AgBr Research Articles

A Novel Interstitial Site in Binary Rock-Salt Compounds.

The energetic and mechanical stability of interstitial point defects in binary rock-salt materials were studied using the first-principles method. A novel, stable, and energetically competitive interstitial site (base-interstitial) was identified for anion interstitials in rock-salts. The formation energies of base-interstitial defects were compared with well-explored tetrahedral (body-interstitial) and split interstitials and were found to be energetically highly competitive. For alkali halides and silver bromide, the lowest formation energies are associated with the base-interstitial site and the <110> split interstitial, which are therefore the predominant interstitial sites. However, split interstitials were found to be the energetically preferred configuration in metal monochalcogenide systems. Electronic band structures are affected by the presence of interstitial defects in rock-salt structures. In particular, the Fermi level is shifted below the valence band maxima for the body, base, and split interstitials in metal halides, indicating p-type conductivity. However, the Fermi level remains within the bandgap for metal monochalcogenides, indicating no preferred conductivity for base- and split-interstitial defects. Allowing the defects to be charged changes the relative stability of the interstitial sites. However, the new base-interstitial site remains preferred over a range of potentials for alkali halides. The anion base-interstitial is found to form a triatomic entity with the nearest lattice anions that affect the electronic structure relative to the body interstitial. The discovery of a new interstitial site affects our understanding of defects in binary rock-salts, including structure and dynamics as well as associated thermodynamic and kinetic properties that are interstitial dependent.

Genotoxic potential of different nano-silver halides in cultured human lymphocyte cells

Most antibacterial applications in nanotechnology are carried out using silver nanoparticles (AgNPs). However, there is a dearth of information on the biological effects of AgNPs on human blood cells. In this study, the cytotoxic and genotoxic potentials of ionic silver (Ag+), AgNP, silver bromide (AgBr), silver chloride (AgCl), and silver iodide (AgI) were evaluated through chromosome aberration (CA) test and cytokinesis-blocked micronucleus (CBMN) test in human cultured lymphocytes in vitro. Furthermore, the potential damages that can cause to DNA were evaluated through alkaline single cell gel electrophoresis (Comet) assay on isolated lymphocytes. The results showed that AgNPs exerted cytotoxic effects by reducing the cytokinesis-block proliferation index and mitotic index at 24 and 48 h. AgNPs also increased micronucleus (MN) formation at both exposure times in the cultured cells. Meanwhile, AgCl had no genotoxic effects on the human lymphocyte cultured cells but had a cytotoxic effect at high doses. AgNP, Ag+, AgBr, and AgI caused substantial DNA damage by forming DNA strand breaks. They may also have clastogenic, genotoxic and cytotoxic effects on human lymphocyte cells. Based on the foregoing findings, silver nanomaterials may have genotoxic and cytotoxic potentials on human peripheral lymphocytes in vitro.

Synthesis of Pincer type carbene and their Ag(I)-NHC complexes, and their Antimicrobial activities

In this study, theophylline (1) compounds were synthesized with addition of 2-bromoetha-nol, 2-bromoacetamide and methyl-2-bromoacetate to attain symmetric connections to NHCs (2a–c). New complexes containing the symmetric N-heterocyclic carbene (NHC) ligands were synthesized using azolium salts in dimethyl formamide (DMF). After the NHC predecessor compounds reacted with Ag2O, Ag(I)-NHC complexes were synthesized in the following: 7,9-di-(2-hydroxyethyl)-8,9-dihydro-1,3-dimethyl-1H-purine-2,6(3H,7H)-dionedium silver(I)bromide (3a), 7,9-di(acetamide)-8,9-dihydro-1,3-dimethyl-1H-purine-2,6(3H,7H)-di-ondium silver(I)bromide (3b) and 7,9-di(methylacetate)-8,9-dihydro-1,3-dimethyl-1H-pu-rine-2,6(3H,7H)-diondiumsilver(I)bromide (3c). Both synthesized NHC predecessors (2a-c) and Ag(I)-NHC complexes (3a-c) were described by FTIR, 1H-NMR, 13C-NMR, liquid and solid-state conductivity values, TGA analysis, melting point analysis and XRD spectroscopy. In-vitro antibacterial activities of NHC-predecessors and Ag(I)-NHC complexes were tested against gram-positive bacteria (Staphylococcus Aureus and Bacillus Cereus), gram-negative bacteria (Escherichia Coli and Listeria Monocytogenes), and fungus (Candida Albicans) in Tryptic Soy Broth method. Ag(I)-NHC complexes showed higher antibacterial activity than pure NHC predecessors. The lowest microbial inhibition concentration (MIC) value of compound 3a was obtained as 11.56 μg/ml for Escherichia Coli and 11.52 μg/ml for Staphylococcus Aureus. All tested complexes displayed antimicrobial activity with different results.

Formation of Metallic Ag on AgBr by Femtosecond Laser Irradiation

Laser irradiation of materials induces changes in their structure and functional properties. In this work, lattice heating and electronic excitation on silver bromide (AgBr), provoked by femtosecond laser irradiation, have been investigated by finite-temperature density functional theory and ab initio molecular dynamics calculations by using the two-temperature model. According to our results, the electronic temperature of 0.25 eV is enough to excite the electrons from the valence to the conduction band, whereas 1.00 eV changes the structural properties of the irradiated AgBr material. Charge density simulations also show that an Ag clustering process and the formation of Br3− complexes take place when the electronic temperature reaches 2.00 eV and 5.00 eV, respectively. The present results can be used to obtain coherent control of the extreme nonequilibrium conditions due to femtosecond laser irradiation for designing new functional materials.

Controlling silver release from antibacterial surface coatings on stainless steel for biofouling control

This study focuses on the in-situ nucleation of silver nanoparticles (AgNPs) on stainless steel (SS) to provide a localized antibacterial action for biofouling control during space missions. Since AgNPs rapidly dissolve in water, partial passivation of AgNPs was provided to slow down silver release and extend the lifetime of the antibacterial coating. Two different passivation approaches, based on the formation of low solubility silver sulfide (Ag2S) or silver bromide (AgBr) shells, were compared to identify the optimal passivation for biofouling control. Highest bacterial inactivation (up to 75%) occurred with sulfidized AgNPs as opposed to bromidized (up to 50%) NPs. The optimal passivation treatment for biofouling control was found at 10−5 M Na2S (for Ag2S) and 10−3 M NaBr (for AgBr) concentrations. Scanning Electron Microscopy (SEM) analyses confirmed the presence of AgNPs on AgBr and Ag2S-coated samples. Further investigation revealed that compared to pristine AgNPs, Ag release from both sulfidized and bromidized NPs was significantly lower (16% vs 6% or less). Overall, both sulfidized and bromidized AgNPs were effective at controlling biofilm formation; however, sulfidized NPs exhibited the maximum antibacterial activity, making it the preferable passivation strategy for AgNPs on SS surfaces.

Cluster-associated Viscosity Model of Silver Bromide

Cluster-associated Viscosity Model of Silver Bromide

Thermodynamic stability of silver bromide sol and its change as a result of exposure to an electromagnetic field. Part 2

Thermodynamic stability of silver bromide sol and its change as a result of exposure to an electromagnetic field. Part 2

Conjugated Polyelectrolyte/Silver Bromide Nanocomposites: Highly Durable and Robust Antibacterial Materials

We report the in situ synthesis of silver bromide nanoparticles (AgBr NPs) in a cationic conjugated polyelectrolyte (CPE) matrix. It is interesting that the obtained CPE/AgBr nanocomposite materials exhibit robust and long-term antimicrobial activity against both Gram-negative bacteria and Gram-positive bacteria by producing a large amount of biologically active Ag+. Meanwhile, it is demonstrated that the antimicrobial activity of CPE/AgBr nanocomposites is also related to the size of the AgBr NPs. Smaller particles show a faster AgBr release rate and hence higher antimicrobial activity than big particles. However, the relatively large-sized nanocomposites are beneficial to obtain long-term antimicrobial activity by substantially producing bioactive Ag+. Consequently, the antimicrobial property of the CPE/AgBr nanocomposites can be manipulated by controlling the dimensions of embedded AgBr NPs. The CPE/AgBr nanocomposites can cause a rapid initial drop of bacterial counts in solution, which makes it a potential candidate for antimicrobial therapy in emergency cases. In addition, the sustained release of Ag+ from large-sized nanocomposites makes them suitable for long-term use.

Ultrahigh Sensitive and Tumor-Specific Photoacoustography in NIR-II Region: Optical Writing and Redox-Responsive Graphic Fixing by AgBr@PLGA Nanocrystals.

The highly up-regulated glutathione (GSH) concentration in the tumor microenvironment is generally identified to be an effective endogenous characteristic of cancerous tissues. Herein, an ultrahigh-sensitive and tumor-specific photoacoustography technique in the near-infrared (NIR-II) region based on optical writing and redox-responsive chromogenic graphic fixing is developed by introducing a self-synthesized photosensitive silver bromide modified with poly lactic-co-glycolic acid (AgBr@PLGA) nanocrystals. After they are optically triggered by external light, the NIR-transparent AgBr@PLGA nanocrystals can be reduced by the tumor-abundant GSH into strongly absorbing silver nanoparticles, significantly boosting the "turn-on" photoacoustic (PA) signal in the NIR-II region; therefore, the tumor area can be graphically fixed and developed in the photoacoustography. Experiments on both in vitro phantoms and in vivo mouse models demonstrate that the tumor area is specifically identified by the photoacoustography with the background signals effectively suppressed by dynamically modulating the exposure time. The tumor-specific photoacoustography technique prefigures great potential for high-precision cancer diagnosis and treatment monitoring.

Improvement in photocatalytic stability of AgBr under visible light through melt processing

Over the past decade, silver bromide (AgBr, mostly as plasmonic photocatalyst: Ag/AgBr) micro or nano crystals have been extensively studied due to its superior photocatalytic activity. However, AgBr and Ag/AgBr suffer from continuous formation of Ag0 in the photocatalytic process and the activity of the photocatalysts will be reduced rapidly, which is recognized as the bottleneck for further development and application of AgBr catalyst. In this study, we present the fabrication of melt-treated AgBr (AgBr-MT) under bromine atmosphere, which exhibits high photocatalytic activity. Surprisingly, AgBr-MT shows a giant improvement in photocatalytic stability compared to conventional powder catalysts, and the self-recovery phenomenon of AgBr was observed for the first time. The melt processing greatly reduces the unstable silver ions at the top and edge sites, and the surface reconstruction under bromine gas also contributes to the improvement of the stability of AgBr. Our findings may contribute to the development of efficient and stable silver halide-based materials and open a new perspective for this interesting material. The next research direction is to find a suitable support or prepare ultra-thin silver bromide film to further increase the effective area of AgBr.

Antifungal activity of TiO2/AgBr nanocomposites on some phytopathogenic fungi.

TiO2/AgBr composites were synthesized by a simple ultrasonic strategy. Various instruments such as SEM, EDX, XRD, and FT‐IR were exploited to investigate their characteristics. Antifungal activities of the as‐obtained samples were assessed through the inactivation of Fusarium graminearum in the spore suspension method and mycelial growth inhibition of F. graminearum, Botrytis cinerea, and Sclerotinia sclerotiorum in the microdilution method. The results represented that the TiO2/AgBr samples possess higher antifungal activities on F. graminearum spores than the pure TiO2. The sample with 20 wt% silver bromide represented the highest inhibitory effect on the growth of F. graminearum so that all fungal spores were degraded in the initial times of the treatment process. The inactivation of fungal spores after 60 min was 35.2%, 97.8%, 98.9%, and 98.7%, in respect, for 5, 10, 20, and 30 weight percent of AgBr in the binary nanocomposites, while the inhibition rate was 13.4% for the pure TiO2. With increasing ultrasound irradiation time for more than 30 min, the inactivation rate constant decreased. It was also found that the antifungal activity of the nanocomposites without calcination was higher than those of the calcined materials. Considering the antifungal potential against phytopathogenic fungi and advantages such as simple synthesis and eco‐friendly nature, it seems that TiO2/AgBr nanocomposites can be used instead of synthetic chemicals after additional field investigations and mass production.

Enhanced photocatalytic activity of AgBr photocatalyst via constructing heterogeneous junctions with reduced graphene

A series of reduced graphene (rGO) and AgBr composite heterojunction photocatalysts were fabricated through a facile solvothermal method. The rGO/AgBr heterostructures were characterized by XPS, XRD, UV–Vis DRS, SEM, TEM, photoluminescence (PL), and the transient photocurrent responses. The XRD, SEM, XPS, and TEM analyses indicated that the graphene and silver bromide were successfully compounded without other impurities. The UV–Vis DRS exhibited that the rGO/AgBr composites have better optical properties than pure silver bromide. The PL and the transient photocurrent responses demonstrated that the addition of graphene significantly promotes the separation of photogenerated electrons and holes. Subsequently, the photocatalytic activities of rGO/AgBr composites were studied by degrading Rhodamine B (RhB). It turned out that the degradation rate of RhB by the rGO/AgBr heterojunction photocatalysts was significantly higher than that by pure AgBr. Furthermore, to study the photocatalytic degradation mechanism of RhB by rGO/AgBr heterostructures, the trapping experiments were used to identify main active components. This work confirmed that the photocatalytic degradation performance of the catalyst was greatly improved after doping graphene, which provided certain data support for degradation of organic contaminants in water.

Synthesis of AgNWs using copper bromide as stabilizing agent and oxygen scavenger and their application in conductive thin films

Silver nanowires (AgNWs) have attracted growing interest because of their wide range of applications in modern nano electronic appliances. During polyol method, the presence of cations and anions in the reaction solution has influence on the final morphology of AgNWs. Here we report a feasible way to prepare AgNWs by polyol method. Copper bromide (CuBr2) salt was used to provide anions and cations in the reaction solution. The anions (Br−) helps in reducing the amount of free Ag+ by forming silver bromide (AgBr) during initial silver seeds formation and the cations scavenge oxygen from the surface of AgNWs during preferential growth of the AgNWs. Ethylene glycol (EG) was used as a solvent and reducing agent, silver nitrate (AgNO3) was used as Ag source and polyvinyl pyrrolidone (PVP) was used as a capping agent. The effects of various factors which influence the final morphology of AgNWs were studied. AgNWs were successfully synthesized in the presence of CuBr2 salt. The morphology of the synthesized AgNWs was characterized by the SEM and TEM. The crystallinity was characterized by HRTEM, SAED and XRD. The LSPR peaks of Ag nanostructures were revealed by UV–Vis spectroscopy. The conductive properties of AgNWs thin conductive films were studied by coating the synthesized nanowires on polyethylene terephthalate (PET) substrate.

Additional dye options for spectral sensitization of photo processes in silver stearate—silver bromide system

The paper discusses spectral sensitized photo processes in silver bromide caused by dyes adsorbed on the surface of silver stearate via the lightguide mechanism and a direct hit of the luminescent light from dye molecules localized near the microcrystal of silver bromide to the microcrystal of silver bromide. The paper submits an estimation of the contribution of dye molecules localized on the surface of silver stearate to overall spectral sensitization. These calculations demonstrate that the contribution of dye molecules adsorbed on the particle of silver stearate to spectral sensitization of silver stearate—silver bromide structure is comparable to the contribution of dye molecules placed on the microcrystal of silver bromide. Dye molecules localized on the particle of silver stearate allow to raise the efficiency of spectral sensitization by 40 to 60 percent.

Luminescent Properties of Composite Materials Based on Nanoporous Silicate Glass Activated by Tb3+ Ions and AgBr

Composite materials (CMs) containing Tb3+ ions and silver bromide, based on matrices of high-silica nanoporous glasses, are synthesized. It is found that the samples, depending on the conditions of their synthesis, possess UV (λlum = 310 nm at λexc = 266 nm) and blue-green (λlum = 400–545 nm at λexc = 316–375 nm) luminescence due to the presence of silicon defect centers and the presence of paired Ag+–Ag+ centers, Tb3+ ions, and isolated Ag+ ions. The concentration distribution of the elements over the thickness of the samples is established by the method of energy-dispersive X-ray spectroscopy.

Kinetic stability of silver bromide sol and its change as a result of exposure to an electromagnetic field

Kinetic stability of silver bromide sol and its change as a result of exposure to an electromagnetic field

AgBr nanoparticles decorated 2D/2D GO/Bi2WO6 photocatalyst with enhanced photocatalytic performance for the removal of tetracycline hydrochloride

Bismuth tungstate (Bi2WO6) was well known for its low price, nontoxicity and stability in the removal of organic pollutions. However, poor visible light absorption and fast carrier recombination led to its moderate activity. Therefore, a Z-scheme photocatalyst constructed by Bi2WO6 nanosheets, graphene oxide (GO) and silver bromide (AgBr) nanoparticles was successfully prepared. Previous reports suggested that Z-scheme structure based on Bi2WO6 nanosheets could obtain more active sites. And characterization results clarified that the addition of AgBr brought broadened visible light response range, inducing more photocarrier generation. Meanwhile, the optimized Z-scheme composite 15%AgBr/5GO/Bi2WO6 (15A/5G/BW) possessed accelerated interfacial charge separation and transfer, which was resulted from excellent electron conductivity in GO. As a result, 15A/5G/BW exhibited superior photocatalytic activities for tetracycline hydrochloride (TC). The highest degradation efficiency could reach 84% under visible light illumination, and the kinetic constant was 0.0515 min−1 which was approximately 4.60 and 3.16 times higher than that of AgBr and Bi2WO6, respectively. Furthermore, liquid chromatography-mass spectrometry (LC-MS) and trapping experiments revealed possible TC degradation pathways and main active radicals during photocatalysis process. A facial strategy for rational design of ternary photocatalyst towards the degradation of refractory antibiotics was proposed.

Switchable Silver Mirror Window without Bromide Ion

The reversible electrochemical switching mirrors between mirror state and transparent state using silver bromide ion complex have been greatly investigated for application to smart windows and mirrors.1,2 There are some advantages to reflect light and not to absorb one in the high reflective silver metal state from the viewpoint of the thermal management. However, there are also some drawbacks to use bromide ion. Silver bromide ion complex is poor solubility in the common solvents, which also required strong polar solvents such as DMSO. In addition, the silver bromide ion complex is light-sensitive and not suitable for many applications. Moreover, Br3 - ion as the redox couple of Br- ion has absorption in the visible wavelength region. Therefore, it was important to find the other systems where Ag may be deposited in a mirror form without the use of bromide ion. In the previous study, a mixed solvent of ionic liquid and acetonitrile has been employed instead of DMSO and silver bromide was not used. This novel reversible silver switching mirror window system is quite simple, stable and safe because the materials used in this system are citric acid as the electrolyte additive and Pd nanoparticles (NPs) as the catalyst which are plated as nuclei on the ITO electrode for facilitating Ag plating and dissolution.3 In this study, the non-bromide ion switchable silver mirror window was prepared and its performance was investigated.The window has the sandwiched structure between Pd NPs deposited on the ITO electrode and semitransparent silver mesh (0.15 mm diameter, 40 mesh size) as a counter electrode on the glass substrate through silicon rubber spacer with 1 mm thickness. Silver plating bath composed of 0.2 M silver nitrite and 80 mM citric acid as an additive dissolved in the mixture solvent of EMIMTFSI ionic liquid and acetonitrile. The window size was 3.0 x 3.0 cm2. The transmittance of the transparent state of the device was 39% at the wavelength of more than 400 nm, which was not very high because of low transmittance of 58% at the silver mesh counter electrode as shown in Fig.1(a). Our college emblem was seen through the transparent state of the window. When the voltage bias was applied at -0.3 V for 7 sec, silver was electroplated on the Pd NP deposited on ITO to become the mirror state as shown in Fig.1(b). When the voltage bias was reversed at +0.3 V for 13 sec, the plated silver was electrodissolved to return to the transparent state of the window. The small voltage bias and the short plating/dissolution time was achieved in the present window.The stability of the mirror state of the device at the open circuit was investigated. The device firstly shows the transparent state at the no bias condition for 3 sec, indicating the transmittance of 39% at the wavelength of 500 nm. When the voltage bias was applied at -0.3 V for 7 sec, the transmittance decreases to 1%. The device was then changed at the open circuit and the transmittance was monitored for 1 hr. The value of the transmittance keeps at 1% after 1 hr. Therefore, our window shows good memory effect because of no use of bromide ion. Thus, the window has superior potential for meeting requirements for practical applications including smart windows.

Constructing a Z-scheme 3D hollow pineal-like AgBr/Bi2O2CO3 hybrid material based on ameliorated p-n heterostructure towards exorbitant photocatalytic performance

Interfacial charge transfer acts as a linchpin role in the research of photogenerated carrier recombination and photocatalysis. In this work, AgBr/Bi2O2CO3 was constructed to explore the structure-activity relationship between heterostructure and catalytic mechanism. The excellent photosensitizer silver bromide nanoparticles were immobilized on the surface of the Bi2O2CO3 hollow pineal-like via a simple hydrothermal method and deliberated the formation mechanism of the heterostructure. The heterostructures were characterized through XRD, BET, XPS, SEM, TEM, EDX, UV–Vis DRS, EIS, PT and TOC. Research demonstrates that owing to the distinct layered structure exhibits fine surface scattering and reflection. It has excellent degradation performance for dyes and PPCPs wastewater and can be completely degraded in a short time. Simultaneously, the introduction of the Z-type mechanism into the p-n type heterojunction photocatalyst, together with the joint contribution of the Schottky barrier, extremely facilitates the charge separation, illustrating brilliant photocatalysis active. Furthermore, Free radical capture experiments certificate that •O2− and h+ are the chief active species in the decomposition of organic pollutants, and the potential photocatalytic mechanism is considered. The consequences of this work will furnish a fresh perspective for the configuration of high-performance visible light-responsive photocatalysts.

Vacancy defects on optoelectronic properties of double perovskite Cs2AgBiBr6

The commonly existed vacancy defects in semiconductors can affect optoelectronic properties. Here, to understand the vacancy defect influences on double perovskite Cs2AgBiBr6, based upon density functional theory calculations and supercell model, we systematically investigated Cs, Ag, Bi, Br, Cs–Br and Ag–Br atomic pair vacancy effects on crystal structure, electronic structures, optical absorption, charge carrier and exciton binding energies. It was found that, the vacancy defects in double perovskite Cs2AgBiBr6 induce slight deformation of crystal lattice. The vacancy defects cannot introduce extra defect states in the gap of energy band. The Cs, Ag, Bi, Ag–Br and Cs–Br defects not only change the band gap into the direct from the indirect of pristine system and reduce the band gap, but also promote the optical absorption capability, and result in red-shift of absorption spectra in low energy region. The Br vacancy leads to a heavy dopant character due to significant elevation of the Fermi level. The Cs, Ag, Bi, Ag–Br and Cs–Br vacancy defects also generate imbalanced charge transport properties, and increase exciton binding energies.