Diffuse Reflectance Spectroscopy Research Articles

Dy doped calcium silicates synthesized using agro-food wastes and conventional chemicals as resources: a comparative study

Based on an earlier study, a mimic composition 38SiO2-60CaO-0.5Dy2O3-0.2Na2O-1MgO-0.1Al2O3-0.1TiO2-0.1Fe2O3 (wt.%) are synthesized by solid-state reaction method. The structural, morphological, and optical properties of the synthesized sample presented in this study are compared with the corresponding properties of a similar sample derived from rice husk ash and eggshell powder as resources. The conventional chemicals derived sample are multi-phasic, containing β−Ca2SiO4, γ−Ca2SiO4, Ca3Si2O7, and CaFeO3 phases, and the CaO/SiO2 ratio was believed to be affecting the room temperature stabilization of the β phase. Field emission scanning electron microscopy images showed that twinned particles, cracks, and edge dislocations were present in the synthesized sample. The presence of precipitates in the micrographs indicated that Dy ions were segregated on the surface of the sample. The optical bandgap of the samples was 3.7 eV, as calculated by diffuse reflectance spectroscopy. The photoluminescence emission spectrum contained characteristic emission peaks of the Dy3+ ions. Apart from these, additional peaks were observed due to the titanium ions present in the sample. Understanding the properties of calcium silicates containing multiple dopant ions is important to develop a white light-emitting diode. The properties of the mineral-derived sample are compared to those of the agro-food waste-derived similar sample.

Advancing solar wastewater treatment: A photocatalytic process via green ZnO/g-C3N4 coatings and concentrated sunlight – Comprehensive insights into ciprofloxacin antibiotic inactivation

In this study, a sustainable method employing concentrated sunlight to achieve environmental remediation of wastewater, contaminated by Ciprofloxacin antibiotic (CIP), is thoroughly investigated. A green ZnO/g-C3N4 nanocomposite (NC) is used as a photocatalyst coating on glass to investigate the inactivation of CIP in water, in a flow-reactor configuration at small-prototype scale (10 liters/h, catalyst area 187.5 cm2). ZnO/g-C3N4 NC coatings were obtained by an in-situ thermal condensation process coupled with a green synthesis protocol and deposited on glass, via a simple drop casting method. Morphological and structural analyses of synthesized composites were performed with Fourier-Transform Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray (EDX) and X-ray diffraction (XRD) techniques, while optical properties were studied with Diffuse Reflectance Spectroscopy (DRS). The degradation of CIP was first tested at a lab scale under simulated sunlight and then studied under sunlight in a parabolic trough concentrator (PTC). Suitable degradation of CIP (100%) was observed at 210 min via High-Performance Liquid Chromatography (HPLC) and the by-products were determined by Liquid Chromatography-Mass Spectroscopy (LC–MS). Microbiological tests revealed the absence of antibacterial activity in CIP water treated with ZnO/g-C3N4 NC photocatalyst against Staphylococcus aureus, Pseudomonas aeruginosa, and Priestia megaterium. Our results directly demonstrate the effective inactivation of CIP with a process designed for sustainability both in terms of energy input (solar) and scalability of materials. Also, the small-prototype scale of this investigation provides insights into the challenges arising from the perspective scale-up to an industrial application, aimed at antibiotics inactivation in wastewater and thus helping to prevent the spread of antimicrobial resistance (AMR).

Preparation of bismuth ferric oxide nanoparticles for the microwave-induced photo-degradation of organic pollutants in greywater.

This work demonstrates a thorough investigation into the synthesis and characterization of bismuth ferric oxide (BFO) photocatalyst for microwave-induced photodegradation of organic pollutants in greywater. Microwave (MW) irradiation was executed to enhance the generation of reactive oxygen species, contributing to the catalytic effectiveness of the synthesized photocatalyst. Through an efficient ultrasound-assisted synthesis process, perovskite BFO nanoparticles with a rhombohedral crystal structure and a crystallite size of around 15nm were successfully manufactured. Comprehensive characterization employing various analytical techniques including X-ray diffraction (XRD), Energy Dispersive X-ray Analysis (EDAX), Fourier Transform Infrared and Raman Spectroscopy, UV-Visible Diffuse Reflectance Spectroscopy (UVDRS), photoluminescence spectroscopy, Scanning Electron Microscopy (SEM), and Brunauer-Emmett-Teller (BET) studies provided insights into the structural, elemental, spectral, optical, morphological, and surface area properties of the nanoparticles. The UV-vis spectroscopy and Tauc's plot were employed to elucidate the band structure of the photocatalyst, providing insights into its essential electronic properties for catalytic applications. With a narrow optical band gap of 2.13eV, the synthesized photocatalyst demonstrated suitability for optical applications and exhibited substantial catalytic activity in the microwave-induced photocatalytic degradation of greywater. Remarkably, it achieved a 93.5% reduction in total organic carbon (TOC) within 180min under moderate 50-W illumination. Refining process parameters through optimization studies notably augmented degradation efficiency. Scavenging investigations validated the efficient mineralization of total organic carbon content. Kinetic assessments provided mechanistic insights into improved catalytic activity of BFO, which was attributed to a changed band structure that allows for fast charge transfer across interfacial layers. Moreover, the stability and reusability of the BFO photocatalyst were assessed over five cycles, highlighting its potential practical application as an efficient and reusable photocatalyst for greywater treatment. These findings underscore the promising prospects of BFO in addressing environmental challenges and advancing sustainable wastewater treatment technologies.

Modulating Electronic Structure of MoS2 nanosheets by Sulfide‐Enrichment‐Induced Vacancies for Enhanced Photocatalytic Hydrogen Production

Enhancing photocatalytic activity by changing the electronic structure of the catalyst is an effective strategy. 2H‐MoS2 has semiconductor properties, and its unsaturated side S atom is the main active site for its photocatalytic activity. However, due to the weak S‐H bond energy, its hydrogen adsorption capacity is weak. In this work, the electronic structure of MoS2 is adjusted by S‐rich treatment, resulting in the formation of Mo vacancy (MoS2‐VMo). The level of Mo vacancies was assessed using UV‐visible diffuse reflectance spectroscopy (UV‐vis DRS). As these vacancies can capture certain photogenerated electrons, thereby reducing the recombination of electron‐hole pairs. Through DFT calculation, it is found that the anti‐bonding orbital electron filling of MoS2‐VMo is weakened, the bond energy of S‐Mo bond is weakened, and the bond energy between S‐H bond is enhanced, which is more conducive to proton adsorption. The photocatalytic activity for hydrogen evolution of MoS2‐3, which underwent the optimal S‐rich treatment, achieved a remarkable rate of 2404.6 μmol g‐1 h‐1 in dye eosin Y (EY) sensitization system, significantly surpassing that of MoS2 lacking the S‐enriched treatment. This study introduces a novel concept for enhancing the photocatalytic hydrogen evolution performance of metal sulfides via defect engineering.

Facile synthesis and characterization of zinc molybdate (ZnMoO4) nanosheets for electrochemical supercapacitor application

Abstract This study explores the synthesis and characterization of zinc molybdate (ZnMoO4) nanosheets with emphasis on their potential application for energy storage devices particularly supercapacitors. The synthesis of ZnMoO4 nanosheets was done through co-precipitation followed by examination of their structure, morphology, optical, thermal behaviour and electrochemical performance by various characterization techniques. X-ray diffraction (XRD) analysis confirmed that the formation of monoclinic ZnMoO4 phase with the average crystallite size 17.93 nm. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) revealed that this material had nanosheets-like structure which helps to increase ion transport and surface area; these two factors are essential for enhancing the material’s supercapacitor efficacy. The semiconductor characteristics were determined using UV–Visible diffuse reflectance spectroscopy (UV-DRS) which indicated a band gap energy of 4.2 eV. Fourier transform infrared (FTIR) analysis confirmed that the presence of Zn–O and Mo–O bonds in their crystal lattice. Thermogravimetric analysis (TGA) showed that the ZnMoO4 nanosheets had thermal stability since they experienced only a slight mass loss of 2.57 % up to 800 °C. Cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) tests were undertaken to find out the specific capacitance and the value is 618 F g⁻1 at a current density of 1 A g⁻1.

Achieving High Photocatalytic NOx Removal Activity Using a Bi/BiOBr/TiO2 Composite Photocatalyst.

Fossil fuel combustion generates nitrogen oxides (NO + NO2 = NOx), which pose threats to the environment and human health. Although commercial products containing titanium dioxide (TiO2) can remedy NOx pollution by photocatalysis, they only function in the ultraviolet (UV). On the other hand, bismuth oxybromide (BiOBr) is active in the visible. BiOBr is stable, affordable, and non-toxic, making it an appealing alternative. In addition, nanoparticulate Bi metal can further enhance visible light absorption through its surface plasmon properties and charge carrier lifetime by spatially separating charge. In this study, to enhance the visible-light activity of TiO2-based photocatalysts for NOx pollution, a composite of Bi-decorated BiOBr/TiO2 was synthesized using a solvothermal method across varying the Ti/Bi atomic ratio (0.2, 2.2, 4.4, and 6.6), and synthesis duration (6h, 12h, and 18h). The photocatalytic performance of the synthesised composites for NO gas removal was investigated using an adapted ISO method (22197-1:2016). Analysis showed that the preferential growth of the (010) crystal facet in BiOBr and the presence of Bi metal both play an important role in the superior photocatalytic activity seen in our Bi-decorated BiOBr/TiO2 composite. The composites were characterised using X-ray diffraction (XRD), attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR), high-resolution scanning electron microscopy (HRSEM), UV-Vis diffuse reflectance (DRS) spectroscopy, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Brunauer-Emmett-Teller (BET) analysis, thermogravimetric analysis (TGA), and diffuse reflectance transient absorption spectroscopy (DR-TAS). Our research shows that the Bi/BiOBr-TiO2 composite synthesised through the 12-hour solvothermal method with a Ti/Bi atomic ratio of 4.4 exhibits the highest photocatalytic performance towards both NO and NO2 oxidation; with 32.8% and 54.9% NO removal and 15.1% and 29.5% NO2 under visible and UV lamps, respectively.

Visible light sensitive BiVO4–TiO2 nanocomposites for photocatalytic dye degradation

Abstract The hydrothermal approach was used to prepare visible light active BiVO4–TiO2 nanosheet composites in varying molar ratios. The photoluminescence (PL) spectrum, X-ray photoelectron spectroscopy (XPS), UV-Visible Diffuse Reflectance Spectroscopy (DRS), Transmission electroscopy (TEM), Brunauer-Emmett-Teller (BET) and field emission scanning electron microscopy (FESEM), were used to analyze the photocatalysts and composites. Photocatalytic activity of BiVO4–TiO2 composites was investigated by decolorizing methylene blue. Out of four different molar ratio BiVO4–TiO2 composites with a molar ratio of 3:1 BiVO4 TiO2 composite showed enhanced photocatalytic activity which is further proved by photoluminescence investigation of coumarin and Scavenger test. The DRS of BiVO4 TiO2 composite showed red shift in optical absorption. The enhanced photocatalytic activity is due to minimizing electron hole recombination by making composite with TiO2.

Synthesis, Structure, and Properties of Dion–Jacobson Double‐Layered Perovskites A′SmNb2O7 (A′=Rb, K, Na, Li, H)

AbstractDion‐Jacobson‐type layered perovskite compounds A′SmNb2O7 (A′=Rb, K, Na, Li, H) were synthesized using solid‐state and ion‐exchange methods. While the parent solid‐state product RbSmNb2O7, has previously been studied, the ion‐exchanged compounds were obtained and studied for the first time. The phase and chemical purity of the compounds were confirmed by X‐ray diffraction (XRD) and energy‐dispersive X‐ray spectroscopy (EDX). The crystal structures of RbSmNb2O7 (I2 cm, a=0.54356(1) nm, b=0.53935(1) nm, c=2.1891(5) nm), KSmNb2O7 (I2 cm, a=0.53660(7) nm, b=0.54481(6) nm, c=2.1527(1) nm) and LiSmNb2O7 (B2 cm, a=0.54546(4) nm, b=0.53567(4) nm, c=2.04582(5) nm) were refined using the Rietveld method. Polyhedral distortions in these structures have been studied in detail. The thermal behavior of the compounds has been determined using differential thermal analysis (DTA), revealing that A′=Na, Li and H compounds are metastable hydrates, while A′=Rb and K compounds are stable. The optical band gap, valence band edge, and conduction band edge potentials of the compounds obtained were calculated using diffuse reflection spectroscopy data. A photocatalytic experiment was performed on the degradation of methylene blue under ultraviolet light. All of the samples obtained showed some asctivity in the reaction of dye photooxidation.

Choose Your Dopant─Ultrananotitania Directing Photocatalytic Electron Destination.

Anatase titania photocatalysts are the subject of thousands of papers annually. Since the photoefficiency is low, doping TiO2 photocatalysts with various elements is a widely employed technique to enhance performance. However, studies involving different catalyst sizes, morphologies, or dopants often yield varied or even contradictory conclusions. Herein, we report a versatile platform based on ultranano, <2 nm, particles, that minimizes defects, produces uniform morphology, and enables systematic investigation of dopant control of product formation. Charge-carrier destination is determined by the redox couple in the oxide matrix; a couple that is measured by diffuse reflectance spectroscopy. Versatility is demonstrated via doping with all fourth-period transition elements (except Sc). For oxidation reactions, two distinct reaction pathways are identified; the balance between the pathways is regulated by the reduction potential of the dopant in the matrix. The prospect for directing charge transfer significantly expands potential applications for titania.

Different metal-doped NiO nanoparticles for sunlight-mediated degradation of low-density polyethylene microplastic films.

Due to the widespread use and incorrect handling of plastics, we need to find a practical and effective way to eliminate plastic waste from the environment. Different metal-doped nickel oxide (DMD-NiO) nanoparticles (NPs) were synthesized using a sol-gel technique and were used to degrade low-density polyethylene (LDPE) microplastic (MP) films when exposed to sunlight. The optical and structural properties of sol-gel method synthesized materials were investigated using a variety of characterization methods (Fourier transform infrared (FT-IR), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), X-ray diffractometer (XRD) analysis, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, and thermogravimetric analysis (TGA). Degradation study results suggest that the photocatalytic activity of DMD-NiO-LDPE nanocomposites (NCs) films was greater than that of pure LDPE and undoped NiO-LDPE films. Because of their increased optical absorption and efficient suppression of photo-produced charge carriers' recombination, the DMD-NiO NPs showed higher photocatalytic degradation of LDPE films. Thus, LDPE films with 2% wt Fe-NiO (iron-doped nickel oxide) nanomaterials showed a degradation of around 38.16% among DMD-NiO-LDPE NCs films under visible light over a short period of 30 days (240 h). The formation of carbonyl groups in the degradation product of LDPE was confirmed by Fourier transform infrared (FT-IR) analysis. When compared to the original LDPE film, the Fe-NiO-LDPE NCs films showed a significant decrease in crystallinity and carbonyl indexes, as much as 8.4% lower. The current project proposes the development of eco-friendly photocatalysts using a sol-gel technique for combating MP pollution in the environment.

Pr3+ ions activated TiO2 nanoparticles as electron transport layer for copper based (CH3NH2)2CuBr4 perovskites solar cells

In emerging organic-inorganic perovskite solar cells (PSCs), the role of efficient electron transport layers (ETLs) is critical for electron transfer and hole blocking. TiO2 is one of the widely reported ETLs but limits the performance of the devices exhibiting restricted electron mobility and numerous defect states. The process of doping rare earth ions has been an effective approach in improving the electronic and optical properties of TiO2 for enhanced efficiency of PSCs. The present work studies the effect of praseodymium (Pr3+) doped TiO2 prepared via sol-gel technique as electron transport layers for lead-free perovskite solar cells. The X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS) studies showed that the crystallite size and bandgap of the particles reduced as a function of Pr3+ doping concentration. The X-ray photoelectron spectroscopy (XPS) analysis of the samples inferred that Pr3+ ions majorly remained on the TiO2 surface. Copper-based (CH3NH2)2CuBr4 perovskites were synthesized by solution method as an active layer for the solar cells. XRD, FTIR (Fourier Transform Infrared Spectroscopy) and XPS analysis confirmed the formation of 2D-perovskite phase of the samples. The scanning electron microscopy (SEM) analysis of the perovskites revealed well crystalline orthorhombic structures. Current-voltage measurements were carried out to study better passivation properties with rare-earth doping of the ETLs and was found to be most enhanced for 0.07 Pr3+ concentration. Electro-chemical Impedance Spectroscopy (EIS) studies of the solar cells showed a reduced interface recombination and enhance charge transfer properties as a function of rare-earth dopant concentration. Further, the fabricated perovskite solar cells showcased better performance with xPr3+:TiO2 ETLs and the maximum efficiency of ∼1.25 % was obtained for TiO2: 0.07 Pr3+.

La-supported SnO2–CaO composite catalysts for efficient malachite green degradation under UV–vis light

This study presents the development and optimization of La@SnO2–CaO composite catalysts for efficient photocatalytic degradation of malachite green dye in aqueous solutions under UV–vis light irradiation. The catalysts were prepared via conventional incipient-wetness impregnation and thoroughly characterized using advanced analytical techniques, including X-ray diffraction, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, N2 adsorption–desorption analysis, and scanning electron microscopy. To optimize photodegradation efficiency, the effects of three independent factors were systematically investigated using response surface methodology: Temperature, pH, and Sn/Ca molar ratio. Our results reveal optimal conditions for maximum dye degradation: pH 7, Sn/Ca molar ratio of 0.33, and a process time of 35 min, resulting in a maximum photodegradation efficiency of 98.80% for malachite green dye. Notably, visible light exhibited a more pronounced effect on dye degradation compared to UV light over time, with visible light achieving 25% greater dye removal after 60 min of illumination. Furthermore, the catalyst showed excellent recyclability, retaining 85% of its initial activity after five consecutive cycles. These findings contribute significantly to the development of sustainable methods for dye removal from wastewater and highlight the potential of La@SnO2–CaO composite catalysts in environmental remediation processes, particularly in treating textile industry effluents.

Theoretical and experimental investigation of BaY2(MoO4)4:xSm3+ phosphors

In this paper, the novel BaY2(MoO4)4:xSm3+ phosphors with strong red emission and high thermal stabilization were prepared by a conventional method of high temperature solid state reaction in air atmosphere. Morphology, phase purity, element distribution, UV–Vis–NIR diffuse reflectance spectroscopy (DRS), and luminescence properties were investigated in detail. The crystal structure of the BaY2(MoO4)4 host was refined with the aid of the Rietveld refinement method by the GSAS program. The electronic band structure and phonon dispersion were performed using plane-wave density functional theory (DFT). The prepared BaY2(MoO4)4:Sm3+ phosphor exhibits excellent red emission under near-ultraviolet excitation. Strong red emission intensity and high thermal stability suggest potential application in backlighting or phosphor-covered white light-emitting diodes (pc-LEDs).

Phytomediated synthesis of WO3 nanoparticles using Solanum lycopersicum fruit extract for enhanced photocatalytic activity of 2,4-dichlorophenol

ABSTRACT In the present study, bio-citric acid/tungsten oxide (WO3) (BCAWO) nanoparticles (NPs) were prepared by using Solanum lycopersicum fruit extract as a reducing as well as a capping agent. The photocatalysts were characterized by UV–vis diffuse reflection spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), high-resolution transmission electron microscopy, and photoluminescence spectroscopy techniques. Diffraction peaks in the XRD spectrum were identified as the crystal planes of crystalline tungsten oxide. The BCAWO had an average size of 23.14 nm. For W–O bonds, the Fourier transform infrared spectrum displays the vibrational peak at 671.23 cm−1. A prominent absorption band was observed at 268 nm, indicating the 1.2 eV bandgap. Under xenon (Xe) lamp irradiation, the synthesized BCAWO nanoparticles showed notable photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP), with a degradation rate of 96%. With BCAWO concentrations of 2.5 g/L, pH of 4, reaction period of 180 min, and 2,4 DCP concentration of 10 mg/L, the degradation of 2,4-DCP had the highest efficacy, 96%. The degradation of phenols in wastewater may be facilitated by using the green WO3 nanoparticles as a photocatalyst, according to the results.

Modulation of ZrO2-Ag2O-MoO3 nanocomposite into ultrasensitive hydrazine electrochemical sensor for environmental remediation

Herein, a facile single-step wet chemical approach was executed for the composition of semiconductor ternary metal oxides (TMO) i.e., ZrO2-Ag2O-MoO3 nanocomposite (NC) in an alkaline medium. For structural as well as morphological elucidation, the calcined nanocomposite was characterized through ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), powdered X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) analysis. Later, the glassy carbon electrode (GCE) was modified into a highly responsive as well as selective hydrazine (HDZN) electrochemical probe (ZrO2-Ag2O-MoO3-NC/PEDOT:PSS/GCE) by the fabrication of thin layered ZrO2-Ag2O-MoO3 NC onto GCE facilitated by 5 % PEDOT:PSS as conducting polymer binder. While examining the analytical parameters through novel current–potential (I-V) electrochemical approach, for the first time, the newly designed electrochemical probe, as selective hydrazine sensor, happened to own the low detection limit (LOD; 0.028 pM) with greater sensitivity (33.86 μAμM−1cm−2) and broad linear dynamic range (LDR; 0.1 M–1.0 nM) in addition to coefficient of correlation (r)/r2 square (r = 0.9941, r2 = 0.9882) and low limit of quantification (LOQ; 0.093 pM). Furthermore, reproducibility as well as prolonged stability of this newly proposed probe towards hydrazine were also assessed and found to be reliable in short response time. Hence, this work presents an inaugural report about the sensing of HDZN through the newly designed non reported ZrO2-Ag2O-MoO3-NC/PEDOT:PSS/GCE via an economical as well as novel electrochemical, current–potential (I-V), approach. Additionally, this proposed method is equally responsive towards both environmental and extracted real samples analysis on large scale.

Isothermal conversion of methane to methanol over Cu-CHA using different oxidants

Methane oxidation to methanol in cyclic processes using CuO-zeolites has traditionally employed O2 and N2O as oxidants. This study explores the use of Cu-CHA zeolite, demonstrating that CO2 can substitute O2 in an isothermal reaction at 400 °C, analogous to previous findings using Cu-MAZ. The use of in situ UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and density functional theory (DFT) theoretical calculations identified the formation of a binuclear copper hydroxide complex, Z-[CuOH-HOCu]2+-Z, on the Cu-CHA. Initial treatment using CO2 led to marginally superior catalytic activity, compared to the use of O2 alone, indicating the stability of the Z-[CuOH-HOCu]2+-Z complex against self-reduction at 400 °C. In subsequent cycles, activation with O2 facilitated the oxidation of adsorbed methanol, yielding water and reconstituting the active sites. Conversely, activation with CO2 led to the partial desorption of methanol, precluding water production and subsequent catalyst regeneration. The findings suggested that both O2 and CO2 activations necessitated a post-reaction water extraction step, followed by thermal treatment to replenish the active sites. Importantly, the results indicated that CO2 could be used as a viable alternative oxidant to O2 in this catalytic process, potentially enhancing the sustainability of industrial methanol production.

Enhancing the Light‐Driven Photocatalytic Degradation Activity of ZnO Nanoparticles With the Synergistic Incorporation of Er and Tb Elements

ABSTRACTThe existence of organic pollutants in aqueous media has become a vital issue and a critical threat to human health, where organic toxic dyes represent the major contaminants in wastewater. Over the past few years, photocatalytic techniques have garnered a lot of interest in dye removal from wastewater. In this study, a series of ErxTbxZn1 − 2xO nanophotocatalysts (where x = 0.00, 0.01, 0.03, and 0.05) were synthesized and coded as ZET0, ZET1, ZET2, and ZET3 NPs (nanoparticles). The chemical and physical characteristics of the NPs were investigated using Fourier‐transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy‐dispersive X‐ray (EDX) spectroscopy, and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS) techniques. Further examination by performing photocatalytic experiments, ZET1 NPs demonstrated effective Rhodamine B (RhB) dye degradation within 60 min. It was found that the kinetic rate constant values were 0.008, 0.097, 0.050, and 0.040 min−1 for ZET0, ZET1, ZET2, and ZET3 NPs, respectively. Aside from their remarkable photocatalytic degradation efficiency, these ZET1 photocatalysts are highly stable even after five consecutive cycles. In addition, the active species test revealed that the primary oxidation species involved in the photocatalytic process are holes (h+) and hydroxyl radicals (•OH), and a possible photocatalytic mechanism for degrading RhB by ZET1 photocatalysts was tentatively proposed. The enhancement of the photocatalytic degradation efficiency is due to the low recombination rate of photogenerated charge carriers, as well as a strong synergistic impact of Tb, Er, and ZnO components. Thus, the current study could offer a versatile strategy for the design of new and effective nano photocatalysts for wastewater purification in the future.

Optical and surface properties of Schiff base ligands and Cu(II) and Co(II) complexes

Objectives. To study the transition of electrons in 1,2-phenyl(4’-carboxy)benzylidene Schiff base ligand and transition metal ions, optical properties, as well as the surface chemistry of supported transition metals using diffuse reflectance spectroscopy (DRS); to study the roughness and morphology of the Schiff base ligand and its complexes using atomic force microscopy (AFM).Methods. DRS, AFM, and Fourier-transform infrared spectroscopy instruments were used to identify electron transitions, optical properties, and surface morphology in Schiff base ligands and their complexes.Results. The DRS revealed the d–d transitions and charge transfer shifts of all compounds, and helped identify the structure of the ligand. One of the optical properties studied was the energy gap calculation of the ligand and its complexes. The copper complex exhibited more semiconducting behavior with surface morphology properties such as surface roughness parameters lower than those of the ligand and the cobalt complex. This can be attributed to the smaller size of the copper atom, as well as lower electron transitions compared to the cobalt complex and the square planar bonding shape.Conclusions. In Schiff base ligands, the reflectance spectrum bands reveal three electron transitions: n→π*, π→π*, and σ→σ* transitions. In cobalt complexes, four transitions are indicated: 4A2(F)→4T1(F), 4A2(F)→4T1(P), charge transfer bands, and tetrahedral geometry. Copper complexes exhibit three transitions: 2B1g→2A1g, 2B1g→2Eg, and charge transfer bands, with a square planar geometry for their structure. The energy gap calculations were 2.42, 2.29, and 2.30 eV, respectively. In the case of the SH ligands, copper complexes, and cobalt complexes, all compounds exhibited semiconductor properties. However, the complexes displayed increased conductivity due to the influence of the metal and coordination structure.

Rational design of ZnO/SrTiO3 S-scheme heterojunction for photo-enhanced piezocatalytic hydrogen production

Photopiezocatalysis have been frequently investigated for hydrogen evolution reactions in recent years. Herein, ZnO, SrTiO3 and ZnO/SrTiO3 S-scheme heterojunction were investigated for photo/piezocatalytic hydrogen production. Piezocatalytic hydrogen production under ultrasonic vibration by using ZnO, SrTiO3 and ZnO/SrTiO3 was obtained as 270 µmol g-1h−1, 200 µmol g-1h−1 and 1265 µmol g-1h−1, respectively. In addition, ZnO/SrTiO3 S-scheme heterojunction showed 2200 µmol g-1h−1 photopiezocatalytic hydrogen production under simultaneous exposure to white LED light and ultrasonic sound. ZnO/SrTiO3 heterojunction displayed significantly higher hydrogen production rate due to the decreased charge recombination, increased charge transfer with strong piezoelectric polarization and internal electrical field. The piezoelectric effect of ZnO/SrTiO3 heterojunction is also confirmed by piezoresponse force microscope technique with butterfly and phase hysteresis loops. Also, piezoelectric coefficient of ZnO/SrTiO3 found about 2-folds higher than those of their pristine forms. Electron transfer and reaction mechanism of ZnO/SrTiO3 and activity differences are confirmed by advanced optical and electrochemical techniques such as diffuse reflectance spectroscopy, electronic impedance spectroscopy, Mott-Schottky calculation and chronoamperometry. The whole electrochemical measurements have been performed with or without mechanical stress and light irradiation, which signify their band bending properties, electron transfer mechanism and catalytic activities.

Enhancing hole-transport efficiency in (CH3NH3)2CuClxBr4-x perovskite solar cells through functionalization of multi-walled carbon nanotubes

This study addresses the conductivity limitation of conventional hole-transporting layers (HTLs) like Spiro-OMeTAD in perovskite solar cells. We integrate functionalized multi-walled carbon nanotubes (MWCNTs) into Spiro-OMeTAD and examine the impact of chemical oxidation/functionalization of MWCNTs on their application in perovskite solar cells. Various ratios of H2SO4/HNO3 mixture were employed to functionalize MWCNTs, with FTIR analysis confirming functional group attachments on the nanotube walls. Raman spectroscopy was utilized to analyze defect formation in the MWCNTs, while FESEM images displayed both the tubular structure and morphological alterations resulting from functionalization. XRD analysis was conducted to examine the structural variances resulting from different functionalization ratios. A lead-free copper-based perovskite (CH3NH3)2CuBr4-xClx (x = 0.5), synthesized via a straightforward solution method, served as the active material for solar cells. The XRD assessment of the active material confirmed perovskite formation, with morphological analysis revealing a layered structure. Diffuse Reflectance Spectroscopy (DRS) measurements yielded a bandgap of approximately 1.86 eV for the perovskite. Dark I–V measurements were executed for Spiro-OMeTAD films incorporated with pure and functionalized MWCNTs, showcasing improved conductivity attributed to charge carrier conduction via defect passivation. Hybrid solar cells were fabricated with structures such as TiO2/(CH3NH3)2CuBr4-xClx (x = 0.5)/Spiro-OMeTAD/Ag, and TiO2/(CH3NH3)2CuBr4-xClx (x = 0.5)/functionalized MWCNTs/Spiro-OMeTAD/Ag. These cells demonstrated enhanced stability, retaining over 65 % of their initial efficiency after 10 days of storage, attributed to improved moisture permeability inferred from contact angle measurements and XRD analysis. Photovoltaic characterization revealed significant improvements in fill factor (∼70 %), short-circuit current density (2.94 mA), open-circuit voltage (0.70 V), and power conversion efficiency (PCE) (1.6 %) for the FTO/TiO2/(CH3NH3)2CuCl0·5Br3.5/Spiro-MWCNT-1/Ag device.