Visualization of gold nanoparticles formation in DC plasma-liquid systems

Dual argon plasmas ignited by one direct current power source are used to treat an aqueous solution of hydrogen tetrachloroaurate-(Ⅲ)trihydrate(HAuCl_(4)·3H_(2)O)which is contained in an H-type electrochemical cell.The solution contained in one cell acts as a cathode,and in the other as an anode.Experiments are carried out to directly visualize the formation process of gold nanoparticles(Au NPs)in separated cells of the H-type electrochemical reactor.The results and analyzes suggest that hydrogen peroxide and hydrated electrons generated from the plasma-liquid interactions play the roles of reductants in the solutions,respectively.Hydrogen peroxide can be generated in the case of the liquid being a cathode or an anode,while most of hydrated electrons are formed in the case of the liquid being an anode.Therefore,the reduction of the AuCl_(4)−ions is mostly attributed to the hydrogen peroxide as the liquid acts as a cathode,while to the hydrogen peroxide and hydrated electrons as the liquid acts as an anode.Moreover,the p H value of the solution can be used to tune the formation processes and final form of the Au NPs due to its mediation of reductants.

Computational simulation of ionization processes in single-bubble and multi-bubble sonoluminescence

The most recent spectroscopic studies of moving-single bubble sonoluminescence(MSBSL)and multi-bubble sonoluminescence(MBSL)have revealed that hydrated electrons(e^(-)_(aq))are generated in MSBSL but absent in MBSL.To explore the mechanism of this phenomenon,we numerically simulate the ionization processes in single-and multi-bubble sonoluminescence in aqueous solution of terbium chloride(TbCl_(3)).The results show that the maximum degree of ionization of single-bubble sonoluminescence(SBSL)is approximately 10000 times greater than that of MBSL under certain special physical parameters.The hydrated electrons(e^(-)_(aq))formed in SBSL are far more than those in MBSL provided these electrons are ejected from a bubble into a liquid.Therefore,the quenching of e^(-)_(aq)to SBSL spectrum is stronger than that of the MBSL spectrum.This may be the reason that the trivalent terbium[Tb(Ⅲ)]ion line intensities from SBSL in the TbCl_(3) aqueous solutions with the acceptor of e^(-)_(aq)are stronger than those of TbCl_(3) aqueous solutions without the acceptor of e^(-)_(aq).Whereas the Tb(Ⅲ)ion line intensities from MBSL are not variational,which is significant for exploring the mechanism behind the cavitation and sonoluminescence.

Hot electrons in water: injection and ponderomotive acceleration by means of plasmonic nanoelectrodes

We present a theoretical and experimental study of a plasmonic nanoelectrode architecture that is able to inject bunches of hot electrons into an aqueous environment.In this approach,electrons are accelerated in water by ponderomotive forces up to energies capable of exciting or ionizing water molecules.This ability is enabled by the nanoelectrode structure(extruding out of a metal baseplate),which allows for the production of an intense plasmonic hot spot at the apex of the structure while maintaining the electrical connection to a virtually unlimited charge reservoir.The electron injection is experimentally monitored by recording the current transmitted through the water medium,whereas the electron acceleration is confirmed by observation of the bubble generation for a laser power exceeding a proper threshold.An understanding of the complex physics involved is obtained via a numerical approach that explicitly models the electromagnetic hot spot generation,electron-by-electron injection via multiphoton absorption,acceleration by ponderomotive forces and electron-water interaction through random elastic and inelastic scattering.The model predicts a critical electron density for bubble nucleation that nicely matches the experimental findings and reveals that the efficiency of energy transfer from the plasmonic hot spot to the free electron cloud is much more efficient(17 times higher)in water than in a vacuum.Because of their high kinetic energy and large reduction potential,these proposed wet hot electrons may provide new opportunities in photocatalysis,electrochemical processes and hot-electron driven chemistry.

Photodegradation of Hexafluoropropylene Oxide Trimer Acid under UV Irradiation

As a novel alternative to traditional perfluoroalkyl substances(PFASs),including perfluorooctanoic acid(PFOA)and perfluorooctane sulfonate(PFOS),hexafluoroproplyene oxide trimer acid(HFPO-TA)has been detected worldwide in surface water.Moreover,recent researches have demonstrated that HFPO-TA has stronger bioaccumulation potential and higher hepatotoxicity than PFOA.To treat these contaminants e.g.PFOA and PFOS,some photochemical techniques by adding exogenous substances had been reported.However,there is still no report for the behavior of HFPO-TA itself under direct UV irradiation.The current study investigated the photo-transformation of HFPO-TA under UV irradiation in aqueous solution.After 72 hr photoreaction,75%degradation ratio and 25%defluorination ratio were achieved under ambient condition.Reducing active species,i.e.,hydrated electrons and active hydrogen atoms,generated from water splitting played dominant roles in degradation of HFPO-TA,which was confirmed by different effects of reaction atmospheres and quenching experiments.A possible degradation pathway was proposed based on the products identification and theoretical calculations.In general,HFPO-TA would be transformed into shorter-chain PFASs,including hexafluoropropylene oxide dimer acid(HFPODA),perfluoropropionic acid(PFA)and trifluoroacetate(TFA).This research provides basic information for HFPO-TA photodegradation process and is essential to develop novel remediation techniques for HFPO-TA and other alternatives with similar structures.

One-step synthesis of hollow UO2 nanospheres via radiolytic reduction of ammonium uranyl tricarbonate

Black precipitates were successfully obtained by radiolytic reduction of ammonium uranyl tricarbonate in the aqueous solution of HCOONH_4 by one step.TEM,SAED,EDS,and XRD analysis indicated that the precipitates consist of hollow UO_2 nanospheres(φ:30-50 nm,wall thickness:8-15 nm,and cavity diameter:10-20 nm).The effect of HCOONH_4 concentration,irradiation time and dose rate on the morphology,and size of nanospheres was investigated.Then,a gas-bubble template mechanism was proposed.