institutions, including the Bangladesh Council of Scientific and Industrial Research (BCSIR), the Centre for Advanced Research in Sciences (CARS), and the Bangladesh Atomic Energy Commission.

Fourier Transform Infrared Spectroscopy (FTIR)

In FTIR characterization, we analyze the infrared absorption spectrum of a material to identify its molecular structure and functional groups. The spectrum consists of distinct regions, each corresponding to specific vibrational modes of chemical bonds. At the high wavenumber end, stretching vibrations of single bonds, such as the broad O-H peak in water, are prominently observed. Triple bond stretching, like the C≡N bond in acetonitrile, appears between 2500 cm⁻¹ and 2000 cm⁻¹, while double bond stretching, such as the C=O bond in carboxylic acids, is detected between 2000 cm⁻¹ and 1500 cm⁻¹. The most complex yet informative part of the spectrum is the fingerprint region, which contains a unique pattern of stretching and bending vibrations that serve as a "chemical fingerprint" for the sample. This detailed spectral analysis helps in confirming the composition, purity, and structural characteristics of synthesized materials.

Raman Spectroscopy

Using Raman characterization, we analyze the chemical structure of materials by measuring their unique vibrational fingerprints. This technique allows us to identify chemical bonds, detect phase and polymorphism, assess intrinsic stress or strain, and determine contamination or impurities. Each material exhibits a distinct Raman spectrum, which we compare with reference spectral libraries for accurate identification and differentiation. By leveraging Raman spectroscopy, we gain deep insights into the structural and compositional properties of our synthesized materials, ensuring precise characterization and validation.

Diffuse Reflectance Spectroscopy (DRS)

Using Diffuse Reflectance Spectroscopy (DRS), we measure the absorbance, reflectance, and transmittance of the powdered sample to analyze its optical properties. The Kubelka-Munk function is often applied to the reflectance data to estimate the absorbance for materials with strong scattering effects. From the absorbance data, TAUC plots are constructed to determine the experimental direct and indirect bandgaps by extrapolating the linear region of (αhν)n vs. hν, where α is the absorption coefficient, hν is the photon energy, and n depends on the nature of the band transition (n = 1/2) for indirect and (n = 2) for direct transitions). These bandgap values are crucial for understanding the material’s electronic structure and its potential applications in photocatalysis, optoelectronics, and energy conversion.

(Field Emission) Scanning Electron Microscopy (FESEM & SEM)

We utilize Scanning Electron Microscopy (SEM) and Field Emission Scanning Electron Microscopy (FE-SEM) to examine the surface morphology of the samples. The morphology is crucial as it provides insights into potential applications and highlights any defects. From the obtained images, we can generate particle size histograms, which help determine the average particle size of the sample, offering valuable information on its structural characteristics.

Energy Dispersive X-ray Analysis (EDX)

We use Energy Dispersive X-ray Spectroscopy (EDX) to analyze the chemical composition and purity of the samples. This technique detects characteristic X-rays emitted by elements, allowing us to identify and quantify them. From the data, we calculate both weight percentage (wt%) and atomic percentage (at%), which help determine the material’s composition, stoichiometry, and potential impurities.

X-ray Photoelectron Spectroscopy (XPS)

X-ray Photoelectron Spectroscopy (XPS) is used to analyze the elemental composition, chemical states, and surface chemistry of the samples. This technique detects photoelectrons emitted from the material when exposed to X-rays, providing insights into oxidation states and bonding environments. XPS also quantifies elements present on the surface, typically within a few nanometers, making it essential for studying chemical purity, surface modifications, and functionalization.

Transmission Electron Microscopy (TEM)

We utilize Transmission Electron Microscopy (TEM) to investigate the microstructure, morphology, and crystallinity of the samples at the nanoscale. This technique allows high-resolution imaging by transmitting an electron beam through the sample, revealing details such as grain boundaries, defects, and lattice fringes. TEM also enables selected area electron diffraction (SAED) analysis, providing crystallographic information essential for understanding the structural properties of the material.

Photoluminescence (PL)

In our photoluminescence (PL) characterization, we analyze the emission and excitation spectra of materials to understand their optical and electronic properties. When excited by light, materials emit photons at characteristic wavelengths, revealing information about band gap energy, defect states, and charge carrier recombination. Shifts or broadening in the PL spectrum indicate impurities, defects, or strain, helping assess material quality. By studying both excitation and emission, PL spectroscopy provides crucial insights into the optical behavior of semiconductors, nanomaterials, and optoelectronic devices.

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