Recombination Of Electron-hole Pairs Research Articles

Construction of Ni–P/TiO2 Schottky heterojunction via photo-deposition to enhance photocatalytic hydrogen evolution activity

Photocatalytic hydrogen evolution (PHE) is sustainable and environmentally friendly. Titanium dioxide (TiO2) is commonly chosen as a photocatalyst of PHE due to its non-toxicity, robust stability, and superior photocatalytic activity. However, the efficacy of TiO2 is restricted by rapid electron–hole pair recombination, limited electron mobility, and sluggish surface reactions. To address these issues, we have synthesized a Ni–P alloy onto the surface of TiO2 (Ni–P/TiO2) using a safe and efficient photo-deposition method, thereby constructing a Schottky heterojunction photocatalyst. The construction of the heterojunction significantly reduces the recombination rates of photoinduced electron–hole pairs and enhances the charge transfer rates within the photocatalyst. Additionally, the incorporation of the Ni–P alloy increases the density of oxygen vacancies, providing abundant active sites for the reduction reaction. The metallic properties of the Ni–P alloy improve the overall light absorption capacity. As a result, Ni–P/TiO2 exhibits exceptional photocatalytic hydrogen production capability. When the mass ratio of the Ni–P alloy to TiO2 is 12 wt. %, the hydrogen evolution rate reaches its maximum value at 1654.2 μmol g−1 h−1. Furthermore, density functional theory calculations substantiate that the formation of an internal electric field between the Ni–P alloy and TiO2 facilitates electron migration and carrier separation. This investigation provides a promising strategy for constructing TiO2-based Schottky heterojunctions to improve the photocatalytic hydrogen evolution performance.

Enhanced Photocatalytic Hydrogen Generation from Methanol Solutions via In Situ Ni/Pt Co-Deposition on TiO2

TiO2 is widely utilized as an excellent photocatalyst in energy production. However, its rapid electron and hole recombination confers poor photocatalytic activity. Cocatalysts are essential for increasing photocatalytic efficacy by introducing improved electron transmission and enlarging the active site. Herein, the photocatalytic degradation of aqueous methanol solution to generate hydrogen was studied with the simultaneous in situ deposition of metals (M = Ag, Cu, Ni, Pd, and Pt) on the TiO2 surface. Adding methanol to water and incorporating a bimetallic cocatalyst enhanced hydrogen production by reducing the electron–hole pair recombination. The studied metal ions could be reduced by the conduction band electrons of TiO2 for the in situ simultaneous deposition of metal. The larger work function value of the studied metals favored the Schottky junction formation, which contributed to increasing photocatalytic efficiency. Among these simultaneous metal-deposited photocatalysts, maximal photocatalytic hydrogen production was achieved with NiPt/TiO2. The optimal component was 0.01 wt.% Ni/1.0 wt.% Pt for TiO2. The hydrogen evolution with NiPt/TiO2 was approximately 341 and 1.3 times better than that with pure TiO2 and Pt/TiO2, respectively. A potential reaction pathway for photocatalytic hydrogen production from an aqueous methanol solution over NiPt/TiO2 photocatalyst has also been proposed.

Magnetic field and photon co-enhanced S-scheme MXene/In2S3/CoFe2O4 heterojunction for high-performance lithium-oxygen batteries

Under the spotlight for their potential to reduce over-potential, photo-assisted Li-O2 batteries still face a key challenge: the rapid recombination of photo-generated electron-hole pairs, which limits their efficiency. In this study, we address this limitation by designing a Li-O2 battery that integrates both photo and magnetic field assistance, using an S-scheme MXene/In2S3/CoFe2O4 heterojunction photocathode. This unique combination enhances visible light absorption and generates a strong built-in electric field, facilitating effective charge separation and boosting photocatalytic activity. During discharge, photo-generated electrons participate in the oxygen reduction reaction, while photo-induced holes contribute to the decomposition of discharge products during charging. Furthermore, the introduction of a magnetic field, confirmed through vibrating sample magnetometer, Mössbauer spectroscopy, X-ray absorption near edge structure, and cyclic voltammetry analyses, enhances electron-hole separation via Lorentz forces and spin-orbit coupling, accelerating the formation and decomposition of Li2O2. With this synergistic approach, the battery achieves a high specific capacity of 26,500mAhg-1, ultra-low oxygen reduction/evolution reaction over-potentials of 0.08V/0.17V, and a long cycle life of 2000 cycles with energy efficiency of 98.11%. This work demonstrates the promising potential of combining photo and magnetic field effects to improve the electrochemical performance of Li-O2 batteries, opening new avenues for high-performance energy storage systems.

Versatile g-C3N4/AlOOH Nanocomposites: Efficient photocatalyst for Dye Removal, Algae Inactivation, and Glucose Detection.

Visible light photocatalysts hold great promise for water purification, yet research on highly efficient, non-toxic photocatalysts is limited. This study synthesized novel g-C3N4/AlOOH photocatalytic nanocomposites via thermal condensation, enhancing adsorption and visible light degradation by 36-fold and 11-fold, respectively, compared to g-C3N4 alone. The nanocomposites achieved a 98% removal rate of methyl orange under xenon lamp irradiation (>400 nm) for 1 hour. This study marked the first demonstration of using a low-power LED (0.6W) for photocatalytic algae inactivation in an aquarium ecosystem. Fluorescence spectroscopy showed a 98.9% removal efficiency of chlorophyll a after 12 hours of photocatalyzing by g-C3N4/AlOOH, doubling that of g-C3N4 alone. Algae inactivation was attributed to rupture, dehydration, and changes in dissolved organic matter. Hole (h+) trapping experiments identified them as the primary active species for degrading methyl orange and algae. Materials analyses confirmed the formation of g-C3N4-AlOOH heterostructures, high surface potential, and Type II heterojunctions, which reduce electron-hole pair recombination. Furthermore, g-C3N4/AlOOH demonstrated selective non-enzymatic fluorescence detection of glucose, showing a linear relationship in 0∼4 mM, suitable for tears glucose detection. This study offers crucial insights and strategies for designing novel, non-toxic, high-performance visible light photocatalytic materials, efficient dye degradation, algae inactivation, and selective glucose detection.

Combining Cocatalyst and Oxygen Vacancy to Synergistically Improve Fe2O3 Photoelectrochemical Water Oxidation Performance

Considering the poor conductivity of Fe2O3 and the weak oxygen evolution reaction associated with it, surface hole accumulation leads to electron hole pair recombination, which inhibits the photoelectrochemical (PEC) performance of the Fe2O3 photoanode. Therefore, the key to improving the PEC water oxidation performance of the Fe2O3 photoanode is to take measures to improve the conductivity of Fe2O3 and accelerate the reaction kinetics of surface oxidation. In this work, the PEC performances of Fe2O3 photoanodes are synergistically improved by combining loaded an FeOOH cocatalyst and oxygen vacancy doping. Firstly, amorphous FeOOH layers are successfully prepared on Fe2O3 nanostructures through simple photoassisted electrodepositon. Then oxygen vacancies are introduced into FeOOH-Fe2O3 through plasma vacuum treatment, which reduces the content of Fe-O (OL) and Fe-OH (-OH), jointly promoting the generation of oxygen vacancies. Oxygen vacancy can increase the concentration of most carriers in Fe2O3 and form photo-induced charge traps, promoting the separation of electron holes and enhancing the conductivity of Fe2O3. The other parts of -OH act as oxygen evolution catalysts to reduce the reaction obstacle of water oxidation and promote the transfer of holes to the electrode/electrolyte interface. The performance of FeOOH-Fe2O3 after plasma vacuum treatment has been greatly improved, and the photocurrent density is about 1.9 times higher than that of the Fe2O3 photoanode. The improvement in the water oxidation performance of PEC is considered to be the synergistic effect of the cocatalyst and oxygen vacancy. All outstanding PEC response characteristics show that the modification of the cocatalyst and oxygen vacancy doping represent a favorable strategy for synergistically improving Fe2O3 photoanode performance.

Silver and Titanium Oxides Coated on g-C3N4 Nanocomposite for Photocatalytic Degradation of Mixture of Brilliant Green-Congo Red Dyes and Ciprofloxacin Antibiotic Under Visible Light Irradiation

Silver and titanium oxides coated graphitic carbon nitride (Ag2O/TiO2/g-C3N4) nanocomposite was created by a single-step thermal polymerization. The Fourier Transform infrared (FT-IR), UV-visible absorption spectroscopy (UV-vis), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) methods, thermal gravimetric analysis (TGA), photoluminescence (PL), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were within the numerous techniques used to characterize this nanocomposite. Both the photoluminescence (PL) spectrum and the Tauc plot indicated that the Ag2O/TiO2/g-C3N4 nanocomposite had a lower electron-hole pair recombination rate and lower band gap energy. The coating of Ag2O and TiO2 on g-C3N4 was verified by TEM. The Ag2O/TiO2/g-C3N4 nanocomposite was used in the photocatalytic degradation of a Brilliant green (BG)-Congo red (CR) dye combination and ciprofloxacin (CIP) antibiotic under visible light irradiation. According to the research, under visible light irradiation, the Ag2O/TiO2/g-C3N4 nanocomposite photocatalytic activity simultaneously degraded a mixture of BG-CR dyes, with BG (93%) and CR (85%) degrading percentages in 70 min and CIP (82%) degrading in 120 min. Superoxide and hydroxyl radicals were primarily responsible for the degradation of BG and CR dyes under visible light irradiation, whereas holes and hydroxyl radicals were investigated as important oxidative species in the photocatalytic degradation of CIP utilizing the Ag2O/TiO2/g-C3N4 nanocomposite.Graphical

Facile Sol-Gel Synthesis of C, N Codoped-TiO2 for Efficient Degradation of Palm Oil Mill Effluent.

Wastewater treatment has been regarded as an effective solution in lowering the potential environmental hazards caused by palm oil mill effluent (POME). To ensure the efficient remediation of POME, the implementation of a promising strategy is necessary to overcome the limitations of conventional water treatment methods for the treatment of this pollutant. In this study, the synthesis of carbon, nitrogen codoped titanium dioxide nanoparticles (C, N-TiO2 NPs) was successfully performed by a sol-gel approach for the treatment of POME as a model pollutant under solar light irradiation. The synthesized C, N-TiO2 NPs displayed unique characteristics including an anatase phase with an average crystallite size of 11.35 nm and irregular spherical structures. Additionally, C, N-TiO2 possessed a lower band gap energy of 2.95 eV than 3.2 V of bulk anatase TiO2 and slower electron-hole (e--h+) pair recombination rate as evidenced by photoluminescence (PL) studies. The adsorption isotherm study of POME was most compatible with the Langmuir isotherm model, and the POME degradation kinetics proceeded according to first-order kinetics. Accordingly, the photocatalytic degradation of POME displayed a maximum degradation efficiency of 100% under the optimum condition of pH 7 in the presence of 0.12 g of the C, N-TiO2 photocatalyst within 150 min. The scavenging study showed that the superoxide radical (•O2 -) was the primary active species in the POME photodegradation. Finally, the reusability analysis confirmed that the C, N-TiO2 NPs could be reused for a maximum of five cycles, making them promising photocatalysts for wastewater treatment.

Data-Driven Machine Learning Strategy for Designing Metal-Ion-Doped γ-Bi2MoO6 Photocatalysts to Enhance Degradation Performance.

Doped semiconductors are often used to improve photocatalytic efficiency and address the challenges of easy recombination of electron-hole pairs and poor photoluminescence. However, the reproducibility and complexity of experimental studies result in time-consuming and less cost-effective studies, and it is difficult to gain insights into the intrinsic properties of doped photocatalysts to control their performance. Introducing a machine learning approach, we constructed a photocatalytic model of transition-metal- and rare earth metal-ion-doped γ-Bi2MoO6. We selected 18 factors of preparation conditions and dopant ion properties, and constructed 806 data sets through literature collection for correlation analysis, paving the way for a more efficient and cost-effective research process. The results of our study are promising. The trained and improved XGboost model demonstrated high resistance to the variability caused by data segmentation, with a cross-validated model showing a coefficient of determination of 0.942. Through the combination of characteristic importance and Shapley additive explanation analysis, the importance and correlation trends of preparation conditions and dopant ion properties are obtained, especially the positive correlation trend of excitation time and preparation time and the negative correlation trend of atomic mass and bandwidth. Model prediction and experimental validation are used to demonstrate the effectiveness and behavioral prediction ability, and the Zn and Cd elements are successfully predicted for doping modification means. This study contributes to the modification and preparation of γ-Bi2MoO6 materials and provides a solid foundation for the efficient design of photocatalysts.

Plasma-Liquid-Induced Synthesis of Scandium-Metalloporphyrin Frameworks for Boosted Sensing and Photosensitization.

Inserting metal ions into the porphyrin ring is one of the primary strategies to enhance the properties of porphyrin-based metal-organic frameworks (MOFs). However, the straightforward, rapid, and energy-efficient synthesis of porphyrin-based MOFs with high metallization for the porphyrin ring remains challenging. Herein, a solution anode glow discharge (SAGD) microplasma is presented for the one-step synthesis of scandium-metalloporphyrin frameworks (ScMPFs). The substantial number of electrons provided by the plasma-liquid interface not only accelerated the rapid nucleation and growth of MOFs but also promoted the incorporation of scandium (Sc3+), which has a small ionic radius and strong coordination ability, into the N atoms in the porphyrin ring, and enhanced the metallization of MOFs. The sufficient Sc3+ in frameworks inhibited the recombination of electron-hole pairs, resulting in boosted reactive oxygen species yield and a low fluorescence background of MOFs. Consequently, the ScMPFs are employed for the sensitive and rapid detection of F- in water with a detection limit of 0.24 µm and for efficient bacteriostasis at low doses (10 µgmL-1, 12mWcm-2 light irradiation for 10min).

Performance of Ti/TiO2-ZIF-67 photoanode under LED irradiation applied to the photoelectrodegradation of the antidepressant venlafaxine (VEN) in municipal wastewater effluent

This work describes the direct deposition of ZIF-67 metal-organic framework (MOF) onto Ti/TiO2 nanotubes forming a photoanode for the degradation of the antidepressant Venlafaxine (VEN). This material combines the excellent characteristics of ZIF-67 MOF in enhancing photocatalytic reduction and oxidation reactions induced by UV LED irradiation, as well as the storage of VEN molecules in its pores. Ti/TiO2-ZIF-67 features an eco-friendly technology for degradation of pharmaceutical micropollutants such as antidepressants. The photoanode was prepared, characterized and applied in the degradation of VEN by photocatalysis (PC), electrocatalysis (EC), photolysis (PL) and PEC processes. PEC process presented the best performance when compared to the others processes in both simulated solutions and real wastewater, achieving 100% and 89% degradation of VEN after 60 and 90min, with TOC removal rates of 50% and 4%, respectively. The lower mineralization rate suggests that the degradation of VEN in complex matrices such as that of real wastewater produced recalcitrant by-products that are difficult to convert into CO2 and H2O. Zeta potential measurement showed that at pH 6 and 8 there is an effect of attraction of opposite electrostatic charges between the surface of ZIF-67 (positive) and VEN (negative), favoring the degradation of VEN in this pH range. The good performance of the Ti/TiO2-ZIF-67 can be attributed to the formation of the Z-scheme heterojunction between the TiO2 nanotubes and the ZIF-67 MOF which contributed to a lower rate of electron-hole (e-/h+) pairs recombination, favoring VEN degradation mainly to higher generation of •OH radical and less contribution of O2•- superoxide produced by UV irradiation forming some degradation by-products through demethylation and oxidation reactions.

In situ self-cleaning removal of emerging organic contaminants with covalent organic framework armed with arylbiguanide.

An in situ self-cleaning covalent organic framework featuring arylbiguanide arms (Aryl-BIG-COF) was first developed to remove emerging organic pollutants such as propranolol (PRO) from water. The main breakthroughs addressed the scarcity of functional active sites, the impracticality of ex situ regeneration, and the rapid recombination of electronhole pairs in the application of COFs. Owing to the directional capture ability and electronic structure regulation of the arylbiguanide arms, the adsorption capacity and photocatalytic degradation rate of the newly synthesized COF increased by nearly four and seven times, respectively. Its self-cleaning ability, driven by the photocatalytic regeneration of active sites, enabled in situ removal of PRO and sustained over 90 % removal efficiency after six cycles. Moreover, it demonstrated broad applicability for removing PRO and other emerging pollutants, such as bisphenol A (BPA), tetracycline (TC), and norfloxacin (NOR), across various water matrices with less residual toxicity. The coexisting organic matter and ions in natural water promoted the removal of PRO. The enhancement mechanism involved arylbiguanide arms narrowing the band gap and inducing local charge polarization, thereby increasing the separation efficiency of electronhole pairs. This work provides significant insights into the structural design and practical applications of COFs for purifying water.

THE HIGHLY EFFICIENT BiOCl/KBiO3 p-n HETEROJUNCTION PHOTO-CATALYSTS UNDER VISIBLE LIGHT IRRADIATION

BiOCl/KBiO3 p-n heterostructures with hierarchical mesoporous architectures were successfully synthesized via a facile in situ method. The X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) results indicate the formation of heterojunctions between BiOCl and KBiO3. The photocatalytic performance of the as-prepared samples was investigated by the degradation of dye Rhodamine B (RhB) under visible light irradiation. BiOCl/KBiO3 composite has never been used to photodegrade the RhB which is a common dye and very difficult to degrade. The results demonstrated that KBiO3 combined with proper amount of BiOCl nanosheets exhibited high efficiency in the photocatalytic process, and BiOCl/KBiO3 with the molar ratio of 70/30 demonstrated the highest photocatalytic activity due to its large surface area, excellent charge separation characteristics and the suppressed recombination of electron-hole pairs. The results of active species detection reveal that the superoxide radical anions (O2-), hydroxyl free radicals (·OH), photogenerated holes (h+) and photogenerated electrons (e-) reactive species work together for the photocatalytic degradation of RhB. A possible and new mechanism of photocatalysis that differs from other teams was also explored and proposed. The present study will benefit the development of the new p-n heterojunction photocatalysts and would be of great importance to meet ever-increasing environmental demands in the future.

Modification of bismuth-rich to synthesize floral spherical Z-type heterojunction CoAl2O4/Bi4O5Br2 photocatalysts for photocatalytic degradation of tetracycline: DFT calculations, toxicity assessment

Modification of bismuth-rich to synthesize floral spherical Z-type heterojunction CoAl2O4/Bi4O5Br2 photocatalysts for photocatalytic degradation of tetracycline: DFT calculations, toxicity assessment

AgIO4 nanoparticles decorated on SrTiO3 microspheres as a novel Z-scheme composite photocatalyst for efficient solar-driven degradation of cefixime

The presence of antibiotics in water bodies poses severe environmental and health risks, necessitating the development of efficient and sustainable remediation technologies. In this context, photocatalysis emerged as a promising approach, leveraging light energy to degrade organic pollutants. This study introduced a novel Z-scheme SrTiO3/AgIO4 composite synthesized via a solvothermal-sonochemical route, which aimed to enhance the photocatalytic degradation of cefixime under simulated sunlight. Characterization techniques such as field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS) and transient photocurrent response (TPR) were employed to elucidate the physicochemical and optoelectronic properties of the as-synthesized composite. The SrTiO3/AgIO4 composite degraded 73.8% cefixime in 120 min, which was remarkably higher compared to its individual components. The enhanced photoactivity was credited to the synergistic interplay of both semiconductors within the Z-scheme heterojunction, which promoted effective charge separation and reduced electron-hole pair recombination.

Vapor-Assisted In Situ Synthesis of the Nb2CTxNS/NbO2F MXene Heterostructure for Enhanced Solar-Driven Photoelectrochemical Performance.

Photocatalytic water splitting holds great potential for transforming solar energy into valuable chemical products. However, obstacles such as the rapid recombination of electron-hole pairs and insufficiently active surface areas of photocatalysts remain significant challenges. In this study, we present the first demonstration that lithium bis(trifluoromethanesulfonyl)imide vapor successfully etches aluminum from Nb2AlC MAX phase powders while concurrently forming NbO2F anchors on Nb2CTx nanosheet (Nb2CTxNS) MXene, leading to the in situ formation of a Nb2CTxNS/NbO2F heterostructure composite. This novel material exhibits a remarkable photoelectrochemical performance, achieving a current density of 252 μA cm-2, which is 1000 and 10 times greater than those of Nb2AlC MAX and Nb2C nanosheet MXene, respectively. These findings shed light on innovative approaches for developing photocatalytic materials via vapor-assisted synthesis, offering a promising pathway for advancing material discovery in both photo- and energy-related fields.

Preparation and Hydrogen Production Application of Core-Shell Heterojunction Photocatalyst (PbS/ZnO)@CuS.

This study employed a hydrothermal method to coat CuS onto PbS quantum dots loaded with ZnO, resulting in a core-shell-structured (PbS/ZnO)@CuS hetero-structured photocatalyst. The sulfide coating enhanced the photocatalyst's absorption in the near-infrared to visible light range and effectively reduced electron-hole (h+) pair recombination during photocatalytic processes. Electron microscopy analysis confirmed the successful synthesis of this core-shell structure using polyvinylpyrrolidone (PVP); however, the spatial hindrance effect of PVP led to a disordered arrangement of the CuS lattice, facilitating electron-hole recombination. Comprehensive analyses using transmission electron microscopy (TEM), photoluminescence (PL), and Brunauer-Emmett-Teller (BET) methods revealed that the (PbS/ZnO)@CuS photocatalyst synthesized at a hydrothermal temperature of 170 °C exhibited optimal hydrogen production efficiency. After conducting a photocatalytic reaction for 5 h in a mixed aqueous solution containing 0.25 M Na2S + Na2SO3 as a sacrificial agent, a hydrogen production rate of 3473 μmol·g-1·h-1 was achieved.

A Review on Photocatalytic Hydrogen Peroxide Production from Oxygen: Material Design, Mechanisms, and Applications.

Hydrogen peroxide (H2O2) finds extensive applications in various industries, particularly in the environmental field. The photocatalytic production of H2O2 through the oxygen reduction reaction (ORR) or the water oxidation reaction (WOR) offers a promising approach. However, several challenges hinder effective on-site production, such as the rapid electron-hole pair recombination, inefficient visible light utilization, and limited selectivity in H2O2 formation. Thus, developing efficient photocatalysts to overcome these challenges is crucial. This review comprehensively outlines the development of photocatalysts and their modification techniques. It also summarizes and compares the H2O2 yield and apparent quantum yield among various photocatalysts with and without the use of organic sacrificial reagents. Density functional theory (DFT) calculations propose the band structure of photocatalysts and the mechanisms underlying oxygen reduction to H2O2. Finally, this review explores the potential environmental applications of photocatalytically produced H2O2. This review guides the design and optimization of photocatalysts, facilitating the continued advancement and application of photocatalysts in environmental contexts.

Design of MnOx/TiO2 Nanostructures for Photocatalytic Removal of 2,4-D Herbicide.

The research and modification of semiconductors through different synthesis routes allow obtaining materials with optimal properties to induce new energy levels and improve charge separation efficiency. In this context, the sol-gel method was used to synthesize TiO2-based materials doped with different percentages of MnOx to evaluate their photocatalytic activity in the degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in water under UV irradiation. Characterization results revealed a reduction in crystallite size to 7.2 nm. Adding MnOx enhanced the optical absorption of TiO2, resulting in a shift toward the red end of the spectrum of the forbidden energy band. The photocatalytic activity increased significantly with the percentage of MnOx, reaching a maximum degradation of 70 % in 6 hours with the 3 MnTi material. This increase was attributed to the synthesis method, which facilitated the formation of nanostructured heterojunctions mainly composed of TiO2 and MnO2, reducing the recombination of electron-hole pairs. TEM analysis confirmed these structures. A reaction mechanism for the 3 MnTi material is proposed, considering the mobility of charge carriers and the photooxidation processes of the pollutant.

Dye-sensitized n-n heterojunction {001}TiO2@NH2-MIL-101(Fe) for degradation of rhodamine B under visible light

Dye-sensitized n-n heterojunction {001}TiO2@NH2-MIL-101(Fe) for degradation of rhodamine B under visible light

Surface effect of cesium and graphene quantum dots doped CaO to enhance catalytic dye degradation and bacterial inactivation with in-silico analysis

Surface effect of cesium and graphene quantum dots doped CaO to enhance catalytic dye degradation and bacterial inactivation with in-silico analysis