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Expanding the optical absorption range of photocatalysts is still a key endeavor in graphitic carbon nitride (g-C3N4) studies. Here, we report on a novel thiophene group extending the optical property, which is assigned to n-π* electronic transitions involving the two lone pairs on sulfur (TLPS). The as-prepared samples, denoted as CN-ThAx (where x indicates the amount of ThA added, mg), showed an additional absorption above 500 nm as compared to pristine g-C3N4. Further, the thiophene group enhanced charge carrier separation to suppress e−/h+ pair recombination. The experimental results suggest that the thiophene group can obstruct the polymerization of melem to generate a large plane, thus exposing the lone electron pairs on the sulfur. The photocatalytic activity was evaluated in the decomposition of bisphenol A and H2 evolution. Compared with g-C3N4, the optimized CN-ThA30 sample led to a 6.6- and 2-fold enhancement of the degradation and H2 generation rates, respectively. The CN-ThA30 sample allowed for synchronous H2 production and BPA decomposition.

Dependency on plastic commodities has led to a recurrent increase in their global production every year. Conventionally, plastic products are derived from fossil fuels, leading to severe environmental concerns. The recent coronavirus disease 2019 pandemic has triggered an increase in medical waste. Conversely, it has disrupted the supply chain of personal protective equipment (PPE). Valorisation of food waste was performed to cultivate C. necator for fermentative production of biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The increase in biomass, PHBV yield and molar 3-hydroxy valerate (3HV) content was estimated after feeding volatile fatty acids. The fed-batch fermentation strategy reported in this study produced 15.65 ± 0.14 g/L of biomass with 5.32 g/L of PHBV with 50% molar 3HV content. This is a crucial finding, as molar concentration of 3HV can be modulated to suit the specification of biopolymer (film or fabric). The strategy applied in this study addresses the issue of global food waste burden and subsequently generates biopolymer PHBV, turning waste to wealth.

g-C3N4/BiOI composites with different ratios were prepared by in-situ generation route at room temperature and applied in antibacterial investigation. Detailed information of the composites was characterized by XRD, TEM, HRTEM, SEM, EDS, BET, XPS, FT–IR, UV–Vis, photocurrent and EIS. The obtained g-C3N4/BiOI composites presented excellent antibacterial performance toward Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under LED track light, with the complete inactivation of bacterial within 30 min. The decomposition of bacterial cells was observed by SEM. The bacterial mechanism was investigated by trapping experiments: holes (h+), superoxide anion free radical (O2−) and hydrogen peroxide (H2O2) were identified as active species for bacterial inactivation, and h+ had a main effect in the antibacterial process. The enhanced photocatalytic activities were assigned to an efficient separation and transition of electrons (e−) and h+ in photocatalytic antibacterial process. This work indicated the g-C3N4/BiOI composites are promising photocatalytic antibacterial materials for water disinfection.

Two methods were studied for selectively measuring the on-chip absorbance of trace sulfate analytes in droplets on a digital microfluidics (DMF) platform. In one method, the direction of measurement was perpendicular to the flat upper and lower surfaces of the DMF platform (vertical), and in the second method, the measurement direction was parallel to the DMF platform surfaces (horizontal). The channel height or the vertical light path length was 0.24 mm, and the droplet diameter was 1 mm. The DMF system employed a silicone oil transport medium whereby a thin, non-uniform oil layer formed between the droplet and the upper/lower plates which was unstable, resulting in randomly formed local oil lenses. The mobile oil lenses caused vertical absorbance measurement errors and uncertainties. The effects of the oil lenses were verified by simulation. Horizontal absorbance measurements were taken with embedded optical fibers (0.2 mm in diameter) aligned over the bottom chip surface in contact with the sides of the droplet, resulting in a horizontal light path length approximately three times that of the vertical light path. Because no oil lenses could form on the droplet’s sides, the stability of repeated horizontal measurements outperformed repeated vertical measurements made on the same droplet and on multiple droplets actuated into the measurement positions. Comparisons were based on measurement standard deviations and limits of detection (LOD). The following LODs and measurement standard deviations were achieved for horizontal measurements of multiple sulfate concentrations in 1.5 µl droplets: 7 ppm for sulfate (0.3–2.7%) and an R2 value of 0.957 from a least square data fit. Measurements on a commercial plate reader gave comparable results (200 µl liquid in each well, LOD equals 11 ppm, CV equals to 0.2–4%), even though the absorbance path was larger (0.7 mm). This LOD value means that the chip could detect 10.5 ng of sulfate. LOD values on vertical measurements were also similar, but large measurement errors from numerous outlier points yielded an R2 value of 0.735 and large average measurement standard deviations (36%).

A high-performance photocatalyst should be superior not only in light absorption and charge transfer but also surface catalytic reaction. Here we report a green and simple strategy for evenly decorating Ag3PO4 particles using magnetic NiFe2O4 nanoparticles (NPs). The NiFe2O4 NPs could act as a magnetic support material for recycling the photocatalysts, as well as in situ catalytically decompose the H2O2 produced on the surface of Ag3PO4 into O2 − and OH radicals via a photo-Fenton process. The catalytic decomposition of H2O2 could produce strong oxidative capacity O2 − and OH radicals for the organic pollutants degradation and reduce host semiconductor holes ( h + ( A g 3 P O 4 ) ) consumption by these produced H2O2. Thus, the photocatalytic activities of Ag3PO4@NiFe2O4 composites were greatly enhanced. Taking the photocatalytic degradation of Methyl orange (MO), hardly decomposed colorless phenol compounds bisphenol A (BPA) and killing Escherichia coli (E. coli) as mode photocatalytic reactions, this system exhibited superior photocatalytic performances than that of pristine Ag3PO4. Electron spin resonance (ESR) spectroscopy and sacrificial-reagent incorporated photocatalytic characterizations indicated that the in situ eliminating/active decomposition of H2O2 produced by Ag3PO4 was the main reason for the enhanced photocatalytic activities.

In this work, a novel Ag 3 PO 4 @CoFe 2 O 4 composite photocatalyst was synthesized via a phosphate salts alkalinity adjustment strategy. Structure, morphology, and chemical component analysis indicated that the magnetic CoFe 2 O 4 nanoparticles (NPs) were evenly decorated on the surface of Ag 3 PO 4 particles, forming a sesame ball like structure. This unique structure ensures that the Ag 3 PO 4 @CoFe 2 O 4 composites could be totally separated by the magnet field. Photocatalytic water disinfection and organic pollutants degradation were employed to evaluate the photocatalytic performance of the as-prepared magnetic photocatalysts. The results showed that the optimum 3% Ag 3 PO 4 @CoFe 2 O 4 composite could completely inactivate 1*10 7 cfu/mL of Escherichia coli within 40 min, much faster than the pristine Ag 3 PO 4 . Meanwhile, the 3% Ag 3 PO 4 @CoFe 2 O 4 composite also showed a dramatic enhancement of photocatalytic activities for the organic pollutants degradation. The reactive oxygen species yield measurements, O 2 control photocurrents experiments, O 2 -TPD tests and photoluminescence spectra analysis indicate that the surface modification of CoFe 2 O 4 NPs could facilitate the O 2 adsorption and O O bond activation/cleavage/oxide removal and accelerate the two-electron oxygen reduction reaction for H 2 O 2 generation on the surface of Ag 3 PO 4 , and thus more ROSs were generated. In addition, due to the acceleration of electrons consumption, more holes will be left for the organic pollutants oxidation, and the photocatalytic activities as well as stability of Ag 3 PO 4 therefore have been greatly improved.

A new tendency in supercapacitor research has focused on the construction of the inexpensive electrode materials with long cycle stability. In this study, TiO2/C3N4 hybrid materials are synthesized through an efficient, low-cost, facile hydrothermal approach followed by a heat treatment for the first time. The hybrid materials are further used as electrodes for supercapacitors. Interestingly, compared to pure TiO2 nanoparticles, TiO2/C3N4 hybrid materials exhibit excellent electrochemical performance with improved specific capacitance, great rate performance and cycling stability (capacitance retention of 100% after 1000 cycles), which can be attributed to good conductivity and low polarization resulting in a high utilization of active materials. Furthermore, it was found that the capacitive properties of TiO2/C3N4 hybrid were related to the pore sizes and electrical resistances of active materials. The electrode materials with smaller pore size and resistance showed higher capacitive properties.

Recently, nano/micro-scale Fe-based ferrites with high electrochemical performances have attracted extensive attention. However, almost all the mixed Fe-based oxide research paid close attention to the crystalline phase, despite the low-crystalline or amorphous phase possessing excellent electrochemical performance. Herein, a low-crystalline mesoporous cobalt ferrite and carbon composite (L-CoFe2O4/C) material with high surface area and superior electrical conductivity was prepared via a simple citric acid assisted sol–gel approach and calcination process. The L-CoFe2O4/C electrode exhibits an unprecedented specific capacitance (600 F g−1 at 1 A g−1), which precedes some of the reported mixed Fe-based ferrite electrodes and their crystalline counterparts. The excellent electrochemical performance can mainly be attributed to the sufficient diffusion and reaction of electrolyte ions, more surface defects (e.g. oxygen vacancies) for redox reactions, and the predominant electro-conductivity of the composite during the charging/discharging process. Moreover, an L-CoFe2O4/C-based asymmetric supercapacitor exhibited high energy density and power density, and outperformed most of the reported mixed Fe-based symmetric and asymmetric supercapacitors. These findings promote new opportunities for low-crystalline Fe-based metal oxides as high performance energy storage devices.

In order to construct a magnetic recyclable photocatalyst with superior photocatalytic performance and stability, Ag/AgBr photocatalysts modified by magnetic CoFe2O4 nanoparticles (NPs) were synthesized via deposition–precipitation followed by a solvothermal process. Such a synthesis strategy allows the even dispersion of CoFe2O4 NPs on the surface of Ag/AgBr. Besides, a Z-scheme photocatalyst with metallic Ag as a solid-state electron mediator was formed, which exhibits excellent photocatalytic activity and stability for photocatalytic degradation of hardly decomposed colorless phenol compounds, namely, endocrine disrupting chemical bisphenol A (BPA) and 4-chlorophenol (4-CP), in an aqueous solution. The results showed that the Ag/AgBr@CoFe2O4 composites not only exhibited enhanced photocatalytic performance but also improved stabilities. More importantly, the photocatalysts could be recycled easily by an external magnetic field. The antibacterial activity of the Ag/AgBr@CoFe2O4 composites have been investigated by eliminating Escherichia coli (E. coli) in water under visible light irradiation, and the results revealed that the Ag/AgBr@CoFe2O4 composites possessed good photocatalytic antibacterial activity. At last, the enhanced photocatalytic mechanisms were discussed by investigating the main reactive species in the photocatalytic process, which revealed that the photo-generated holes (h+) and O2˙− were the main reactive species.

Visible-light-driven magnetic CoFe2O4/Ag/Ag3VO4 photocatalysts with different weight ratios of CoFe2O4 were successfully synthesized by a hydrothermal method. The as-prepared samples have been characterized by X-ray diffraction (XRD), infrared (IR), scanning electron microscopy with an energy-dispersive X-ray spectroscope (SEM-EDS), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Ultraviolet–visible absorption spectroscopy (UV–vis) and vibrating sample magnetometer (VSM). The photocatalytic experiments indicate that the CoFe2O4/Ag/Ag3VO4 composites possess enhanced visible-light-driven photocatalytic activity towards the degradation of methyl orange (MO), tetracycline (TC) and killing Escherichia coli (E. coli). Electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectra analysis indicate that the introduction of CoFe2O4 could efficiently promote the separation efficiency of photogenerated charge carriers in Ag/Ag3VO4. It is obvious that the composites show better photocatalytic activity than the pure Ag/Ag3VO4 and CoFe2O4. In particular, the 5% CoFe2O4/Ag/Ag3VO4 sample shows the highest photocatalytic activity and the degradation constant of 5% CoFe2O4/Ag/Ag3VO4 is as high as 3.4 times to that of Ag/Ag3VO4. The trapping experiments show that O2− and h+ are the major reactive species for the CoFe2O4/Ag/Ag3VO4 photocatalytic system. In addition, the as-prepared CoFe2O4/Ag/Ag3VO4 composite can be quickly separated from the solution by an extra magnetic field after the photocatalytic reaction. The cyclic test and the XRD patterns before and after cyclic test show that the CoFe2O4/Ag/Ag3VO4 hybrid materials have the stable degradation ability and crystal structure during the photodegradation process. Furthermore, it shows highly efficient visible light photocatalytic antibacterial activity. In all, the CoFe2O4/Ag/Ag3VO4 photocatalyst, as the magnetic photocatalyst and antibacterial, is promising for the further practical application of photocatalysis in wastewater treatment.

Light absorption and carrier transfer, are two sequential and complementary steps related to photocatalysis performance, whereas the collective integration of these two aspects into graphitic carbon nitride (g-C3N4) photocatalyst through polycondensation optimization have seldom been achieved. Herein, we report on tailoring the crystalline structure of g-C3N4 by avoiding the formation of incompletely reacted N-rich intermediates and selective breaking the hydrogen bonds between the layers of g-C3N4 simultaneously. The obtained layer plane ordered porous carbon nitride (LOP-CN) material shows efficient photocatalytic H2 generation performance. The highest H2 evolution rate achieved is 53.8 μmol under λ ≥ 400 nm light irradiation, which is 7.4 times higher than that of g-C3N4 prepared by convention thermal polycondensation. The substantially boosted photocatalytic activity is mainly ascribed to the efficient charge separation on long-range atomic order layer plane and the extended visible light harvesting ability. This work highlights the importance of crystalline structure tailoring in improving charge separation and light absorption of g-C3N4 photocatalyst for boosting its photocatalytic H2 evolution activity.

For this study, ionic liquid-modified carbon nitride (hm-CN) was one-step synthesized by 1-butyl-3-methylimidazolium cyanamide and carbon nitride (g-C3N4). After the addition of ionic liquids, the structural change of hm-CN increases the separation of photogenerated electron holes and improves the photocatalytic performance. The colorless pollutant bisphenol A (BPA) is degraded as the target pollutant under the visible light irradiation. The catalytic performance of g-C3N4 modified by ionic liquid is better than pure g-C3N4. The best performance is 30hm-CN, which degrades 95% of the pollutants in 3 hours. Its degradation performance is 4.5 times that of pure g-C3N4 and the degradation performance is still excellent after three cycles. According to electron spin resonance (ESR) and trapping experiments, h+ and •O2− play a key role in the photocatalytic degradation process. In addition, we conducted a series of condition experiments to perform degradation under different catalyst concentrations, different ions and different pH to fully understand the impact of external interference on the catalyst. At the same time, the sample also has good activity in degrading other pollutants (Rhodamine B, Methylene blue, Tetracycline, Ciprofloxacin). This study simply designed a method to synthesize ionic liquid modified g-C3N4 for improving photocatalytic performance, and provided a new idea for the research of carbon nitride modification at the same time.

A novel ternary composite photocatalyst (g-C3N4/BiOI/BiOBr) was prepared via a facile solvothermal method. The samples were characterized by powder X-ray diffraction, transmission electron microscopy, UV-visible diffuse reflection spectrometry, X-ray photoelectron spectrometry and photoluminescence measurements. Under irradiation with visible light, the g-C3N4/BiOI/BiOBr photocatalyst showed a higher photocatalytic activity than pure g-C3N4 and BiOI/BiOBr for the degradation of methylene blue. Among the hybrid photocatalysts, 3% g-C3N4/BiOI/BiOBr showed the highest photocatalytic activity for the degradation of MB. These results suggest that the heterostructure combination of g-C3N4, BiOI and BiOBr provides a synergistic effect through an efficient charge transfer process.

CNT/AgI composite with the diameter smaller than 1 µm was synthesized through a solvothermal method. The CNT/AgI hybrids were characterized by XRD, SEM, XPS, UV-Vis, photocurrent and so on. The results showed that the introduced CNT can greatly reduce the particle size of AgI without using surfactant. Besides, the introduced CNT transferred the electrons efficiently and enhanced the photoactivity of the CNT/AgI hybrids in degrading RhB dye. 0.3% CNT/AgI showed the highest photocatalytic activity, which was as high as about 2 times that of pure Ag/AgI. Trapping experiments and the electron spin resonance (ESR) results suggested the reactive species in the degradation process were h+, ˙OH and ˙O2−. Furthermore, the CNT/AgI still showed high photoactivity after 4 cycle experiments. Photocatalytic antibacterial experiments showed that the 0.3% CNT/AgI had better antibacterial ability than pure Ag/AgI. The results showed that the CNT/AgI can be used as a dual functional material in water treatment of removing the organic pollutant and killing the bacterium at the same time.

Black phosphorus (BP) is one of the most attracting materials that has been the subject of a theoretically predicted on photocatalytic CO2 reduction reactions. However, due to the limited stability, it has not been reported as a main catalyst in the photocatalytic reduction of CO2. For the first time, we have successfully demonstrated that an excellent stable monolayer BP with hydroxyl modification (M-BP-OH) can be in-situ obtained via a green exfoliation method assisted by liquid nitrogen, and used as photocatalysts for CO2 reduction. The hydroxy functional groups could occupy the lonely pair electrons site, inhibiting the reaction between this lonely pair electrons and oxygen to finally form stable monolayer BP. The as-prepared M-BP-OH showed a visible light active photocatalytic CO production rate of 112.6 μmol h−1 g−1, which was 4 times higher than that of bulk BP (25.3 μmol h−1 g−1). Moreover, the M-BP-OH survived with the stringent humid air (90 % humidity, 24 h), ambient conditions (30 days) and cycling tests (300 W Xe lamp, 60 h). Metal-free BP as a main catalyst, has high potential in photocatalytic CO2 reduction demonstrated by the combined characteristics of high stability, high performance and low cost.

A prototype aerosol detection system is presented that is designed to accurately and quickly measure the concentration of selected inorganic ions in the atmosphere. The aerosol detection system combines digital microfluidics technology, aerosol impaction and chemical detection integrated on the same chip. Target compounds are the major inorganic aerosol constituents: sulfate, nitrate and ammonium. The digital microfluidic system consists of top and bottom plates that sandwich a fluid layer. Nozzles for an inertial impactor are built into the top plate according to known, scaling principles. The deposited air particles are densely concentrated in well-defined deposits on the bottom plate containing droplet actuation electrodes of the chip in fixed areas. The aerosol collection efficiency for particles larger than 100 nm in diameter was higher than 95%. After a collection phase, deposits are dissolved into a scanning droplet. Due to a sub-microliter droplet size, the obtained extract is highly concentrated. Droplets then pass through an air/oil interface on chip for colorimetric analysis by spectrophotometry using optical fibers placed between the two plates of the chip. To create a standard curve for each analyte, six different concentrations of liquid standards were chosen for each assay and dispensed from on-chip reservoirs. The droplet mixing was completed in a few seconds and the final droplet was transported to the detection position as soon as the mixing was finished. Limits of detection (LOD) in the final droplet were determined to be 11 ppm for sulfate and 0.26 ppm for ammonium. For nitrate, it was impossible to get stable measurements. The LOD of the on-chip measurements for sulfate was close to that obtained by an off-chip method using a Tecan spectrometer. LOD of the on-chip method for ammonium was about five times larger than what was obtained with the off-chip method. For the current impactor collection air flow (1 L/min) and 1 h collection time, the converted LODs in air were: 0.275 μg/m3 for sulfate, 6.5 ng/m3 for ammonium, sufficient for most ambient air monitoring applications.

Antibiotics in natural waters have posed serious threats to our ecosystem due to its potent biological toxicity. In the present work, a visible-light-driven PANI/Bi4O5Br2 composite photocatalyst was fabricated and used for the degradation of ciprofloxacin (CIP) and tetracycline (TC) antibiotics under visible light (λ ＞ 420 nm). The PANI/Bi4O5Br2 composite presented a significantly improved ability of CIP and TC photodegradation, which is about 2.2 times and 1.6 times to that of Bi4O5Br2, respectively. The promoted photocatalytic activity results from the interface interaction between PANI and Bi4O5Br2, which contributes to the electron-hole separation. The degradation process of CIP was monitored by mass spectrometry, and a possible degradation pathway was proposed based on the analysis of the product. A microbiological antibacterial experiment was designed, proving that the degraded products of CIP and TC have lower toxicity. Furthermore, long wavelength light irradiated (λ ＞ 550 nm) experiment indicated that the introduction of PANI helps to extend the light absorption region and use the long wavelength light more efficiently, thereby promoting the photocatalytic ability. The optimal composite applied for TC degradation was 0.1% PANI/Bi4O5Br2. Its reaction rate constant was 2.8 times to that of Bi4O5Br2 (λ ＞ 550 nm). Eventually, a possible photocatalytic mechanism over PANI/Bi4O5Br2 composite was proposed.

ZnFe2O4/AgI composites were first prepared successfully with a hydrothermal method, and ZnFe2O4 nanoparticles were uniformly decorated on the surface of AgI particles. The photocatalytic activities of the obtained ZnFe2O4/AgI composites were investigated by the degradation of organic pollutants and the inactivation of bacteria under visible light irradiation. The results showed that the introduction of ZnFe2O4 greatly enhanced the light harvesting ability and improved the separation efficiency of the photogenerated charge carriers, which contributed to the enhanced generation of reactive species and thus promoted the photocatalytic performance. The 5% ZnFe2O4/AgI composite exhibited the optimal photocatalytic disinfection of E. coli (100% removal efficiency in 80 min) as well as the photocatalytic degradation of rhodamine B (RhB) (98.5% removal rate in 40 min). Furthermore, four consecutive cycles also demonstrated the stable photocatalytic activity of the as-prepared ZnFe2O4/AgI composites. In addition, H2O2 was identified as the predominant active species in the photocatalytic inactivation of bacteria. This study indicated that ZnFe2O4/AgI composites are a promising candidate for the treatment of wastewater.

A magnetic photocatalytic CoFe2O4/g-C3N4 composite was successfully synthesized by a simple calcination method. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared (IR) spectra, UV–Vis diffuse reflection spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS) were applied to characterize the as-prepared samples. The magnetic properties of CoFe2O4 and CoFe2O4/g-C3N4 composites were measured by using a vibrating sample magnetometer (VSM) at room temperature. Photocatalytic property of the CoFe2O4/g-C3N4 composite was assessed by degrading methylene blue (MB) in aqueous medium under visible light irradiation. The results showed that the composite of 41.4% CoFe2O4/g-C3N4 exhibited the highest photocatalytic activity. It could activate H2O2 to degrade MB up to 97.3% in 3 h under the visible light irradiation. This enhancement could be attributed to the synergistic effect between CoFe2O4 and g-C3N4, which could enhance their activity of activating H2O2 to degrade MB under visible light. The CoFe2O4/g-C3N4 composites also have a strong magnetic ability. After the photocatalytic reaction, it can be quickly separated from the water by an extra magnetic field. Moreover, a possible photocatalytic mechanism was proposed.

A core–shell structured magnetic Ag/AgBr@Fe2O3 composite was synthesized through a facile solvothermal method. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible absorption spectroscopy (UV-vis) were applied to characterize the structures and properties of the as-prepared samples. The results indicate that Fe2O3 was coated on the surface of Ag/AgBr and heterostructures were formed. Electrochemistry analysis and photoluminescence (PL) spectra analysis indicate that the introduction of Fe2O3 could improve electron and hole separation efficiency. The photocatalytic activity of the Ag/AgBr@Fe2O3 composites was evaluated by using organic dye methyl orange (MO), endocrine disrupting chemical bisphenol A (BPA) and Escherichia coli (E. coli) as the target pollutants. The as-prepared Ag/AgBr@Fe2O3 composites exhibited much higher photocatalytic activities than pure Ag/AgBr, which was attributed to the effective charge separation of the Ag/AgBr@Fe2O3 composite. In addition, the as-prepared Ag/AgBr@Fe2O3 composite has magnetic properties, therefore after the photocatalytic reaction, it can be quickly separated from solution by an extra magnetic field. Trapping experiments and ESR analysis indicate that the h+ and ˙O2− are the main active species for the photocatalytic degradation. A possible Z-scheme pathway photocatalytic mechanism was proposed.

Novel plasmonic photocatalysts, Ag/AgCl/CoFe2O4, were prepared via a two-step synthesis method. The obtained Ag/AgCl/CoFe2O4 composites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible absorption spectroscopy (UV-vis). The magnetic properties of the samples were studied by vibrating sample magnetometer (VSM) analysis. Methyl orange (MO), bisphenol A (BPA) and ciprofloxacin (CIP) were used as target pollutants to investigate the degradation capability of Ag/AgCl/CoFe2O4. Results showed that the composite can degrade both colored and colorless pollutants, while Ag/AgCl/CoFe2O4 (3 : 1) composite showed the highest photoactivity in the degradation of MO. It can degrade about 93.38% MO in 1.5 h. The reactive species scavenger results indicated that hydroxyl radicals (˙OH) were not the main photooxidant, while holes (h+) and superoxide anion radicals (˙O2−) played key roles in MO decoloration. Furthermore, the degraded solution of BPA was analyzed using high performance liquid chromatography (HPLC). The results showed that BPA was decomposed gradually. The composite was magnetically separated and investigated using three successive recycle experiments under visible light. The results exhibited that the photoactivity of Ag/AgCl/CoFe2O4 is stable. Besides, Ag/AgCl/CoFe2O4 also exhibited good antibacterial activity against Escherichia coli (E. coli). The method used to prepare the composite can be expanded and applied to synthesize other magnetically separable photocatalysts.

A two-step method was developed to prepare magnetic separable Fe2O3/g-C3N4 photocatalysts. The samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible absorption spectroscopy (UV-vis), photoluminescence (PL) spectroscopy and X-ray photoelectron spectroscopy (XPS). The magnetic capability of the samples was investigated by vibrating sample magnetometer (VSM) analysis. The crystal phase and the magnetic property of the Fe2O3 can be tuned by changing the calcination temperature. The Fe2O3/g-C3N4 photocatalyst showed enhanced photoactivity in degrading the rhodamine B (RhB) dye. Among the samples, the 10% Fe2O3/g-C3N4 showed the highest photocatalytic activity. It can degrade about 96.7% RhB in 4 h. The photocurrent results confirm that the combination of the two materials is beneficial for the separation of electron–hole pairs. The electron spin resonance (ESR) results indicates that ˙O2− and ˙OH are the main active species in the degradation process.

Nano-size g-C3N4 derivatives were fabricated by a simple dissolve-regrowth method in HNO3 solution followed by a calcination process. X-ray diffraction (XRD), Z-potential, elemental analysis and IR are used to investigate the structure, composition and the properties of the samples. Scanning electron microscopy (SEM) shows the average size of the nano-size g-C3N4 derivatives increases with increasing calcination temperature. Methyl orange (MO) dye was used as the target pollutant to investigate the photoactivity of the samples. The pure g-C3N4 can only degrade about 1.1% MO, while the g-C3N4 derivatives calcined at 300 °C can decompose about 31.9% of MO in 4 h. Besides, when a small amount of methylene blue (MB) solution was introduced, the g-C3N4–HNO3-300 can decompose about 75.8% in 4 h. The photoactivity of g-C3N4 was greatly enhanced after the modification process (especially with the assistance of MB). Additionally, this work supplied a simple method to modify materials with enhanced photoactivity. Finally, the possible reactive species and the possible mechanism were proposed based on Electron spin resonance (ESR) and XPS results.

The Ag/AgCl/g-C 3 N 4 composites were prepared by in situ oxidation process. During the process, the prefabricated Ag nanoparticles well dispersed on the surface of g-C 3 N 4 employed as a template and oxidized by FeCl 3 to form the Ag/AgCl core–shell structure. The resultant samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (IR) spectroscopy and UV–vis diffuse-reflection spectra (DRS). As a kind of visible-light-driven plasmonic photocatalysts, the Ag/AgCl/g-C 3 N 4 with the Ag/AgCl amount of 2.7 at% achieved the best photocatalytic activity for the methyl orange (MO) dye degradation. The photocatalytic degradation rate was 6.77 and 6.27 times as that of the g-C 3 N 4 and Ag/g-C 3 N 4 composites. The results indicated that the cooperative or synergistic effects between Ag/AgCl and g-C 3 N 4 was existed which facilitated the separation of photo-induced electron–hole pairs and enhanced the photoactivity. Based on the results, a possible visible-light photocatalytic degradation mechanism was also discussed.