Conventional Wet Chemical Methods Research Articles

Direct incorporation of silver nanoparticles onto thin-film composite membranes via arc plasma deposition for enhanced antibacterial and permeation performance

We report on a new technique that incorporates silver nanoparticles (AgNPs) onto polyamide (PA) thin film composite (TFC) reverse osmosis membranes via arc plasma deposition (APD) to impart antibacterial properties and simultaneously improve membrane performance. APD allows the direct deposition of AgNPs under vacuum dry condition, overcoming the drawbacks of the conventional wet-chemical methods. AgNPs (~7.6nm in diameter) were uniformly distributed without aggregation throughout the PA selective layer with some partially implanted into the PA matrix. Ag loading could be tuned by simply adjusting the number of APD purse shots. The deposited AgNPs exhibited good leaching stability, presumably due to the strong Ag-PA chemical interaction and partially buried AgNP morphology. The resulting Ag-incorporated TFC (Ag-TFC) membrane showed the strong and long-lasting antibacterial properties for both gram-negative and -positive bacteria. Simultaneously, the Ag-TFC membrane exhibited an enhancement in water flux of approximately 40% without deterioration in NaCl rejection. These performance changes were tentatively attributed to the partial destruction of the PA layer under the high energetic APD condition along with the increased membrane hydrophilicity. Hence, the APD process provides a simple and effective route to modify membranes with functional NPs.

Plasma Spray Pyrolysis: A Rapid, Scalable Method for Making Mixed Metal Oxide Alloys for Enabling Accelerated Materials Discovery

Many grand challenges in energy conversion and storage need discovery of new materials. However, there are not too many reported synthesis approaches that could easily be implemented for screening and rational understanding of structure-behavior relationships. Specifically, the challenges include semiconductors for photoelectrochemical water splitting, stable electrocatalysts for oxygen evolution and reduction, and nitrogen reduction and for many heterogeneous gas-solid reactions including carbon dioxide reduction. Many of the above challenges require synthesis of multi-element alloys with composition over entire range regardless of phases present. Here, we report a new synthesis technique that can be used to accelerate the discovery of materials for various energy conversion and storage applications. Specifically, this technique allows a rapid and controlled synthesis of mixed metal oxide particles using plasma oxidation of liquid droplets containing mixed metal precursors. The conventional wet chemical methods for synthesis of multi-metal oxide alloys often require time-consuming high pressure and temperature processes, and so the challenge is to develop rapid and scalable techniques with precise compositional control. The concept is demonstrated by synthesizing binary and ternary transition metal oxide alloys with control over entire composition range using metal precursor solution droplets oxidized using atmospheric oxygen plasma. The results show the selective formation of metastable spinel and the rocksalt solid solution phases with compositions over the entire range by tuning the metal precursor composition. The synthesized manganese doped nickel ferrite nanoparticles, NiMnzFe2- zO4 (01), exhibits considerable electrocatalytic activity towards oxygen evolution reaction (OER), achieving an overpotential of 0.39V at a benchmarking current density of 10 mAcm-2 for a low manganese content of z = 0.20.

A rapid and scalable method for making mixed metal oxide alloys for enabling accelerated materials discovery

Abstract

Organo-Metallic Chemical Deposition of Metal Oxide Supported Electrocatalysts for ORR with High Noble Metal Utilization

Oxygen electrocatalysis is a key enabling technology for a sustainable future. The oxygen reduction reaction (ORR) has received extensive research attention as it is central to the development of several renewable energy technologies such as fuel cells and metal-air batteries [1]. Governed by sluggish kinetics, this reaction requires expensive noble metal based catalysts that require an efficient utilization in regard of the economic competitiveness of the respective technologies. In the case of the polymer electrolyte fuel cell (PEFC), Pt supported on high surface area carbon is at present the state-of-the-art material. However, the carbon support is thermodynamically unstable at high oxidative potentials leading to Pt detachment and severe fuel cell performance losses [2]. This presents a major hurdle to the widespread availability of commercial applications. In order to overcome the problem of carbon support corrosion, chemically robust, conductive metals oxides in their thermodynamically favorable oxidation states have been shown to be a promising alternative [3]. However, conventional wet-chemical methods of Pt nanoparticle deposition on high-surface-area support materials yield much lower specific Pt surface areas when applied to metal oxide supports as compared to the results for carbon supports. The resultant reduction in Pt utilization thwarts the performance of such metal oxide supported Pt catalysts. In this study, we have developed an organo-metallic chemical deposition method to produce Pt nanoparticles supported on several TiO2 and SnO2 based materials with a high Pt utilization for PEFC applications. The resultant Pt particle size distribution and dispersion on the support was determined by transmission electron microscopy. The Pt metal loading was determined by inductively-coupled plasma optical emission spectroscopy. The ORR activity and durability of the metal oxide supported Pt nanoparticles was tested by cyclic voltammetry (CV) in oxygen saturated 0.1 M HClO4 using the thin-film rotating disk electrode technique [4]. Here, a known aliquot of catalyst ink is drop-coated onto a glassy carbon disk as the working electrode. The Pt utilization of the catalyst was evaluated in terms of the electrochemically active surface area (ECSA) by hydrogen underpotential deposition [5]. For the durability studies, CV measurements were performed over 1000 potential cycles between 0.5 and 1.5 V versus a hydrogen reference electrode (RHE) using a scan rate of 50 mV s-1 at room temperature. The performance and stability of the prepared catalysts for the ORR will be discussed. Acknowledgements We thank the South African Department of Science and Technology for financial support in the form of HySA/Catalysis Centre of Competence programme funding and HySA/Catalysis student bursary. The financial assistance of the National Research Foundation (DAAD-NRF) towards this research is hereby acknowledged. Opinions expressed and conclusions arrived at, are those of the authors and are not necessarily to be attributed to the DAAD-NRF. Financial support from the Competence Center for Energy and Mobility (CCEM) Switzerland and Umicore AG & Co. KG is greatly acknowledged.

Application of Cold Atmospheric Pressure Plasmas for Biological Tissue Treatment

New experiments using atmospheric pressure plasma have found large application in biology and medicine. Cold air plasma treatment can be used to modify the surface of different materials for a variety of applications. The emission spectroscopy data confirmed the presence of different reactive species in the discharge gap. Surface treatments using this dry plasma technology offer an environmentally friendly alternative to the conventional wet chemical methods of microorganisms destruction, biological tissue treatment, in vitro and in vivo cell treatment. The use of cold plasma technology removes contaminants at the nanometer level.

Synthesis and Characterization of Double-Doped Bismuth Oxide Electrolytes for Lower Temperature SOFC Application

Introduction A critical hurdle to the commercialization of SOFCs is the ability to reduce system cost. A lower temperature would allow for the use of less expensive interconnect materials, reduction of the start-up time, longer mechanical and chemical stability, thus reducing total system cost. However, lowering the operation temperature of SOFCs is difficult due to ionic conductivity limitations of electrolyte materials. For example, yttria-stabilized zirconia (YSZ) is a widely used electrolyte material but its ionic conductivity is very low at temperatures below 700⁰C. It has been demonstrated that erbium stabilized bismuth oxide (ESB) has one to two orders of magnitude higher ionic conductivity than YSZ due to ESB's high oxygen vacancy concentration. Furthermore, we have developed dysprosium-tungsten doped bismuth oxide (DWSB) which has an even higher conductivity and stability at lower temperatures as compared to ESB. In this presentation, we report our recent progress in developing DWSB and other high performance double doped bismuth oxide (DD-SB) electrolytes for SOFCs. In order to further enhance the performance we developed nano-sized DD-SB powder using wet chemical methods and investigated the effect of powder morphology on the performance of DD-SBs using AC impedance spectroscopy. Experimental Procedure DD-SB powders were prepared via conventional solid state and wet chemical methods. Solid state (SS) powder was fabricated by milling Bi2O3 and MOx dopants in a HDPE mill for 24h. The milled powder was calcined at 800⁰C for 16 hours to achieve the desired phase. To make coprecipitated (CP) powder, appropriate amounts of Bi(NO3)3-xH2O and dopant metal nitrate salts were dissolved in nitric acid and for DWSB (NH4)6W12O36-xH2O was dissolved in NH4OH. The acid solution is added drop wise to the base solution while stirring with a magnetic stir bar. The precipitate was washed in DI H2O, filtered, dried at 100⁰C, and fired at 550⁰C to achieve the appropriate phase. Additionally, glycine nitrate combustion is used. Appropriate amounts of the metal salts and NH2CH2COOH (glycine) are dissolved in DI H2O and 10 vol% HNO3. The solution is evaporated at 100 °C. The resulting gel is heated to 350 °C until auto-ignition occurs. The resulting ash is collected and fired at 550 - 650 °C to achieve the desired phase.The phase analysis of the powders was performed by means of X-ray diffraction (XRD). BET surface area, and particle size calculations were used to quantify the geometric powder properties. SEM images were taken to observe the morphology of the powder. Symmetric cells were fabricated using uniaxial pressing. Thin DD-SB electrolytes were also colloidally deposited onto NiO-GDC anodes and sintered at 750⁰C. Conductivity measurements using electrochemical impedance spectroscopy (EIS) were performed. Results Fig.1 shows an example of a deposited thin film of wet chemically synthesized DWSB onto a pre-fabricated anode supported NiO-GDC with a GDC electrolyte.

Two‐Dimensional CuSe Nanosheets with Microscale Lateral Size: Synthesis and Template‐Assisted Phase Transformation

Semiconducting nanosheets with microscale lateral size are attractive building blocks for the fabrication of electronic and optoelectronic devices. The phase-controlled chemical synthesis of semiconducting nanosheets is of particular interest, because their intriguing properties are not only related to their size and shape, but also phase-dependent. Herein, a facile method for the synthesis of phase-pure, microsized, two-dimensional (2D) CuSe nanosheets with an average thickness of approximately 5 nm is demonstrated. These hexagonal-phased CuSe nanosheets were transformed into cubic-phased Cu(2-x)Se nanosheets with the same morphology simply by treatment with heat in the presence of Cu(I) cations. The phase transformation, proposed to be a template-assisted process, can be extended to other systems, such as CuS and Cu1.97 S nanoplates. Our study offers a new method for the phase-controlled preparation of 2D nanomaterials, which are not readily accessible by conventional wet-chemical methods.

ChemInform Abstract: Application of Heterogeneous Catalysts Prepared by Mechanochemical Synthesis

AbstractReview: 75 refs.

Preparation of fracture-free, uniform, crystallized titania hollow nanospheres by spray pyrolyzing core–shell seeds

Crystalline hollow nanospheres that are potentially applicable for optical, catalytic, and electronic devices have been generally synthesized by wet chemical approaches with multiple steps. Colloidal aerosol pyrolysis is a valuable approach producing crystallized hollow nanospheres with mass-production, minimum manufacturing steps, and less chemical usage than conventional wet chemical methods. However, conventional gas phase pyrolysis strategy has unsolved critical issues when synthesizing uniform shell-type nanoparticles including uncontrollable fracturing by sharp thermal shocks and material shrinking during crystallization. In this manuscript, the shell fracture in the gas phase continuous process is eliminated utilizing two stage pyrolysis which removes significant stresses from thermal treatment and gas emission. Advantages of solution chemistry and gas phase continuous process are combined by exploiting colloidal spray pyrolysis with two stages, therefore enabling continuous synthesis of uniform hollow spheres accompanying with organic core burning and nanoshell crystallization without fracture.

Application of heterogeneous catalysts prepared by mechanochemical synthesis

Mechanochemical synthesis has the potential to provide more sustainable preparative routes to catalysts than the current multistep solvent-based routes. In this review, the mechanochemical synthesis of catalysts is discussed, with emphasis placed on catalysts for environmental, energy and chemical synthesis applications. This includes the formation of mixed-metal oxides as well as the process of dispersing metals onto solid supports. In most cases the process involves no solvent. Encouragingly, there are several examples where the process is advantageous compared with the more normal solvent-based methods. This can be because of process cost or simplicity, or, notably, where it provides more active/selective catalysts than those made by conventional wet chemical methods. The need for greater, and more systematic, exploration of this currently unconventional approach to catalyst synthesis is highlighted.

Synthesis and characterization of hydroxyapatite/β-tricalcium phosphate nanocomposites using microwave irradiation

Microwave assisted synthesis method is a relatively new approach employed to decrease synthesis time and form a more homogenous structure in biphasic calcium phosphate bioceramics. In this study, nanocrystalline HA/β-TCP composites were prepared by microwave assisted synthesis method and, for comparison reason, by conventional wet chemical methods. The chemical and phase composition, morphology and particle size of powders were characterized by FTIR, XRD and SEM, respectively. The use of microwave irradiation resulted in improved crystallinity. The amount of hydroxyapatite phase in BCP ranged from 5% to 17%. The assessment of bioactivity was done by soaking of powder compacts in simulated body fluid (SBF). The decreasing pH of the solution in the presence of β-TCP indicated its biodegradable behavior. Rod-like hydroxyapatite particles were newly formed during the treatment in SBF for microwave assisted substrate synthesis. In contrast, globular particles precipitate under same conditions if BCP substrates were synthesized using conventional wet chemical methods.

Rapid simultaneous multi-element determination of soils and environmental samples with polarizing energy dispersive X-ray fluorescence (EDXRF) spectrometry using pressed powder pellets

A rapid simultaneous multi-element analysis method for soils and environmental samples has been established using polarizing energy dispersive X-ray fluorescence (EDXRF) spectrometry. The pressed powder pellet technique was adopted because it is simple and requires no specialized skills for sample preparation. The analytes examined were: Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, Fe2O3, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Sn, Sb, Cs, Ba, La, Ce, Pr, Nd, Pb and Th. Twenty-six reference samples were used for the calibrations. Compton scatter radiation was used as an internal standard to compensate for variations in the sample matrix, particle size, packing density and operating characteristics of the instrument. The correlation coefficients of the linear regression lines were >0.98, with the exception of Na2O, MgO, Al2O3, SiO2, P2O5, Co, Pr and Nd. The values obtained using the proposed EDXRF spectrometry were compared with the values obtained using other methods. Out of the 31 analytes examined, the results for 12 compounds (CaO, K2O, TiO2, MnO, Fe2O3, Ni, Zn, Rb, Sr, Cs, Ba and Ce) obtained by the proposed EDXRF spectrometry compared favorably with those determined through conventional wet chemical methods. In contrast, the results for eight compounds (Na2O, MgO, Cr, Co, Zr, Sn, Sb and Pr) obtained by the proposed EDXRF spectrometry exhibited poor agreements with those obtained using chemical methods. Among these analytes, the poor agreements of Cr, Zr and Sn were attributable to incomplete dissolution and/or volatilization losses during the chemical treatments based on an acid attack. It can be concluded, therefore, that there is a high possibility of underestimating the concentrations of these elements if wet chemical methods are used. Although the results of the other 11 analytes were not as good as those of the first group, they still appeared to be of practical use, considering the time consuming and potentially hazardous wet chemical pretreatment.

Optical spectroscopy of lanthanides doped in wide band-gap semiconductor nanocrystals

Currently, tripositive lanthanide (Ln3+) ions doped wide band-gap semiconductor nanocrystals (NCs) have been the focus of research interest due to their distinct optical properties and potential applications in optical devices and luminescent biolabels. Because of the low absorptions of parity-forbidden 4f–4f transitions for Ln3+, it is highly anticipated that the luminescence of Ln3+ ions embedded in wide band-gap NC lattices can be sensitized efficiently via exciton recombination in the host. For this purpose, the successful incorporation of Ln3+ into the lattices of semiconductor NCs is of utmost importance, which still remains intractable via conventional wet chemical methods. Here, the most recent progress in the optical spectroscopy of Ln3+ ions doped wide band-gap semiconductor NCs is discussed. Much attention was focused on the optical properties including electronic structures, luminescence dynamics, energy transfer as well as the up-conversion emissions of Ln3+ ions in ZnO, TiO2, SnO2 and In2O3 NCs that were synthesized in our laboratory using wet chemical methods.

Stepwise in situ synthesis and characterization of metallophthalocyanines@mesoporous matrix SBA-15 composites

The successful in situ synthesis of metallophthalocyanines in mesoporous matrices is presented in this report. To overcome the high hydrophobicity of phthalocyanine (Pc) compounds in conventional wet chemical methods, a simple but effective route is developed to incorporate the metallophthalocyanines into the mesoporous matrix via an in situ reaction process between pre-loaded metal ions and 1,2-dicyanobenzene (DCB) introduced by chemical vapor deposition. The Pcs are not directly loaded into the pores, but the precursors of metallophthalocyanines (metal ions and small DCB molecules) are introduced stepwise into the pore channels, which are then used as 'micro-reactors" to produce incorporated MePcs by in situ reactions. The structural and optical characteristics of the as-synthesized composites are carefully investigated using X-ray diffraction, transmission electronic microscopy, scanning electronic microscopy, infrared and ultra violet spectra, and BET methods. The results show that the metallophthalocyanines disperse homogeneously in the mesopores, mostly as monomers, accompanied by a small number of dimers.

Modular integration of electronics and microfluidic systems using flexible printed circuit boards

Microfluidic systems offer an attractive alternative to conventional wet chemical methods with benefits including reduced sample and reagent volumes, shorter reaction times, high-throughput, automation, and low cost. However, most present microfluidic systems rely on external means to analyze reaction products. This substantially adds to the size, complexity, and cost of the overall system. Electronic detection based on sub-millimetre size integrated circuits (ICs) has been demonstrated for a wide range of targets including nucleic and amino acids, but deployment of this technology to date has been limited due to the lack of a flexible process to integrate these chips within microfluidic devices. This paper presents a modular and inexpensive process to integrate ICs with microfluidic systems based on standard printed circuit board (PCB) technology to assemble the independently designed microfluidic and electronic components. The integrated system can accommodate multiple chips of different sizes bonded to glass or PDMS microfluidic systems. Since IC chips and flex PCB manufacturing and assembly are industry standards with low cost, the integrated system is economical for both laboratory and point-of-care settings.

Determination of the Hydroxyl Value of Soybean Polyol by Attenuated Total Reflectance/Fourier Transform Infrared Spectroscopy

AbstractA rapid method for the quantitative determination of the hydroxyl value (OHV) of hydroxylated soybean oils by HATR/FTIR spectroscopy is described. Calibration standards were prepared by the formic acid/hydrogen peroxide method and OH values were determined by the official method of AOCS Tx 1a‐66, covering an analytical range of 3.5–125 mg of KOH/g of sample. A partial least squares (PLS) calibration model for the prediction of the hydroxyl value (OHV) was developed based on eight different spectral subregions between 3,150 and 990 cm−1 and combinations of them. On average, 36 samples were used for the modeling and 17 were used for external validation. The resulting calibration was linear over the analytical range and had a standard deviation of 2.334. Validation of the method was carried out by comparing the OHV of a series of hydroxylated soybean oils predicted by the PLS model to the values obtained by the AOCS standard method. A correlation coefficient of R2 = 0.9843 and RMSEC and RMSEP values of, respectively, 3.393 and 3.643 were obtained. After the calibration of the spectrometer, the OHV could be obtained in 2–3 min per sample, a major improvement over conventional wet chemical methods. The advantages of these methodologies are that they do not destroy the sample, have a lower cost, expedite the analysis and do not produce residues. Therefore, they may yield excellent results when used to quantify OHV of soybean polyols obtained by hydroxylation reaction.

Plasmachemical Dehydroxylation of High Surface Area Silica at Room Temperature

Compared to conventional thermal and wet chemical methods, nonisothermal plasma treatment is found to be a viable alternative for carrying out dehydroxylation of porous silica. Changes in hydroxyl population and distribution within silica particles have been followed using solid state 1H NMR, temperature programmed desorption, and optical emission spectroscopy.

Determination of Calcium Carbonate in Limestone by Attenuated Total Reflectance Fourier Transform Infrared Spectrometry.

Attenuated total reflectance Fourier transform infrared (ATR/FT-IR) spectrometry was applied to the determination of calcium carbonate in limestone. Both of the simple and multiple linear regression methods have been investigated. The correlation coefficient was found to be increased to 0.985 when the multiple linear regression analyses using the absorbance values at all of the wavelengths were applied. The standard deviation of calibration for 37 samples by this method was 0.601. In order to test the applicability of the multiple linear regression method to routine analyses of limestones, 31 samples collected from the various mines distributed in Korea were analyzed by chemical and ATR/FT-IR methods. The range of CaCO 3 concentrations of the tested samples were 86-97%. The standard error of prediction (SEP) was found to be 0.294 when the absorbance values at all of the three wavelengths were used, whereas the SEP values were 1.340, 1.072 and 0.961 for the wavenumbers of 711, 1406 and 875 cm -1 , respectively. The results indicate that the ATR/FT-IR method can be applied to the routine determination of CaCO 3 in limestone by mid-infrared spectroscopy. The present method required virtually no pretreatment procedure and thus took less time comparing with the conventional wet chemical methods.

Molecular-beam mass-spectrometric analysis of lignocellulosic materials: I. Herbaceous biomass

A rapid analytical technique has been developed to qualitatively screen and quantitatively analyze biomass feedstocks for conversion into hydrocarbon fuels and chemicals. In this rapid analytical pyrolysis approach, herbaceous biomass feedstocks stored in the open without cover for 6 to 9 months were characterized using the molecular-beam mass spectrometer (MBMS). The biomass materials were pyrolyzed at 600°C and the volatile pyrolysis products were analyzed in real time by the MBMS. The mass spectral data were further analyzed by multivariate statistical techniques (Factor Analysis). The contents of nitrogen compounds, pentosans and hexosans estimated from the pyrolysis mass-spectrometric/multivariate analysis techniques correlated well with the results obtained by conventional wet chemical methods. However, lignin correlation was very weak because of the presence of microbial degradation products of biomass (humic material) that interfered with the Klason lignin analysis. This rapid analytical technique was used to analyze various fractions of the stored biomass feedstocks. A comparison of exposed surface biomass materials and the unexposed materials showed that the exposed fraction lost 30% (wt) of the carbohydrate component of the biomass relative to the fresh material.

Rapid and direct lodine value and saponification number determination of fats and oils by attenuated total reflectance/fourier transform infrared spectroscopy

A simple, rapid and reproducible method of determining the iodine value (IV) and saponification number (SN) for fats and oils was developed with an attenuated total reflectance/Fourier transform infrared spectrometer and commercially available triglycerides as calibration standards. Partial least squares was used to determine the spectral regions correlating with the known chemical IV and SN values, and the calibration set was augmented with additional standards generated by spectral co‐adding techniques. The calibration model obtained was used to analyze commercially available fats and oils with a wide range of IV and SN values, and the results were compared to the values obtained by American Oil Chemists’ Society methods. With the spectrometer calibrated and programmed, IV and SN results could be obtained within 2–3 min per sample, a major improvement over conventional wet chemical methods.