AgInS2-Embedded Photocatalytic Membrane: Insights into the Excited State and Electron Transfer Dynamics.

Photocatalytic reactions at semiconductor nanocrystal surfaces are useful for synthesizing value-added chemicals using sunlight. Semiconductor nanocrystals dispersed in a rigid framework, such as polymer film, can mitigate issues such as aggregation, product separation, and other challenges that are usually encountered in suspensions or slurries. Using a cation exchange technique, we successfully embedded AgInS2 nanoparticles into a Nafion matrix, termed AgInS2-Nafion. This was achieved through a galvanic exchange between In and Ag in In2S3 present within the Nafion film, enabling an adjustable Ag:In ratio for optimized photophysical properties. As in the case of colloidal suspension, the AgInS2 particles embedded in Nafion exhibit a long absorption tail, a broad emission band with a large Stokes shift, and emission lifetimes extending into the microseconds that are characteristic of donor-acceptor pairs, DAP. Remediation of surface states with the treatment of 3-mercaptopropionic acid resulted in significant enhancement in the emission yield. Charge carrier generation through bandgap excitation as well as activation of DAP states which reside within the bandgap is probed through transient absorption spectroscopy. The photocatalytic activity of AgInS2-Nafion was probed by using thionine as an electron acceptor. The electron transfer rate constant from excited AgInS2 to thionine as observed from transient absorption spectroscopy was determined to be ∼6.3 × 1010 s-1. The design of a photoactive membrane offers new ways to carry out photocatalytic processes with greater selectivity.

Unraveling the Synergy of Anion Modulation on Co Electrocatalysts by Pulsed Laser for Water Splitting: Intermediate Capturing by In Situ/Operando Raman Studies.

Herein, the authors produce Co-based (Co3 (PO4 )2 , Co3 O4 , and Co9 S8 ) electrocatalysts via pulsed laser ablation in liquid (PLAL) to explore the synergy of anion modulation on phase-selective active sites in the electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Co3 (PO4 )2 displays an ultralow overpotential of 230 mV at 10 mA cm-2 with 48.5 mV dec-1 Tafel slope that outperforms the state-of-the-art Ir/C in OER due to its high intrinsic activity. Meanwhile, Co9 S8 exhibits the highest HER performance known to the authors among the synthesized Co-based catalysts, showing the lowest overpotential of 361 mV at 10 mA cm-2 with 95.8 mV dec-1 Tafel slope in the alkaline medium and producing H2 gas with ≈500 mmol g-1 h-1 yield rate under -0.45 V versus RHE. The identified surface reactive intermediates over in situ electrochemical-Raman spectroscopy reveal that cobalt(hydr)oxides with higher oxidation states of Co-cation forming under oxidizing potentials on the electrode-electrolyte surface of Co3 (PO4 )2 facilitate the OER, while Co(OH)2 facilitate the HER. Notably, the fabricated two-electrode electrolyzers using Co3 (PO4 )2 , Co3 O4 , and Co9 S8 electrocatalysts deliver the cell potentials ≈2.01, 2.11, and 1.89 V, respectively, at 10 mA cm-2 . This work not only shows PLAL-synthesized electrocatalysts as promising candidates for water splitting, but also provides an underlying principle for advanced energy-conversion catalysts and beyond.

Silane-treated BaTiO3 ceramic powders for multilayer ceramic capacitor with enhanced dielectric properties.

Silane/ceramic combination provides the composites with several advantages from the advancements of new ceramic composite materials with good thermal conductivity, high mechanical and dielectric properties have wide significant applications in electrical and electronic industries. In this study, to enhance the dispersibility of dielectric barium titanate (BaTiO3) ceramic powder and additives for the fabrication of multilayer ceramic capacitors (MLCCs), surface treatment of the precursor of ceramic powder was performed using silane coupling agents. Dielectric ceramic sheets fabricated from ceramic powders that had been surface-treated with different amounts of N-[3-(trimethoxysilyl)propyl]aniline (TMSPA) which increased the surface gloss. In particular, the dielectric properties of the multilayer ceramic sheet fabricated by stacking sheets from the TMSPA-treated ceramic powder sintering at 1200 °C, it was confirmed that the dielectric constant increased from 881 to 2382 and the dielectric loss dropped from 1.96 to 1.34% with utilization of the TMSPA treatment. The physical and dielectric properties of the TMSPA-treated multilayer ceramic sheet were also determined by Fourier-transform infrared spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, glossmetry, and electrochemical impedance analysis. The results revealed that the TMSPA-modified BaTiO3 surfaces considerably increased the dielectric property of the fabricated nanocomposite.

Nanogap-tailored Au nanoparticles fabricated by pulsed laser ablation for surface-enhanced Raman scattering.

Herein, gold nanoparticles (Au NPs) were synthesized by pulsed laser ablation (PLA) in a mixed-phase solvent of acetonitrile and water. The size of Au NPs and the number of graphitic carbon (GC) layers were controlled by varying the ratio of the solvent mixture. The surface-enhanced Raman scattering (SERS) of the Au NPs was investigated using 10-3 M 4-aminobenzenethiol and 10-4 M 4-nitrobenzenethiol as probe molecules. The SERS activity strongly depended on the nanogaps between particles owing to the formation of hot spots. In the present work, the nanogaps were controlled by changing the amount of GC layers. No GC layers were produced in water, resulting low SERS intensity. In contrast, Au NPs prepared in 30 vol% of acetonitrile showed significant SERS enhancement, which was attributed to the optimal size of the GC-coated NPs and a reasonable gap between them. The obtained results revealed that Au NPs produced by PLA in liquid could be applied in SERS-based microsensors.

Method development and mechanistic study on direct pulsed laser irradiation process for highly effective dechlorination of persistent organic pollutants.

Chlorine-based compounds are typical persistent organic pollutants (POPs) that are widely generated in industrial production. This paper reports an effective and rapid pulsed laser irradiation technique for the dechlorination of hexachlorobenzene (HCB), a model pollutant, without additional catalysts or supports. The effects of the laser parameters, including the laser wavelength and power, on the dechlorination efficiency, were also investigated. The optimized results showed that a lower laser wavelength of 266 nm with 10 mJ/pulse power exhibited the highest dechlorination efficiency with 95% within 15 min. In addition, the laser beam effect was examined by designing the direct-pulsed laser single and multipath irradiation system. The results showed that improving the laser beam profile resulted in more than 95% dechlorination efficiency within 5 min. Thus, the dechlorination reaction proceeded much faster as the surface area that the laser beam came in contact with increased due to the multipath system than the single pathway. Gas chromatography identified benzene as the final product of HCB with pentachlorobenzene (PCB), tetrachlorobenzene (TeCB), trichlorobenzene (TCB), dichlorobenzene (DCB), and chlorobenzene (CB) as intermediate products. The mechanism of HCB dechlorination was explained by a comparison of theoretical calculations with the experimental results. The present study reports an advanced technique for the complete dechlorination of chlorobenzenes, which holds great application potential in environmental remediation.

Fabrication strategies and surface tuning of hierarchical gold nanostructures for electrochemical detection and removal of toxic pollutants.

The intensive research on the synthesis and characterization of gold (Au) nanostructures has been extensively documented over the last decades. These investigations allow the researchers to understand the relationships between the intrinsic properties of Au nanostructures such as particle size, shape, morphology, and composition to synthesize the Au nano/hybrid nanostructures with novel physicochemical properties. By tuning the properties above, these nanostructures are extensively employed to detect and remove trace amounts of toxic pollutants from the environment. This review attempts to document the achievements and current progress in Au-based nanostructures, general synthetic and fabrication strategies and their utilization in electrochemical sensing and environmental remediation applications. Additionally, the applications of Au nanostructures (e.g., as adsorbents, sensing platforms, catalysts, and electrodes) and advancements in the field of electrochemical sensing of different target analytes (e.g., proteins, nucleic acids, heavy metals, small molecules, and antigens) are summarized. The literature survey concludes the existing methods for the detection of toxic contaminants at various concentration levels. Finally, the existing challenges and future research directions on electrochemical sensing and degradation of toxic contaminants using Au nanostructures are defined.

Lignin-mediated green synthesis of functionalized gold nanoparticles via pulsed laser technique for selective colorimetric detection of lead ions in aqueous media.

A versatile green synthesis technique of pulsed laser irradiation and the sonochemical process was used for the production of functionalized gold nanoparticles (Au NPs) in the presence of lignin matrixes. In this study, the futuristic advantages of the lignin biopolymer were explored for the preparation of zero-valent Au NPs in the absence of any other reducing agents. The resulting lignin functionalized Au NPs (L-Auf NPs) were characterized via high-resolution transmission electron microscopy, X-ray diffraction, UV-vis spectroscopy, and Fourier-transform infrared spectroscopy. The optimum lignin concentration can generate uniformly dispersed crystalline L-Auf NPs. The optimized L-Auf (1-5) NPs permit the selective colorimetric detection of heavy metal ions; thus, the L-Auf (1-5) NPs demonstrated a highly selective colorimetric sensing tendency toward Pb2+ ions within a short time interval among the various metal ions (Pb2+, Fe3+, Cu2+, Cr6+, Co2+, Ag2+, Ca2+, Cd2+, Ba2+, and Hg2+). The prominent color change of L-Auf NPs from red wine to purple indicates the detection of Pb2+ ions. This robust characteristic nature of L-Auf (1-5) NPs can also detect very low concentrations of 1.8 µM in the linear range of 0.1-1 mM. Hence, the outcome of this study coincides with existing studies and indicates that L-Auf (1-5) NPs can also be used as effective sensors for the rapid and selective detection of Pb2+ ions via the colorimetric analysis using the real environmental samples.

Rapid and highly selective electrochemical sensor based on ZnS/Au-decorated f-multi-walled carbon nanotube nanocomposites produced via pulsed laser technique for detection of toxic nitro compounds.

Novel ZnS/Au/f-multi-walled carbon nanotube (MWCNT) nanostructures were produced via a pulsed laser-assisted technique followed by a wet chemical process. ZnS nanospheres were synthesized via pulsed laser ablation of a Zn target in DMSO, which was used as a solvent and sulfur source. Notably, no additional sulfur sources, surfactants, or reducing agents were used during the synthesis. The structure and morphology of the prepared materials were characterized by X-ray diffraction, micro-Raman spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. The fabricated electrochemical sensor based on ZnS/Au/f-MWCNT nanocomposites exhibited rapid and highly selective detection of a toxic pollutant, namely 4-nitrophenol (4-NP). Linear sweep voltammetry analysis revealed that the optimized ZnS/Au10/f-MWCNT3 nanocomposite displayed a wide linear dynamic response (10-150 µM) with high sensitivity (0.8084µAµM-1cm-2) and low limit of detection (30 nM). The excellent 4-NP sensing performance of the modified electrode was attributed to the availability of numerous active sites (electrochemical surface area=0.00369µFcm-2) and an enhanced electron transfer rate. Interference and stability studies were also conducted. A 100-fold excess of competing ions (Na+, K+, Mg2+, Cl-, NO3-, 4-AP, AA, and 2-NP) did not interfere with the selective detection of 4-NP. The newly fabricated ZnS/Au10/f-MWCNT3 nanocomposite could be an effective sensor for the selective and sensitive detection of toxic organic nitro compounds.

In-situ thermal phase transition and structural investigation of ferroelectric tetragonal barium titanate nanopowders with pseudo-cubic phase.

Optimization and miniaturization of existing electronic devices require the development of advanced nanostructured materials with high phase and structural purity. Over the past decade, barium titanate (BaTiO3) has attracted considerable attention due to its outstanding ferroelectric and dielectric properties. The present study involved the investigation of the phase transition and structural stability of tetragonal BaTiO3 nanopowders with pseudo-cubic phase using an in-situ high resolution and high temperature X-ray diffraction method. Under ambient conditions, the coexistence the tetragonal and cubic phases with weight fractions of 75.7% and 24.3%, respectively, was determined in BaTiO3. In the temperature range of 25 °C-300 °C, phase boundaries of BaTiO3 (180 nm in size) exhibiting several phases were detected. The phase transformation behavior, relative crystal phase content, lattice parameters, crystallite size, and tetragonality of the BaTiO3 nanopowders were established by the Rietveld refinement method at the onset temperature from 25 °C to 300 °C. Up to 150 °C, the nanopowders exhibited a complete transition of the cubic phase. Additionally, a complete tetragonal to cubic transformation was accomplished by a decrease of tetragonality at 125 °C and an increase in the crystallite size at 300 °C.

Solvent-mediated synthesis of BiOI with a tunable surface structure for effective visible light active photocatalytic removal of Cr(VI) from wastewater.

The present study investigated the effect of various solvents on the tunable surface morphology and photocatalytic activity (PCA) of bismuth oxyiodide (BiOI), which could be used for the reduction of Cr(VI) under visible light irradiation (VLI). BiOI samples exhibiting different morphologies, i.e., two-dimensional square-like nanosheet and three-dimensional hierarchical flower-like morphology, were synthesized by a hydro/solvothermal process using different solvents, namely H2O, MeOH, EtOH, and ethylene glycol (EG). The crystal structure, surface morphology, surface area, light-absorption capability, and recombination rate of the photogenerated charge carriers were examined by X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller analysis, UV-vis diffuse reflectance spectroscopy, photoluminescence, and transient photocurrent analyses, respectively. The BiOI sample fabricated in EG showed excellent photocatalytic efficiency (~99%) for the reduction of Cr(VI) after 90 min under VLI. The enhanced PCA demonstrated that the high surface area and well-structured surface characteristics of flower-like 3D BiOI microspheres played important roles in the photoreduction process. Moreover, a plausible mechanism for the reduction of Cr(VI) over the EG-BiOI photocatalyst was proposed. The results of the PCA evaluation and recycle test revealed that 3D EG-BiOI microspheres could serve as promising materials for the efficient removal of Cr(VI) from wastewater. Additionally, EG-BiOI could be utilized in other environmental remediation processes.

Pulsed laser-assisted synthesis of metal and nonmetal-codoped ZnO for efficient photocatalytic degradation of Rhodamine B under solar light irradiation.

Solar light-active silver nanoparticle (Ag NP) and nonmetal nitrogen (N)-codoped zinc oxide (ZnO:N/Ag) nanocomposites were fabricated by a pulsed laser-assisted method. N was considered as a promising candidate for tailoring the bandgap of ZnO due to the similar atomic radius as well as lower ionization energy and electronegativity compared to oxygen, which resulted in the formation of a shallow acceptor level in ZnO. Moreover, Ag NPs could enhance the optical properties of the ZnO materials as a consequence of the surface plasmon resonance (SPR) effect. The synthesized ZnO:N/Ag composite materials were characterized by X-ray diffraction (XRD), micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) analysis. The photocatalytic activity of the ZnO:N/Ag materials was evaluated for the efficient degradation of Rhodamine B (Rh.B) under solar light irradiation. The optimized ZnO:N/Ag-2 nanocomposite exhibited six times higher Rh·B degradation rate than pure ZnO. This was attributed to the enhanced absorption behavior in the solar region as well as the formation of the Schottky junction between ZnO:N and Ag NPs, which resulted in effective charge separation. In addition, the scavenger study revealed that •O2- radicals facilitated the degradation of Rh.B. The reusability test of the ZnO:N/Ag nanocomposite confirmed high photostability and efficiency of the material in each successive cycle. The present investigation illustrates a rational design of metal and nonmetal-codoped ZnO nanostructures employing a pulsed laser-assisted technique for effective application in photocatalytic remediation of wastewater.

Production of copper nanoparticles exhibiting various morphologies via pulsed laser ablation in different solvents and their catalytic activity for reduction of toxic nitroaromatic compounds.

Comparative experiments were conducted to determine the effects of various solvents (i.e., deionized water, methanol, ethanol, 1-propanol, butanol, ethylene glycol, hexane, and acetonitrile) on the final compositions, morphologies, and catalytic activities of copper-based nanoparticles (NPs). The NPs were effectively synthesized by pulsed laser ablation (PLA) using a copper plate as the target. The obtained copper NPs were characterized utilizing various analytical techniques. It was established that the developed methodology allows for the production of NPs with different morphologies and compositions in a safe and simple manner. When laser ablation of a solid copper plate was performed in acetonitrile, the formation of copper(I) cyanide cubes was observed. On the other hand, in deionized water and methanol, spherical and rod-like particles of copper(I) and copper(II) oxide were detected, respectively. The catalytic activity of the prepared copper NPs in the reduction of aromatic nitro compounds, such as 4-nitrophenol and nitrobenzene, was also evaluated. A high k value was determined for the reduction over the copper(II) oxide NPs produced in methanol. Moreover, particles with graphitic carbon (GC) layers exhibited superior catalytic performance in the reduction of a hydrophobic substance, i.e., nitrobenzene, over the reduction of 4-nitrophenol. The enhanced catalytic activity of this catalyst may be due its unique surface morphology and the synergistic effects between the copper nanostructure and the GC layer. Lastly, a detailed reduction pathway mechanism for the catalytic reduction of 4-nitrophenol and nitrobenzene has been proposed.

Enhanced photocatalytic activity at multidimensional interface of 1D-Bi2S3@2D-GO/3D-BiOI ternary nanocomposites for tetracycline degradation under visible-light.

Structural dimensionality and surface morphology are key properties that greatly affect the functionalities of materials. Herein, we report a synthesis of dimensionally coupled ternary nanocomposites from three-dimensional (3D) bismuth oxyiodide (BiOI), two-dimensional (2D) graphene oxide (GO), and one-dimensional (1D) bismuth sulfide (Bi2S3) nanomaterials for tetracycline degradation under visible-light irradiation. The 2%-Bi2S3@1%-GO/BiOI ternary nanocomposites show higher degradation efficiency than neat 3D-BiOI. The coupling of neat 1D-Bi2S3 with the 1%-GO/BiOI binary nanocomposite does not increase the specific surface area of the resulting 2%-Bi2S3@1%-GO/3D-BiOI ternary nanocomposite, but enhances notably its charge carrier separation and migration, according to the analysis of the higher photocurrent, smaller arc radius of the electrochemical impedance spectroscopy and lower photoluminescence intensity. The observed results suggest that the combination of dimensionally coupled composites provides a synergistic effect through an efficient charge transfer process. This work offers new insights into the design and construction of dimensionally coupled ternary nanocomposites for environmental remediation applications.

Plasmonic ZnO/Au/g-C3N4 nanocomposites as solar light active photocatalysts for degradation of organic contaminants in wastewater.

In the present study, novel ZnO/Au/graphitic carbon nitride (g-C3N4) nanocomposites were fabricated via a facile and eco-friendly liquid phase pulsed laser process followed by calcination. Notably, the approach did not necessitate the use of any capping agents or surfactants. The as-prepared photocatalysts were evaluated by various electron microscopy and spectroscopy techniques. The obtained results confirmed good dispersion of the Au nanoparticles (NPs) on the surface of spherical ZnO particles deposited on the g-C3N4 nanosheets. The ZnO/Au/g-C3N4 nanocomposite exhibited substantially enhanced catalytic activity toward the degradation of methylene blue (MB) under simulated solar light irradiation. In particular, the ZnO/Au15/g-C3N4 composite containing 15 wt% Au displayed a rate constant, which was approximately 3 and 5 times greater than those of pristine g-C3N4 and ZnO, respectively. This improved photocatalytic activity of ZnO/Au15/g-C3N4 was attributed to the surface plasmon resonance of Au NPs and the synergistic effects between ZnO and g-C3N4. The boundary between ZnO/Au and g-C3N4 enabled direct migration of the photogenerated electrons from g-C3N4 to ZnO/Au, which hindered the recombination of electron-hole pairs and enhanced the carrier separation efficiency. Additionally, a plausible MB degradation mechanism over the ZnO/Au/g-C3N4 photocatalyst is proposed based on the results of the conducted scavenger study.

Efficient recovery of palladium nanoparticles from industrial wastewater and their catalytic activity toward reduction of 4-nitrophenol.

Discharge of heavy metals from various sources of industrial wastewater poses significant environmental and health concerns. Thus, efficient recovery of precious metals from wastewater employing sustainable, rapid, and cost-effective treatment methods is highly desirable. In this work, palladium nanoparticles (Pd NPs) were successfully recovered from industrial wastewater using a pulsed laser process in the absence of additives or reducing agents. Notably, the developed approach is faster and more environmentally friendly than other conventional recovery methods. The recovered Pd NPs were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Various pulsed laser parameters (i.e., laser wavelength, power, and irradiation time) were optimized to obtain ideal conditions for the pulsed laser ablation process. Effective recovery of the Pd metal from industrial wastewater was achieved at a laser wavelength of 355 nm, power of 40 mJ/pulse, and irradiation time of 30 min. The Pd NPs exhibited excellent catalytic activity toward the reduction of 4-nitrophenol. Thus, the recovered materials showed remarkable potential for application in degradation of toxic aromatic nitro compounds in the environment.

Pulsed laser synthesis of reduced graphene oxide supported ZnO/Au nanostructures in liquid with enhanced solar light photocatalytic activity.

ZnO/Au/rGO ternary nanocomposites possessing a high photocatalytic response under solar irradiation were synthesized by a two-step process via a pulsed laser synthesis and a wet chemical process. The crystalline structure, surface morphology, size distribution, elemental composition, and optical properties of the prepared ZnO/Au/rGO ternary nanocomposites were characterized using X-ray diffraction, field-emission scanning electron microscope, high-resolution transmission electron microscope, energy-dispersive X-ray spectroscopy, UV-vis diffuse reflectance spectra, and photoluminescence analysis. The photocatalytic activity of the as synthesized nanocomposites was evaluated for the degradation of methylene blue (MB) under solar light irradiation (SLI). The density of the elemental and carbonaceous components, such as the Au nanoparticles (NPs) and the rGO nano-matrix on ZnO, could be altered by changing the concentration of HAuCl4.3H2O (5, 10, 15, and 20 wt%) or rGO (2.5, 5, and 7.5 wt%) using the same synthetic processes. The ZnO/Au15/rGO5 nanocomposite showed the highest photocatalytic degradation efficiency of 95% MB after 120 min under SLI, potentially due to the increased absorption of solar light or the efficient separation and migration of charge carriers by the anchored Au NPs and rGO onto the ZnO NPs. Further, the observed results and reusability of ZnO/Au15/rGO5 makes it an exceptionally promising material for diverse applications in the field of wastewater treatment and other types of environmental remediation.

Enhanced dechlorination of m-DCB using iron@graphite/palladium (Fe@C/Pd) nanoparticles produced by pulsed laser ablation in liquid.

In this work, the zero valent Fe (ZVI) and graphite-encapsulated Fe (Fe@C) nanoparticles (NPs) were easily and selectively prepared by a pulsed laser ablation (PLA) method in an aqueous sodium borohydride solution and ascorbic acid dissolved in methanol, respectively. Here, the Fe@C NPs were uniquely synthesized by PLA in methanol, where the solvent is used as both a carbon source for the graphitic layers and solvent, which is very unique. Furthermore, Pd NPs were loaded onto the surface of the Fe@C NPs to prepare bimetallic (Fe@C/Pd) NPs for the enhancement of the degradation efficiency of m-dichlorobenzene (m-DCB). The morphology, crystallinity, and surface composition of the prepared NPs were carefully characterized by high-resolution transmission electron microscopy (HRTEM), energy dispersive x-ray spectrometer (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The degradation rate of m-DCB using single (Fe and Pd) or bimetallic (Fe/Pd and Fe@C/Pd) NPs were compared by using gas chromatography. Among these NPs produced in this work, the Fe@C/Pd NPs with 1.71 wt % of Pd showed an excellent dechlorination efficiency for m-DCB with 100% degradation within 75 min. The graphitic layer on the Fe NPs played as not only an oxidation resistant for the Fe NPs to surroundings, but also a supporter of the Pd NPs for the enhanced degradation efficiency of m-DCB.