In Vitro Cytotoxicity Evaluation of Highly Absorbent Foam Dressings Based on Silver Zirconium Phosphate via IC50 Value

In this study, we, for the first time, tried to apply IC50 values (inhibitory concentration estimated to affect the endpoint in question by 50%) in the MTT colorimetric assay to investigate the cytotoxic effects of highly absorbent foam dressings based on silver zirconium phosphate, a newly nano-based matrix. Our results showed that silver released from dressings based on silver zirconium phosphate attributed mainly to highly cytotoxic to L929 cells cultured with MEM containing 10% fetal bovine serum. In addition, we have also compared the IC50 values among different dilutions of AgNO3 solution, silver based dressing extracts and material reference control (ZDEC) extracts using the optimized MTT assay, along with characterizing the silver content in the dressing extracts using atomic absorption spectroscopy. Results have shown that the IC50 values of AgNO50 solution, silver based dressing extracts and ZDEC extracts are 3.5 μg/mL, 3.8 μg/mL and 8.4%, respectively. And there exist some good agreements between qualitative and quantitative evaluation method as well. In conclusion, our study has led to the view that the IC50 value is a promising quantitative index for screening cytotoxicity with regard to silver based dressings.

Ag_3PO_4/Ag_2CO_3 p–n heterojunction composites with enhanced photocatalytic activity under visible light

Formation of a p–n heterojunction rather than p-type or n-type semiconductors can enhance the separation of photogenerated electrons and holes and increase the quantum efficiency of photocatalytic reactions owing to the difference of the electric potential in the inner electric field near the junction,pointing from n toward p. n-Ag3PO4/p-Ag2CO3 p–n heterojunction composites are prepared through a facile coprecipitation process. The obtained Ag3PO4/Ag2CO3 p–n heterojunctions exhibit excellent photocatalytic performance in the removal of rhodamine B（RhB） compared with Ag3PO4 and Ag2CO3. The 40%-Ag3PO4/Ag2CO3 composite photocatalyst（40 mol% Ag3PO4 and 60 mol% Ag2CO3） exhibits the best photocatalytic activity under visible light,demonstrating the ability to completely degrade RhB within 15 min. Transient photovoltage characterization and an active species trapping experiment further indicate that the formation of a p–n heterojunction structure can greatly enhance the separation efficiency of photogenerated carriers and produce more free h＋active species,which is the predominant contributor for RhB removal.

Construction of Ag_3PO_4/Ag_2MoO_4 Z-scheme heterogeneous photocatalyst for the remediation of organic pollutants

Hole/electron separation and charge transfer are the key processes for enhancing the visible-light photocatalysis performance of heterogeneous photocatalytic systems.To better utilize and understand these effects,binary Ag3PO4/Ag2MoO4 hybrid materials were fabricated by a facile solution-phase reaction and characterized systematically by X-ray diffraction（XRD）,energy-dispersive spectroscopy,Fourier transform infrared spectroscopy,Raman spectroscopy,field-emission scanning electron microscopy and ultraviolet-visible diffuse-reflectance spectroscopy.Under visible-light illumination,a heterogeneous Ag3PO4/Ag/Ag2MoO4 photocatalyst was constructed and demonstrated enhanced photocatalytic activity and photostability compared with pristine Ag3PO4toward the remediation of the organic dye rhodamine B.The Ag3PO4/Ag2MoO4 hybrid catalyst with8%mole fraction of Ag2MoO4 exhibited the highest photocatalytic activity toward the removal of typical dye molecules,including methyl orange,methylene blue and phenol aqueous solution.Moreover,the mechanism of the photocatalytic enhancement was investigated via hole- and radical-trapping experiments,photocurrent measurements,electrochemical impedance spectroscopy and XRD measurements.The XRD analysis revealed that metallic Ag nanoparticles formed initially on the surface of the Ag3PO4/Ag2MoO4 composites under visible-light illumination,leading to the generation of a Ag3PO4/Ag/Ag2MoO4 Z-scheme tandem photocatalytic system.The enhanced photocatalytic activity and stability were attributed to the formation of the Ag3PO4/Ag/Ag2MoO4Z-scheme heterojunction and surface plasmon resonance of photo-reduced Ag nanoparticles on the surface.Finally,a plasmonic Z-scheme photocatalytic mechanism was proposed.This work may provide new insights into the design and preparation of advanced visible-light photocatalytic materials and facilitate their practical application in environmental issues.

Photocatalytic degradation of dyes by AgBr/Ag_3PO_4 and the ecotoxicities of their degraded products

Ag3PO4 powders were prepared through a precipitation reaction between AgNO3 and precipitating agent solutions that were prepared by adjusting the amount of H3PO4 in the Na3PO4 solutions. The Ag3PO4 powders prepared from the precipitation solution with a pH of 6 showed the highest photocatalytic activity for decolorizing the methylene blue and rhodamine B dyes. These Ag3PO4 powders were further modified by the addition of KBr solutions to obtain AgBr/Ag3PO4 powders and these photocatalysts can decolorize the anionic dyes as reactive orange and methyl orange. The reactive species involved in the photocatalytic degradation process were evaluated for their inhibitory activity using the appropriate scavengers. After photocatalysis, mass spectrometry confirmed that the dyes were degraded to smaller molecules. The ecotoxicities of the dye solutions before and after treatment were evaluated by studying their ability to inhibit the growth of the bioindicator Chlorella vulgaris.

Recent progress in Ag_3PO_4-based all-solid-state Z-scheme photocatalytic systems

Heterogeneous semiconductor photocatalysis is a promising green technology solution to energyand environmental problems.Traditional photocatalyst TiO2,with a wide band gap of3.2eV,canonly be excited by UV light and utilizes less than4%of solar energy.Silver phosphate(Ag3PO4)isamong the most active visible‐light‐driven photocatalysts reported.Unfortunately,unwanted photocorrosionis the main obstacle to the practical application of Ag3PO4.Much effort has been made inrecent years to address this issue and further enhance the photocatalytic performance of Ag3PO4.The construction of Z‐scheme photocatalytic systems that mimic natural photosynthesis is a promisingstrategy to improve the photocatalytic activity and stability of Ag3PO4.This brief review conciselysummarizes and highlights recent research progress in Ag3PO4‐based all‐solid‐state Z‐schemephotocatalytic systems with or without a solid‐state electron mediator,focusing on their construction,application,and reaction mechanism.Furthermore,the challenges and future prospects ofAg3PO4‐based Z‐scheme photocatalytic systems are discussed.

Ag3PO4 colloidal nanocrystal clusters with controllable shape and superior photocatalytic activity

Cluster-like Ag3PO4 nanostructures including nanoparticles, trisoctahedrons, tetrahedrons and tetrapods have been prepared by the synergetic reaction of Ag nanocrystals, phosphate anions and hydrogen peroxide. The acidity and alkalinity of the reaction solution are tuned to adjust the oxidizing ability of H2O2, and thus control the final morphology. Ag nanocrystals function as a sacrificial precursor, leading to the generation of clusterqike nanostructures. Through a kinetic study, the formation of Ag3PO4 nanocrystal clusters can be understood as the conversion from Ag to AgBPO4 nanocrystals assisted by H2O2, followed by the oriented attachment of nanocrystals into cluster-like colloids with specific shapes. The as-prepared AgBPO4 nanostructures have higher photocatalytic activity than commercial TiO2 and some reported AgBPO4 microcrystals in the degradation of dyes. The catalytic activity decreases in the order nanoparticles 〉 trisoctahedrons 〉 tetrahedrons 〉 tetrapods, while the stability increases in the order nanoparticles 〈 tetrahedrons 〈 trisoctahedrons 〈 tetrapods, which can be explained by the extent of absorption of visible light and structural factors, including size and exposed crystal facets.

Highly Efficient Photocatalytic Remediation of Simulated Polycyclic Aromatic Hydrocarbons （PAHs） Contaminated Wastewater under Visible Light Irradiation by Graphene Oxide Enwrapped Ag3PO4 Composite

Effective removal of polycyclic aromatic hydrocarbons （PAHs） from wastewater before their discharge into the environment is an ever pressing requirement. In this study, for the first time, simulated PAHs contaminated wastewater was photocatalytically remediated with graphene oxide （GO） enwrapped silver phosphate as visible light-driven photocatalysts. The GO/Ag3PO4 photocatalysts exhibited superior photocatalytic activity and stability compared with pure Ag3PO4, g-C3N4 and TiO2 （P25）. The degradation efficiency of naphthalene, phenanthrene and pyrene could reach 49.7%, 100.0% and 77.9%, rspectively within 5 min irradiation. The apparent rate constants of photocatalytic degradation of 3 wt% GO/Ag3PO4 composRe photocatalyst were 0.14, 1.21 and 2.46 rain^-1 for naphthalene, phenanthrene and pyrene, respectively. They were about 1.8, 1.5 and 2.0 times higher than that of pure Ag3PO4, and much higher than that of g-C3N4 and TiO2. Meanwhile, the efficiencies of 44.6%, 95.2% and 83.8% were achieved for naphthalene, phenanthrene and pyrene degradation even after 5 times of recycling in the GO/Ag3POa-PAHs photocatalysis system. Reactive species of O2^- and h^＋ were considered as the main partici- pants for oxidizing naphthalene, phenanthrene and pyrene.

Cytocompatible 3D chitosan/hydroxyapatite composites endowed with antibacterial properties:toward a self-sterilized bone tissue engineering scaffold

Bone tissue scaffolds based on bioactive polymer–hydroxyapatite composites have caused infections that seriously limit their extended application. In this study, we proposed a practical ion substitution method to synthesize in situ silver phosphate on the surface of a two-level, threedimensional chitosan/nano-hydroxyapatite scaffold. A release test of silver ions in a phosphate buffered saline(PBS) solution was performed to demonstrate that silver ions were released continuously from the silver phosphate during the initial 6 days of the study. The antibacterial property and cytocompatibility of the scaffolds treated with different concentrations of silver nitrate solution were assessed by in vitro assays with Escherichia coli and MC3T3-E1, respectively. The ability of the silver-containing scaffolds to induce bacteriostasis was confirmed by the inhibition zone(15 mm) and high bactericidal rate([99 %). Cell proliferation, morphology and the alkaline phosphatase activity of MC3T3-E1 cultured on the scaffold with low silver phosphate contents were comparable with those cultured on control samples.