Aqueous-phase Reduction Research Articles

Facile and controllable hybrid-nanoengineering of MWCNTs/Au@ZIF-8 and AuPt@CeO2 based sandwich electrochemical aptasensor for AFB1 determination in foods and herbs

Herein, a sandwich electrochemical sensing strategy for aflatoxin b1 (AFB1) detection based on hybrid-nanoengineering was presented. First, Au nanoparticle was doped into zeolitic imidazolate framework-8 (ZIF-8) to form Au@ZIF-8 by in-situ growth method, followed by multi-walled carbon nanotubes (MWCNTs) addition to synthesize MWCNTs/Au@ZIF-8 via self-assembly. The structural “confinement effect” of ZIF-8 afforded a microenvironment for Au nanoparticles and SMCNTs in a certain spatial region, giving MWCNTs/Au@ZIF-8 excellent electrochemical property as the substrate material. In addition, Au-Pt bimetallic nanoparticle, which exhibited excellent stability and catalytic activity was loaded on the hollow cerium oxide (CeO2) to form AuPt@CeO2 nanoparticle through one-step aqueous phase reduction. Owning to its high surface-to-volume ratio, satisfied electron transfer efficiency and biocompatibility, massive toluidine blue (TB) and AFB1 antibody (Ab) could be modified on the AuPt@CeO2 to form AuPt@CeO2-Ab-TB, which acted as signal tag for the ultrasensitive assay of AFB1. The proposed electrochemical sensing system exhibited wide detection range (2 × 10-5 − 20 ng/mL) and low detection limit (2.13 fg/mL), which has been successfully applied to AFB1 determination in four real samples. The hybrid nanoengineering presented in this work is an active attempt to prepare high-performance substrate material and signal tag, which provides a new insight for the development of highly sensitive and specific electrochemical sensing systems.

The role of superoxide anion to Cr(VI) reduction by pine biochar

It has been reported that Cr(VI) can be reduced by biochar because of its redox activity. Considering the anionic form of Cr(VI), we hypothesize that the reduction in aqueous phase is significant. However, the contribution of different reactive oxygen species in the biochar-Cr(VI) reaction system has not been distinguished. Herein, we quantitatively identified Cr(VI) adsorption and reduction in biochar systems. The reduction content of Cr(VI) was 1.5 times higher in untreated conditions than in anaerobic conditions. The disappearance of·O2- under anaerobic conditions illustrated that·O2- may be involved in the reduction of Cr(VI). Quenching of·O2- resulted in a decrease of Cr(VI) reduction by 34%, while 1O2 was negligible, probably due to the stronger electron-donating capacity of·O2-. The degradation of nitrotetrazolium blue chloride (quenching agent of·O2-) confirmed that the reduction process of·O2- mainly occurred in the liquid-phase. Boehm titration and quantification of·O2- further elucidated the significant correlation (P < 0.05) between phenolic groups and the formation of·O2-, which implied that phenolic groups acted as the primary electron donors in generating·O2-. This study highlights the importance of the liquid-phase reduction process in removing Cr(VI), which provides theoretical support for biochar conversion of Cr(VI).

Ultra-rapid catalytic reduction of methyl green dye using tetra methyl ammonium bromide derived cobalt nanoparticles

Cobalt nanoparticles (CoNPs) were fabricated from cobalt chloride hexahydrate (CoCl2·6H2O) through a novel aqueous phase reduction protocol using sodium borohydride (NaBH4) as reducer and tetra methyl ammonium bromide (TMAB) as stabilizing reagent. As synthesized CoNPs were characterized via different advanced techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and Fourier transform infra-red (FTIR) spectroscopy. The results depict that as prepared CoNPs were spherical in shape, evenly distributed, crystalline in nature and possessed an average diameter of 10 nm. These CoNPs (1.3 mg) were found to play the role of highly efficient catalysts for ultra-rapid reduction of methyl green (MG) designated as a model dye in one minute of time for 0.1 mM (≈ 45.5 ppm) MG as evident from ultra-violet visible (UV–Vis) spectroscopy. These CoNPs were reused 5 times with 100–94.2 % catalytic efficiency. CoNPs were applied for reduction of MG dye in tap water demonstrated as representative environmental sample with outstanding performance. The application of this catalyst could be extended for rapid reduction of other toxic dyes in several types of aqueous matrices. This study is important because the synthesis of cheaper catalyst like CoNPs is quite easy while its significance is enhanced catalytic reduction efficiency for MG. These findings can be used by our group to solve the issue of environmental contamination especially caused by synthetic dyes like methyl violet, methylene blue, eosin B and so on. We can use the waste water from textile and food industry for this study.

Production of rhenium nanoparticles by low-temperature aqueous-phase reduction of NH4ReO4 using NaBH4

The synthesis of refractory rhenium (Re) powders is significant for the production of rhenic products. In this work, the ultra-fine Re nanoparticles were synthesized via a combination of aqueous-phase reduction and rapid hydrogen reduction using NH4ReO4 as Re source. The theoretical reduction route was determined by investigating the Eh-pH diagram of the Re-H2O system and conducting thermodynamic calculations. The optimal results were achieved by adjusting the experimental parameters like acid type, initial acidity, molar ratio of BH4−: ReO4−, feed rate of reductant, reaction temperature (T), and reaction time (t). The amorphous Re powders with minor oxide inclusions can be prepared under the optimized conditions of [HCl] = 1.35 mol L−1, BH4−: ReO4− molar ratio = 5.32, feed rate = 15 mL min−1, reaction temperature = 30 °C, and reaction time = 30 min. The maximum reduction efficiency reaches 99.5%. After annealing in hydrogen for 30 min, the crystalline Re nanoparticles with low oxygen content can be obtained. This work demonstrates the feasibility and efficacy of rapidly synthesizing ultra-fine Re nanoparticles in a solution-based approach.

Monomeric and Polymeric Mesoionic N-Heterocyclic Carbene-Tethered Silver Nanoparticles: Synthesis, Stability, and Catalytic Activity.

In recent years, N-heterocyclic carbenes (NHCs) have garnered significant attention as promising alternatives to thiols to stabilize metallic nanoparticles and planar surfaces. While most studies thus far have focused on NHC-functionalized gold nanoparticles (AuNPs), as an ideal platform to investigate the role of NHCs in stabilizing such nanoparticles, their ability to protect more unstable coinage metal nanoparticles, such as silver nanoparticles (AgNPs), has been largely overlooked. This is despite the fact that AgNPs possess a much more sensitive optical response that, upon their enhanced stability, can broaden their scope of application in various fields, including nanomedicine and catalysis. In this study, the synthesis and use of monomeric and polymeric mesoionic NHC-Ag(I) complexes as precursors to mono- and multidentate NHC-tethered AgNPs are reported. The polymeric analog was obtained by first synthesizing a polymer, containing 1,2,3-triazole repeat units, employing the copper-catalyzed alkyne-azide cycloaddition click polymerization of monomers containing diazide- and dialkyne functional groups. Subsequent quaternization of the triazole moieties and Ag insertion yielded the target NHC-Ag-containing polymer. Using this polymer as well as its monomeric analog as substrates, AgNPs with either catenated networks of NHCs or monomeric NHCs were fabricated by their reduction using borane-tert-butylamine complex. Our stability studies demonstrate that while monomeric NHCs impart some degree of stability to AgNPs, particularly at elevated temperatures in aqueous as well as organic medium, their polymeric analogs further enhance their stability in acidic environment (pH = 2) and against glutathione (3 mM), as an example of a biologically relevant thiol, in aqueous media. To highlight the application of these NHC-functionalized AgNPs in catalysis, we explore the aqueous phase reduction of methyl orange and 4-nitrophenol.

Electrochemical Reduction of Halogenated Alkanes and Alkenes Using Activated Carbon-Based Cathodes.

Granular activated carbon (GAC) is used to sorb a broad range of halogenated contaminant classes, but spent GAC disposal is costly. Taking advantage of GAC's conductivity, this study evaluated the conversion of the GAC to cathodes for electrochemical reductive dehalogenation of 15 halogenated alkanes and alkenes exhibiting a diversity of structures (type of halogen, number of halogens, functional groups) and including contaminants of practical importance (e.g., trichloroethylene). Alkane degradation rates increased with the number of halogens and in the order: chlorine < bromine < iodine. Quantitative structure-activity relationships (QSARs) correlating experimental first-order degradation rate constants for alkanes with molecular descriptors associated with an outer-sphere one-electron transfer calculated using density functional theory indicated that correlations with molecular descriptors improved in the order: aqueous phase reduction potentials (E0,aq) < energy of the substrate's lowest unoccupied molecular orbital (ELUMO) < Marcus theory activation free energies (ΔG‡) ∼ gas-phase standard reduction free energies (ΔG0,gas). Chlorinated alkene degradation rates increased with decreasing number of chlorines, and QSAR correlations were opposite those of alkanes, indicating a different reaction mechanism. Degradation timescales ranged from 1 min to 3 h with halides as predominant products. These results suggest that the electrochemical reduction of halogenated alkanes and alkenes can be used to regenerate spent GAC.

Improved Electron Efficiency of Zero-Valent Iron towards Cr(VI) Reduction after Sequestering in Al2O3 Microspheres.

Zero-valent iron (ZVI) is widely used for groundwater remediation, but suffers from high electron consumption because of its free contact with non-target substrates such as O2. Here, ZVI-ALOX particles were prepared via in situ NaBH4 aqueous-phase reduction of ferrous ions (Fe2+) preabsorbed into Al2O3 microspheres. The electron efficiency (EE) and long-term performance of the material were improved by sequestering ZVI in the interspace of the Al2O3 microspheres (ZVI-ALOX). During long-term (350 days) continuous flow, Cr(VI) was removed to below the detection limit for over 23 days. Based on the high reactivity of ZVI towards Cr(VI), the EE of ZVI-ALOX was evaluated by measuring its Cr(VI) removal efficiency at neutral pH and comparing it with that of ZVI. The results showed that the EE of ZVI-ALOX during long-term continuous flow could reach 39.1%, which was much higher than that of ZVI (8.68%). The long-term continuous flow results also demonstrated that treatment of the influent solution achieved higher EE values than in the batch mode, where the presence of dissolved oxygen reduced EE values. At lower pollutant concentrations, the sequestering of ZVI was beneficial to its performance and long-term utility. In addition, measurement of the acute toxicity of treated column effluent using the indicator organism Photobacterium phosphoreum T3 showed that ZVI-ALOX could reduce the toxicity of 5 mg/L Cr(VI) solution by ~70% in 350 d. The results from this study provide a basis for the development of permeable reactive barriers for groundwater remediation based on sequestered ZVI.

A specific identification platform based on biscuit-like bismuth nanosheets for label-free electrochemical immunosensor.

A label-free electrochemical immunosensor based on the biscuit-like bismuth nanosheets (BiNSs) and multi-wall carbon nanotubes-chitosan-gold nanoparticles (MWCNTs-Chit-AuNPs) was constructed for the detection of human immunoglobulin G (hIgG). The biscuit-like BiNSs prepared by one-step aqueous phase reduction method had a large electroactive surface area, 1.7 times that of bare glassy carbon electrode (GCE), which could load more antibodies and were used as a larger platform for the specific identification of antigens and antibodies. In addition, MWCNTs and AuNPs with good conductivity could be used to regulate the sensing interface, which promoted electron transfer greatly. Moreover, the AuNPs could stably anchor anti-hIgG by the affinity interaction between amine group of antibody and AuNPs, which greatly increased the number of anti-hIgG attached to the sensing platform. Under the optimal conditions, the proposed immunosensor exhibited excellent analytical performance for hIgG with a wide linear response of 0.01-1000ng/mL and a low detection limit of 4.26pg/mL. The electrochemical immunosensor exhibited favorable reproducibility, excellent specificity and high storage stability. Additionally, the immunosensor could be applied to determining hIgG in human serum samples as well. Considering these advantages, the electrochemical immunosensor has the potential application in clinical diagnosis.

Recent advancement in heterogeneous CO2 reduction processes in aqueous electrolyte

This review provides an in-depth general overview on various types of heterogeneous CO2 reduction in aqueous phase with a detailed discussion on EC, PEC and PV-EC/PEC processes including a thorough coverage on the futuristic MEA system.

Carbon dioxide capturing evaluation of polyacryloyl hydrazide solutions via rheological analysis for carbon utilization applications

PAHz is a relatively inexpensive material which has several industrial applications but its interaction and utilization in conjunction with CO2 has not been explored. In this study, carbon dioxide (CO2) capturing potential of a polymeric material viz., polyacryloyl hydrazide (PAHz) with specific hydrazide functional group is reported. Characterization tools i.e., microscopic, absorption rate kinetics and rheological analysis were used to determine optimum composition ensuing CO2 uptake via interaction between functional group and CO2 molecules. A varying concentration i.e., 5–30 wt% of PAHz was used. PAHz solution with ≤10 wt% was entirely saturated by small size CO2 bubbles and absorption increases with increasing equilibrium pressure as shown by molality results. With high PAHz concentration >10 wt%, capturing of CO2 markedly decreased and globules of moderately entrapped gas caused reduction in aqueous phase participating in CO2 absorption. CO2 responsiveness with a functional group to develop gelling in solution depended on PAHz concentration. At low concentration, PAHz chains were lesser in population which developed preliminary gelling in solution while high concentration produced sufficient PAHz chains for CO2 interaction. This resulted in the solution to display premature gelling that restricted further entry of CO2, and several CO2 bubbles aggregated near top of solution. In presence of CO2, a sol-gel transition in PAHz solution was anticipated when concentration ∼15 wt%. Finally, rheological investigations were performed to find out the effect of CO2 capturing on the rheological behaviour of solutions. The rheological properties (viscosity and moduli) for 5 and 10 wt% PAHz solutions did not change much after CO2 capturing and stable Newtonian behaviour was observed. The observations presented in the study present a strong case for application of liquid PAHz sample for use as mobility control agent during CO2 injection for EOR and carbon geo-sequestration.

Organoselenium ligand-stabilized copper nanoparticles: Development of a magnetically separable catalytic system for efficient, room temperature and aqueous phase reduction of nitroarenes

Herein, we report the synthesis of a novel selenoether ligand L1 (pyren-1-yl-CH2-NH-CH2-CH2-SePh) and the first example of organoselenium compound stabilized-copper nanoparticles (NPs) with long term stability. Such stabilized nanoparticles (NPs) have been immobilised non-covalently on a chitosan-layered magnetic support to obtain Fe3O4@CS@L1-stabilized-CuNPs, characterized very well by various techniques. It has been explored as an extremely efficient and recyclable catalytic system for cost effective and green borohydride reduction reactions of a variety of nitroarenes (4-nitrophenol, nitrobenzene, 2-nitrophenol, 4-nitroaniline, 2-nitroaniline, 4-nitrotoluene, 1-chloro-4-nitrobenzene and 4-nitroanisole) in an eco-friendly solvent i.e. water at room temperature with ≥99% conversions into aminoarenes in very short reaction times. Additional advantages, offered by the catalyst, are its magnetic separability and recyclability. A very high value of rate constant (0.350 per minute) and a very low value (31.7 KJ per mol) of activation energy (Ea) have been found. Catalyst is very robust and does not let the copper species and ligand leach into the solution during the course of reduction reaction. Kinetics and Hammett plot of the catalytic reaction have been studied. It appears that the catalysis proceeds via a cationic transition state.

Schottky Junctions with Bi Cocatalyst for Taming Aqueous Phase N2 Reduction toward Enhanced Solar Ammonia Production

Solar‐powered N2 reduction in aqueous solution is becoming a research hotspot for ammonia production. Schottky junctions at the metal/semiconductor interface have been effective to build up a one‐way channel for the delivery of photogenerated electrons toward photoredox reactions. However, their applications for enhancing the aqueous phase reduction of N2 to ammonia have been bottlenecked by the difficulty of N2 activation and the competing H2 evolution reaction (HER) at the metal surface. Herein, the application of Bi with low HER activity as a robust cocatalyst for constructing Schottky‐junction photocatalysts toward N2 reduction to ammonia is reported. The introduction of Bi not only boosts the interfacial electron transfer from excited photocatalysts due to the built‐in Schottky‐junction effect at the Bi/semiconductor interface but also synchronously facilitates the on‐site N2 adsorption and activation toward solar ammonia production. The unidirectional charge transfer to the active site of Bi significantly promotes the photocatalytic N2‐to‐ammonia conversion efficiency by 65 times for BiOBr. In addition, utilizing Bi to enhance the photocatalytic ammonia production can be extended to other semiconductor systems. This work is expected to unlock the promise of engineering Schottky junctions toward high‐efficiency solar N2‐to‐ammonia conversion in aqueous phase.

Facile synthesis of branched Au nanocrystals with sub-10-nm arms and their applications for ethanol oxidation reaction

Branched Au nanocrystals with sub-10-nm arms are synthesized via a one-pot reduction in aqueous phase. The success of current work relies on the use of octadecyltrimethylammonium chloride as the shape-directing capping agent to facilitate the formation of branched products in high purity. Their overall size could be controlled in the range of 16–60 nm by varying the Au precursor amount or concentration of capping agent, and the diameter of arms is limited to sub-10-nm size range. Interestingly, Au nanocrystals with a unique morphology, sheet-wrapped dendrites, could be obtained when the concentration of a reductant was varied. The current strategy is also validated effective in the fabrication of dendritic products composed of other noble metals or alloys in addition to Au by simply using the alternative metal precursor. As compared to spherical counterparts, the current branched Au nanocrystals exhibited noticeable red-shift in UV-Vis extinction spectrum and enhanced catalytic activities for electrooxidation of ethanol in alkaline media.

Active biochar support nano zero-valent iron for efficient removal of U(VI) from sewage water

The goals of this study were to prepare activated biochar-loaded nano zero-valent iron (A-BC-NZVI) and implemented to remove heavy metal uranium (U(VI)) in sewage water. The A-BC-NZVI composite was successfully synthesized by aqueous phase reduction using biomass longan shell as carbon source under N2 at 800 °C. The influence of solution pH, A-BC-NZVI dosage, temperature, time and U(VI) concentration on U(VI) remediation via A-BC-NZVI were investigated. The batch sorption experiments reveal that the sorption capacity of U(VI) decreases from pH 7 to 10, and the adsorption kinetic experiments of pseudo-first-order, pseudo-second-order and reduction kinetics were conducted, pseudo-second-order kinetic model was well fitted through the correlation coefficient (R2). At pH 6.0, the maximum U(VI) adsorption amount of Langmuir model was calculated to be 331.13 mg/g, and the thermodynamic constants manifested that U(VI) removal by A-BC-NZVI is an endothermic and spontaneous system. XPS analysis displayed that A-BC-NZVI has two effects on U(VI), including adsorption and reduction. The results proved that A-BC-NZVI is considered highly desirable material on remediation of U(VI) from polluted groundwater.

Reduction of dissolved carbon dioxide in aqueous solution by UV-LED/TiO2 process under periodic illumination

The application of controlled periodic illumination (CPI) using ultraviolet light-emitting diodes (UV-LED) for the photocatalytic reduction of CO2 in the aqueous phase was investigated in this study. The experiments were conducted with P-25 TiO2 as photocatalyst under the UV light intensity of 160 mW/cm2 with 60 min of total illumination time and pH 2. The target product of the photocatalytic reduction of CO2 by UV-LED process was methanol with the highest selectivity of 28.31 %. The reduction efficiency of CO2 and the reaction rate reached the highest value of 86.31 % and 15.76 × 10−5 M min−1, respectively, for experiment conducted with the smallest duty cycle of 0.09. The photonic efficiency was enhanced from 0.47 % to 2.7 % with decreasing duty cycle from 1.00 to 0.09. The electric energy saving increased significantly from 13.11%–93.34%, including with a decrease of electric energy per order from 139.68 to 10.71 kW h m-3 order-1 for experiments conducted with decreasing γ from 0.91 to 0.09. The photocatalytic reduction of CO2 in the aqueous phase was well modeled by the Langmuir-Hinshewood kinetic equation. Furthermore, the proposed mechanism for photocatalytic CO2 reduction in aqueous phase under CPI was introduced.

Fabrication of highly dispersed Pd nanoparticles supported on reduced graphene oxide for solid phase catalytic hydrogenation of 1,4-bis(phenylethynyl) benzene

In this work, nanopalladium catalysts supported on the surface of reduced graphene oxide (rGO/Pd) with different palladium loadings have been prepared by one-step reduction in aqueous phase. They were mixed with 1,4-bis(phenylethynyl)benzene (DEB) to form rGO/Pd-DEB composites according to a mass ratio of 1:3. It was shown that nanopalladium particles with particle size of about 2–6 nm were disperse uniformly on the surface of rGO when the Pd loadings were in the range of 3.97–10.60 wt%. The maximum hydrogen uptake capacity of rGO/Pd-DEB composites at 25 °C determined according to PCT method was about 182.5 ml/g after reacted with hydrogen for about 20 h, which was some lower than that of the common Pd/C-DEB pallet getter (216 ml/g) but significantly higher than alkynyl modified polyvinyl alcohol supported palladium hydrogen absorbing materials (0.32 ml/g), indicating that rGO/Pd could be used in solid phase catalytic hydrogenation due to the high dispersion of palladium nanoparticles and the physical proximity of rGO/Pd catalyst with DEB organic molecules. This provides a good potential technical way for perparing the moldable carbon aerogel hydrogen absorption materials.

Immobilization of Pt nanoparticles on magnetite–poly (epoxyamine) nanocomposite for the reduction of p-nitrophenol

Recently the magnetic nanoparticle earns more attention in the field of catalysis for their enhanced loading capacity and magnetic recylability. In this study, we intended to focus the synthesis of polymer coated iron oxide nanoparticle as support for the immobilization of metal nanoparticles. The typical synthetic statergy involves the synthesis of 1,4-diaminobutane functionalized superparamagnetic Fe3O4 nanoparticle, followed by epoxyamine polymer coating on amine functionalised Fe3O4 using 1,4 diaminobutane and epichlorohydrin monomers through one pot method. Further, ultrafine Pt nanoparticle was immobilised onto poly (epoxyamine) coated Fe3O4. These materials were characterized using FT-IR, XRD, VSM, EDS, SEM HRTEM etc. The semiheterogenous catalytic efficiency of the material was examined in aqueous phase reduction of p-nitrophenol. The catalyst was reused up to 5 times without loss of activity.

Synthesis of Silver Flakes and Their Application as Conductive Filler for Low-Curing-Temperature Silver Pastes

Silver microparticles have inspired much research interest due to their enhanced properties for use in optical, electric, catalytic, and magnetic applications. One such use is as electrically conductive filler for printed electronics. A manufacturing approach has been developed to prepare low-curing-temperature silver pastes. Firstly, silver flakes were synthesized directly by a one-step aqueous-phase reduction reaction, using silver nitrate as silver salt precursor and iron(II) sulfate heptahydrate as reducing agent. Various silver flake samples were synthesized by controlling experimental parameters such as the reaction temperature, surfactant concentration, and reducing agent concentration. The obtained silver powders were characterized by x-ray diffraction analysis, scanning electron microscopy, and dynamic light scattering measurements. The results revealed that the morphology of the silver powders was a plate-like structure with diameter of 1 μm to 1.5 μm and thickness of 30 nm. The prepared silver flakes were then used directly without ball milling to prepare low-curing-temperature silver pastes. The bulk resistivity of a line screen-printed using silver paste containing 48 wt.% (34 ± 5 vol.%) silver flakes and cured at 140°C for 30 min in air was about (1.773 ± 0.118) × 10−6 Ω m. More importantly, the prepared screen-printed patterns exhibited excellent durability in terms of peel strength and folding endurance.

Highly efficient aqueous phase reduction of nitroarenes catalyzed by phosphine-decorated polymer immobilized ionic liquid stabilized PdNPs

Phosphino-decorated polymer immobilised ionic liquid-stabilised PdNPs are highly efficient catalysts for the aqueous phase hydrogenation and transfer hydrogenation of aromatic nitro compounds in batch and continuous flow.

Aqueous Phase Synthesis of Cu-in-Ga Photovoltaic Nanoparticles for the CIGS Printable Solar Cell Application

It is well known that CIGS (Cu(In,Ga)Se2) is one of the most effective photovoltaic devices for developing low cost and high efficiency solar cell. Bandgap of these can be adjusted from 1.04eV to 1.67eV by controlling the ratio of Ga in materials [1]. Moreover, it is ecological and economical solar cell since it needs only 1-2µm thickness because of its high optical absorption coefficient (105cm-1) [2]. Until now, CIGS solar cell, synthesized by utilizing gas phase method, achieved high conversion efficiency above 20%, nevertheless gas phase evaporation process consume high energy and natural resources. Therefore the cost of CIGS is still high and is not be widely used [3]. To solve this problem, we reported completely new approach to synthesize low cost CIGS solar cell [4]. This process consists of three steps; 1) synthesis of CI and/or CIG nanoparticles by utilizing aqueous phase reduction method, 2) print of these precursor nano-materials on a substrate, 3) selenization/sulfurization of these to form CIS/CIGS solar cell. As a result, CIS solar cell with the conversion efficiency of c.a. 3% was successfully synthesized. To increase the conversion efficiency, Ga should be incorporated into CI nanoparticles during aqueous phase synthesis procedure. However, co-reduction of Ga with Cu and/or In cannot be achieved until now, because of the reduction potential difference between Ga and Cu-In, and of low melting point of Ga (29.76℃). Therefore, in this study, aqueous phase synthesis procedure of Cu-In-Ga nanoparticles were developed. To reduce the Ga ion in aqueous phase, Ga complex species should be homogenized. So, appropriate complexing reagent, concentration of metals and/or complexing reagent, pH of solution were expected by utilizing calculation using critical stability constants. Reduction potential of homogenized Ga complex was measured by CV (cyclic voltammetry) analysis method. Co-deposition of Ga with Cu and In under expected condition were also progressed, and synthesized particles were evaluated by SEM-EDX, TEM-EDX and XRD. Results of XRD and SEM/EDX measurement demonstrated that Ga can be doped into CI nanoparticles, and doping ratio of Ga into CI nanoparticles were depended on the reduction rate and also reduction method. For example, maximum Ga concentration in CIG nanoparticles were reached c.a. 20% when the molar ratio of reducing agent against to metals reached to ten. Moreover, these results shows that reduction procedure was seriously affected to the doping ratio of Ga. Ratio of synthesized CIG particles were close to the target composition, by controlling solution condition and reaction field. In addition, large scale synthesis enough to make CIG precursor film were successfully achieved. By applying PVP as a dispersing agent, generation of aggregate particles was suppressed, and therefore smooth CIG film was successfully fabricated. Another detailed results will be presented in our session. [1] Appl. Phys. A, 74 (2002), pp. 659–664, [2] Basic technic of CIGS solar cell, Nakata, Nikkankougyoshinbunsha, 2010, [3] Phys. Status Solidi RRL, 9 (2015), pp. 28–31, [4] For example, 228th ECS meetings, Z01-1846 (2015)