Antimicrobial Activity, Structural, Crystallographic and Thermal Characteristics of Alpha-Titanium Phosphate Promoted by Silver Ions

The recent global spread of the pandemic underscores the necessity of seeking new materials effective against microorganisms. Nanotechnology offers avenues for developing multifunctional materials. In this study, alpha-titanium phosphate (α-TiP) nanoparticles were synthesized and treated with silver salt to enhance their antimicrobial properties. The physicochemical characteristics and antimicrobial activity were evaluated. It was revealed by X-ray diffraction analysis that the structural integrity of α-TiP was influenced by ethylenediamine and silver ions. Distinct degradation profiles for each chemical modification were shown by thermogravimetric analysis. Infrared spectroscopy detected shifts and new absorption peaks in the spectra depending on the type of modification. Energy dispersive spectroscopy confirmed the disaggregation of α-TiP galleries following the addition of silver salt, which increased their effectiveness against microorganisms. Notably, only the sample treated with silver ions exhibited antimicrobial action. Antimicrobial activity was tested against the bacteria of medical importance Escherichia coli, Salmonella Enteritidis, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus cereus, Listeria momocytogenes and the yeast Candida albicans. All microorganisms were inhibited by sample containing silver. Minor inhibition was observed against the Gram-positive bacteria L. monocytogenes and Bacillus cereus, while the greatest inhibition occurred against the fungus (yeast) C. albicans. The results revealed a potential application of the nanoparticles for control of microorganisms in public health.

One-year water-ageing of calcium phosphate composite containing nano-silver and quaternary ammonium to inhibit biofilms

Dental composites are commonly used restorative materials; however, secondary caries due to biofilm acids remains a major problem. The objectives of this study were （1） to develop a composite containing quaternary ammonium dimethacrylate （QADM）, nanoparticles of silver （NAg）, and nanoparticles of amorphous calcium phosphate （NACP）, and （2） to conduct the first investigation of the mechanical properties, biofilm response and acid production vs water-ageing time from 1 day to 12 months. A 4 x 5 design was utilized, with four composites （NACP-QADM composite, NACP-NAg composite, NACP-QADM-NAg composite, and a commercial control composite）, and five water-ageing time periods （1 day, and 3, 6, 9, and 12 months）. After each water- ageing period, the mechanical properties of the resins were measured in a three-point flexure, and antibacterial properties were tested via a dental plaque biofilm model using human saliva as an inoculum. After 12 months of water-ageing, NACP-QADM- NAg had a flexural strength and elastic modulus matching those of the commercial control （P〉 0.1）. Incorporation of QADM or NAg into the NACP composite greatly reduced biofilm viability, metabolic activity and acid production. A composite containing both QADM and NAg possessed a stronger antibacterial capability than one with QADM or NAg alone （P〈0.05）. The anti-biofilm activity was maintained after 12 months of water-ageing and showed no significant decrease with increasing time （P〉0.1）. In conclusion, the NACP-QADM-NAg composite decreased biofilm viability and lactic acid production, while matching the load- bearing capability of a commercial composite. There was no decrease in its antibacterial properties after 1 year of water-ageing. The durable antibacterial and mechanical properties indicate that NACP-QADM-NAg composites may be useful in dental restorations to combat caries.

Antimicrobial effects of silver zeolite,silver zirconium phosphate silicate and silver zirconium phosphate against oral microorganisms

Objective:To evaluate the antimicrobial activities of silver inorganic materials,including silver zeolite(AgZ),silver zirconium phosphate silicate(AgZrPSi)and silver zirconium phosphate(AgZrp),against oral microorganisms.In line with this objective,the morphology and structure of each type of silver based powders were also investigated.Methods:The antimicrobial activities of AgZ,AgZrPSi and AgZrP were tested against Streptococcus mutans,Lactobacillus casei,Candida albicans and Staphylococcus aureus using disk diffusion assay as a screening test.The minimum inhibitory concentration(MIC)and minimum lethal concentration(MLC)were determined using the modified membrane method.Scanning electron microscope and X-ray diffraction were used to investigate the morphology and structure of these silver materials.Results:All forms of silver inorganic materials could inhibit the growth of all test microorganisms.The MIC of AgZ,AgZrPSi and AgZrP was 10.0 g/L whereas MLC ranged between 10.0-60.0 g/L.In terms of morphology and structure.AgZrPSi and AgZrP had smaller sized particles(1.5-3.0μm)and more uniformly shaped than AgZ.Conclusions:Silver inorganic materials in the form of AgZ,AgZrPSi and AgZrP had antimicrobial effects against all test oral microorganisms and those activities may be influenced by the crystal structure of carriers.These results suggest that these silver materials may be useful metals applied to oral hygiene products to provide antimicrobial activity against oral infection.

One-step electrodeposition to fabricate robust superhydrophobic silver/graphene coatings with excellent stability

A facile method was proposed to prepare stretchable silver-based composite coatings with excellent conductivity and stability for flexible electronics.Silver coating was firstly deposited on thermoplastic polyurethane(TPU)elastomer rubber surface via two-component spraying technique,then the superhydrophobic surface was obtained by one-step electrodeposition of cerium compounds(CeM)and graphene nanosheets(GNS)to produce Ag/CeM/GNS composite coatings.The obtained Ag/CeM/GNS composite coatings maintained high conductivity after experiencing bending cycles and stretching cycles.Furthermore,the as-prepared Ag/CeM/GNS composite coatings showed excellent self-cleaning and anti-fouling properties,and the corrosion resistance has improved significantly compared to the original Ag coating.In addition,the Ag/CeM/GNS composite coatings could drive the circuit normally in the states of tensile,bending and twisting deformation,showing excellent mechanical stability and applicability.As a result,it is believed that the prepared Ag/CeM/GNS composite coatings with excellent conductivity and stability have promising applications for flexible electronics in harsh conditions.

Preparation, Characterization and Properties of Graphene-silver Sulphide Hybrid

A facile and efficient strategy was reported for the preparation of graphene nanosheets-Ag2S hybrid by a simple hydrothermal process. First, Ag2S particles deposited on the surface of graphene oxide（GO） sheet. GO was then reduced by hydrazine hydrate to graphene. The results of X-ray diffraction（XRD） and Fourier transform infrared（FTIR） demonstrated the efficient reduction of GO to graphene. Transmission electron microscopy（TEM） image of the sample reveals the morphology of the architecture of graphene-Ag2S hybrid. Ultraviolet-visible spectroscopy（UV-Vis） and photoluminescence（PL） measurement were further employed to study the optical properties of the obtained nanocomposite. This work can be extended to design other graphene-based hybrid nanomaterials, and the as-grown architectures may hold promise for many applications.

Optical properties of phosphate glasses co-doped with Yb^(3+) and silver nanoparticles

We report the fabrication and spectroscopic characterization of Yb^3＋-doped phosphate glass, also containing silver nitrate. Scanning electron microscopy（SEM） provides the evidence of the formation of silver nano-particles（SNPs）, which are formed as a consequence of melting and thermal decomposition of Ag NO3. Absorption spectra of the samples in the visible-to-near-infrared spectral range reveal the presence of bands centered at 410 nm associated with the SNP-plasmon resonance, and at 976 nm due to the Yb^3＋. Under 916-nm laser-diode pumping, the effect of the SNP reflects that： i） the fluorescence in the 950-nm–1150-nm spectral range is strongly enhanced（～ 30 times）, while the fluorescence decay time associated with the ^2F5/2→^2F7/2transition of Yb^3＋ increases 25%, and ii） the basic lasing properties（saturation pumping intensity, the emission and absorption cross sections） are substantially improved.

Thermoelectric characteristics of flexible reduced graphene oxide/silver selenide nanowire composites prepared by a facile vacuum filtration process

The reduced graphene oxide/silver selenide nanowire(rGO/Ag;Se NW)composite powders were fabricated via a wet chemical approach,and then flexible rGO/Ag;Se NW composite film was prepared by a facile vacuum filtration method combined with cold-pressing treatment.A highest power factor of 228.88μW·m;·K;was obtained at 331 K for the cold-pressed rGO/Ag;Se NW composite film with 0.01 wt%r GO.The rGO/Ag;Se NW composite film revealed superior flexibility as the power factor retained 94.62%after bending for 500 times with a bending radius of 4 mm,which might be due to the interwoven network structures of Ag;Se NWs and pliability of r GO as well as nylon membrane.These results demonstrated that the GO/Ag;Se NW composite film has a potential for preparation of flexible thermoelectric devices.

Malus domestica and Solanum lycopersicum Mixtures for the Synthesis of Graphene Silver and Zinc Oxide Nanocomposites

This study reports on the novel and simple green method involving the use of apple (Malus domestica) and tomato (Solanum lycopersicum) extracts in the synthesis of electroactive layers of silver nanoparticles|graphene oxide (AgNPs|GO) and zinc oxide nanoparticles|graphene oxide (ZnONPs|GO). The surface morphology of the green synthesized nanocomposites was studied using High-Resolution Transmission Electron Microscopy (HRTEM), High-Resolution Scanning Electron Microscopy (HRSEM) while the elemental analysis was studied using Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy and X-Ray diffraction (XRD) and their optical properties were further characterised using Ultraviolet Spectroscopy (UV-vis). The electrochemical studies of these nanocomposites were achieved using cyclic voltammetry (CV) where an increase in electron conductivity of the AgNPs|GO and ZnONPs|GO nanocomposite was observed. Comparatively, the silver nanoparticulate-based platforms were observed to have superior electrochemical properties as opposed to the zinc oxide-based platform. The observed electrochemical activities of the synthesized nanocomposites are a good indication of their suitability as electroactive platforms towards the development of electrochemical sensors. Electrochemical sensors are popular in the Electrochemistry field because they may be developed using different methods in order to suit their intended analytes. As such, the synthesis of a variety of electrochemical platforms provides researchers with a vast range of options to select from for the detection of analytes.

About New Inorganic Polymers-Double Condensed Phosphates of Silver and Trivalent Metals

A distinctive feature of phosphates is their special and significant ability to form inorganic polymeric compounds---condensed phosphates, which are destined to play a considerable role in our ＂high-tech＂ society in the future. Numerous olygophosphates, polyphosphates, double condensed phosphates and cyclophosphates with diverse formula, such as double tetra-, octa- and dodecaphosphates were obtained and described by us last years. The offered data are the outcomes of our scientific researches： of synthesis, analysis, and estimation of results in correlation with new achievements in inorganic polymer＇s chemistry. Many double condensed compounds, containing monovalent metals are obtained by us during systematic investigation of polycomponent systems, containing mono- and trivalent metals at temperature range 100-600 ~C. Synthesised condensed phosphates, in fact--inorganic polymers were examined in detail by chemical and thermogravimetric analysis, most compounds were examined by paper chromatography and the structures are determined by X-ray structural techniques/diffraction analysis. During our fundamental researches numerous new （about 70） unknown until now condensed phosphates have been obtained. Dependency of composition VS temperature and molar ratio, reliance of structure from duration of synthesis and radius of the ions are revealed.

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.

Zinc and Silver Salts-Containing Lamellar Titanium Phosphate: A Multifunctional Filler

Zinc and silver compounds have been studied because they have ultraviolet light barrier properties and bactericidal action, respectively. Materials with multifunctional characteristics have been sought to produce polymeric nanocomposites. In this work, the chemical modification of titanium phosphate (TiP) was carried out through a route with successive intercalations. TiP was synthesized and consecutively pre-expanded with ethylamine and pyromellitic acid. Then it was modified with zinc acetate and silver nitrate. The final product was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, wide-angle X-ray diffractometry, field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and thermogravimetry. Infrared revealed dislocation and appearance of bands according to the intercalating agent. Inorganic salts interfered in the crystallization and melting processes of pyromellitic acid. Vanishing of the TiP hkl plane and variation and appearance of new crystallographic planes at low diffraction angles induced intercalation. SEM showed agglomerated structures. New thermal degradation events at higher temperatures endorsed the formation of zinc and silver carboxylate salts. We concluded that a new miscellaneous and multifunctional matter was achieved.

Composites of Graphene and LiFePO_4 as Cathode Materials for Lithium-Ion Battery:A Mini-review

This mini-review highlights selectively the recent research progress in the composites of Li Fe PO4 and graphene. In particularly, the different fabrication protocols, and the electrochemical performance of the composites are summarized in detail. The structural and morphology characters of graphene sheets that may affect the property of the composites are discussed briefly. The possible ongoing researches in area are speculated upon.

3D amorphous carbon and graphene co-modified LiFePO_4 composite derived from polyol process as electrode for high power lithium-ion batteries

Amorphous carbon and graphene co-modified LiFePO4 nanocomposite has been synthesized via a facile polyol process in connection with a following thermal treatment.Various characterization techniques,including XRD.Mossbauer spectra,Raman spectra,SEM,TEM,BET,O2-TPO,galvano charge-discharge,CV and EIS were applied to investigate the phase composition,carbon content,morphological structure and electrochemical performance of the synthesized samples.The effect of introducing way of carbon sources on the properties and performance of LiFePO4/C/graphene composite was paid special attention.Under optimized synthetic conditions,highly crystalized olivine-type LiFePO4was successfully obtained with electron conductive Fe2P and FeP as the main impurity phases.SEM and TEM analyses demonstrated the graphene sheets were randomly distributed inside the sample to create an open structured LiFePO4 with respect to graphene,while the glucosederived carbon mainly coated over LiFeP04 particles which effectively connected the graphene sheets and LiFePO4 particles to result in a more efficient charge transfer process.As a result,favorable electrochemical performance was achieved.The performance of the amorphous carbon-graphene co-modified LiFePO4 was further progressively improved upon cycling in the first 200 cycles to reach a reversible specificcapacity as high as 97 mAh·g-1 at 10 C rate.

All laser direct writing process for temperature sensor based on graphene and silver

A highly sensitive temperature sensing array is prepared by all laser direct writing(LDW)method,using laser induced silver(LIS)as electrodes and laser induced graphene(LIG)as temperature sensing layer.A finite element analysis(FEA)photothermal model incorporating a phase transition mechanism is developed to investigate the relationship between laser parameters and LIG properties,providing guidance for laser processing parameters selection with laser power of 1–5 W and laser scanning speed(greater than 50 mm/s).The deviation of simulation and experimental data for widths and thickness of LIG are less than 5%and 9%,respectively.The electrical properties and temperature responsiveness of LIG are also studied.By changing the laser process parameters,the thickness of the LIG ablation grooves can be in the range of 30–120μm and the resistivity of LIG can be regulated within the range of 0.031–67.2Ω・m.The percentage temperature coefficient of resistance(TCR)is calculated as−0.58%/°C.Furthermore,the FEA photothermal model is studied through experiments and simulations data regarding LIS,and the average deviation between experiment and simulation is less than 5%.The LIS sensing samples have a thickness of about 14μm,an electrical resistivity of 0.0001–100Ω・m is insensitive to temperature and pressure stimuli.Moreover,for a LIS-LIG based temperature sensing array,a correction factor is introduced to compensate for the LIG temperature sensing being disturbed by pressure stimuli,the temperature measurement difference is decreased from 11.2 to 2.6°C,indicating good accuracy for temperature measurement.

3D graphene foam-supported cobalt phosphate and borate electrocatalysts for high-efficiency water oxidation

The cobalt phosphate-/cobalt borate-based oxygen-evolving catalysts （OECs） are the important class of earth-abundant electrocatalysts that can operate with high activity for water splitting under benign conditions. This article reports the integration of cobalt phosphate （Co- Pi） and cobalt borate （Co-Bi） OECs with three-dimensional （3D） graphene foam （GF） for the electrocatalytic water oxidation reaction. The GF showed a unique advantage to serve as a highly conductive 3D support with large capacity for anchoring and loading Co-OECs, thereby facilitating mass and charge transfer due to the large amount of active sites provided by the 3D graphene scaffold. As a result, this integrated system of GF and Co-OECs exhibits synergistically enhanced catalytic activity. The overpotential （η） of Co-Pi and Co-Bi/graphene catalysts is about 0.390 and 0.315 V in neutral solutions, respectively. Besides, the integrated Co-OECs/graphene catalysts have also exhibited improved and stable oxygen evolution catalytic ability in alkaline solution.

Light-induced ZnO/Ag/rGO bactericidal photocatalyst with synergistic effect of sustained release of silver ions and enhanced reactive oxygen species

Silver nanoparticles (Ag NPs) can effectively address the issue of antibiotic-resistant bacterial infections to reduce the potential toxicity of Ag NPs. Although challenging, it is, therefore, necessary to achieve the sustainable release of Ag+ ions from a finite amount of Ag NPs. This study aims at designing an efficient and benign antimicrobial silver-based ternary composite composed of photocatalysis zinc oxide (ZnO) and reduced graphene oxide (rGO) as a carrier, in which the reactive oxygen species (ROS) excited from ZnO and Ag+ ions released from the Ag NPs cooperate to realize an effective antibacterial activity against E. coli and S. aureus. The constant effective bacterial performance of the ternary photocatalyst with minimum Ag content can be attributed to the increase in the available quantity of ROS, which results from the enhanced separation efficiency of the photogenerated carriers. The proposed system notably realized the long-term sustainable release of Ag+ ions with low concentration for 30 days when compared with an equivalent amount of silver nitrate. Moreover, the use of the composite prevents biotoxicity and silver wastage, and imparts enhanced stability to the long-lasting antibacterial efficacy.

Graphene oxide coated three-dimensional printed biphasic calcium phosphate scaffold for angiogenic and osteogenic synergy in repairing critical-size bone defect

The custom-tailored medicine requires a developmental strategy that integrates excellent osteogene-sis with mechanical stability to enhance the reconstruction of the critical-size bone defect(CSBD)and the healing process in weight-bearing bone.We prepared three-dimensional(3D)printed biphasic cal-cium phosphate(BCP)scaffolds composited with nano-graphene oxide(GO).The biological effects of the GO/BCP composite scaffolds could induce the differentiation of rat bone marrow stem cells(BM-SCs)and the migration of human umbilical vein endothelial cells(HUVECs)for bone repair.The proper ratio of GO in the composite scaffold regulated the composites’surface roughness and hydrophilicity to a suitable range for the adhesion and proliferation of BMSCs and HUVECs.Besides,the GO/BCP composite scaffold increased osteogenesis and angiogenesis by activating BMP-2,RUNX-2,Smad1/4,and VEGF.The customized intramedullary nail combined with GO/BCP scaffold was applied to repair CSBD(2.0 cm in length)in a beagle femur model.This fixation strategy was confirmed by finite element analysis.In vivo,the results indicated that the custom-made internal fixation provided sufficient stability in the early stage,ensuring bone healing in a considerable mechanical environment.At 9 months postoperatively,longitudi-nal bony union and blood vessels in osteon were observed in the CSBD area with partial degradation in the 0.3%GO/BCP group.In the three-point bending test,the ultimate load of 0.3%GO/BCP group reached over 50%of the normal femur at 9 months after repair.These results showed a promising application of osteogenic GO/BCP scaffold and custom-made intramedullary nails in repairing CSBD of the beagle femur.This effective strategy could provide an option to treat the clinical CSBD in weight-bearing bones.

Effects of phosphate on the transport of graphene oxide nanoparticles in saturated clean and iron oxide-coated sand columns

In this study, transport behaviors of graphene oxide(GO) in saturated uncoated(i.e., clean sand) and goethite-coated sand porous media were examined as a function of the phosphate. We found that phosphate enhanced the transport of GO over a wide range of solution chemistry(i.e., pH 5.0–9.0 and the presence of 10 mmol/L Na^(+) or 0.5 mmol/L Ca^(2+)). The results were mainly ascribed to the increase of electrostatic repulsion between nanoparticles and porous media. Meanwhile, deposition site competition induced by the retained phosphate was another important mechanism leading to promote GO transport. Interestingly, when the phosphate concentration increased from 0.1 to 1.0 mmol/L, the transportenhancement effect of phosphate in goethite-coated sand was to a much larger extent than that in clean sand. The observations were primarily related to the difference in the total mass of retained phosphate between the iron oxide-coated sand and clean sand columns, which resulted in different degrees of the electrostatic repulsion and competitive effect of phosphate. When the background solution contained 0.5 mmol/L Ca^(2+), phosphate could be bind to sand/goethite-coated sand surface by cation bridging;and consequently, promoted competition between phosphate and nanoparticles for deposition sites, which was an important mechanism for the enhanced effect of phosphate. Moreover, the DLVO theory was applicable to describe GO transport behaviors in porous media in the absence or presence of phosphate. Taken together, these findings highlight the important status and role of phosphate on the transport and fate of colloidal graphene oxide in the subsurface environment.

新型光催化剂磷酸银的研究进展

磷酸银(Ag_(3)PO_(4))光催化剂的量子产率高达90%,在可见光照射下具有极强的光催化活性,但是Ag_(3)PO_(4)存在光腐蚀严重、光生电子和空穴寿命短等缺点,限制了其在生活实际的应用.本文首先介绍了Ag_(3)PO_(4)光催化剂的结构特点、制备方法与反应机理,然后着重评述了通过形貌调控、贵金属沉积、负载、构建半导体异质结等方法改善Ag_(3)PO_(4)的光催化性能以及在降解污染物、光催化制氢、光催化还原CO_(2)中的应用,最后指出目前关于Ag_(3)PO_(4)光催化剂研究中仍存在的不足,对Ag_(3)PO_(4)光催化剂未来的发展趋势进行展望.

Ag_(3)PO_(4)基光催化材料合成及改性的研究进展

介绍了目前合成磷酸银(Ag_(3)PO_(4))光催化材料的主要制备方法,综述分析了形态控制、贵金属沉积、非负载和构建半导体异质结等改性Ag_(3)PO_(4)光催化材料的途径,阐述了Ag_(3)PO_(4)光催化材料在降解有机污染物和水分解领域的应用现状,指出了Ag_(3)PO_(4)光催化材料目前存在的问题,对今后的研究重点和方向做出了展望。