Abstract

Global fossil fuel consumption has induced emissions of anthropogenic carbon dioxide (CO₂), which has emanated global warming. Significant levels of CO₂ are released continually into the atmosphere from the extraction of fossil fuels to their processing and combustion for heat and power generation including the fugitive emissions from industries and unmanaged waste management practices such as open burning of solid wastes. With an increase in the global population and the subsequent rise in energy demands and waste generation, the rate of CO₂ release is at a much faster rate than its recycling through photosynthesis or fixation, which increases its net accumulation in the atmosphere. A large amount of CO₂ is emitted into the atmosphere from various sources such as the combustion of fossil fuels in power plants, vehicles and manufacturing industries. Thus, carbon capture plays a key role in the race to achieve net zero emissions, paving a path for a decarbonized economy. To reduce the carbon footprints from industrial practices and vehicular emissions and attempt to mitigate the effects of global warming, several CO₂ capturing and valorization technologies have become increasingly important. Hence, this article gives a statistical and geographical overview of CO₂ and other greenhouse gas emissions based on source and sector. The review also describes different mechanisms involved in the capture and utilization of CO₂ such as pre-combustion, post-combustion, oxy-fuels technologies, direct air capture, chemical looping combustion and gasification, ionic liquids, biological CO₂ fixation and geological CO₂ capture. The article also discusses the utilization of captured CO₂ for value-added products such as clean energy, chemicals and materials (carbonates and polycarbonates and supercritical fluids). This article also highlights certain global industries involved in progressing some promising CO₂ capture and utilization techniques.

Abstract

Manganese (Mn) doped copper (II) oxide (CuO) thin films with 0 to 6 at% Mn doping were prepared onto the glass substrates at a temperature of 523 K using spray pyrolysis technique. The CuO and Mn doped CuO films showed monoclinic structure with the preferential orientation along (1̅11) and (111) planes after being annealed at 723 K in air for 60 min. The film surface was observed to be comprised of agglomerated nanoparticles under Scanning Electron Microscopy. Elemental composition of the films was confirmed by Energy Dispersive X-ray analysis. Optical transmittance and band gap of CuO thin film increased with Mn doping up to 4 at% in the visible-infrared region of light. Electrical resistivity of the samples decreased from 2.69×103 to 1.62×103 Ω-m with the increase of Mn doping. Activation energy of the films varied from 0.08 to 0.29 eV in the temperature region 323 - 383 K, whereas it varied from 0.29 to 0.40 eV in the temperature region 383 - 423 K.

Abstract

A novel semi-organic crystal has been grown using slow evaporation technique by doping organic compound L-asparagine monohydrate (C4H8N2O3⋅H2O) with inorganic material Magnesium sulphate heptahydrate (MgSO4⋅7H2O). The crystallographic parameters like strain, dislocation density and crystallite size were calculated by powder X-ray diffraction method. Functional groups were identified and bond length, force constants were calculated from FT-IR spectroscopy. Energy dispersive X-ray (EDX) analysis was used to identify the constituent elements of the crystal. Kinetic and thermodynamic parameters, such as, activation energy Ea, change in Gibb’s free energy (ΔG) and change in enthalpy (ΔH) have been determined by thermogravimetric analysis (TGA) analysis. Ea, ΔH and ΔG show positive values and change in entropy (ΔS) shows negative ones. The thermal degradation behavior of the crystals has been analyzed by differential scanning calorimetry (DSC) analysis. Various optical constants such as optical band gap, lattice dielectric constant, absorbance, extinction coefficient, the ratio of free charge carrier concentration to the effective mass, Urbach energy, optical and electrical conductivities were estimated from UV–vis transmittance data. High optical conductivity (1010 s − 1 ) justifies the good photo response nature of the semi-organic crystal.

Abstract

Thin films of pristine titanium dioxide (TiO2) and doped with different concentrations (0–8) at.% of nickel (Ni) were synthesized onto transparent glass substrates using the spray pyrolysis deposition technique. Field emission scanning electron microscopy revealed the porous and agglomerated surface morphology of the films. X-ray diffractometer demonstrated the anatase crystal structure with a nominal increment of (101) peak. The shifting of peak position revealed the expansion of the unit cell volume from 134.64 to 137.54 (Å)3 whereas crystallite size increased from 34 to 63 nm. Using the Fizeau fringes technique, the thickness of the films was determined between 165 and 190 nm. UV–Vis measurements were employed to examine the optical characteristics of the films. The red shift was observed for 2 at.% Ni content (3.38 eV) while the blue shift was observed for (4–8) at.% Ni content. The wavelength-dependent refractive index and dielectric constant showed anomalous dispersion in the absorption band, representing the transparency of the films. The 4-point probe measurement showed a decreasing trend of resistivity with increasing temperature, whereas the resistivity increased with Ni content. Activation energy indicated a higher amount of adsorbed oxygen in the films due to the high amount of Ni content.

Abstract

Here we discuss the synthesis of copper (II) oxide (CuO) and manganese (Mn)-doped CuO thin films varying with 0 to 8 at% Mn using the spray pyrolysis technique. As-deposited film surfaces comprised of agglomerated spherical nanoparticles and a semi-spongy porous structure for 4 at% Mn doping. Energy dispersive analysis of X-rays confirmed the chemical composition of the films. X-ray diffraction spectra showed a polycrystalline monoclinic structure with the predominance of the ( 11) peak. Optical band gap energy for direct and indirect transitions was estimated in the ranges from 2.67–2.90 eV and 0.11–1.73
eV, respectively. Refractive index and static dielectric constants were computed from the optical spectra. Electrical resistivity of CuO and Mn-doped CuO (Mn:CuO) thin films was found in the range from 10.5 to 28.6 Ω·cm. The tiniest electron effective mass was calculated for 4 at% Mn:CuO thin films. P to n-type transition was observed for 4 at% Mn doping in CuO films. Carrier concentration and mobility were found in the orders of 1017 cm–3 and 10–1 cm2/(V·s), respectively. The Hall coefficient was found to be between 9.9 and 29.8 cm3/C. The above results suggest the suitability of Mn:CuO thin films in optoelectronic applications.
 

Abstract

'With growing population and rapid urbanization, the solid waste management is now a global issue for sustainable human health and environments. In our daily lives, we encounter a lot of amount of wastes like tea waste, coffee residues, fruit waste, etc. that are usually discarded or dumped in the landfills. However, a proper waste management strategy is necessary to build up a strong economy through proper design and optimization for reuse and recycling of the abundantly available biomasses. Activated carbon has become an essential component of the modern world. Finding cost-effective alternatives to synthesize activated carbon for future diverse industrial applications and compete with the existing commercial activated carbon is gaining popularity in the community from the environmental and commercial perspective. This study will mainly elucidate the potential of tea waste as a promising renewable biomass source owing to its abundant availability, low-cost and interesting inherent physicochemical properties to produce highly porous activated carbon with desired surface functionalities. Furthermore, highlighting the usage of tea waste derived activated carbon for potential application in the field of energy harvesting, which includes as high-performance electrode materials of super capacitor and energy storage devices'.

Abstract

In this study, we have delineated the preparation and influence of Fe doping on microstructural and optical properties of the undoped and Fe-doped TiO2 thin film with different Fe concentrations (0, 2, 4, 6, and 8 at.%). The samples are prepared by a simple and cost-effective spray pyrolysis technique (SPT) using Ti (OCH2CH2CH2CH3)4 as a precursor of mother material. The effect of Fe on the microstructure and phase formation of TiO2 thin films is investigated by XRD analysis. XRD investigation depicts that the undoped product corresponds to anatase phase of TiO2 and remains uncontaminated with addition of 2 at.% Fe impurity. It is also observed that Fe introduces a phase transition from anatase to rutile after adulterating more Fe contents (4, 6 and 8 at.%). In order to study the optical characteristics, UV–vis spectroscopy has been employed, which reveals that UV absorption for the Fe incorporated TiO2 products are observed to move to a longer wavelength (red shift) and lower bandgap energy from 3.81 eV (0 at.% Fe) to 3.70 eV (8 at.% Fe) of the TiO2 thin films. The optical constants such as refractive index, complex dielectric constants, tanδ, volume energy loss (VELF) and surface energy loss (SELF) functions, dispersion parameters of synthesized titanium dioxide samples has been studied. The results of optical constant values and the dispersion enegy parameters depicts the influence of Fe on microstructural and optical transportation properties of the as prepared samples more appropriately and effectively.

Abstract

"The excessive dependency on fossil fuel resources could be curtailed by the efficient conversion of lignocellulosic biomass. Biochar, a porous carbonaceous product synthesized exploiting thermochemical conversion pathway, could be an environmentfriendly replacement of fossil fuel resources. Slow pyrolysis, a sub-class among various thermochemical conversion techniques, has gained immense popularity owing to its potential to convert biomass to biochar. Furthermore, biochar obtained as the byproduct of slow pyrolysis has attracted enormous popularity due to its proven role and application in the multidisciplinary areas of engineering and environmental remediation applications. The physicochemical quality of biochar and its performance is significantly dependent on the feedstock type and pyrolysis process parameters. Therefore, further experimental research and investigations in terms of lignocellulose biomass type and pyrolytic process parameters (temperature, heating rate and reaction time) are essential to produce biochar with desired physicochemical features for effective utilization. This review presents an updated report on slow pyrolysis of lignocellulosic biomass, impact of different pyrolysis parameters and degradation pathway involved in the evolution properties of biomass. The influence of the feedstock type and lignocellulosic composition on the biochar properties are also discussed meticulously. The co-relationship between biochar yield at different pyrolysis temperatures and the development of textural properties provides valuable information for their effective utilization as a functional carbon material. Additionally, an extensive study was undertaken to collate and discuss the excellent physicochemical characteristics of biochar and summarizes the benefits of biochar application for diverse industrial purposes. Biochar is acknowledged for its excellent physicochemical properties owing to the thermal treatment and as a result its prospective diverse industrial applications such as for soil treatment, carbon sequestration, adsorbent (wastewater treatment or CO2 capture), producing activated carbon for gold recovery, energy storage and supercapacitor are summarized systematically in this review paper. For instance, biochar when applied in soil have shown improvement in soil respiration by 1.9 times. Furthermore, biochar when used to capture CO2 from flue gas stream under post-combustion scenario has demonstrated superior capture performance (2.8 mmol/g) compared to commercial activated carbon. This paper identified the knowledge gaps and outlooks in the field of the advancements of biochar from slow pyrolysis for targeted engineering applications mainly in the field of environmental remediation and energy harvesting".

Abstract

Non-toxic lead free inorganic metal halide cubic double perovskites have drawn a lot of attention for their commercial use in optoelectronic and photovoltaic devices. Here we have explored the structural, electronic, optical and mechanical properties of lead-free non-toxic inorganic metallic halide cubic double perovskite Cs2AgBiBr6 in its ordered and disordered forms using first-principles density functional theory (DFT) to verify the suitability of its photovoltaic and optoelectronic applications. The indirect bandgap of Cs2AgBiBr6 is tuned to a direct bandgap by changing it from an ordered to disordered system following the disordering of Ag+/Bi3+ cations by creating antisite defects in its sublattice. In the disordered Cs2AgBiBr6, the Bi 6p orbital modifies the conduction band significantly and leads to a shift the conduction band minimum (CBM) from L to G-point. Consequently, the system changes from indirect to direct band gap material. At the same time the band gap reduces significantly. The band gap of Cs2AgBiBr6 decreases from 2.04 eV to 1.59 eV. The absorption edge towards the lower energy region and strong optical absorption in the visible to the UV region indicate that the disordered direct band gap material Cs2AgBiBr6 is appropriate for use in solar cells and optoelectronic and energy harvesting devices. Dielectric function, reflectivity and refractive index of disordered direct band gap material Cs2AgBiBr6 is favorable for its optoelectronic and photovoltaic applications. However, its stability and ductility favor its thin film fabrication. The creation of antisite defects in the sublattice of double perovskites opens a new avenue for the design of photovoltaic and optoelectronic materials.

Abstract

Double halide perovskites (A2MþM3 þX6) have been considered as high-performance material for optoelectronic and photovoltaic devices. Here, we investigate the structural, thermodynamic, optical, mechanical and electronic properties of pressure-induced Cs2AgBiCl6 samples. The phase stability is confirmed by the tolerance and octahedral factor calculations. The thermodynamic potentials such as enthalpy, free energy, entropy, and heat capacity are observed in the phonon modes. The indirect to direct band gap is observed due to disorders of Agþ/Bi3þ cations in their sub-lattice. In this study, the induced pressure was varied between 0 and 80 GPa and the transition of the band gap energy from semiconductor to metal was observed at a hydrostatic pressure of 80 GPa. The bond length in between Ag and Bi atoms is reduced due to crystal defect, occurred under induced pressure. The narrow band gap energy and the partial density of states of the disordered Cs2AgBiCl6 samples refer to the relocation of charge carriers to facilitate the photocatalytic reaction. As the pressure changes, the absorbing edge also moves into the lower energy region. The pressure-inducted Cs2AgBiCl6 sample has a strong absorption in the range of visible wavelength of light and shifted in the ultraviolet region. Simultaneously, the pressure-driven material extend the symmetry breaking of [AgBi]6 and [AgCl]6 octahedra and hence the total energy decreased due to narrow band gap energy. Phase-change dihalide materials have excellent properties, opening up new avenues for device applications. The mechanical properties suggest that the pure and pressure-inducted Cs2AgBiCl6 samples have potential characteristics for an optoelectronic and photovoltaic applications.

Abstract

In this study, pristine titanium dioxide (TiO2) and tungsten (W) doped TiO2 (W: TiO2) thin films with concentrations of 2, 4, 6 and 8 at. % has been deposited on a soda lime glass substrate at 450 ◦C using a simple spray pyrolysis (SP) technique. The surface morphology of TiO2 and W: TiO2 thin films showed a mixed phases of particle and reticulated fiber nature as observed by the field emission scanning electron microscopy (FESEM). The average size of the particles was found to be 1.094 μm and the thickness of the reticulated fiber varies between 0.230 and 0.651 μm. Energy dispersive X-ray (EDX) analysis demonstrate stoichiometric distribution of Ti, W, and O elements in the as-deposited films. Ultraviolet–visible (UV–Vis) spectroscopy was used to estimate the optical band gap of the thin films and was found to be decreased monotonically from 3.36 eV to 3.02 eV due to the incorporation of W into the TiO2 thin films. The effect of W-doping on the variation of edge potentials of the conduction bands (CB) and valence bands (VB) of the TiO2 thin films were studied. Furthermore, the effect of W-doping on the degradation of the methylene blue (MB) under UV-light illumination was studied. 6 at. % W: TiO2 thin films demonstrate the highest degradation efficiency (76%) among all the samples. This can be attributed to the reduction of electron-hole recombination due to reduced band gap together with production of adsorption sites at the cylindrical pores of the thin films.

Abstract

In the present study, we propose a novel type of lead-free double halide perovskite Cs2AgAsCl6 material exhibiting exceptional photovoltaic and photocatalytic properties. Density functional theory (DFT) is employed to investigate the photovoltaic and photocatalytic properties based on several significant properties of the Cs2AgAsCl6 material. The thermodynamic stability of Cs2AgAsCl6 has been confirmed by the enthalpy formation, which is 32.36 eV f.u.1 Dispersion of phonons near the gamma point confirmed the existence of dynamical stability. The constant value of the heat capacity is 59.45 cal per cell K, which is calculated by the Dulong–Petit limit. The GGA-PBE and HSE-06 functional approaches determined indirect bandgaps of 1.31 and 2.49 eV, respectively, for a semiconductor whose electronic properties revealed photocatalytic efficiency. The effective masses of an electron and a hole are 0.46 me and 0.61 me, respectively, which may enhance the photocatalytic dye degradation owing to their low carrier effective mass. Notably, better photocatalytic properties, i.e., dye degradation, are confirmed by the redox potential. The estimated edge potentials of the conduction band (CB) and valence band (VB) are 0.048 and 2.448 eV, respectively, which are greater than the H+/H2 and O2/H2O potentials. The Cs2AgAsCl6 material reveals an outstanding optical property that is suitable for photovoltaic applications. Therefore, Cs2AgAsCl6 can act as a potential candidate in the field of photovoltaic and photocatalytic applications

Abstract

Nanostructured cobalt oxide (Co3O4) and Cu-doped Co3O4 thin films were synthesized by a simple spray pyrolysis technique at 450oC substrate temperature onto the plain glass substrate. The surface morphological, structural, optical, electronic, and glucose sensing effects of the deposited thin films were explored. Scanning Electron Microscope (SEM) images revealed a uniform, dense and porous surface morphology of Co3O4 and Cu doped Co3O4 thin films. X-ray diffraction (XRD) pattern showed the spinel cubic structure of lattice parameters a = b = c = 8.0764 Å and well agrees with the JCPDS card file no. 42-1467. The crystallite sizes were calculated as 29, 27, 24, and 26 nm with the variation of 0, 2, 4, and 6 % Cu doping concentrations, respectively. The obtained optical band gaps were about 2.02, 2.00, 2.09, and 1.98 eV for 0, 2, 4, and 6 % Cu doped Co3O4 thin films. The glucose sensing properties revealed that Cu doping greatly improved the sensing properties of Co3O4 thin film, and the highest glucose sensitivity was found at about 43%, and fast response time was about 0.97 sec at 4 % Cu doped Co3O4 thin-film.

Abstract

Nanostructured copper oxide (CuO) thin films have been synthesized onto the glass substrates from aqueous solutions of copper (II) acetate monohydrate precursor salt by a cost effective spray pyrolysis technique at various substrate temperatures between 473 and 673 K. The effects of varying substrate temperature on the structure, surface morphology, optical and electrical properties of the synthesized CuO thin films were studied. Scanning Electron Microscopic (SEM) images revealed agglomerated nanoparticles on the surface of CuO thin films. X-Ray Diffraction (XRD) analysis revealed monoclinic structure with the predominant (̅111) orientation of the synthesized films. Crystallite size increased (9.15 to 10.29 nm) with the increase of substrate temperature. In UV-vis-NIR spectroscopy, CuO thin films showed higher transparency in the NIR region. An optical band gap of CuO thin film was found in the range of 2.04 - 2.49 eV. Transmittance and band gap decreased with the increase of substrate temperature up to 573 K and found to increase at 673 K. On the other hand, extinction coefficient and refractive index increased with the increase of substrate temperature up to 573 K and decreased afterwards. Electrical resistivity of CuO thin films was found in the range 1.16 ×103 - 4.61 ×103 Ω-m and decreased with the increment of the substrate temperature up to 573 K. Activation energies of CuO thin film were found in the range 0.08 - 0.57 eV. Hence, we report the influence of substrate temperature for the synthesis of nanostructured CuO thin films, best fit for optoelectronic applications.

Abstract

In this paper, we present a detailed study of the opto-structural properties of Mn doped CuO (MCO) thin films with 0.0, 2.0, 4.0, 6.0 and 8.0 at.% doping concentrations, using a thermal spray pyrolysis technique as well as Density Functional Theory (DFT) calculations for the first time. The experimental characterizations are done through Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-rays spectroscopy (EDX), Xray diffraction (XRD), UV–Visible spectroscopy (UV–Vis) and Hall Effect measurement. FESEM images show the petal-like and closed packed flower-like spherical structure surface morphology. EDAX spectra confirm the presence of Cu, O and Mn atoms. The XRD pattern reveals that synthesize thin films have a monoclinic structure with some impurity phases. The estimation of crystallite size ranging from 17.11 to 31.96 nm observed using Debye-Scherrer and Halder-Wagner method. The Cu–O bond length is found consistent between the Rietveld refinement and DFT function, which controls the experimental optical band gap in between 3.00 to 2.31 eV. Further, a standard value of Urbach energy, steepness parameter, electron–phonon interaction, refractive index, dielectric constant and static dielectric constant is found in 4.0 at. % Mn dopant. Moreover, p to n-type conductivity is confirmed by 4.0 at. % Mn concentration. By a meticulous analysis, it is observed that 4.0 at. % of MCO thin films might have a potential application in electronic and optoelectronic device industry.

Abstract

Phase transitions in metal halide perovskites triggered by external provocations produce significantly different material properties, providing a prodigious opportunity for comprehensive applications. In the present study, the first principles calculation has been performed with the help of density functional theory using the Cambridge Serial Total Energy Package code to investigate the physical properties of lead-free CsSnBr3 metal halides under various hydrostatic pressures. The effect of pressure is determined in the range of 0–28 GPa by the generalized gradient approximation and Becke, three-parameter, Lee–Yang–Parr functions. Subsequently, a significant change is observed in the lattice constant and volume with increasing pressure. The electronic band structure shows a semiconductor to metal phase transition under elevated pressure. The investigation of optical functions shows that the absorption edge of the CsSnBr3 perovskite is shifted remarkably toward the low energy region (red shift) with improved pressure up to 16 GPa. In addition, the absorptivity and dielectric constant also upsurge with the applied hydrostatic pressure. Finally, the mechanical properties reveal the fact that the CsSnBr3 perovskite is mechanically stable and highly
ductile; the ductility is increased with increasing pressure. This type of semiconductor to metal phase transition may inspire a wide range of potential  applications.

Abstract

In this paper, we have investigated the antibacterial potentials of organic single crystals, 3,4-dimethoxybenzoic acid (DMBA) grown by the slow evaporation solution growth technique. The crystallinity and structural orientation of as-grown DMBA compound was thoroughly studied using single-crystal X-ray diffraction and powder Xray diffraction (XRD) and found to be a triclinic crystal system with P1 space group. The Fourier transform infrared spectroscopy was used to understand the nature of bonding and functionalization, while the UV–Vis spectroscopic analysis provided the linear optical properties at the lower cutoff wavelength of 350 nm and transparency of 87%. Also, the photoluminescence spectrum shows the ultraviolet emission of the DMBA single crystal. Further, the antibacterial efficacy of DMBA crystals is investigated by means of percentage (%) inhibition and zone of inhibition (ZoI) against the two different bacterial stains of Klebsiella pneumoniae and Staphylococcus aureus. The results confirmed that the DMBA compound has higher activity against Staphylococcus aureus growth (75% inhibition efficiency and 5 mm ZoI at 100 μg/mL) than that of Klebsiella pneumoniae (55% inhibition and 2 mm ZoI at 100 μg/mL) and thereby providing evidence for the potential role of the DMBA compound in future medicinal drugs.

Abstract

Transparent conducting titanium dioxide (TiO2) thin films were synthesized by a spray pyrolysis technique. In this work, the effect of Al doping on the structural, morphological, topographical, optical, and electronic properties of TiO2 thin film samples was studied in detail. The deposited film shows 66 nm to 82 nm nanostructured crystallite size. The cell parameters are found in good agreement with the experimental and theoretical calculations. The pore diameters are found to be between 6 nm and 9 nm as revealed by the field emission scanning electron microscopy images. The energy dispersive X-ray analysis, spectra show that all the samples are in stoichiometric conditions. Atomic force microscope images show that the surface roughness varies from 34.72 nm to 89.83 nm. The bandgap tuning has been observed both experimentally and theoretically. The study of optical properties shows that the absorption limit of the Al-doped TiO2 sample is shifted towards the lower energy region compared with the un-doped sample. The electrical band structure energy (3.11 to 3.64 eV) values are much closer to those of the optical band structure energy (3.18 to 3.01 eV for indirect and 3.70 to 3.49 eV for direct). The charge density map ensures that the covalent bond is present in the as-deposited sample. A combined analysis of the structural, morphological, topographical, optical, and electronic properties of the compound suggests that Ti1-x AlxO2 is a potential candidate for gas sensing and photovoltaic device.

Abstract

In this paper, we reported the nonmagnetic semiconductor to half metal transition behavior of Co doped CuO (CCO) thin films with p-to n-type characteristics for the first time. The thin films are prepared using a thermal spray pyrolysis technique with variations of Co doping concentration from 0 to 8 at.% in the steps of 2 at.%. Subsequently, the surface morphological, structural, optical, electrical properties and electronic band structures by density functional theory (DFT) have been studied intensively. The surface morphology of the CCO thin films is significantly influenced by Co doping concentrations and agglomerated spherical grains are formed, as indicated by field emission scanning electron microscopy (FESEM). The quantitative analysis is carried out by the energy dispersive X-ray (EDX) analysis that confirms the presence of Cu, O and Co atoms. X-ray diffraction (XRD) reveals all the deposited CCO thin films are belong to monoclinic structure with mixed phases, and average crystallite size shrinkages from 28.67 to 18.96 nm with Co doping concentrations. The optical transmittance and the band gap decrease noticeably from 85% to 58%, and 3.00 to 1.98 eV, respectively. Several significant optical parameters such as Urbach energy, steepness parameter, electron–phonon interaction, refractive index, dielectric constant and static dielectric constant is examined. Enhancement of Cu-O bond length is determined and found similarities between the Rietveld refinement and DFT studies. With the spin polarized density of state (DOS),
polarized value lies between 0 and above 1 which confirms that semiconductor to half metal phase transition. Using the Hall Effect measurement, p- to n-type conductivity is determined, and finally a lower resistivity and mobility is found to be 07.83×10􀀀 3 Ω cm and 0.003 cm2V􀀀 1s􀀀 1, respectively at 8 at.% CCO thin film. Thus, the above results depict that 8 at.% of CCO thin films may have potential application in the field of spintronic and optoelectronic devices.

Abstract

Nanostructured copper oxide (CuO) and Nickel (Ni)-doped CuO thin films with different concentrations of Ni ranging from 2 to 8 at.% were synthesized onto a plain glass substrate at the substrate temperature, 350 ◦C by a thermal spray pyrolysis technique. Field emission scanning electron microscopy (FESEM) analysis of CuO and Nidoped CuO thin films detected the closely spaced rock-like nanostructures, evenly distributed on the film surfaces. The average particle sizes of CuO and Ni-doped CuO thin films were calculated from the FESEM and found between 260 and 63 nm. Energy-dispersive X-ray analysis revealed that CuO and Ni-doped CuO thin films were stoichiometric and typically comprised of Cu, O, and Ni. X-ray diffraction analysis showed the monoclinic structure of the films with the most preferred orientation plane (111) along with the (111), (202) and (022) crystalline planes. The maximum crystallite size was found at about 81 nm for 6 at% Ni-doped CuO thin film. CuO film showed an optical transmittance of about 33% in the visible-NIR region. Ni-doping enhanced the absorbing nature of CuO thin films in the vis-NIR region of light. With the rise of Ni content in CuO thin films, the optical bandgap gradually increased from 2.28 to 2.78 eV. Resistivity raised from 9.28 × 103 to 49.01 × 10³ Ω-cm with the increase of the amount of Ni.

Abstract

Inorganic double halide perovskites have a wide range of applications in low-cost photovoltaic and optoelectronic devices. In this manuscript, we have studied their structural, electronic, mechanical and optical properties using density functional theory (DFT) simulations. In this work, hydrostatic pressure is induced from 0 to 50 GPa. Disordered Ag and Bi atoms have a large impact on band gap energy; in this case, the indirect band gap is transferred towards a direct band gap. We have seen that pressure-driven samples have transformed a band energy semiconductor into a metallic one. Under the induced hydrostatic pressure, the covalent bond is transformed into a metallic bond and the bond lengths are reduced. Meanwhile, pressure-induced samples enhance symmetry breaking in [AgBr6]5
and [BiBr6]3
 octahedra, which reduces the density of states of the Fermi surface and lowers the total energy. The mechanical behaviors demonstrated that the studied materials are mechanically stable as well as ductile and their ductile nature is enhanced by the driving pressure. The absorption peak is shifted towards the low energy region with increased hydrostatic pressure. The absorptivity and dielectric constant values are also increased with driving pressure. Phase transformed double halide perovskites triggered by outside stimuli produce several outstanding materials properties, giving great scope for a broad range of applications. This type of pristine and disordered double halide perovskite with pressure-driven semiconductor-to-metal phase transition samples may have potential applications in optoelectronic and photovoltaic devices.

Abstract

Undoped and manganese (Mn)-doped zinc oxide (ZnO) thin films have been deposited onto glass substrates at 300∘∘C using a low cost spray pyrolysis technique. Structural, optical and electrical properties of the as-deposited films have been investigated. Scanning electron microscopy images show the existence of clusters with well-defined nucleation centers consisting of highly dense ganglia-like fibers over a large area around the nucleation center. Chemical compositions of the ZnO and Mn-doped ZnO thin films are studied by using energy dispersive X-ray (EDX) analysis. X-ray diffraction spectra depict that the films have polycrystalline wurtzite structure. The average crystallite sizes are calculated in the range of 8–16 nm by Williamson–Hall method and found in good agreement with Scherer method. Optical transmittance of the films is about 80% in the visible region. Bandgap energy is tuned to 2.83 eV from 3.10 eV with increasing Mn doping. Electrical resistivity at room-temperature decreases significantly with increasing Mn doping as well as increasing temperature from 300–440 K. The activation energies in the temperature ranges 300–350 K and 350–440 K are found to be in the range of 0.25–0.16 eV and 0.35–0.59 eV, respectively. Hall Effect measurements show that the thin films have negative Hall co-efficient indicating nn-type conductivity at room-temperature. Carrier concentration is found to be of the order of 10¹⁸cm⁻³.

Abstract

In the present study, we have evaluated the gas sensing and photocatalytic activity of reduced graphene oxide (rGO) conjugated titanium dioxide (TiO2) nanoparticles (NPs) formed by the hydrothermal method. The assynthesized rGO-TiO2 nanocomposite were characterized for the physicochemical properties such as the nature of crystallinity, functionalization, and morphology by making use of the powder X-ray diffraction, Fourier transform-infrared spectroscopy, and scanning electron microscopy, respectively. On testing the gas sensing properties, we found that the rGO-TiO2 nanocomposite can serve as the chemoresistive-type sensor because of its sensitivity and selectivity towards different concentrations of hydrogen and oxygen at room temperature conditions. However, the rGO-TiO2 sensor’s response and recovery speed towards hydrogen and oxygen needs further optimization. Test of photocatalytic activity of TiO₂-rGO catalyst for the removal of two model contaminant dyes, RhB and MB showed effective removal, with respective degradation percentages of about 80 and 90% within the first 50 min of irradiation under visible light irradiation. Besides, MB was more effectively degraded using TiO2-rGO than pure TiO2 during the first 30 min of irradiation and this enhanced activity can be attributed to the increased capacity of light absorption, the efficiency of charge carriers separation, and the specific surface area maintained by the rGO-TiO2 nanocomposite to effectively utilize the photo-generated holes (h+) and superoxide radicals (O2􀀀 •), responsible for the degradation of the dye. Based on the overall analysis, the formation of rGO-TiO2 nanocomposite can significantly improve the gas sensing and photocatalytic properties of TiO2 NPs and thus can be potential for practical applications in future nanotechnology.

Abstract

In the present study, we have evaluated the gas sensing and photocatalytic activity of reduced graphene oxide (rGO) conjugated titanium dioxide (TiO2) nanoparticles (NPs) formed by the hydrothermal method. The assynthesized rGO-TiO2 nanocomposite were characterized for the physicochemical properties such as the nature of crystallinity, functionalization, and morphology by making use of the powder X-ray diffraction, Fourier transform-infrared spectroscopy, and scanning electron microscopy, respectively. On testing the gas sensing properties, we found that the rGO-TiO2 nanocomposite can serve as the chemoresistive-type sensor because of its sensitivity and selectivity towards different concentrations of hydrogen and oxygen at room temperature conditions. However, the rGO-TiO2 sensor’s response and recovery speed towards hydrogen and oxygen needs further optimization. Test of photocatalytic activity of TiO₂-rGO catalyst for the removal of two model contaminant dyes, RhB and MB showed effective removal, with respective degradation percentages of about 80 and 90% within the first 50 min of irradiation under visible light irradiation. Besides, MB was more effectively degraded using TiO2-rGO than pure TiO2 during the first 30 min of irradiation and this enhanced activity can be attributed to the increased capacity of light absorption, the efficiency of charge carriers separation, and the specific surface area maintained by the rGO-TiO2 nanocomposite to effectively utilize the photo-generated holes (h+) and superoxide radicals (O2􀀀 •), responsible for the degradation of the dye. Based on the overall analysis, the formation of rGO-TiO2 nanocomposite can significantly improve the gas sensing and photocatalytic properties of TiO2 NPs and thus can be potential for practical applications in future nanotechnology.

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The antiperovskites based on metal halides have emerged as potential materials for advanced photovoltaic and electronic device applications. But the wide bandgap of non-toxic CsSnCl3 reduces its photovoltaic efficiency. Here, we report the change of electronic structure of CsSnCl3 at different pressure by using GGA-rPBE and GGAPBEsol functionals and the GW method. We have shown that the prediction of electronic structure transition (semiconducting to metallic state) strongly depends on the exchange-correlation and the GW method gives the most reasonable values of the bandgap under pressure. The pressure increases the electronic density of states close to the Fermi level by pushing the valence electrons upward and thus, reduces the bandgap linearly. Afterward, we have also investigated the influence of pressure on absorption coefficient, and mechanical properties meticulously. Although the pressure shifts the absorption peak to lower photon energies, the absorption coefficient is slightly improved.

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The antiperovskites based on metal halides have emerged as potential materials for advanced photovoltaic and electronic device applications. But the wide bandgap of non-toxic CsSnCl3 reduces its photovoltaic efficiency. Here, we report the change of electronic structure of CsSnCl3 at different pressure by using GGA-rPBE and GGAPBEsol functionals and the GW method. We have shown that the prediction of electronic structure transition (semiconducting to metallic state) strongly depends on the exchange-correlation and the GW method gives the most reasonable values of the bandgap under pressure. The pressure increases the electronic density of states close to the Fermi level by pushing the valence electrons upward and thus, reduces the bandgap linearly. Afterward, we have also investigated the influence of pressure on absorption coefficient, and mechanical properties meticulously. Although the pressure shifts the absorption peak to lower photon energies, the absorption coefficient is slightly improved.

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Non-toxic lead-free halide metal perovskites have gained significant interest in photovoltaic and optoelectronic device applications. In this manuscript, we have studied the structural, electronic, mechanical, and optical properties of eco-friendly cubic CsSn1
xCuxI3, (x ¼ 0, 0.125, 0.25, 0.5, 1) perovskites applying first-principles pseudopotential-based density functional theory (DFT). Cu-doped CsSnI3 has a large impact on the band gap energy viz. the transition of direct band gap towards the indirect band gap. The mechanical properties demonstrate that the pristine and Cu-doped CsSnI3 samples are mechanically stable and their ductility is enhanced by Cu doping. The mechanical stability and ductility favors the suitability of pure and Cu-doped samples in the thin film industry. The absorption edge of Cu-doped CsSnI3 moves towards the lower energy region in comparison with their pure form. In addition, the high dielectric constant, high optical absorption, and high optical conductivity of Cudoped CsSnI3 materials suggests that the studied materials have a broad range of applications in
optoelectronic devices, especially solar cells. A combined analysis of the structural, electronic, mechanical and optical properties suggests that CsSn1
xCuxI3, (x ¼ 0, 0.125, 0.25, 0.5, 1) samples are a suitable candidate for photovoltaic as well as optoelectronic device applications.

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Nanostructured cobalt oxide (Co3O4) and Cu-doped Co3O4 thin films were synthesized by a simple spray pyrolysis technique at 450oC substrate temperature onto the plain glass substrate. The surface morphological, structural, optical, electronic, and glucose sensing effects of the deposited thin films were explored. Scanning Electron Microscope (SEM) images revealed a uniform, dense and porous surface morphology of Co3O4 and Cu doped Co3O4 thin films. X-ray diffraction (XRD) pattern showed the spinel cubic structure of lattice parameters a = b = c = 8.0764 Å and well agrees with the JCPDS card file no. 42-1467. The crystallite sizes were calculated as 29, 27, 24, and 26 nm with the variation of 0, 2, 4, and 6 % Cu doping concentrations, respectively. The obtained optical band gaps were about 2.02, 2.00, 2.09, and 1.98 eV for 0, 2, 4, and 6 % Cu doped Co3O4 thin films. The glucose sensing properties revealed that Cu doping greatly improved the sensing properties of Co3O4 thin film, and the highest glucose sensitivity was found at about 43%, and fast response time was about 0.97 sec at 4 % Cu doped Co3O4 thin-film.

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Iron (Fe) doped manganese dioxide (MnO2) nanostructured thin films (Fe: MnO2) were prepared by a spray pyrolysis deposition technique to explore their morphological, structural, and electronic properties suitable for glucose sensing abilities. Many useful characteristics were observed in the growth process and phase transformation due to the addition of Fe concentration in the range of 0–8 at %. Fe concentration strongly influenced the crystallite size of MnO2 analyzed by field emission scanning electron microscope. Powder X-ray diffraction (PXRD) pattern of the deposited thin films showed the tetragonal crystal structure with a body-centered space group (I41/acd) having lattice parameters a ¼b ¼9.787 Å and c ¼2.865 Å and well agrees with the JCPDS card file no. 44–0141. Crystallite size was measured ranging from 20 nm to 30 nm using Debye Scherer relation. Williamson-Hall plot results indicated the appearance of strain for Fe doping. Maximum carrier concentration was found at 4 at% Fe concentration using Hall Effect measurement. The highest glucose-sensing response was recorded at about 29% at 5 min for 4 at% Fe concentration.

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In this work, we emphasize the green synthesis of cuprous oxide (Cu2O) nanoparticles (NPs) by Fehling's route using banana (Musa acuminate) fruits where the formation of products by the involvement of natural ingredients is considered to be the solvent-free route. The as-synthesized Cu2O samples were thoroughly characterized by various analytical techniques in order to fully understand the surface bonding and functional groups, optical properties, surface charges, phase
purity and crystallinity, surface morphological features, and elemental analysis. On testing of the photocatalytic activity, the material is investigated to be p-type Cu2O and exhibited highly efficient photocatalytic behavior due to the interfacial structure that tends to reduce the recombination rate of a photogenerated electron (e−) - hole (h+) pairs. Further, we have explored this property for the degradation of organic contaminants, methylene blue and fo

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This study is aimed to investigate the photocatalytic efficiencies of two different metal oxide nanoparticles (NPs), SnO2 and CdO formed by the simple chemical precipitation route. The synthesized metal oxide NPs were examined by several techniques in order to understand the morphological (FESEM), structural (XRD), functional (FTIR), and optical (UV-vis) characteristics. The analysis of results confirmed the successful formation of SnO2 and CdO NPs along with their desired chemical compositions and electronic band structures. Further testing of their photocatalytic efficiency with the use of methylene blue (MB) degradation in the presence of sunlight confirmed their catalytic efficiency. Within the two NPs, the SnO2 has a little higher activity as compared to the CdO NPs and this can be attributed to the increased surface area by means of the formation of nanospheres for the SnO2 ones, while the rod-shaped agglomerated structure with less surface area delaying the rate of degradation. Further from the analysis, it can be confirmed for the superior photocatalytic activity of SnO2 particles having spherical shape against the rodshaped CdO NPs.

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The present work describes the deposition and investigation of structural and optical characteristics of bare and
doped TiO2 thin films. The TiO2 products are obtained through simple and cost effective spray pyrolysis technique
(SPT) using titanium (IV) butoxide as Ti precursor. The impact of Zn doping on the crystal structure and
phase formation is studied by X-ray diffraction (XRD) analysis. The formation of anatase phase relative to pure
TiO2 along with preferred orientation along the [101] direction is confirmed with the help of XRD analysis. Zn
doping into TiO2 lattice network leads to an identical diffraction pattern. A deterioration of crystallinity is
obtained in crystallite size employing the numerous methods such as Scherrer method, Williamson–Hall,
Halder–Wagner and Wagner–Agua analysis in accordance with Zn. In addition, absorbance results obtained from
UV–vis spectroscopy has been exerted to examine the optical characteristics. It is noted that the dopant introduction
has an impact on the optical properties and the direct band gap value obtained from Tauc relation
exhibits a red shift with Zn content. The influence of the Zn doping elements on the optical constants of TiO2
product has been investigated. The dielectric constants, dispersion parameters, loss factor and distribution of
volume and surface energy loss of the TiO2 products have been computed as well. The as-prepared nanostructured
Zn-doped TiO2 thin films can be used as potential candidates for different optoelectronic devices

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In this article, we have explored the influence of Fe3+ ion on the surface morphological, structural, optical and
electrical properties of TiO2 thin films grown on glass substrates by thermal spray pyrolysis technique. The
FESEM micrographs of the deposited TiO2 thin films reveal that the surface consists of agglomerates of small
grains. The anatase and rutile phase is confirmed by XRD and Debye-Scherer (D-S), Uniform Deformation Model
(UDM) and Halder-Wagner (HW) method are employed to determine the structural parameters using XRD peak
profile analysis. A red shift occurs in absorption spectra and band gap decreases with Fe content. The optical
parameters such as skin depth, optical static dielectric constant, Urbach energy, etc and Electron-phonon
interaction are increased with increasing Fe contents, whereas steepness parameter decreases. The electrical
properties are studied by Hall Effect measurements. The paramount study is useful for standardizing the Fedoped
TiO2 thin films for optoelectronic device applications.

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Iron (Fe) doped manganese dioxide (MnO2) nanostructured thin films (Fe: MnO2) were prepared by a spray pyrolysis deposition technique to explore their morphological, structural, and electronic properties suitable for glucose sensing abilities. Many useful characteristics were observed in the growth process and phase transformation due to the addition of Fe concentration in the range of 0–8 at %. Fe concentration strongly influenced the crystallite size of MnO2 analyzed by field emission scanning electron microscope. Powder X-ray diffraction (PXRD) pattern of the deposited thin films showed the tetragonal crystal structure with a body-centered space group (I41/acd) having lattice parameters a ¼b ¼9.787 Å and c ¼2.865 Å and well agrees with the JCPDS card file no. 44–0141. Crystallite size was measured ranging from 20 nm to 30 nm using Debye Scherer relation. Williamson-Hall plot results indicated the appearance of strain for Fe doping. Maximum carrier concentration was found at 4 at% Fe concentration using Hall Effect measurement. The highest glucose-sensing response was recorded at about 29% at 5 min for 4 at% Fe concentration.

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This study is aimed to investigate the photocatalytic efficiencies of two different metal oxide nanoparticles (NPs), SnO2 and CdO formed by the simple chemical precipitation route. The synthesized metal oxide NPs were examined by several techniques in order to understand the morphological (FESEM), structural (XRD), functional (FTIR), and optical (UV-vis) characteristics. The analysis of results confirmed the successful formation of SnO2 and CdO NPs along with their desired chemical compositions and electronic band structures. Further testing of their photocatalytic efficiency with the use of methylene blue (MB) degradation in the presence of sunlight confirmed their catalytic efficiency. Within the two NPs, the SnO2 has a little higher activity as compared to the CdO NPs and this can be attributed to the increased surface area by means of the formation of nanospheres for the SnO2 ones, while the rod-shaped agglomerated structure with less surface area delaying the rate of degradation. Further from the analysis, it can be confirmed for the superior photocatalytic activity of SnO2 particles having spherical shape against the rodshaped CdO NPs.