Retardation Of Recombination Research Articles

Synthesis, characterization, and photocatalytic application of cadmium(II) sulfide-magnetite in one-pot multi-component synthesis of some 1-amidoalkyl-2-naphthols

Cadmium(II) sulfide-magnetite is disclosed as a new magnetic separable photocatalyst in the one-pot multi-component synthesis of 1-amidoalkyl-2-naphthols, as significant pharmaceuticals that have diverse biological activities including antifungal, anti-inflammatory, antioxidant, and antidiabetic properties. This novel and environmental-friendly photocatalyst is biosynthesized from C. Cretica L. leaf extract and characterized by FT-IR, XRD, FE-SEM, EDS, XPS, UV–Vis, and VSM analytical techniques. Results exhibited that the nano-photocatalyst has significantly higher photocatalytic activity compared to individual components Fe3O4 and CdS. This property would be corresponded to retarded recombination of hole-electron pairs in this nanomaterial compared to the individual species. The effective species like OH•, •O2−, and h+ are proposes to be involved in the photocatalytic process. This new green method brings several key benefits like quick reaction time, easy work-up, cost-effectiveness, wide range of applicable substrates, and high yields.

Remarkable Enhancement of Photocatalytic Activity of High-Energy TiO2 Nanocrystals for NO Oxidation through Surface Defluorination.

The superior photocatalytic activity of TiO2 nanocrystals with exposed high-energy (001) facets, achieved through the use of hydrofluoric acid as a shape-directing reagent, is widely reported. However, in this study, we report for the first time the detrimental effect of surface fluorination on the photoreactivity of high-energy faceted TiO2 nanocrystals towards NO oxidation (resulting in a NO removal rate of only 5.9%). This study aims to overcome this limitation by exploring surface defluorination as an effective strategy to enhance the photocatalytic oxidation of NO on TiO2 nanocrystals enclosed with (001) facets. We found that surface defluorination, achieved through either NaOH washing (resulting in an improved NO removal rate of 23.2%) or calcination (yielding an enhanced NO removal rate of 52%), leads to a large increase in the photocatalytic oxidation of NO on TiO2 nanocrystals with enclosed (001) facets. Defluorination processes stimulate charge separation, effectively retarding recombination and significantly promoting the production of reactive oxygen species, including superoxide radicals (·O2-), singlet oxygen (1O2), and hydroxyl radicals (·OH). Both in situ diffuse reflectance infrared Fourier-transform spectroscopy and density functional theory calculations confirm the higher adsorption of NO after defluorination, thus facilitating the oxidation of NO on TiO2 nanocrystals.

Construction of BiOCl/Clinoptilolite Composite Photocatalyst for Boosting Formaldehyde Removal.

Binary composite was synthesized via coupling BiOCl with alkali leached natural clinoptilolite (40B0/CN), which showed retarded recombination of photo-generated carriers. The clinoptilolite was pretreated with alkali leaching, resulting in a larger pore size and high cation exchange capacity. The modified clinoptilolite was more feasible for the growth of BiOCl and to promote the adsorption ability for formaldehyde (HCHO). In addition, the cation exchange capacity was conducive to anchor Bi3+, further leading to the reduction of the particle size of BiOCl. The carrier effect of alkali leached natural clinoptilolite promoted the amorphous transformation of BiOCl at low temperature, which simultaneously produced more distortions and defects in the BiOCl lattice. The 40B0/CN composite exhibited the superior light absorption ability with a narrower band gap. The photocatalytic degradation rate for HCHO of 40B0/CN under solar light reached 87.7%, and the reaction rate constant was 0.0166 min−1, which was 1.6 times higher than that of BiOCl. This paper gave a deep insight into photocatalytic technology to efficiently degrade formaldehyde.

Self-powered photoelectrochemical quartz/TiO2 microsystem through piezopotential sensitized photocatalytic process

A self-powered photoelectrochemical microsystem comprising quartz prism microrods assembled with TiO2 nanoparticles (NPs; quartz/TiO2) is developed and demonstrates a marked catalytic effect on organic dye degradation and hydrogen evolution through a piezopotential sensitized photocatalytic process (referred to as synergistically piezophotocatalytic processes or piezophototronics herein). The results of piezoresponse force microscopy (PFM) and the electrical output of the piezoelectric nanogenerator suggest that the quartz microrods act as a self-powered bias subjected to mechanical stress that can produce an additional electric field around the surrounding TiO2 NPs. With the finite element method, the simulation results indicate that the interfacial stress effect between the two materials plays a vital role in enhancing piezoelectric potential (piezopotential). The reaction rate constant (kobs) for the dye degradation of the quartz/TiO2 heterostructure reaches 0.0624 min−1 under a piezophototronic effect, approximately 2.2 times greater than that for photocatalysis (rate constant kobs = 0.0281 min−1). Additionally, hydrogen production reaches 438.48 µmol·g−1·h−1 through the synergistic piezophototronic effect, a 225% increase when compared with that of pristine quartz. This improvement is attributable to mechanical force–induced piezoelectric polarization, which acts as an internal bias modulating the TiO2 band structure and ejecting the photogenerated electrons and holes in opposite directions, thereby retarding recombination behaviors and facilitating redox reactions.

Modification of compact TiO2 layer by TiCl4-TiCl3 mixture treatment and construction of high-efficiency carbon-based CsPbI2Br perovskite solar cells

In the construction of high performance planar perovskite solar cells (PSCs), the modification of compact TiO2 layer and engineering of perovskite/TiO2 interfaces are essential for efficient electron transfer and retarded charge recombination loss. In this work, a facile and effective strategy is developed to modify the surface of compact TiO2 layer by TiCl4-TiCl3 mixture treatment. Compared with conventional sole TiCl4, the TiCl4-TiCl3 treatment takes the advantage of accelerated and controlled hydrolysis of TiCl3, therefore TiO2 with dominating anatase phase and moderate roughness is obtained to facilitate the growth of CsPbI2Br perovskite layer with high quality. Furthermore, the oxidation-driven hydrolysis of TiCl3 component results in surface Cl doping that facilitates interfacial electron transfer with retarded recombination loss. The average power conversion efficiency (PCE) of carbon-based CsPbI2Br planar PSCs based on TiCl4-TiCl3 treatment increases to 14.18% from the intial 13.04% based on conventional sole TiCl4 treatment. The champion PSC exhibits a PCE of 14.46% (Voc = 1.28 V, Jsc = 14.21 mA/cm2, and FF = 0.794), which is one of the highest PCEs for carbon-based CsPbI2Br PSCs.

Photoelectrochemical Properties of SnO2 Photoanodes Sensitized by Cationic Perylene-Di-Imide Aggregates for Aqueous HBr Splitting.

Perylene-sensitized mesoporous SnO2 films were used as electrodes for photoelectrochemical HBr splitting in aqueous solution. Upon AM 1.5 G illumination a 3-4 fold increase of the saturated photocurrent was observed when decreasing the pH of the aqueous solution from pH 3 to pH 0 (j max = 0.05 ± 0.01 mAcm-2 at pH 3 and 0.17 ± 0.02 mAcm-2 at pH 0, respectively). A detailed spectroscopic and electrochemical analysis of the hybrid material was carried out in order to address the impact of interfacial energetics on charge separation dynamics. UV/Vis spectroelectrochemical measurements showed that the energy of semiconductor states in such systems can be adjusted independently from the molecular levels by varying proton concentration. Photoelectrochemical measurements and ns-μs transient absorption spectroscopy reveal that pH-related changes of the interfacial energetics have only a minor impact on the charge injection rate. An increase of the proton concentration improves charge collection mainly by retarding recombination, which in the case of Br- oxidation is in critical competition with perylene regeneration. Control of the back recombination appears to be a key feature in heterogeneous molecular systems tasked to drive energetically demanding redox reactions.

NiS/BiOBr hybrids with retarded carrier recombination and enhanced visible-light-driven photocatalytic activity

In this work, nickel sulfide (NiS)/bismuth oxybromide (BiOBr) hybrids were synthesized by a two-step hydrothermal method. Some advanced tools were employed to characterize the crystal phase, morphological evolution, light absorption and photocatalytic performance. Significantly, NiS/BiOBr hybrids exhibited enhanced photocatalytic activity toward rhodamine B (RhB) degradation under visible light irradiation. Comparatively, NS/BOB-3.0 showed the highest degradation rate, over 2.5 times higher than that of pure BiOBr. Furthermore, the retarded recombination rate of photogenerated carriers contributed to the improved photocatalytic performance. The results indicate that hybrids may be a promising method for enhancing the photocatalytic ability of BiOX-based semiconductor.

Photocatalytic reduction of carbon dioxide using graphene oxide wrapped TiO2 nanotubes

Photocatalytic conversion of carbon dioxide to valuable chemicals by using semiconductor materials is one of the major challenges in materials science. Higher efficiency and product yield can be achieved by designing of a suitable photocatalyst with retarded recombination of photogenerated electron-hole pair and sufficient potential for the reduction of CO2. In this work, unique composite architecture of graphene-oxide wrapped TiO2 nanotubes for the photocatalytic reduction of CO2 has been developed. The TiO2 nanotubes formed by electrochemical anodization are wrapped with graphene oxide/reduced graphene oxide (GO/rGO) layers which also form interconnecting bridges between the adjacent nanotubes. Such a unique nanostructure helped the separation of photogenerated electron-hole pairs with better charge transfer to perform the reduction of adsorbed CO2 molecules. The rGO/TiO2 multi-leg nanotubes (MLNTs) have shown the highest photocatalytic activity with maximum yield of CO c.a. 1348 μmol g−1 within the first 20 min, which stabilize to about 760 μmol g−1 after 2 h of UV-A irradiation. More importantly, the CO formation rate is about an order of magnitude higher than that from graphene supported TiO2 nanocrystals.

Dependence of power conversion properties of perovskite solar cells on operating temperature

Power conversion properties of perovskite solar cells are studied in the temperature range of 310 K to 240 K (and recovering back). As the temperature lowers down, the fill factor (FF) decreases while the open circuit voltage (VOC) increases in the case of reverse scans (scanning from positive voltages to negative ones). The decreased FF is ascribed to the increased resistance of charge transport materials (both TiO2 and Spiro-OMeTAD) as well as the increased interfacial charge transfer resistance, while the increased VOC is due to retarded recombination which is revealed by the transient photovoltage decay measurement. Hysteresis appears in the current-voltage curves, but it shrinks with temperature decreasing and even vanishes as the temperature becomes lower than 270 K. Mott-Schottky capacitance analysis shows that ion migration exists in the device, especially for temperatures >270 K. The “S shape” current-voltage characteristic is observed at lowered temperatures, which is caused by retarded charge extraction across the interface between the active layer and charge-transport materials. Similar power conversion properties are observed when elevating the temperature from 240 K to 310 K; thus, the temperature-sensitive behavior is reversible. The observed behavior is compared with silicon solar cells. The study shows that lowering the temperature is harmful to the charge extraction processes of perovskite solar cells. Highly conductive charge-transport materials are needed for the devices to operate in a colder environment.

Efficient Dye-Sensitized Solar Cells with Voltages Exceeding 1 V through Exploring Tris(4-alkoxyphenyl)amine Mediators in Combination with the Tris(bipyridine) Cobalt Redox System

Tandem redox electrolytes, prepared by the addition of a tris(p-anisyl)amine mediator into classic tris(bipyridine)cobalt-based electrolytes, demonstrate favorable electron transfer and reduced energy loss in dye-sensitized solar cells. Here, we have successfully explored three tris(4-alkoxyphenyl)amine mediators with bulky molecular structures and generated more effective tandem redox systems. This series of tandem redox electrolytes rendered solar cells with very high photovoltages exceeding 1 V, which approaches the theoretical voltage limit of tris(bipyridine)cobalt-based electrolytes. Solar cells with power conversion efficiencies of 9.7–11.0% under 1 sun illumination were manufactured. This corresponds to an efficiency improvement of up to 50% as compared to solar cells based on pure tris(bipyridine)cobalt-based electrolytes. The photovoltage increases with increasing steric effects of the tris(4-alkoxyphenyl)amine mediators, which is attributed to a retarded recombination kinetics. These results hi...

Inhibition Mechanisms of Human Indoleamine 2,3 Dioxygenase 1.

Human indoleamine 2,3-dioxygenase 1 (hIDO1) and tryptophan dioxygenase (hTDO) catalyze the same dioxygenation reaction of Trp to generate N-formyl kynurenine (NFK). They share high structural similarity, especially in the active site. However, hIDO1 possesses a unique inhibitory substrate binding site (Si) that is absent in hTDO. In addition, in hIDO1, the indoleamine group of the substrate Trp is H-bonded to S167 through a bridging water, while that in hTDO is directly H-bonded to H76. Here we show that Trp binding to the Si site or the mutation of S167 to histidine in hIDO1 retards its turnover activity and that the inhibited activity can be rescued by an effector, 3-indole ethanol (IDE). Kinetic studies reveal that the inhibited activity introduced by Trp binding to the Si site is a result of retarded recombination of the ferryl moiety with Trp epoxide to form NFK and that IDE reverses the effect by preventing Trp from binding to the Si site. In contrast, the abolished activity induced by the S167H mutation is primarily a result of ∼5000-fold reduction in the O2 binding rate constant, possibly due to the blockage of a ligand delivery tunnel, and that IDE binding to the Si site reverses the effect by reopening the tunnel. The data offer new insights into structure-based design of hIDO1-selective inhibitors.

Synthesis of 2-amino-4-(4-(methylamino)phenyl)-6-phenylnicotinonitrile as a new additive for the passivation of the TiO2 surface and retarding recombination in dye-sensitized solar cells

In this research, we synthesized a phenylnicotinonitrile derivative as a new type of additives and studied its effect on the performance of dye-sensitized solar cells by UV–Vis spectroscopy, cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). In comparision with a blank electrolyte (0.35 M lithium iodide, 0.035 M iodine and 0.01 M guanidium thiocyanate in a much less leakage and volatile solvent such as propylene carbonate, PC-liquid), addition of 0.5 M phenylnicotinonitrile derivative caused an increase in the open-circuit potential (Voc) of 209 mV but a decrease in the short current density (Jsc) of 3.36 mA/cm2. The increase could be attributed to the negative shift of the conduction bond of TiO2 semiconductor potential (Voc, ∼34% of the voltage increase) and to the increase of the photo-conversion efficiency (PCE, ∼21% of the efficiency increase). The decrease in Jsc was because of the reduction of dye regeneration and the catalytic activity of the photocathode in electrolyte regeneration. It was shown that the fabricated dye-sensitized solar cells (DSSCs)-based different electrolytes displayed the relative standard deviation (RSD) range of 3.24%–4.36% for six repetitive measurements (n = 6).

Passivating ZnO Surface States by C60 Pyrrolidine Tris-Acid for Hybrid Solar Cells Based on Poly(3-hexylthiophene)/ZnO Nanorod Arrays.

Construction of ordered electron acceptors is a feasible way to solve the issue of phase separation in polymer solar cells by using vertically-aligned ZnO nanorod arrays (NRAs). However, the inert charge transfer between conducting polymer and ZnO limits the performance enhancement of this type of hybrid solar cells. In this work, a fullerene derivative named C60 pyrrolidine tris-acid is used to modify the interface of ZnO/poly(3-hexylthiophene) (P3HT). Results indicate that the C60 modification passivates the surface defects of ZnO and improves its intrinsic fluorescence. The quenching efficiency of P3HT photoluminescence is enhanced upon C60 functionalization, suggesting a more efficient charge transfer occurs across the modified P3HT/ZnO interface. Furthermore, the fullerene modified hybrid solar cell based on P3HT/ZnO NRAs displays substantially-enhanced performance as compared to the unmodified one and the devices with other modifiers, which is contributed to retarded recombination and enhanced exciton separation as evidenced by electrochemical impedance spectra. Therefore, fullerene passivation is a promising method to ameliorate the connection between conjugated polymers and metal oxides, and is applicable in diverse areas, such as solar cells, transistors, and light-emitting dioxides.

Facile photohydroxylation of ZnS nanobelts for enhanced photocatalytic activity

The photocatalytic performances of ZnS photocatalysts have been extensively enhanced by treating ZnS nanobelts for 10min with hydrogen peroxide under Xe-lamp irradiation. The photocatalytic degradation reaction of 4-nitrophenol via photohydroxylated ZnS nanobelts takes place faster six times than that via pristine ZnS nanobelts, demonstrating that the simple and facile photohydroxylation process increases the photocatalytic activity of ZnS nanobelts extensively. Photoluminescence spectra and kinetic profiles have suggested that surface hydroxyl groups as well as surface defects increase the separation rate of photogenerated charges, enhancing the photocatalytic activity of 4-nitrophenol degradation. Radical species tests have indicated that the photocatalytic performance of ZnS nanobelts is mainly contributed by hydroxyl radicals generated by the photooxidation of surface-adsorbed hydroxyl groups. Because hydroxyl groups are adsorbed on the surfaces of photocatalysts, diffusion is not necessary when hydroxyl radicals are formed by photoexcited holes. Thus, the photocatalytic degradation of 4-nitrophenol via ZnS nanobelts follows the zero-order kinetics. The generation of hydroxyl radicals is promoted by the retarded recombination of photoexcited charges, leading to the enhancement of the photocatalytic activity of ZnS nanobelts. Overall, a simple and facile photohydroxylation process increases the photocatalytic performances of ZnS photocatalytsts enormously via forming reactive hydroxyl radicals, which are readily generated by the photooxidation of surface-adsorbed hydroxyl groups. Overall, our facile and eco-friendly photohydroxylation method is suggested to have great potential for industrial applications.

Polaronic Charge Carrier-Lattice Interactions in Lead Halide Perovskites.

Almost ten years after the renaissance of the popular perovskite-type semiconductors based on lead salts with the general formula AMX3 (A=organic or inorganic cation; M=divalent metal; X=halide), many facets of photophysics continue to puzzle researchers. In this Minireview, light is shed on the low mobilities of charge carriers in lead halide perovskites with special focus on the lattice properties at non-zero temperature. The polar and soft lattice leads to pronounced electron-phonon coupling, limiting carrier mobility and retarding recombination. We propose that the proper picture of excited charge carriers at temperature ranges that are relevant for device operations is that of a polaron, with Fröhlich coupling constants between 1<α<3. Under the aspect of light-emitting diode application, APbX3 perovskite show moderate second order (bimolecular) recombination rates and high third-order (Auger) rate constants. It has become apparent that this is a direct consequence of the anisotropic polar A-site cation in organic-inorganic hybrid perovskites and might be alleviated by replacing the organic moiety with an isotropic cation.

A facile synthesis of Fe3O4@SiO2@ZnO with superior photocatalytic performance of 4-nitrophenol

Nitrophenols in wastewater have posed a serious threat to ecosystem and human health, hence it is very important to remove them from wastewater using an environmental-friendly and effective method. In this study, Fe3O4@SiO2@ZnO magnetic nanoparticles (ZnO MNPs) were synthesized via a moderate and rapid route using microwave irradiation and diethylene glycol (DEG) as solvent. The facile synthesis conditions of ZnO nanoparticles coating on Fe3O4@SiO2 were confirmed owing to lower reaction temperature (160°C) and quick reaction time (15min microwave irradiation). In addition, the synthesized ZnO MNPs demonstrated the comparable or even better photocatalytic activity for 4-nitrophenol (4-NP) as compared with TiO2 with respect to small catalyst dosage, quick degradation rate and broad pH range. Moreover, ZnO MNPs exhibited good stability and reusability after eight times successive degradation experiments of 4-NP. The mechanism of the enhanced photocatalytic activity of ZnO MNPs was mainly related to the stronger adsorption ability for 4-NP, the improved light absorption ability and the retarding recombination of hole–electron pairs. In summary, ZnO MNPs is a promising candidate for 4-NP photocatalytic degradation from wastewater.

Time-varied synthesis of hierarchical ZnO microspheres and their applications in dye-sensitized solar cells

Hierarchically nano-structured ZnO microspheres have been synthesized solvothermally at variable reaction times (6, 12, 36, and 48 h) by using ethylene glycol as a solvent, zinc acetate as precursor, and hexamethylene triamine (HMT) as structure directing agent. The study also focused on the mechanism of time-dependant growth of hierarchical ZnO microspheres and their deployment in dye-sensitized solar cells (DSSCs) as photoanode. Longer reaction times lead to formation of nearly spherical ZnO microspheres. The structural and morphological analysis reveals the formation of a wurtzite hexagonal crystalline structure having a microsphere-like morphology. ZnO hierarchical microspheres synthesized at different reaction times have been used as photoanode in DSSCs which show enhanced light-harvesting properties than the commercial ZnO powders. ZnO microspheres synthesized at 48 h show maximum current density and cell efficiency of 8.51 mA/cm2 and 3.31%, respectively. This enhancement in photovoltaic parameters could be due to highly porous microspheres which provide more specific surface area for dye loading, retardation of recombination, and better charge transport.

Synergetic effects of solution-processable fluorinated graphene and PEDOT as a hole-transporting layer for highly efficient and stable normal-structure perovskite solar cells.

We demonstrate that a bi-interlayer consisting of water-free poly(3,4-ethylenedioxythiophene) (PEDOT) and fluorinated reduced graphene oxide (FrGO) noticeably enhances the efficiency and the stability of the normal-structure perovskite solar cells (PeSCs). With simple and low temperature solution-processing, the PeSC employing the PEDOT + FrGO interlayer exhibits a significantly improved power conversion efficiency (PCE) of 14.9%. Comprehensive investigations indicate that the enhanced PCE is mostly attributed to the retarded recombination in the devices. The minimized recombination phenomena are related to the interfacial dipoles at the PEDOT/FrGO interface, which facilitates the electron-blocking and the higher built-in potential in the devices. Furthermore, the PEDOT + FrGO device shows a better stability by maintaining 70% of the initial PCE over the 30 days exposure to ambient conditions. This is because the more hydrophobic graphitic sheets of the FrGO on the PEDOT further protect the perovskite films from oxygen/water penetration. Consequently, the introduction of composite interfacial layers including graphene derivatives can be an effective and versatile strategy for high-performing, stable, and cost-effective PeSCs.

Grafting Fe(III) species on carbon nanodots/Fe-doped g-C3N4 via interfacial charge transfer effect for highly improved photocatalytic performance

Carbon quantum dots (CQDs) are coupled with Fe-doped g-C3N4 to prepare a binary composite photocatalyst, which shows retarded recombination of photo-induced carriers and enhanced surface absorption active sites. Then, interfacial charge transfer effect (IFCT) is introduced the binary composite by grafting Fe(III) species on the surface of CQDs/Fe-doped g-C3N4 via a facile impregnation method. The obtained ternary Fe(III)/CQDs/Fe-doped g-C3N4 composite photocatalyst exhibits largely increased optical absorption with its absorption region extended to 1200nm and efficiently inhibited charge recombination through the IFCT effect. It is revealed that the increased surface absorption active sites provided by CQDs lead to more amount of Fe(III) species anchored in the ternary photocatalyst than in the binary Fe(III)/Fe-doped g-C3N4 composite, which favors the photocatalytic activity. The EPR probe experiments elucidate that OH active species could be generated from the ternary Fe(III)/CQDs/Fe-doped g-C3N4 photocatalyst under visible light irritation, originating from the cooperation between the IFCT effect and the photo-Fenton reaction due to the existence of the Fe(III) species, which accounts for its highly enhanced photocatalytic performance on the degradation of MO and phenol.

A facile and novel construction of attapulgite/Cu2O/Cu/g-C3N4 with enhanced photocatalytic activity for antibiotic degradation

A high-performance photocatalyst, attapulgite/Cu2O/Cu/g-C3N4 (ATP/Cu2O/Cu/g-C3N4), was constructed via a one-pot redox strategy under anoxic calcination. The as-prepared composites were characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption isotherms (BET), photoluminescence emission (PL), and electrochemical impedance spectra (EIS). Results indicate that ultra-fine CuO nanoparticles on the surface of rod-like attapulgite are in-situ reduced by NH3 gas to generate Cu and minority Cu2O during the pyrocondensation of melamine. Meanwhile, the generated g-C3N4 membrane is uniformly encapsulated on the surface of attapulgite/Cu2O/Cu to assemble Z-scheme Cu2O/Cu/g-C3N4 heterostructure. ATP/Cu2O/Cu/g-C3N4 shows improved visible light response ability and hole-electron suppression compared with ATP/g-C3N4. The photocatalytic performance and mechanism of the obtained photocatalyst for antibiotic degradation were evaluated by UV–Vis spectrometer and liquid chromatograph. ATP/Cu2O/Cu/g-C3N4 can exhibit favorable photocatalytic activity and reusability for chloramphenicol. In addition, h+ and·OH radicals are the main active sites in the photocatalytic process, and Cu species play a vital role in separation and retarding recombination of electron-hole pairs.