Tauc-plot scale and extrapolation effect on bandgap estimation from UV–vis–NIR data – A case study of β-Ga2O3

Comparative study on structural, morphological, and optical properties of MS/Fe3O4 nanocomposites and M-doped Fe3O4 nanopowders (M = Mn, Zn)

In the present work, the un-doped, M-doped magnetite (Fe3O4); (M = Mn, Zn), and MS/Fe3O4 composite nanopowders with a cubic spinel-type structure and average crystallite size range from 8.30 to 12.33 nm were synthesized by co-precipitation method. The FESEM images revealed the shape of particles are spherical with a grain size in the range of 33.44-49.77 nm. Through the analysis of reflectance data using Tauc's model, the direct band gap energies of 2.98 eV, 2.93 eV, 3.01 eV, 2.85 eV, and 2.95 eV were determined for Un-doped Fe3O4, Mn-doped Fe3O4, Zn-doped Fe3O4, MnS/Fe3O4 composite, and ZnS/Fe3O4 composite NPs respectively. The parameters such as extinction coefficient and refractive index of the nanoparticles were computed by the Kramers-Kronig (K-K) method. Non-linear optical (NLO) parameters were computed from DRS data using the Wemple-Di-Domenico (WDD) model. The calculated third-order NLO susceptibilityχ ( 3 ) and also electrical susceptibility χ e represented the maximum value for MnS/Fe3O4 composite NPs compared to the other samples. Considering the advanced optical parameters of MS/Fe3O4 composite samples, these particles can be suitable candidates for non-linear optical applications.

Evaluating Optical Properties of Mixed-Phase 2D MoSe2/Poly(vinyl alcohol) Nanocomposite Film

Highly solar light-absorbing poly(vinyl alcohol) (PVA) nanocomposite films have garnered wide attention in fields such as flexible optoelectronics, solar energy harvesting, and photothermal therapy. However, fabricating PVA nanocomposite films with a broad spectrum of solar absorption using cost-effective and non-toxic nanofillers remains challenging. Herein, nanocomposite films of PVA incorporating various concentrations of mixed-phase 2D MoSe2 nanosheets (i.e., a combination of the 2H and 1T phase) were prepared using a solution casting technique. Scanning electron microscopy (SEM) shows homogenous dispersion of MoSe2 nanosheets in the PVA matrix even at higher concentrations, while atomic force microscopy (AFM) reveals increasing surface roughness with increasing MoSe2 content, reaching a plateau after 20 wt%. With the increase in the concentration of MoSe2, the nanocomposite films exhibit interesting light absorption characteristics reaching their highest absorption (average 94.9%) at 40 wt% MoSe2. The incorporated mixed-phase MoSe2 nanosheets induce a significant change in the energy levels of the PVA matrix, which is reflected in the reduced optical band gap energy (2.63 eV) at 40 wt% MoSe2 against pure PVA (5.28 eV). The excellent light absorption of PVA nanocomposite films across the entire range from 250 nm to 2500 nm is attributed to the thin 2D structure of MoSe2 and the presence of its mixed phase.

Bioinspired copper oxide nanocomposites: harnessing plant extracts for enhanced photocatalytic performance

This study focuses on developing copper oxide-based nanocomposites using plant extracts for photocatalytic applications. Curcuma amada leaf and Alysicarpus vaginalis leaf extracts were utilized alongside recycled copper precursors to synthesize photocatalysts via a green synthesis approach. Structural characterization through X-ray diffraction confirmed the formation of monoclinic CuO with reduced crystallite sizes due to plant extract incorporation. Fourier-transform infrared spectroscopy identified additional functional groups from the plant extracts, enhancing the material's properties. UV-Vis spectroscopy demonstrated increased light absorption and narrowed bandgaps in the nanocomposites, crucial for efficient photocatalysis under visible light. Morphological studies using FESEM revealed unique leaf-like structures in nanocomposites, indicative of the plant extract's influence on morphology. Photocatalytic degradation of methylene blue, rhodamine B, Congo red, and reactive blue 171 dyes showed enhanced performance of plant extract-modified CuO compared to without plant extract mediated CuO, attributed to improved charge carrier separation and extended lifetime. The effects of pH, catalyst dosage, and dye concentration on degradation efficiency were systematically investigated, highlighting optimal conditions for each dye type. Radical scavenger studies confirmed the roles of holes and hydroxyl radicals in the degradation process. Kinetic analysis revealed pseudo-second-order kinetics for dye degradation, underscoring the effectiveness of the nanocomposites. Overall, this research provides insights into sustainable photocatalytic materials using plant extracts and recycled copper, showcasing their potential for environmental remediation applications.

Structural, photoluminescence and energy transfer investigations of novel Dy3+ → Sm3+ co-doped NaCaPO4 phosphors for white-light-emitting diode applications

In this study, Dy3+-doped and Dy3+/Sm3+ co-doped NaCaPO4 white-emitting polycrystalline phosphor samples were synthesized using a solid-state reaction method. The samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field-emission scanning electron microscopy (FE-SEM), and Photoluminescence (PL) analysis. The phase purity characterization and crystal structural analysis were done using the Rietveld refinement-based FullProf Suite software. The Rietveld refinement result confirms single-phase formation for both Sm3+ and Dy3+/Sm3+ co-doped NaCaPO4 samples with an orthorhombic structure and with a monotonic change in lattice parameters with doping. The PL studies of the Dy3+-doped samples revealed two emission bands. However, at 352 nm, the Dy3+/Sm3+-co-doped samples revealed distinctive emission bands for both ions. The emission peaks at 480 nm (blue) and 573 nm (yellow) are related to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions; however, the emission peaks at 600 nm and 647 nm are attributed to the 4G5/2 → 6H7/2 and 4G5/2 → 6H7/2 transitions of Sm3+ ions. The intensity of the Dy3+ emissions decreased as the Sm3+ levels increased but the emission intensity of the Sm3+ ions increased. The co-doping of Sm3+ ions in Dy3+-doped phosphors results in unique characteristics due to the energy transfer (ET) from Dy3+ → Sm3+ ions. The effectiveness of this ET from Dy3+ → Sm3+ ions is positively correlated with the dopant amounts of the Sm3+ ions. The interaction mechanisms have been identified as dipole-dipole based on Dexter's energy transfer and Readfield's approaches. All decay curves can be adequately fitted via bi-exponential functions, suggesting the movement of energy between Dy3+ → Sm3+ ions. Temperature-dependent PL measurements and CIE color coordinate analysis reveal excellent luminescent properties, making these Dy3+/Sm3+ co-doped phosphors advantageous for white light-emitting diode (WLED) technologies.

Novel kinetic modeling of photocatalytic degradation of ethanol and acetaldehyde in air by commercial and reduced ZnO: Effect of oxygen vacancies and humidity

A comprehensive kinetic model has been developed to address the factors and processes governing the photocatalytic removal of gaseous ethanol by using ZnO loaded in a prototype air purifier. This model simultaneously tracks the concentrations of ethanol and acetaldehyde (as its primary oxidation product) in both gas phase and on the catalyst surface. It accounts for reversible adsorption of both compounds to assign kinetic reaction parameters for different degradation pathways. The effects of oxygen vacancies on the catalyst have been validated through the comparative assessment on the catalytic performance of commercial ZnO before and after the reduction pre-treatment (10% H2/Ar gas at 500 °C). The influence of humidity has also been assessed by partitioning the concentrations of water molecules across the gas phase and catalyst surface interface. Given the significant impact of adsorption on photocatalytic processes, the beginning phases of all experiments (15 min in the dark) are integrated into the model. Results showcase a notable decrease in the adsorption removal of ethanol and acetaldehyde with an increase in relative humidity from 5% to 75%. The estimated number of active sites, as determined by the model, increases from 7.34 10-6 in commercial ZnO to 8.86 10-6 mol gcat-1 in reduced ZnO. Furthermore, the model predicts that the reaction occurs predominantly on the catalyst surface while only 14% in the gas phase. By using quantum yield calculations, the optimal humidity level for photocatalytic degradation is identified as 25% with the highest quantum yield of 6.98 10-3 (commercial ZnO) and 10.41 10-3 molecules photon-1 (reduced ZnO) catalysts.

Copper perchlorate catalyzed oxidative cyclisation of a novel bishydrazone ligand, formation of an unusual copper complex and in vitro biological implications

A novel hexadentate bishydrazone ligand, 1,10-bis(di(2-pyridyl)ketone) adipic acid dihydrazone (H2L1) is synthesized and characterized. With copper perchlorate as a catalytic oxidant, the ligand undergoes oxidative cyclisation and resulted in the formation of an unusual copper complex [Cu(L1a)2Cl]ClO4 (1), where L1a is 3-(2-pyridyl)triazolo[1,5-a]-pyridine. The Cu(II) complex was characterized physicochemically, while the molecular structure was confirmed by single crystal X- ray diffraction. In the complex cation, copper(II) is in a distorted trigonal bipyramidal coordination environment, surrounded by two triazolo nitrogen atoms and two pyridyl nitrogen atoms of L1a and a chloride atom. The relevant non covalent intermolecular interactions of the complex quantified using Hirshfeld surface analysis reveals that the O···H/ H···O (27.2%) contacts has the highest contribution. The solution phase bandgaps of the compounds were calculated using Tauc plot, whereas the solid-state band gaps were calculated by Kubelka-Munk model. DFT studies of the compounds indicate that the theoretical calculations corroborate with the experimental data. DPPH antioxidant activity assay of the synthesized compounds showed that the proligand H2L1 has a lower IC50 value (24.1 μM) than that of complex 1 (29.7 μM). The in vitro antibacterial activity was evaluated against Escherichia coli and Staphylococcus aureus, which revealed that complex 1 have excellent activity against E. coli, much as the standard ciprofloxacin. The cytotoxic efficacy investigation of the compounds against A549 (lung) adenocarcinoma cells suggested that H2L1 has more anticancer activity (IC50 value of 149.08 μM) than that of complex 1(IC50 value of 176.70 μM).

Comparison of the antimicrobial photocatalytic activities of SiO2 and Au@SiO2 nanostructures in water decontamination

Photocatalytic disinfection of Escherichia coli suspension by silicon dioxide nanoparticles and silicon dioxide/gold nanocomposite in a batch reactor is investigated experimentally and results are compared. Silica nanoparticles were synthesized by Stöber method and pulsed laser ablation method was employed to prepare gold nanoparticles in distilled water. Composition of two nanoparticles species was carried out, using the second harmonic pulse of Nd:YAG laser, whose wavelength is in the absorption spectra of gold nanoparticles. Results confirm a decrease in the bandgap energy of silica nanoparticles after composition. Escherichia coli were selected as an indicator of the microbial water contamination. Disk diffusion method was used to evaluate the antimicrobial potential of SiO2 and Au@SiO2 nanostructures. Photocatalytic activities of both nanostructures were examined in dark, and under the irradiation of UV and visible light. In all conditions, the performance of Au@SiO2 nanocomposites was higher than SiO2 nanoparticles. In dark condition the higher biocidal nature and activity of Au nanoparticles and for the case of UV radiation, decreasing the bandgap energy and recombination rate of SiO2 nanoparticles after composition with Au increased the efficiency. For the case of visible light radiation, surface plasmon resonances effects, and local heat of Au nanoparticles were responsible for increasing the efficiency. RESEARCH HIGHLIGHTS: Doping large bandgap semiconductors nanostructures, such as silica with metal nanoparticles, such as gold will improve their photocatalytic activity to work in visible light. In this mechanism, gold nanoparticles act as effective traps to prevent the recombination of photogenerated electron-hole pairs. Other mechanisms, such as Schottky barrier formation, surface plasmon resonance absorption of gold nanoparticles, and biocidal nature of the gold nanoparticles are effective in increasing the efficiency of Au doped silica nanostructures.

Optical and dielectric properties of divalent copper based double perovskite compound, Gd2CuTiO6

In this work, we have investigated high temperature dielectric properties and room temperature optical properties on rare earth ion based orthorhombic Gd2CuTiO6(GCTO). Optical properties like reflectance and band gap were determined from ultra-violet visible (UV-Vis) diffuse reflectance spectroscopy technique and photoluminescence (PL) spectrum. The compound exhibited substantial optical absorption and emission in the visible region. Our findings reveal the presence of an intermediate band, as evidenced by the difference between the band gap values obtained from the Tauc plot using the diffuse reflectance spectrum (3.07 eV) and the PL spectrum (2.4 eV). Furthermore, thermogravimetric analysis demonstrated high thermal stability with <0.4% change in mass over a wide temperature range of 30 °C-1200 °C in air environment. Moreover, lead-halide free compound, GCTO is highly thermally stable oxide double perovskite with wide band gap and absorption in the UV-Vis range are highly suitable for optical applications In addition, dielectric properties of the compound have been examined using impedance spectroscopy as a function of frequency ranging from 500 Hz to 1 MHz and temperature between 300 K and 550 K. Compounds with relaxor behaviour at high temperatures and high thermal stability are desired for several applications. Because of the cation disorders present in this compound, GCTO displays dielectric relaxor behaviour indicative of a distribution of relaxation times. Furthermore, the frequency-dependent modulus illustrated a thermally activated conduction mechanism. Cole-Cole plots of electrical modulus suggest prominent grain contribution above 350 K.

Enhanced thermal conductivity of plasma generated ZnO-MgO based hybrid nanofluids: An experimental study

Hybrid nanofluids (HNFs) of metallic oxide-based nanoparticles (NPs) have been prepared in different basefluids (BFs) employing the thermal plasma technique. NPs of ZnO-MgO were directly dispersed into pristine coolant, engine oil, distilled water (DW), and coconut oil. Plasma was generated between two identical electrodes applying 8.0 kV at the ambient conditions and proved economically viable in preparing stable HNFs. X-ray Diffractometry (XRD) showed ZnO and MgO NPs possessed hexagonal and cubic crystal structures, respectively. The band gap is calculated through UV-visible spectroscopy. The thermal conductivity (TC) of the HNFs has been measured using a thermal conductivity analyzer based on the transient hot wire method. The band gaps of pristine coolant and its HNFs were obtained to be 3.35 eV and 3.33 eV, respectively. In engine oil and its HNFs, band gaps of 3.16 eV and 3.02 eV have been extracted. There appears to be a slight reduction in band gap for coolant and engine oil-based HNFs. The band gap value of coconut oil-based HNFs was 4.05 eV, which showed a higher value than the pristine coconut oil-based HNFs (3.95 eV). The band gap calculated in the case of DW-based HNFs was 3.79 eV. TC of HNFs with volume concentration of 0.019 % for DW, 0.020 % for coolant, 0.016 % for engine oil, and 0.017 % for coconut oil were tested between 20 and 60 °C. An increase in TC was observed with the rise in temperature of the HNFs. Maximum increment in TC was observed at 60 °C for coolant-based HNFs, which was 19 %, followed by DW (18%), coconut oil (18%), and engine oil (16%), respectively. DW-based HNFs can be used as a coolant and optical filter for optoelectronics devices like photovoltaic cells for better performance. The study underscores precise control of NPs size as pivotal for band gap influence. HNFs hold promise as the next-gen heat transfer fluids (HTFs), revolutionizing thermal conductivity across industries. This research lays a firm foundation for plasma-synthesized HNFs' application in enhanced heat transfer and optoelectronic devices. Coolant-based HNFs excel in thermal conductivity, addressing heat transfer challenges.

Multicomponent Photocatalytic-Dispersant System for Oil Spill Remediation

In the present work, the potential application of a fabricated halloysite nanotubes-Ag-TiO2 (HNT-Ag-TiO2) composite loaded with a binary surfactant mixture made up of lecithin and Tween 80 (LT80) in remediating oil spillages was examined. The as-prepared Ag-TiO2 that was used in the fabrication of the HNT-Ag-TiO2-LT80 composite was characterized by X-ray diffraction, Raman spectroscopy, UV-vis and diffuse reflectance spectroscopy, CV analyses, and SEM-EDX. The synthesized composite was also characterized by thermogravimetric analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. The synthesized composite was active in both the UV and visible light regions of the electromagnetic spectrum. The oil-remediating potential of the as-prepared composite was examined on crude oil, and aromatics and asphaltene fractions of crude oil. The composite was able to reduce the surface tension, form stable emulsions and smaller oil droplet sizes, and achieve a high dispersion effectiveness of 91.5%. A mixture of each of the crude oil and its fractions and HNT-Ag-TiO2-LT80 was subjected to photodegradation under UV light irradiation. The results from the GC-MS and UV-vis analysis of the photodegraded crude oil revealed that the photocatal composite was able to photodegrade the crude oil, aromatics, and asphaltene fractions of crude oil with the formation of intermediate photodegradation products depicting that the HNT-Ag-TiO2-LT80 has a potential as an oil spill remediation material.

Visible-light S-scheme heterojunction of copper bismuthate quantum dots decorated Titania-spindles for exceptional tetracycline degradation

The rational heterojunctions for antibiotics degradation have sparked significant attention in wastewater purification. In this study, we report a unique S-scheme photocatalytic system by in-situ growth of CuBi2O4 quantum dots (QDs) onto {101} facet of TiO2 spindles (TiO2-P) via hydrothermal transformation of Na-titanate nanotubes, which is observed by transmission electron microscopy technology. The CuBi2O4/TiO2-P effectively achieves photo-degradation of tetracycline (TC) using visible light (e.g. an 82% TC degradation efficiency at 60 min), which is attributed to the promotion of the charge separation and retaining strong redox capacity at the heterojunction interfaces via the active species of O2-, OH, and h+. Moreover, density functional theory (DFT) calculations show that a built-in electric field forms at the interface of the S-scheme heterojunction. In all, this work introduces a straightforward in-situ hydrothermal growth method to construct S-scheme photocatalysts for effective water treatment.

Magnetic Carbon Quantum Dots/Iron Oxide Composite Based on Waste Rice Noodle and Iron Oxide Scale: Preparation and Photocatalytic Capability

To provide an economical magnetic photocatalyst and introduce an innovative approach for efficiently utilizing discarded waste rice noodle (WRN) and iron oxide scale (IOS), we initially converted WRN into carbon quantum dots (CQDs) using a hydrothermal method, simultaneously calcining IOS to obtain iron oxide (FeOx). Subsequently, we successfully synthesized a cost-effective, magnetic CQDs/FeOx photocatalytic composite for the first time by combining the resulting CQDs and FeOx. Our findings demonstrated that calcining IOS in an air atmosphere enhanced the content of photocatalytically active α-Fe2O3, while incorporating WRN-based CQDs into FeOx improved the electron-hole pair separation, resulting in increased O2 reduction and H2O oxidation. Under optimized conditions (IOS calcination temperature: 300 °C; carbon loading: 11 wt%), the CQDs/FeOx composite, utilizing WRN and IOS as its foundation, exhibited exceptional and reusable capabilities in photodegrading methylene blue and tetracycline. Remarkably, for methylene blue, it achieved an impressive degradation rate of 99.30% within 480 min, accompanied by a high degradation rate constant of 5.26 × 10-3 min-1. This composite demonstrated reusability potential for up to ten photocatalytic cycles without a significant reduction in the degradation efficiency, surpassing the performance of IOS and FeOx without CQDs. Notably, the composite exhibited strong magnetism with a saturation magnetization strength of 34.7 emu/g, which enables efficient and convenient recovery in photocatalytic applications. This characteristic is highly advantageous for the large-scale industrial utilization of photocatalytic water purification.

Achieving Broadband NIR-I to NIR-II Emission in an All-Inorganic Halide Double-Perovskite Cs2NaYCl6:Cr3+ Phosphor for Night Vision Imaging

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) offer numerous advantages, including compact size, tunable emission spectra, energy efficiency, and high integration potential. These features make them highly promising for various applications, such as night vision monitoring, food safety inspection, biomedical imaging, and theragnostics. All-inorganic halide double-perovskite materials, known for their large absorption cross section, excellent defect tolerance, and long carrier diffusion radius, serve as unique matrices for constructing near-infrared fluorescent materials. In this study, we successfully prepared the all-inorganic metal halide double-perovskite Cs2NaYCl6:Cr3+ using a grinding-sintering method. A small fraction of the [YCl6] octahedra within the host material's lattice was substituted with Cr3+ ions, resulting in the creation of the Cs2NaYCl6:Cr3+ phosphor. When excited with λ = 310 nm UV light, the phosphor exhibited a broad emission range spanning from 800 to 1400 nm, covering the NIR-I and NIR-II regions. It had a broad bandwidth emission of 185 nm and achieved a fluorescence quantum yield of 20.2%. The unique broadband emission of the phosphor originates from the weak crystal field environment provided by the Cs2NaYCl6 host matrix, which enhances the luminescence properties of the Cr3+ ions. To create NIR pc-LEDs, the phosphor was encapsulated onto a commercially available UV LED chip operating at 310 nm. The potential application of these NIR pc-LEDs in night vision imaging was successfully validated.

Aerosol-Assisted Chemical Vapor Deposition of MoS2 with a Thiourea Sulfur Source: Single-Source Precursors vs Coreactant Mixtures

Aerosol-assisted chemical vapor deposition of MoS2 from solutions containing the single-source precursors cis-Mo(CO)4(TMTU)2 and Mo(CO)5(TMTU) in toluene was compared to depositions from the coreactant solution containing Mo(CO)6 and uncoordinated TMTU in toluene. The results were used to assess the significance of ligand precoordination on the properties of the deposited films. Raman spectra and GI-XRD patterns of the films show that the single-source precursors produced more intense and sharper signals for 2H-MoS2 as compared to the coreactant system of Mo(CO)6 and TMTU, which is indicative of improved crystallinity. SEM and XPS were also used to assess morphology and film composition. Thermolysis of cis-Mo(CO)4(TMTU)2 and analysis of the pyrolysis products by GC-MS and 1H NMR suggested a decomposition mechanism of the TMTU ligand where a terminal sulfido is generated on the molybdenum center with loss of a heteroatom stabilized carbene.

Idealizing Tauc Plot for Accurate Bandgap Determination of Semiconductor with Ultraviolet-Visible Spectroscopy: A Case Study for Cubic Boron Arsenide

The Tauc plot is widely used to determine the bandgap of semiconductors, but the actual plot often exhibits significant baseline absorption below the expected bandgap, leading to bandgap discrepancies from two different extrapolations. In this work, we first discuss the origin of baseline absorption and show that both extrapolation methods can produce significant errors by simulating Tauc plots with varying levels of baseline absorption. We then propose and experimentally verify a new method that idealizes the absorption spectrum by removing its baseline before constructing the Tauc plot. Finally, we apply this new method to cubic boron arsenide (c-BAs), resolve its bandgap discrepancies, and obtain a converging bandgap of 1.835 eV based on both previous and new transmission spectra. The method is applicable to both indirect and direct bandgap semiconductors with absorption spectrum measured via transmission or diffuse reflectance, which will become essential to obtain accurate values of their bandgaps.

Effect of Doping Heteroatoms on the Optical Behaviors and Radical Scavenging Properties of Carbon Nanodots

Heteroatom doping is regarded as a promising method for controlling the optoelectronic properties of carbon nanodots (CNDs), notably their fluorescence and antioxidation activities. In this study, phosphorous (P) and boron (B) are doped at different quantities in the CNDs' structures to investigate their effects on the optical and antioxidation properties. Both the dopants can enhance light absorption and fluorescence, yet via different approaches. After doping, the UV-vis absorption of high P%-CNDs demonstrated a slight blue shift (348-345 nm), while the high B%-CNDs showed a minor red shift (348-351 nm), respectively. The fluorescence emission wavelength of doped CNDs changes marginally while the intensity increases significantly. Structural and composition characterizations show elevated levels of C=O on the surface of high P%-CND compared to low P%-CNDs. In B-doped CNDs, more NO₃ ^- functional groups and O-C=O bonds and fewer C-C bonds form at the surface of high B%-CNDs compared to the low B%-CNDs. A radical scavenging study using 2,2-diphenyl-1-picrylhydrazyl (DPPH) was carried out for all CNDs. It was found that the high B%-CNDs exhibited the highest scavenging capacity. The effects of the atomic properties of dopants and the resulting structures of CNDs, including atomic radius, electronegativity, and bond lengths with carbon, on the optoelectronic property and antioxidative reactions of CNDs are comprehensively discussed. It suggests that the effect of P-doping has a major impact on the carbogenic core structure of the CNDs, while the B-doping mainly impacts the surface functionalities.

Different additives of gold nanoparticles and lithium oxide loaded chitosan based films; controlling optical and structural properties, evaluating cell viability

Natural chitosan-based films (CS) were fabricated by changing ingredient corporations between gold nanoparticles (AuNPs), lithium oxide (Li₂O), and graphene oxide (GO). A Series of films with different components were obtained. The structural examination is executed by XRD, FTIR, and EDX to analyze crystal structure, chemical bonding, and chemical contents, respectively. The findings illustrated that, the Li₂O@CS exhibited the lowest contact angle with 70 ± 4.6°. Scanning Electron Microscopy (SEM) displayd rod-shaped AuNPs with an average length of 0.3 μm and an average width of 90 nm. The refractive index of CS recorded 2.142, while AuNPs/Li₂O/GO@CS slightly declined to 2.085. Concerning AuNPs/Li₂O/GO@CS, the detected cell viability percentage of normal lung cells among the usage of 156.25 μg/mL is 98.91%, while 9.77 μg/mL achieved 125.78%. Therefore, combining AuNPs, GO and Li₂O within the CS matrix results in films of boosted biocompatibility and can be suggested for medical applications.

Origanum vulgare manganese ferrite nanocomposite: An advanced multifunctional hybrid material for dye remediation

The purpose of the study was to fabricate sustainable and cost-effective material for the thorough cleansing of polluted water. In this context, an economical, phytogenic and multifunctional Origanum vulgare plant-based nanocomposite material, MnFe₂O₄/OV, was prepared via one-pot synthetic technique. The synthesized nanocomposite with a band gap of 2.02 eV behaved as an efficient nano-photocatalyst for the degradation of both cationic (crystal violet) and anionic (congo red) dyes under direct sunlight irradiation. The material also inhibited the growth of E. coli and S. aureus bacteria and simultaneously adsorbed both cationic and anionic dyes from water through adsorption. A variety of techniques have been used to characterize the nanocomposite, including X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). Additionally, the kinetics of photodegradation of the aforementioned organic dyes has also been investigated. The MnFe₂O₄/OV exhibited excellent photocatalytic performance, leading to 43% and 72% degradation within 3 h at rate constants of 2.0 × 10^-3 min^-1 and 6.0 × 10^-3 min^-1 for crystal violet and congo red, respectively. The crystal violet and congo red were used to testify to the composite's potential for adsorption under the influence of several process variables, including initial solution pH, contact time, temperature, initial dye concentration, and amount of MnFe₂O₄/OV. The Langmuir maximum adsorption capacity Q_max as in the range 14.06-14.59 mgg^-1 for crystal violet and 34.45-23.93 mgg^-1 for congo red at pH 7 within 90 min contact time in the temperature range of 30-50 °C. The phenomenon of adsorption was found feasible and endothermic at all the investigated temperatures. Also, E. coli and S. Aureus bacteria have shown growth suppression activity when exposed to MnFe₂O₄/OV.As a result, the synthesized nanocomposite, MnFe₂O₄/OV, proved to be an antimicrobial, multifunctional novel nanocomposite, which is in high demand, and could serve as an affordable, and sustainable material for comprehensive water filtration.

Efficient wastewater disinfection by raised 1O2 yield through enhanced electron transfer and intersystem crossing via photocatalysis of peroxymonosulfate with CuS quantum dots modified MIL-101(Fe)

Peroxymonosulfate (PMS)-based photocatalysis is a promising alternative approach for wastewater disinfection. Singlet oxygen (¹O₂) is sensitive and efficient for bacterial inactivation. This study developed a ¹O₂-predominated PMS disinfection technique under visible light with CuS quantum dots (QDs) modified MIL-101(Fe) (CSQDs@MF). CuS QDs modification greatly enhanced the ¹O₂ quantum yield by 80% than that of MIL-101(Fe). Photoelectricity and photoluminescence tests demonstrated that both the enhanced electron transfer and energy transfer were responsible for improved ¹O₂ generation in Vis/PMS/CSQDs@MF system. The system took 60 min to inactivate 7.5-log E. coli, and it could be applied in a broad pH and dissolve oxygen range. Bacterial inactivation mechanism suggested that ¹O₂ attacked cell membrane first, then induced oxidative stress, up-regulated intracellular ROS level, eventually broke DNA strand. The system showed good disinfection performance on Gram-positive B. subtilis and fecal coliforms in practical wastewater, implying it is a promising alternative disinfection technology for wastewater treatment.

Biochar from Cyperus alternifolius Linn.: from a waste of phytoremediation processing to efficient depolluting agent

Phytoremediation is one of the most powerful and viable solutions for developing countries to clean the soil and water bodies from metallic pollutants. Cyperus alternifolius Linn. (CAL), a tropical wetland plant, has been widely researched for removing harmful contaminants due to its hyperaccumulation ability. However, the waste biomass of phytoremediation processing may risk secondary environmental pollution. Thus, the preparation and application of biochar from metal-contaminated plants can be considered a new approach. In a 60-day experiment, CAL plants were irrigated with different concentrations of Zn(II) (200, 700, 1200, 1700, and 2200 mg·L^-1), and then the plants were converted into biochar via the pyrolysis process. The characteristics of biochar including of surface composition and morphology, phase formation, and optical property were analyzed. The biochar enriched with Zn(II) at 1200 mg·L^-1 had a bandgap value of 3.17 eV and consisted of carbon microparticles intermingled with ZnO and SiO₂ nanoparticles. Furthermore, the adsorption and photocatalysis of the biochar were studied in the discolouration of methylene blue (MB), as a test reaction, with the maximum MB removal capacities of 55.2 mg·g^-1. Such results will serve as the basis for new research aiming at the potential for reusing metal-contaminated plants to produce efficient depolluting biochar.

Multipollutant Abatement through Visible Photocatalytic System

Water pollution damages the aquatic environment due to the presence of organic contaminants, which in turn is distressing to the ecosystem. Photocatalytic activity is a greener and promising method to degrade these organic contaminants. In this research, we present the degradation of diverse water pollutants through zinc/iron oxide nanoparticles serving as photocatalysts. The photocatalyst was studied for its efficiency to photodegrade congo red, brilliant green and para nitro phenol. Moreover, it also presented an antibacterial activity against the bacterium E. coli. Photocatalyst was characterized via X-ray diffraction, scanning electron microscopy-energy dispersive X-ray spectroscopy, and fourier-transform infrared spectroscopy. Tauc plot was used to measure the optical band gap (1.84 eV). The effect of various parameters such as catalyst dose, contact time, dye dose/concentration and pH were also investigated to determine the optimum point of maximum degradation through response surface methodology. A face-centered composite design was used, and a quadratic model was followed by congo red, brilliant green dyes and para nitrophenol. The maximum photodegradation efficiencies were 99%, 94.3%, and 78.5% for congo red, brilliant green and phenol, respectively. Quantum yield for congo red, brilliant green and para-nitrophenol were 9.62 × 10−8, 1.17 × 10−7 and 4.11 × 10−7 molecules/photons, while the reaction rates were 27.1 µmolg−1h−1, 29.61 µmolg−1h−1 and 231 µmolg−1h−1, respectively.

Colloidal Synthesis, Characterization, and Photoconductivity of Quasi-Layered CuCrS2 Nanosheets

The current need to accelerate the adoption of photovoltaic (PV) systems has increased the need to explore new nanomaterials that can harvest and convert solar energy into electricity. Transition metal dichalcogenides (TMDCs) are good candidates because of their tunable physical and chemical properties. CuCrS₂ has shown good electrical and thermoelectrical properties; however, its optical and photoconductivity properties remain unexplored. In this study, we synthesized CuCrS₂ nanosheets with average dimensions of 43.6 ± 6.7 nm in length and 25.6 ± 4.1 nm in width using a heat-up synthesis approach and fabricated films by the spray-coating method to probe their photoresponse. This method yielded CuCrS₂ nanosheets with an optical bandgap of ~1.21 eV. The fabricated film had an average thickness of ~570 nm, exhibiting a net current conversion efficiency of ~11.3%. These results demonstrate the potential use of CuCrS₂ as an absorber layer in solar cells.

Morphotropic Phase Boundary Enhanced Photocatalysis in Sm Doped BiFeO3

This paper presents the results of the synthesis of samarium-doped bismuth ferrite (BFO) nanoparticles by the solution combustion method. The dependence of BFO properties on the amount of the samarium (Sm) in the composition was studied. The synthesized nanocomposites were characterized by scanning electron microscopy SEM), X-ray diffractometry (XRD), Raman, Electron Diffuse Reflectance Spectroscopy (EDRS) and Electron Magnetic Resonance (EMR). The photocatalytic (PC) measurements showed the absence of a strict correlation between the PC activity and the crystallite size and band gap. An increase in the PC activity of BFO samples with 10 and 15% doping was observed and it was concluded that in controlling the PC properties in doped BFO, the processes of interfacial polarization at the boundaries of the morphotropic phase transition are of decisive importance. It was supposed that the internal electric field formed at these boundaries contributes to the efficient separation of photogenerated charge carriers.

Spin-Coating and Aerosol Spray Pyrolysis Processed Zn1-xMgxO Films for UV Detector Applications

A series of Zn_1-xMg_xO thin films with x ranging from 0 to 0.8 were prepared by spin coating and aerosol spray pyrolysis deposition on Si and quartz substrates. The morphology, composition, nano-crystalline structure, and optical and vibration properties of the prepared films were studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and optical and Raman scattering spectroscopy. The optimum conditions of the thermal treatment of samples prepared by spin coating were determined from the point of view of film crystallinity. The content of crystalline phases in films and values of the optical band gap of these phases were determined as a function of the chemical composition. We developed heterostructure photodetectors based on the prepared films and demonstrated their operation in the injection photodiode mode at forward biases. A device design based on two Zn_1-xMg_xO thin films with different x values was proposed for extending the operational forward bias range and improving its responsivity, detectivity, and selectivity to UV radiation.

Integration of quantum dots with Zn2GeO4 nanoellipsoids to expand the dynamic detection range of uranyl ions in fluorescent test strips

Fluorescent colorimetric test strips normally have a narrow dynamic detection-range due to the limited responsive range from single responsive materials, which cannot meet the wide detection requirement in practical applications. Herein, we developed an approach to detect uranyl ions (UO₂²⁺) with a broad detection range using the synthesized ZnS:Mn quantum dots (QDs) modified Zn₂GeO₄ nanoellipsoids (Zn₂GeO₄ @ZnS:Mn NEs), containing two responsive materials with the opposite signal responses at different UO₂²⁺ concentrations. Specifically, a red to chocolate color change was observed at low analyte concentrations (0.01-100 μM) resulting from the photoinduced electron transfer effect from ZnS:Mn QDs to UO₂²⁺. A sequentially olive drab to green color change has been observed when further increasing the UO₂²⁺ concentration (100-1000 μM) as a result of the antenna effect between Zn₂GeO₄ nanoellipsoids and UO₂²⁺. In addition, a low-cost and portable fluorescent test strip has been further fabricated through embedding Zn₂GeO₄ @ZnS:Mn NEs on a microporous structure membrane, demonstrating a facile yet effective colorimetric response to UO₂²⁺ in lab water, lake water, and seawater with a wide dynamic range. Therefore, it is potentially attractive for real-time and on-site detection of UO₂²⁺ in sudden-onset situations.

Remarkable sunlight-driven photocatalytic performance of Ag-doped ZnO nanoparticles prepared by green synthesis for degradation of emerging pollutants in water

In this work, Ag-doped ZnO nanoparticles (NPs) were synthesized by a simple green method using a toxic agent-free route for photocatalytic purposes, toward methylene blue (MB) removal in water under sunlight irradiation. The effects of operating parameters, such as catalyst dosage, dye concentration, and pH, on the MB removal efficiency, were investigated. The presence of Ag on the ZnO structure resulted in superior catalytic activity compared to the pure ZnO sample. High removal efficiency for MB, corresponding to 95%, was obtained in 30 min of reaction time only, using Ag-doped ZnO NPs. This result can be related to its smaller bandgap energy (1.92 eV) when compared to the ZnO sample (2.85 eV). The material presented a satisfactory level of reusability after three consecutive cycles. In addition, a reaction mechanism for MB photodegradation onto Ag-doped ZnO NPs under sunlight irradiation was suggested. Overall, the catalyst prepared via the green route in this work exhibited excellent photocatalytic activity under sunlight for MB degradation in an aqueous solution.

Flexible Nano-TiO2 Sheets Exhibiting Excellent Photocatalytic and Photovoltaic Properties by Controlled Silane Functionalization-Exploring the New Prospects of Wastewater Treatment and Flexible DSSCs

TiO₂ nanoparticles surface-modified with silane moieties, which can be directly coated on a flexible substrate without the requirement of any binder materials and postsintering processes, are synthesized and characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, time-correlated single-photon counting, and transmission electron microscopy. The viability of the prepared surface-modified TiO₂ (M-TiO₂) sheets as a catalyst for the photo-induced degradation of a model dye, methylene blue, was checked using UV-visible absorption spectroscopy. The data suggest that, compared to unmodified TiO₂, M-TiO₂ sheets facilitate better dye-degradation, which leads to a remarkable photocatalytic activity that results in more than 95% degradation of the dye in the first 10 min and more than 99% of the degradation in the first 50 min of the photocatalytic experiments. We also demonstrate that M-TiO₂ can be recycled with negligible reduction in photocatalytic activity. Further, the photovoltaic properties of the developed M-TiO₂ sheets were assessed using UV-visible absorption spectroscopy, electrochemical impedance spectroscopy (EIS), and photochronoamperometry. Dye-sensitized solar cells (DSSC) fabricated using M-TiO₂ as the photoanode exhibited a photoconversion efficiency of 4.1% under direct sunlight. These experiments suggested that M-TiO₂ sheets show enhanced photovoltaic properties compared to unmodified TiO₂ sheets, and that, when N-719 dye is incorporated, the dye-TiO₂ interaction is more favorable for M-TiO₂ than bare TiO₂. The simple solution processing method demonstrated in this paper rendered a highly flexible photoanode made of M-TiO₂ with superior charge-separation efficiency to an electrode made of bare TiO₂. We propose that our findings on the photovoltaic properties of M-TiO₂ open up arenas of further improvement and a wide scope for the large-scale production of flexible DSSCs on plastic substrates at room temperature in a cost-effective way.

WO3·nH2O Crystals with Controllable Morphology/Phase and Their Optical Absorption Properties

In this work, a one-step hydrothermal route is developed to prepare WO₃·nH₂O crystals with various morphology/phases, for which any surfactants, templates, or structure-directing agents are not used. Five types of WO₃·nH₂O crystals, including o-WO₃·H₂O nanoplates, rectangular m-WO₃ nanosheets, o-WO₃·0.33H₂O microspheres, h-WO₃ nanorods, and bundle-like h-WO₃ hierarchical structures, are successfully obtained by adjusting the amount of H₂SO₄ and reaction temperature. According to the experimental results, the formation mechanism for various WO₃·nH₂O species is proposed. In addition, the optical absorption properties of these WO₃·nH₂O crystals are also investigated by UV-vis absorption spectra.

Facile Synthesis, Characterization, and Photocatalytic Activity of Hydrothermally Grown Cu2+-Doped ZnO–SnS Nanocomposites for MB Dye Degradation

The morphology, chemical composition, and doping process of metal oxides and sulfides play a significant role in their photocatalytic performance under solar light illumination. We synthesized Cu2+-doped ZnO–SnS nanocomposites at 220 °C for 10 h, using hydrothermal methods. These nanocomposites were structurally, morphologically, and optically characterized using various techniques, including powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-visible absorption spectroscopy. Their photocatalytic activity (PCA) on methylene blue (MB) pollutant dye was examined under 150 W solar light illumination. Mixed-phase abundances with hexagonal ZnO and orthorhombic SnS structures were observed. TEM micrographs showed changes in morphology from spherical to nano-flake structures with an increasing doping concentration. XPS indicated the chemical states of the constituent elements in the nanocomposites. UV-visible absorption spectroscopy showed a decrease in the bandgap with an increasing doping concentration. Strong PCA was observed due to the separation of charge carriers, a change in bandgap, and a high light absorption ability under solar light irradiation. The measured photodegradation efficiency of the MB dye was approximately 97% after 2 h. The movement of the charge carriers and the bandgap alignment of the synthesized composites are briefly discussed.

Active terahertz modulator based on optically controlled organometal halide perovskite MAPbI2Br

In this paper, an active terahertz modulator based on optically controlled organometal halide perovskite MAPbI₂Br is proposed. The terahertz wave time-domain transmission of the MAPbI₂Br/Al₂O₃ sample was measured by a terahertz time-domain spectrometer. Experimental results indicate that the MAPbI₂Br/Al₂O₃ sample showed an obvious optical-power-dependent modulation effect on transmission of the terahertz wave; the maximum modulation depth of the modulator can reach 59.99% at 0.3 THz when the external pump optical power is up to 1500 mW.

Design and synthesis of benzothiadiazole-based molecular systems: self-assembly, optical and electronic properties

A comprehensive study was conducted to determine the effect of the donor-group on the solid-state organization and electronic properties of stimuli-responsive benzothiadiazole-based D–A–D building blocks.

Biomineralized Prussian Blue Nanotherapeutic for Enhanced Cancer Photothermal Therapy

Photothermal therapy is a promising tumor ablation technique that converts light into heat energy to kill cancer cells. Prussian blue (PB), a biocompatible photothermal reagent, has been widely explored for...

Carrier-Gas Induced Changes in the Structural, Stoichiometric and Photocatalytic Characteristics of Gallium Oxide Nanostructures

Ga₂O₃/ITO/glass photoelectrodes prepared by the CVD method has rarely been tested in the electrochemical cell for water splitting. In this study, we investigate the photoelectrolytic performance of Ga₂O₃/ITO-glass photocatalysts produced by the high-temperature CVD route. The changing of N₂ carrier gas flow rate from 0 to 1800 seem induces change in the materials properties. XRD signal strength of the produced bi-phase Ga₂O₃ is observed to deteriorate, while diffraction line width broadens with increasing N₂ supply. Films show a combination of nanoclumps and nanostrips morphology. Ga/O ratio decreases, while the optical bandgap gradually increases from 4.37 to 4.42 eV with increasing O content and crystallite size. Photoluminescence measurements show UV, blue, green and red emissions, respectively. Linear sweep voltammetry of the electrodes in 0.1 M KOH electrolyte shows improvement in photocurrent density from 160 to 257 μA/cm² versus Ag/AgCl at 1 V bias, and a maximum photon-to-current conversion efficiency 0.06%.

Construction of Bi2O2CO3/Ti3C2 heterojunctions for enhancing the visible-light photocatalytic activity of tetracycline degradation

Bi₂O₂CO₃ (BOC) was successfully loaded on a highly conductive Ti₃C₂ surface by the hydrothermal method, forming a unique BOC/Ti₃C₂ heterostructure. The use of advanced characterization methods reveals the composition, morphology and photoelectric properties of the material. The results show that the interface formed by close contact between BOC and Ti₃C₂ provides an effective channel for charge transfer between the two. Importantly, the photocatalytic degradation efficiency of BOC/Ti₃C₂ for tetracycline (TC) is ~80%, which is significantly higher than the degradation efficiency of pure BOC and pure Ti₃C₂ for TC. In addition, BOC/Ti₃C₂ still has high catalytic activity in the degradation of complex mixed antibiotics. This is because BOC and Ti₃C₂ have large specific surface areas, high light absorption capacity and efficient carrier separation after recombination. At the same time, the detected superoxide radicals (O^2-) and holes (h⁺) are the main active substances. The degradation pathway and catalytic mechanism of the photocatalytic degradation of TC by BOC/Ti₃C₂ are further explained. This research designed and developed a BOC/Ti₃C₂ composite material for the photocatalytic degradation of tetracycline and mixed antibiotic wastewater, providing experimental methods and ideas for actual wastewater treatment.

Synthesis of PVA/CeO2 Based Nanocomposites with Tuned Refractive Index and Reduced Absorption Edge: Structural and Optical Studies

In the current study, polymer nanocomposites (NCPs) based on poly (vinyl alcohol) (PVA) with altered refractive index and absorption edge were synthesized by means of a solution cast technique. The characterization techniques of UV–Vis spectroscopy and XRD were used to inspect the structural and optical properties of the prepared films. The XRD patterns of the doped samples have shown clear amendments in the structural properties of the PVA host polymer. Various optical parameters were studied to get more insights about the influence of CeO₂ on optical properties of PVA. On the insertion of CeO₂ nanoparticles (NPs) into the PVA matrix, the absorption edge was found to move to reduced photon energy sides. It was concluded that the CeO₂ nanoparticles can be used to tune the refractive index (n) of the host polymer, and it reached up to 1.93 for 7 wt.% of CeO₂ content. A detailed study of the bandgap (BG) was conducted using two approaches. The outcomes have confirmed the impact of the nanofiller on the BG reduction of the host polymer. The results of the optical BG study highlighted that it is crucial to address the ε” parameter during the BG analysis, and it is considered as a useful tool to specify the type of electronic transitions. Finally, the dispersion region of n is conferred in terms of the Wemple–DiDomenico single oscillator model.

Nuclearity growth of new PdII complexes induced by the electronic effect of selenium-containing ligands

This work provides a systematic study of how the electronic effect of EDG or EWG in selenium-containing ligands influences the nuclearity of PdII complexes. The solid-state, solution and gas phase behaviors were evaluated for the complexes.

Cost-Effective Production of TiO2 with 90-Fold Enhanced Photocatalytic Activity Via Facile Sequential Calcination and Ball Milling Post-Treatment Strategy

Titanium dioxide (TiO₂), the golden standard among the photocatalysts, exhibits a varying level of photocatalytic activities (PCA) amongst the synthetically prepared and commercially available products. For commercial applications, superior photoactivity and cost-effectiveness are the two main factors to be reckoned with. This study presents the development of simple, cost-effective post-treatment processes for a less costly TiO₂ to significantly enhance the PCA to the level of expensive commercial TiO₂ having demonstrated superior photoactivities. We have utilized sequential calcination and ball milling (BM) post-treatment processes on a less-costlier KA100 TiO₂ and demonstrated multi-fold (nearly 90 times) enhancement in PCA. The post-treated KA100 samples along with reference commercial samples (P25, NP400, and ST01) were well-characterized by appropriate instrumentation and evaluated for the PCA considering acetaldehyde photodegradation as the model reaction. Lattice parameters, phase composition, crystallite size, surface functionalities, titanium, and oxygen electronic environments were evaluated. Among post-treated KA100, the sample that is subjected to sequential 700 °C calcination and BM (KA7-BM) processes exhibited 90-fold PCA enhancement over pristine KA100 and the PCA-like commercial NP400 (pure anatase-based TiO₂). Based on our results, we attribute the superior PCA for KA7-BM due to the smaller crystallite size, the co-existence of mixed anatase-srilankite-rutile phases, and the consequent multiphase heterojunction formation, higher surface area, lattice disorder/strain generation, and surface oxygen environment. The present work demonstrates a feasible potential for the developed post-treatment strategy towards commercial prospects.