Recombination Rate Of Charge Carriers Research Articles

Black TiO2‐g‐C3N4 heterojunction coupled with MOF (ZIF‐67)‐derived Co3S4/ nitrogen‐doped carbon hollow nanobox

AbstractIn this research, the ultrasound (US) technique was applied as a facile synthesis method for preparing the black TiO2‐g‐C3N4 type II heterojunction, coupled with a Schottky junction MOF (ZIF‐67)‐derived x wt% Co3S4/nitrogen‐doped carbon (NC) (x = 3, 10, and 15) with hollow nanobox (HNB) morphology, as a smart nanoheteroarchitecture (NHA) photocatalyst to enhance visible‐light photocatalytic activity. Additionally, the solvothermal synthesis route was employed to fabricate the MOF (ZIF‐67)‐derived Co3S4/NC cubic hollow nanoboxes (CHNBs) before the pyrolysis process. The black TiO2‐g‐C3N4 wt% Co3S4/NC (TiCN‐15% CoS/NC) NHAs exhibited high photocatalytic activity in degrading methylene blue. The synergetic effect of all components in black TiCN‐x wt% CoS/NC NHAs resulted in efficient electron‐hole pair separation and charge mobility on Co3S4/NC HNB and g‐C3N4 surfaces, which led to a highly effective recombination rate of charge carriers and an excellent improvement in photocatalytic performance.

Theoretical analysis of backside polycrystalline silicon layer in the TOPCon solar cells

As an upgraded version of passivated emitter and rear cell (PERC) solar cells, the performance of tunnel oxide passivating contacts (TOPCon) solar cells is very dependent on the silicon oxide layer and poly-Si layer. We found that different crystallization rates or doping of germanium, carbon and other elements in poly-Si can change the band gap of poly-Si, which has an impact on the efficiency (Eff) of TOPCon solar cells. Therefore, the appropriate band gap is particularly important. At the same time, the internal defect of poly-Si also have great influence on the performance of solar cells. The simulated band diagram, charge carrier concentration and recombination rate were used to deeply explore the defect in poly-Si and the influence of poly-Si with different band gap on the performance of TOPCon solar cells.

Construction of Z-scheme FeTiO3/g-C3N4 heterojunction system: Characterization and statistical optimization of photocatalytic behavior under visible light irradiation

Construction of low-cost and green photocatalysts is an emerging subject in wastewater treatment processes. In the present study, FeTiO3/g-C3N4 (FTO/CN) photocatalytic system was constructed via ultrasonication followed by thermal mixing method. The synthesized FTO/CN hybrids with different CN ratios were characterized by SEM-EDX, TEM, XRD, XPS, XRF, UV–vis DRS, PL techniques. The photodegradation efficiencies of the hybrid materials were systematically examined towards decolorization of tartrazine dye under visible light irradiation. Using the FTO/CN hybrid catalyst, the photocatalytic efficiency of the pristine FeTiO3 greatly enhanced from 39.8% to 90.5%, which was attributed to appropriate band alignment and heterojunction transfer mechanism to hinder the recombination rate of photo-excited charge carriers. The effects of initial pollutant concentration (10–30 mg/L), catalyst dosage (0.1–0.5 g/L) and peroxymonosulfate (PMS) concentration (1–3 mM), as independent variables on the degradation efficiency were investigated by response surface methodology with Box-Behnken design model. Under optimized conditions (R2 = 0.99, R2adj = 0.98), the highest removal efficiency (100 %) was obtained with 0.5 g/L catalyst, 10 mg/L initial dye concentration and 3 mM PMS. The photodegradation efficiency of the hybrid system was investigated towards other pollutants (Sunset yellow, orange II, tetracycline and ciprofloxacin) and recyclability of the catalyst was also explored. The obtained results demonstrated that the hybridization of FeTiO3 particles with g-C3N4 sheets greatly enhanced the photocatalytic properties of FeTiO3 under different conditions.

Oxidized Graphitic-C3N4 with an Extended π-System for Enhanced Photoelectrochemical Property and Behavior

In this work, an oxidized g-C3N4 film was successfully synthesized using a two-step acid treatment and electrophoretic deposition method. The delocalized π-system of the oxidized g-C3N4 film was extended via an annealing treatment. We investigated the influence of hydrogen bonding reversibility and the oxidation treatment of g-C3N4 on the photoelectrochemical property and photocathodic protection for 304 stainless steel (304 SS). The resulting oxidized g-C3N4 photoelectrode with an extended π-system presents a remarkably enhanced photogenerated electron transfer capability from the photoelectrode to 304 SS (photoinduced OCP negative shift of −0.55 VAgCl) compared with oxidized g-C3N4 and protonated g-C3N4. The oxidation of g-C3N4 facilitates the formation of a porous structure and the introduction of abundant oxygen functional groups, which could promote the effective separation and transport of photogenerated electron–hole pairs. The hydrogen bonding reversibility contributes to the extension of the delocalized π-conjugation system, which could enhance light absorption efficiency. Meanwhile, the annealing treatment is beneficial for prolonging the lifetime of photoelectrons, which could reduce the recombination rate of charge carriers. In addition, to understand how the oxidation treatment and annealing treatment affect the charge transfer behavior, the electronic band structure was investigated, and we found that the oxidized g-C3N4 film with an extended π-system possesses a more negative conduction band position, which could reduce the energy barrier of the photogenerated electron transfer.

Construction of rGO/BP/COF high-low heterojunction for efficient photocatalytic hydrogen evolution

The covalent organic frameworks (COFs) have emerged as potential photocatalysts for solar-driven hydrogen evolution, but the disadvantage that photogenerated electrons and holes are prone to recombination limits their applications. Here, a rGO/BP/TpPa-1 high-low heterojunction with electron acceptors was prepared by integrating reduced graphene oxide (rGO) and black phosphorus (BP) into COF TpPa-1 to reduce the recombination rate of photoinduced charge carriers. The photocatalytic hydrogen evolution rate reached 18.09 mmol h−1 g−1, about 3.3 times higher than pure TpPa-1. Here, a two-step photogenerated electron transfer mechanism is proposed. Firstly, a high-low heterojunction is formed between TpPa-1 and BP through an internal electric field from BP to TpPa-1, facilitating photogenerated electrons transfer from TpPa-1 to BP, then rGO attached to the BP surface acts as an electron acceptor, further collecting photogenerated electrons for reaction. This work provides a novel strategy for synthetizing efficient COF-based photocatalysts.

Effect of Bi doping on the opto-electronic properties of ZnO nanoparticles for photodetector applications

Bi (0, 1, 3 and 5 wt%) doped ZnO nanopowders were generated in this study using a simple and inexpensive wet chemical method. X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning electron microscopy, photoluminescence spectroscopy, UV–Vis-DRS, studies are used to evaluate the effect of dopants in ZnO sample. Crystallite size and grain size of the samples were reduced and enhanced the surface to volume ratio due to Bi doping. Oxygen vacancies and shrinkage of bandgap plays a significant role in enhancement of photosensing property. Bi doped ZnO nanopowders had better photosensing activity than pristine ZnO nanopowders. Also, the doped metal ions improved the photosensing efficiency by increasing electromagnetic wave absorption and inhibiting the recombination rates of charge carriers resulting raise of hole-electron pair production. The significant photosensing parameters responsivity (R), detectivity (D*) and external quantum efficiency (EQE) of the 3 % of Bi doped ZnO sample exhibited maximum values such as 0.163 AW−1, 1.26 × 1010 Jones and 53% respectively. The findings of this present study show that the3 % Bi doped ZnO can be an excellent photosensing material.

Synergistic photocatalytic performance through Z-Scheme charge transfer in organic dye degradation using α-MnO2 nanorods and Co3O4 nanoparticles combined with eggshell derived hydroxyapatite

HAp-α-MnO2-Co3O4 nanocomposite was prepared by the wet impregnation technique. Various analytical techniques were used to study the structural, morphology and photophysical characteristics. In the present study, the degradation of MB dye under the visible light irradiation in existence of HAp-α-MnO2-Co3O4 nanocomposite has been examined and the detailed mechanism for the photocatalytic degradation was discussed. The improved photocatalytic degradation activity over the HAp-α-MnO2-Co3O4 nanocomposite can be ascribed to the efficient high generation and low recombination rate of charge carriers under the UV-Visible light. Also, the key features for HAp-α-MnO2-Co3O4 nanocomposite including enhancement of light absorbance, recombination rate of photogenerated charge carriers have also been found for the nanocomposites. Based on photocatalytic degradation, it was found that the HAp-α-MnO2-Co3O4 nanocomposite has the highest photocatalytic activity among all freshly prepared samples. In particular, the MB dye was almost completely degraded (95.5 %) by exposure to UV–visible light in 60 min of irradiation, the observed degradation result was relatively higher than that of pristine HAp, α-MnO2 and Co3O4, respectively. HAp-α-MnO2-Co3O4 nanocomposite efficiently degraded 94.42 % colorless phenol, demonstrating its dual ability to break down hazardous dyes and organic compounds under the same conditions. In addition, the HAp-α-MnO2-Co3O4 nanocomposite has a good recyclability of 90.25 % after five successive cycles. These observed results show that the HAp-α-MnO2-Co3O4 nanocomposite is an environmentally friendly material for environmental remediation.

Unveiling the multifaceted applications of magnetically responsive chitosan capped ZnS QDs for sensing and annihilation of pharmaceutical drugs

The persistence of active pharmaceutical ingredients in water bodies has lead to detrimental impacts on public health as well as deteriorated aquatic resources at breakneck pace. To address this, highly fluorescent chitosan capped ZnS QDs (CZS QDs) were integrated with nickel ferrite nanoparticles (NF NPs) through ultrasonic assisted method to yield a series of magnetically responsive CZS-xNF nanohybrids (x = 5, 10, 15 and 20 wt% of NF). The successful fabrication of nanohybrids were affirmed through various techniques such as Fourier transform infra-red spectroscopy (FT-IR), powder X-ray diffraction (XRD), X-ray photoelectron microscopy (XPS), high resolution transmission electron microscopy (HRTEM), vibrating sample magnetometer (VSM) and diffused reflectance spectroscopy (DRS). The dual applicability of CZS-xNF nanohybrid was witnessed for the detection of pharmaceutical waste by fluorescence sensing and their concomitant annihilation via visible light driven photodegradation reactions. The developed nanohybrid showed exceptional selectivity towards tetracycline antibiotics, with ultra-low limit of detection of 0.53 μM for tetracycline (TC) and 0.30 μM for minocycline (MC), respectively. The fluorescent sensor was also analysed for trace level detection of tetracyclines in real water samples that showed satisfactory recoveries of 90–106%, depicting practical applicability of sensor. Additionally, the excellent photocatalytic features of synthesized nanohybrid prompted their use in photodegradation of TC and MC and a superior photocatalytic performance was achieved in comparison to CZS QDs. The enhanced photocatalytic performance of CZS-xNF nanohybrid can be attributed to type-I charge transfer mechanism, which resulted in efficient charge separation and reduced photo-induced recombination rate of charge carriers. The nanohybrids were recyclable up to four cycles after being utilized in sensing and photocatalysis, thus offering a promising strategy for environmental remediation through synchronized sensing and extirpation of pharmaceutical waste.

Fabrication of an S-Scheme Heterojunction Photocatalyst MoS2/PANI with Greatly Enhanced Photocatalytic Performance.

As a promising catalyst, MoS2 has been widely studied owing to its high chemical reactivity, excellent electrical carrier mobility, good optical properties, and narrow band gap. However, the high recombination rate of photoinduced charge carriers limits its practical application in photocatalysis. In this study, MoS2 was coupled with PANI to fabricate an S-scheme heterojunction MoS2/PANI. The synthesized products were characterized systematically, and their photocatalytic properties were evaluated by photocatalytic degradation of norfloxacin (NOR) and rhodamine B (RhB). The obtained results indicated that the fabricated MoS2/PANI inorganic-organic heterojunction displayed tremendously enhanced photocatalytic activity. The degradation efficiencies for 60 mg L-1 of NOR and RhB are 86 and 100% under the simulated sunlight irradiation for 1 h with 10 mg of catalyst, which are 13 and 47 times higher than those of pure MoS2, respectively. Interestingly, it is superior to the previously reported related materials. The remarkably enhanced photocatalytic activity of MoS2 is assigned to the high charge conductivity feature of PANI and the formed S-scheme heterojunction that result in a steric separation of holes and electrons and conserve the initial powerful redox ability of the parent catalysts. This study provides a facile method to greatly improve the photocatalytic activity of MoS2 and facilitates its application for highly efficient removal of organic pollutants, such as antibiotic drugs and organic dyes, utilizing solar energy.

Facile synthesis of Cu-doped BiVO4 using domestic microwave-assisted chemical precipitation method with fleeting time of microwave irradiation for the photocatalytic application

Semiconductor-based visible light active photo-catalyst has been synthesized through microwave-assisted chemical precipitation method under acidic pH with minimal time of reaction using microwave irradiation. The monoclinic crystal phase of the material with no impurity is confirmed with XRD data. We can observe slight left shift after doping with copper (Cu) in 2Θ peak of XRD data. SEM analysis exhibits a gradual change in morphology with the increase in doping concentration. UV–Vis data confirms an improvement in absorption with the increase in dopant concentration. PL analysis further clarifies the change in recombination rate of photo-induced charge carriers. Photocatalysis has been tested with methylene blue (MB) synthetic dye. The maximum percentage of degradation was determined to be 61.08% and it is obtained for 0.25% Cu-doped BiVO4. It is also observed that 0.25% Cu-doped BiVO4 has lower energy band gap value, i.e., 2.03 eV and lesser PL intensity than pure un-doped BiVO4. The HRTEM analysis proves that 0.25% Cu-BiVO4 is well crystalline in nature with the d spacing corresponding to (121) plane of BiVO4.

Synthesis of efficient light harvesting Cr, N Co-doped TiO2 nanoparticles for enhanced visible light photocatalytic degradation of xanthene dyes; eosin yellow and rose bengal.

To solve the problem of water pollution, using environment friendly and cost effective method in short time is the need of hour. In this work, chromium (Cr) and nitrogen (N) co-doped TiO2 nanoparticles were synthesized and were used for the photocatalytic degradation of dyes under visible light. The synergistic effect of metal and non-metal co-dopants added would result in appropriate reduction of band gap {from 3.2 eVof TiO2 to 2.67eV}, decrease in recombination rate of charge carriers by trapping electrons and holes, and in better light harvesting capacity. Nanoparticles were synthesized by sol-gel method and characterized using ultraviolet-visible (UV-VIS) spectroscopy, fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), zeta potential, X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET)analysis, field emission scanning electron microscopy (FE-SEM), and RAMAN spectroscopy. Eosin yellow (EY) and rose bengal (RB) were subjected to photocatalytic degradation under solar light to check the photocatalytic activity of the synthesized nanoparticles. Effects of dye concentration, the concentration of nanoparticles, time, and pH were investigated to optimize the parameters. The results obtained were remarkable for 20ppm EY solution took 10min using 1 gL-1 NPs at pH 3 and 10ppm RB solution took 5min using 0.75 gL-1 NPs at pH 5.78 (original pH) for complete degradation. Kinetics studies were also performed and both dyes followed pseudo-second-order kinetics with R2 values 0.99312 and 0.99712 for EY and RB, respectively. The study of degraded products was conducted using high-performance liquid chromatography (HPLC) hyphenated with electron spray ionization mass spectroscopy (ESI-MS) (LC-MS) and possible degradation pathways were made for both dyes. A reusability test was also performed showing the efficiency of the particles was up to 88% after 3 cycles of use. These notable results can be attributed to the efficient removal of organic pollutants using the proposed dopants in this study.

The photocatalytic and antibacterial potential of highly efficient S-scheme binary S-gC3N4@Co-zinc ferrite nanocomposite

Dye contamination of water resources is a global issue threatening aquatic life and humans due to its persistence, toxicity, and carcinogenic potential; it must be resolved immediately. This paper reports the hydrothermally synthesized S-gC3N4/cobalt-zinc ferrite (S-GCN/Co-ZF) binary s-scheme heterojunction and its remarkable characteristics, including the lowest rate of charge carrier recombination and the highest absorption of solar energy with excellent photocatalytic and antibacterial potential. The photocatalytic performance of Co-ZF nanoparticles (0.5–12.5 wt%) was tested in the first phase to determine the ideal Co-doping into the ZF. The highest methylene blue photocatalytic degradation was shown by the as-synthesized 6.5% Co-ZF nanoparticles, which were then disseminated on sulphur-doped graphitic carbon nitride (S-GCN) nanosheets as an active constituent to create a series of 25–70 wt % S-GCN@6.5% Co-ZF nanocomposites in the subsequent stage. The optimized composite (55% S-GCN@6.5% CO-ZF) performed excellent photocatalytic performance and accomplished about 93% degradation of methylene blue within 120 min. The antibacterial potential of ZF, S-GCN, 6.5% Co-ZF, 55% S-GCN@6.5 %Co-ZF was examined against Escherichia coli and Bacillus subtilis bacteria. Among these samples, the 55% S-GCN@6.5%CO-ZF nanocomposite demonstrates excellent antibacterial potential. All the synthesized photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-disperse X-ray (EDX), Fourier transform infrared (FTIR) and ultraviolet–visible (UV–Visible) spectroscopic techniques.

Scalable ambient conditions-based fabrication of flower-like bismuth vanadate (BiVO4) film incorporating defects aimed at visible-light-induced water-splitting application

The scalable application of bismuth vanadate (BiVO4) in photoelectrochemical water splitting is restricted by its low charge separation efficiency and slow water oxidation kinetics. Here, modified BiVO4 photoanodes were fabricated at ambient conditions with polyethylene glycol (PEG) and potassium hydroxide (KOH) for improving the electron-hole generation rate and lowering the charge carrier recombination rate. Modification by PEG produced 3D flower-like BiVO4 microspheres, along with Bi5+, Bi(3−x)+, and V4+ species onto the PEG-BiVO4 surface, which were accompanied by oxygen vacancies (OVs) working in tandem with these species and acting as surface-active intermediates, thereby facilitating hole transfer to the electrolyte. Under visible light irradiation (100 mW/cm2), 3D flower-like PEG-BiVO4 microspheres produce the maximum photocurrent density of 5.75 mA/cm2 in water splitting at 1.23 V against a reverse hydrogen electrode (RHE). The superior photoelectrochemical performance of PEG-BiVO4 over its counterparts is attributed to the incorporation of 3D flower-like microspheres and band structure modulation by the O vacancies, Bi(3−x)+, Bi5+, and V4+ species. The synthesized PEG-BiVO4 is expected to attract attention as a scalable photocatalyst for oxidation of water because it is easy to synthesize at room temperature and it exhibits superb photocatalytic performance.

BiOI/PPy/cotton photocatalytic fabric for efficient organic dye contaminant degradation and self-cleaning application

Water pollution caused by industrial organic dyes poses a serious threat to human health and the ecological environment. Natural cellulose fibers functionalized with photocatalysts are regarded as promising materials for removing organic dyes. However, the immobilized photocatalysts usually exhibit a high recombination rate of photo-generated charge carriers, which seriously reduces the photocatalytic efficiency. Herein, a photocatalytic functional cotton fabric was prepared by a two-step process, including in-situ gas-phase polymerization of pyrrole and layer-by-layer self-assembly process of bismuth oxyiodide. The conjugated molecular structure of polypyrrole (PPy) conductive polymer could effectively facilitate the separation of photo-generated electron-hole pairs of bismuth oxyiodide photocatalyst on the fiber surface. The ability of composite fabrics to absorb visible light was greatly enhanced. The photocatalytic functional fabric exhibited a high photocatalytic degradation efficiency towards organic dye contaminants. On the other hand, the PPy nano-layers on cotton fibers induced bismuth oxyiodide nanosheets to self-assemble a more dense porous structure, which trapped a large amount of tiny air. The prepared fabric exhibited an obvious superhydrophobicity with a water contact angle above 150° and an excellent self-cleaning ability toward liquid/solid contaminants. This work provides a new insight into water treatment through the development of efficient photocatalytic textiles.

A novel tertiary magnetic ZnFe2O4/BiOBr/rGO nanocomposite catalyst for photodegrading organic contaminants by visible light

A novel tertiary magnetic ZnFe2O4/BiOBr/rGO visible light-driven photocatalytic system was successfully synthesized from graphite, bismuth nitrate pentahydrate, iron (III) nitrate, and zinc nitrate precursors. The produced materials were characterized regarding micro-structure, chemical composition and functional groups, surface charge properties, photocatalytic characteristics such as band gap energy (Eg), recombination rate of charge carriers, and magnetic properties. ZnFe2O4/BiOBr/rGO heterojunction photocatalyst exhibited a saturation magnetization of 7.5 emu/g, and a visible light response (Eg = 2.08 eV). Thus, under visible light, these materials could generate effective charge carriers responsible for forming free hydroxyl radicals (HO•) for degrading organic pollutants. ZnFe2O4/BiOBr/rGO also exhibited the lowest charge carriers recombination rate compared to all individual components. The construction of ZnFe2O4/BiOBr/rGO system resulted in 1.35 to 2.55 times higher in photocatalytic degradation of DB 71 compared to individual components. At the optimal conditions (0.5 g/L catalyst load and pH 7.0), the ZnFe2O4/BiOBr/rGO system could completely degrade 30 mg/L DB 71 after 100 min. DB 71 degradation process was best described by the pseudo-first-order model, with the coefficient of determination within the range of 0.9043–0.9946 for all conditions. HO• radicals were mainly responsible for degrading the pollutant. The photocatalytic system could be effortlessly regenerated, very stable, which showed an efficiency of >80.0 % after 5 repetitive runs regarding the DB 71 photodegradation. The photocatalyst was easily recovered by a magnet. This research provides a novel approach for producing an effective and practical photocatalyst that can be applied in real organic pollutants-containing waste water treatment systems.

Zn/Fe bimetallic modified Spartina alterniflora-derived biochar heterostructure with superior catalytic performance for the degradation of malachite green

In this study, the synchronous magnetized carbonization method was utilized for preparing photocatalysis ZnO-Fe@SC heterostructure, which exhibited degradation efficiency 99.14% (60 min) for malachite green (200 mg/L) and could still maintain good performance after 5 cycles. The prepared ZnO-Fe@SC was analyzed using UV–Vis DRS, PL, SEM, TEM, BET, FTIR, XPS and VSM, and LC–MS for degradation products. The results indicate that photocatalyst has favorable magnetic properties, chemical stability and low charge carriers (e−/h+) recombination rate. The modification of bimetals enables the composite photocatalyst to enhance the intensity of photogenerated electron transition. Moreover, quenching experiment revealed that the photo-generated holes (h+) and superoxide radicals (·O2−) were the dominant active species during the photocatalytic process, which degraded malachite green into small molecules by demethylation, deamination, ring-opening reactions as deducted from LC–MS analysis. ZnO-Fe@SC was prepared using a green, safe, low cost and operable synthetic method, which has a broad market potential in the field of environmental remediation.Graphical

One-step synthesis of porous thin-layered graphitic carbon nitride for enhanced photocatalytic dye degradation

The application of graphitic carbon nitride (g-C3N4) as a non-metallic photocatalyst for removing harmful pollutants in the wastewater environment has received considerable attention in recent years. Nevertheless, its low activity is primarily restricted by a high rate of charge carrier recombination. Herein, a green and straightforward method for synthesizing small-sized porous thin g-C3N4 nanosheets directly from urea solution has been developed. This new photocatalyst can effectively remove 99.3% of rhodamine B within 15 min, exhibiting a degradation rate 16.8 times greater than that of conventionally synthesized bulk g-C3N4, under visible light irradiation. Additionally, this photocatalytic efficiency is comparable or even superior to that of previously reported literature, while requiring significantly less catalyst usage. From the experimental results, we have confirmed that the outstanding structural property as well as the stronger oxidizability of the valence-band holes (h+) are responsible for its greater photocatalytic activity. Its increased specific surface area and abundant pore structure significantly improve contaminant adsorption and charge separation and transfer. Meanwhile, the positive shift of the valence band enhances the oxidation of photogenerated h+, resulting in higher photocatalytic activity. This work can provide newly insights for designing highly efficient and easily-constructed g-C3N4 photocatalysts for practical photocatalytic water treatment applications.

Synthesis of two-dimensional CeO2-δ-GQD composites and their structural and optical properties

The present study reports on the synthesis of two-dimensional (2D) ceria and graphene quantum dots (CeO2-δ-GQD) composites and their functional properties. Composites were prepared by a simple liquid phase deposition (LPD) method followed by a thermal treatment in air at 250 and 400 °C. The structural and optical properties of composites were investigated by X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), High-Resolution Transmission Electron Microscopy (HR-TEM), Raman spectroscopy, Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), UV-Vis and photoluminescence (PL). The composites consist of crystalline CeO2-δ regions of about 1.8–2.9 nm in size, coexisting with highly disordered GQDs areas. The CeO2-δ-GQD composites experience gradual dehydration and oxidation of carbon processes during thermal treatment, influencing the CeO2 crystal size, Ce3+/Ce4+ ratio, and O vacancies presence. These effects allow for the control of some of the composite functional properties. Specifically, the CeO2-GQD250 composites exhibit a low recombination rate of charge carriers due to the synergistic interaction between the components and low presence of Ce3+. In contrast, the CeO2-GQD400 composites show a high Eg of 3.8 eV (Eg ∼3.2 eV for CeO2NPs) associated with a CeO2 quantum size effect and extremely low fraction of GQDs.

Solar Light-Induced Photocatalytic Response of BiOCl/PANI Composite towards the Degradation of Tetracycline

Photocatalytic degradation has gained much attention as a means of reducing water contamination as, with increasing industrialization and population growth, water pollution is a menace to both individuals and the environment. In this respect, metal oxide photocatalysts demonstrate effectiveness due to their excellent properties, such as their narrow band gap and low recombination rate of charge carriers. Here, various weight ratios of BiOCl/PANI composites have been synthesized by the simple wet chemical method. The crystallinity, oxidation state and surface chemical composition of the elements were analyzed by XRD and XPS techniques. FESEM and HRTEM images verified the formation of BiOCl nanosheets, covered well with PANI nanofibers, while EDX spectra revealed the uniform distribution of elements. The high surface area of the photocatalyst with a mesoporous nature was revealed by BET analysis. Low recombination rate and narrow band gap, suitable for photocatalysis, were confirmed by PL and UV–DRS spectroscopy. The photocatalytic performance of the photocatalyst was tested for the photodegradation of rhodamine-B (Rh-B) and tetracycline (TC) under natural sunlight irradiation. Kinetic results demonstrated that the 15% BiOCl/PANI hybrid exhibits excellent photocatalytic activity, degrading 97% of Rh-B and 77% of TC with a high rate constant (for Rh-B 0.0236 min−1 and for TC 0.0106 min−1). Trapping experiments highlighted that O2•− radicals play a vital role in the photodegradation mechanism. The reusability studies confirmed the good stability of the catalyst for the degradation of Rh-B (~85%) after five sequential runs. Considering its superior properties and ease of preparation, the synthesized photocatalyst can be used for ecological remediation.

Growth of TiO2–CdO coated films: A brief study for optoelectronic applications

Current work reports the deposition of pure and TiO2 doped CdO printed films on glass substrate via cost-effective screen-printing method and then sintered at 550 °C for 10 min. The pure TiO2, CdO and TiO2–CdO coated films were used to investigate the structural, morphological and opto-electrical properties by different analytical techniques. X-ray diffraction pattern of polycrystalline doped analogue confirms the existence of TiO2 anatase phase and cubic phase of CdO with a maximum diffraction of (101) plane. Surface morphology is derived from scanning electron microscopy finding out porous images along with EDS results to confirm the desired composition. The spectra of UV–Vis diffused reflectance spectroscopy and photoluminescence absorbance peaks show a red shift due to change in reflectance. IR transmittance spectra recorded in 4000-400 cm−1 region exhibits the stretching modes of O–Ti–O and Cd–O groups present in these samples. The current vs. voltage (IV) characteristics and direct current conductivity measurement shows p-n junction diode behaviour. All the parameters were calculated and described in-depth, including structural, optical and electrical properties. The obtained results suggest that TiO2–CdO thick film could be used in optoelectronic applications due to the shift in optical radiation absorption to visible region, reduction in recombination rate of charge carriers and increase in electrical conductivity.