pH Value Of Reaction Solution Research Articles

In situ loading of Ag2MoO4 nanoparticles onto oxygen-doped porous g-C3N4 for enhanced photocatalytic H2 evolution

Photogenerated carriers transfer and separation from the substance itself to produce spatial isolated electron-hole pairs is crucial for the utilization of composite photocatalysts in the field of photocatalytic hydrogen (H2) evolution. Herein, novel oxygen-doped porous graphitic carbon nitride (g-C3N4) micro-sheets decorated with Ag2MoO4 have been fabricated by a facile calcination method followed by in situ deposition strategy. The physicochemical properties of the obtained Ag2MoO4/OC3N4 composites were characterized via SEM, TEM, EDS, XRD, N2 adsorption-desorption, XPS, UV–vis DRS, PL, transient photocurrent response, and EIS, as well as DFT calculation. In addition, the effects of Ag2MoO4 content, type of scavengers, pH value of reaction solution and dosage of scavenger on photocatalytic H2 production were investigated. The results show that the modification of ammonium acetate thermal polymerization with urea could enhance the porosity of g-C3N4 and its specific surface area. The Ag2MoO4 nanoparticles are highly dispersed on the OC3N4 surface, reducing the charge transfer resistance at their interfaces. The OC3N4 photocatalyst achieves H2 yield of 8629.11 μmol/g over 2 h, which is about 1.46 times higher than that of C3N4. The H2 production amount over the optimal Ag2MoO4/OC3N4 composite photocatalyst (50 mg) is further enhanced to 16619 μmol/g, which is 1.93 and 180 times higher than that of OC3N4 and Ag2MoO4, respectively. The S-scheme charge transfer mechanism of Ag2MoO4/OC3N4 is proposed based on the DFT calculation. This work provides a facile and easy strategy to develop g–C3N4–based photocatalysts through adjusting chemical composition and photocatalytic properties.

The enhancement of photocatalytic hydrogen production over Ag2WO4 modified g-C3N4 with Pt as cocatalyst

ABSTRACT The construction of heterojunction photocatalyst is an effective mean to improve the photoexcited electron–hole pair separation. The Ag2WO4-doped graphitic carbon nitride (g-C3N4, C3N4 for short) composite photocatalysts were fabricated by a simple calcination and in-situ depositing strategy. The composites were characterized by different techniques. The effects of Ag2WO4 content, type of scavengers, pH value of reaction solution and dose of scavenger on photocatalytic hydrogen (H2) generation were studied. It was found that the Ag2WO4 micro-nano particles were highly dispersed on the C3N4 surface. After doping Ag2WO4, the light absorption range of Ag2WO4-C3N4 material was broadened effectively from 440 nm to 448 nm, and the BET surface area of C3N4 was increased from 35.63 to 40.73 cm2·g−1, indicating that Ag2WO4 loading could provide some new BET surface areas. The binding energy of all elements in Ag2WO4-4/C3N4 was clearly shifted due to the charge transfer from C3N4 to Ag2WO4, implying a strong interaction between C3N4 and Ag2WO4. The photocatalytic H2 production rate of the optimized Ag2WO4-4/C3N4 was 6047.4 μmol·g−1·h−1, which was 2.04 and 171.8 times that of C3N4 and Ag2WO4, respectively. While Ag2WO4-4/C3N4 exhibited a poor H2 production performance in the absence of Pt co-catalyst (309.3 μmol·g−1·h−1), indicating the formation of heterojunction among Ag2WO4, C3N4 and Pt.

Bamboo leaf-derived biochar/iron silicate composite for an adsorption-degradation synergistic removal of ciprofloxacin

Antibiotics pose significant risks to both the environment and human health. Herein, we develop a collaborative strategy for the enhanced removal of a typical antibiotic, Ciprofloxacin (CIP), by using a bamboo leaf-derived biochar/iron silicate composite (BL-FeSi) with the assistance of peroxymonosulfate (PMS). The rationale behind the design is the construction of composited material with synergistic adsorption-catalysis functions, based on covalent bonding networks of the biochar and specific Fe(III)/Fe(II) redox chemistry of iron silicate in PMS activation system. H2 reduction of pristine BL-FeSi increases Fe(II) content and thus improves catalytic activity. Batch experiments demonstrate that the preferred BL-FeSi400 (H2 treatment at 400 °C) exhibits superior efficiency in activating PMS. The CIP removal efficiency is highly dependent on pH value of reaction solution. A remarkable 97% removal is achieved at pH = 5.5 (CIP: 60 mL, 20 mg/L; BL-FeSi400: 0.2 g/L, PMS: 0.2 g/L), and the pH increase to 11 results in 100% CIP removal. The BL-FeSi400 shows robust resistance to inorganic ions (NO3−, SO42−, HCO3−, and H2PO4−), and the catalytic activity remains consistently high (>82%) even after four consecutive cycles, making it highly promising for practical applications. It is found that both radical pathway (•OH and SO4•−) and non-radical pathway (1O2) contribute to CIP degradation in the BL-FeSi400/PMS system, while the active •OH dominates the oxidization process. The coupling of adsorption and degradation holds great potentials for effective removal of more organic contaminants.

Simultaneous morphology, phase modulation and luminescence enhancement in α/β-NaYF4: Yb3+, Er3+, Gd3+ microcrystals

In this paper, α/β-NaYF4: Yb3+, Er3+, Gd3+ microcrystals with multiform morphologies were successfully fabricated through hydrothermal approach. The crystal phase of the product can be regulated from cubic to hexagonal, and the overall morphology can be modulated from spherical to rod-like by precisely increasing the pH value of reaction solution. Morphology-dependent luminescence spectra show that the emission intensity gradually increases as the morphology transforms from microsphere to microrod, and the luminescence color changes from green to yellow-green. After tri-doping with 9 mol% Gd3+ ions, the luminescence intensity of cubic and hexagonal NaYF4: Yb3+, Er3+ microcrystals is increased by 2 and 5 times, respectively, and the luminescence brightness is also significantly enhanced. The as-prepared α/β-NaYF4: Yb3+, Er3+, Gd3+ microcrystals with excellent luminescence performance may have potential applications in display and lighting device fields.

Insights into the efficient degradation of metformin - An emerging antidiabetic medicine by UV/Sulfite process

The growing utilization of metformin (MET) in diabetes treatment has resulted in its occurrence in wastewater treatment plants, where conventional techniques were proved inadequate in eliminating it. The present study evaluated the potential of UV/sulfite system in degrading MET and analyzed the influence of common factors (i.e UV intensity, dosage of reagent, the pH value of reaction solution) on the target contaminant removal. In comparison with both direct UV photolysis and merely sulfite reduction, the UV/sulfite process had a remarkable enhancement in MET removal, with 96.54% of MET (initial concentration of 15 mg/L) being degraded within 30 minutes. A strong linear relationship (R2 > 0.99) was observed between MET degradation kinetics and UV intensity. The increase of sulfite dosage and solution pH could promote MET degradation to a certain extent in the studied system. Additionally, the hydrated electron (eaq-) was found played the principle role in MET removal through scavenging reactions.

Impact of reaction parameters for photodegradation pharmaceuticals in wastewater over gold/titania photocatalyst synthesized by pyrolysis of NH2-MIL-125(Ti)

The efficient remediation of pharmaceuticals, including wastewater, remains a remarkably challenging issue for water regeneration. Herein, porous Au/TiO2 synthesized by pyrolysis of NH2-MIL-125(Ti) was utilized to be an efficient photocatalyst for mineralization of trimethoprim (TMP) and Metronidazole (MNZ) as the parent compound. The effects of different factors, including TMP and MNZ concentrations, light intensity, H2O2 concentration, Au/TiO2 dosage, and pH value of reaction solution on the degradation and mineralization performances during UV and visible light (VIS), were addressed. The porous Au/TiO2 photocatalyst exhibited superior photocatalytic degradation of TMP and MNZ under UV and VIS illumination. The optimum pH values were 4; the optimum dosage of Au/TiO2 was 1.5 g/L, H2O2 concentration was 9.8 mM, TMP and MNZ concentrations was 10 ppm, and their photodegradation efficiency was 100% after 30 min illumination time and mineralization efficiency 98.2% after 3 h illumination for TMP and MNZ, respectively under UV illumination, however, the photodegradation efficiency was 100% after 50 min illumination and mineralization efficiency 96.3% after 4.5 h illumination time for TMP and MNZ, respectively under VIS illumination. The real wastewater matrix with 10 mg/L of TMP and MNZ were subjected to 60 min of illumination under similar optimum conditions of synthetic solution. The results indicated that photodegradation efficiency was determined to be 100% after 70 min illumination time for removal of both TMP (k = 3.4 × 10−2 min−1) and MNZ (k = 2.87 × 10−2 min−1). This is ascribed to the incorporation of Au NPs onto TiO2, reducing the photoinduced electron-hole recombination, thus promoting the photocatalytic performance. The possible mechanism for photodegradation of antibiotics was also discussed. The demonstration of photocatalysis mechanism over Au/TiO2 photocatalyst can provide some directing in the enhancement of novel photocatalysts based on MOFs doped by noble metal.

Study on the Pretreatment of COD in Brewing Wastewater Based on the Ozone Oxidation Technology

The high content of COD has always been a difficult problem for the efficient treatment of brewing wastewater. Pretreatment of brewing wastewater to reduce the content of COD was considered as a better solution. In this paper, ozone oxidation technology was used to pretreat brewing wastewater to preliminarily reduce the COD content, so as to provide beneficial conditions for further efficient treatment. The results showed that the reaction temperature (A), ozone intake (B), pH value of reaction solution (C) and reaction time (D) were the main factors affecting the removal of COD from brewing wastewater by ozone oxidation. Combined with the orthogonal test method, the optimum process conditions were A2B3C2D2. It was that the reaction temperature was 50 °C, the ozone intake flow was 7 L/min, the pH value of reaction solution was 7 and the reaction time was 1 h, which made the removal rate of COD reach 40.5%, and realized the goal of pre-removal of COD in brewing wastewater.

Synthesis of taurine-Cu3(PO4)2 hybrid nanoflower and their peroxidase-mimic and antimicrobial properties

Herein, we report the synthesis of taurine incorporated (sulfur containing organic molecule derived from methionine and cysteine) hybrid nanoflowers (thNFs) with an intrinsic peroxidase-mimic and antimicrobial activities in the presence of H2O2. Formation of thNFs using non-enzyme molecules was for the first time and systematically studied as a function of the taurine concentration, types of metal ions (Cu2+, Fe2+ and Fe3+) and pH values of reaction solution. The peroxidase like activities of thNFs rely on Fenton-like reaction against guaiacol used as a model substrate. The efficiency of Fenton reaction can be attributed to porous structure and presence of ions of transition elements in the thNFs. The thNFs were further characterized using FTIR, XRD, SEM and EDX. The thNFs also showed remarkable antimicrobial properties against S. aureus, E. coli, B. cereus and C. albicans. We claim that nonprotein-based NFs can be considered as new generation nano-biocatalysts as an alternative to enzymes and can be used in various medicinal, biochemical, immunological, biotechnological, and industrial applications.

Pronounced interfacial interaction in icosahedral Au@C60 core-shell nanostructure for boosting direct plasmonic photocatalysis under alkaline condition

The unique hot carrier-driven direct plasmonic photocatalysis of coinage metal nanomaterials (NMs) via energetic localized surface plasmon resonance (LSPR) in visible-light region has been explored in recent years. However, the low photoinduced electron transfer efficiency and insufficient separation of electron-hole pairs would severely preclude their widespread practical applications. Herein, we demonstrate an interesting plasmonic photocatalyst based on the construction of icosahedral (Ih) [email protected]60 core-shell NMs, taking advantage of specific delocalized π electrons structure of a tight C60 shell and enhanced LSPR property of Ih Au core. Then, the pronounced interfacial interaction at junction region endows the obtained [email protected]60 NMs with an outstanding photoinduced hot carrier-transmission during photocatalytic reaction, facilitating a remarkably higher (1.89 times) photocatalytic activity toward visible-light driven degradation of crystal violet (CV) dyes, as compared to bare Au NMs. Impressively, the photocatalytic activity of Ih [email protected]60 NMs can be effectively optimized by changing the pH value of reaction solution, with the kinetic rate constant reaching the maximum value of 0.179 min−1 in pH0 11.4 solution, while 0.005 min−1 at pH0 3.0. Moreover, due to the protection of a tight C60 shell, the Ih [email protected]60 NMs also possess excellent photocatalytic stability/reusability in recycling runs, holding great potential for the design of robust and high-performance plasmonic photocatalysts in repeated practical applications.

Oxidative polymerization of hydroxytyrosol catalyzed by laccase, tyrosinase or horseradish peroxidase: influencing factors and molecular simulations

Hydroxytyrosol oligomer from bioenzymatic catalysis indicates a pleiotropic wellness improving (e.g. antioxidation, anti-inflammatory and anti-carcinogenesis) than its monomer. However, the processing parameters and the insightful mechanism of hydroxytyrosol polymerization are still lacking. To explore in detail the process of hydroxytyrosol polymerization, the effects of different reaction factors (solvent type, pH value of reaction solution, reaction temperature and time) on the polymerization yield were investigated, and molecular docking was executed to reveal the relevant structural variations of these enzymes. The results showed hydroxytyrosol polymerization implemented by laccase performed the best at 50 °C for 20 min in the aqueous buffer solution of pH 5.0. The docking results demonstrated PRO4, TYR7, ASP8, PRO12, LEU121 and VAL14 in site 9 of laccase interacted with hydroxytyrosol in hydrogen bonding, pi-sigma, pi-alkyl and van der Waals’ force. Moreover, the molecular dynamic results implied their interaction-energy variation reaching balance within 175 ps, which confirmed the enzymes’ structural changes. Meanwhile, structural analysis in torsion and bond lengths showed that the C–O of phenolic bonds from hydroxytyrosol evidently rotated and its length of the relevant O–H became longer when binding to laccase compared with free hydroxytyrosol. All the findings are helpful to strengthen the understanding for the enzymatic polymerization of catechol-based structures and the resulting o-dihydroxy-grafting oligomers could be potentially used in the field of functional foods, cosmetics and pharmaceuticals, even or an innovative bioenzyme design such as biosensor for measuring phenols in industrial effluent or preparing the singular oligomer oriented is worth being explored in future. Communicated by Ramaswamy H. Sarma

Novel Two-Dimensional Porous Materials for Electrochemical Energy Storage: A Minireview.

Two dimensional (2D) porous materials have great potential in electrochemical energy conversion and storage. Over the past five years, our research group has focused on Simple, Mass, Homogeneous and Repeatable Synthesis of various 2D porous materials and their applications for electrochemical energy storage especially for supercapacitors (SCs). During the experimental process, through precisely controlling the experimental parameters, such as reaction species, molar ratio of different ions, concentration, pH value of reaction solution, heating temperature, and reaction time, we have successfully achieved the control of crystal structure, composition, crystallinity, morphology, and size of these 2D porous materials including transition metal oxides (TMOs), transition metal hydroxides (TMHOs), transition metal oxalates (TMOXs), transition metal coordination complexes (TMCCs) and carbon materials, as well as their derivatives and composites. We have also named some of them with CQU-Chen (CQU is the initialism of Chongqing University, Chen is the last name of Lingyun Chen), such as CQU-Chen-Co-O-1, CQU-Chen-Ni-O-H-1, CQU-Chen-Zn-Co-O-1, CQU-Chen-Zn-Co-O-2, CQU-Chen-OA-Co-2-1, CQU-Chen-Co-OA-1, CQU-Chen-Ni-OA-1, CQU-Chen-Gly-Co-3-1, CQU-Chen-Gly-Ni-2-1, CQU-Chen-Gly-Co-Ni-1, etc. The introduction of 2D porous materials as electrode materials for SCs improves the energy storage performances. These materials provide a large number of active sites for ion adsorption, supply plentiful channels for fast ion transport and boost electrical conductivity and facilitate electron transportation and ion penetration. The unique 2D porous structures review is mainly devoted to the introduction of our contribution in the 2D porous nanostructured materials for SC. Finally, the further directions about the preparation of 2D porous materials and electrochemical energy conversion and storage applications are also included.

Experimental Investigation of Chloride Uptake Performances of Hydrocalumite-Like Ca-Al LDHs with Different Microstructures

In this study, hydrocalumite-like Ca2Al-NO3− layered double hydroxides (Ca-Al LDHs) with different microstructures were synthesized. The crystalline properties, structure composition, morphology and particle size distribution of the Ca-Al LDH (CAL) samples were illustrated. To obtain the chloride uptake performances of CAL, the influences of contact time, initial concentration of Cl−, pH of reaction solution and coexistence anions on the chloride uptake were examined systematically. Compared to the CAL samples obtained at a higher aging temperature, CAL synthesized at 60 °C demonstrated the minimum average particle size (6.148 μm) and the best Cl− adsorption capacity (211.324 mg/g). Based on the test results, the main adsorption mechanism of chloride ion on CAL was recognized as an interlayer anion exchanging reaction other than the dissolution-precipitate mode. With the increase in the pH value of reaction solution from 7 to 13, it was found that the amount of chloride ion adsorbed by CAL increased slightly, and the solution could remain at relatively high pH value even after the adsorption. The presence of CO32− and SO42− reduced the adsorption capacity of CAL dramatically as compared with OH− due to the destruction of layered structure and the formation of precipitates (CaCO3 or CaSO4). The interference sequence of the investigated anions on the chloride uptake of CAL was SO42−, CO32− and OH−, and the order of interlayer anionic affinity was Cl− > OH− > NO3−. The results illustrated that the synthesized CAL could be used as a promising chloride ion adsorbent for the corrosion inhibition of reinforcement embedded cement-based materials.

One step preparation of stable gold nanoparticle using red cabbage extracts under UV light and its catalytic activity

Herein, we have reported the synthesis, characterization and catalytic activity of highly stable gold nanoparticles (Au NPs) using red cabbage extract (RCE) under UV irradiation. The anthocyanin groups predominantly existing in RCE play an essential role for biosynthesis of stable Au NPs. The reasons for using anthocyanins: 1) they act as chelating agents for preferentially reacting with gold ions (Au3+) to form Au3+- anthocyanin complexes, 2) as light-active reductants for reduction of Au3+ to zero valent Au0 under UV irradiation and 3) as stabilizing agent for preventing Au NPs from aggregation in high salt concentration owing to their unique salt tolerance property. We also demonstrate that how reaction time, concentration of RCE, pH value of reaction solutions and using one more reducing agent affected formation of the Au NPs. The stability of RCE Au NPs was comparatively studied with commercial (citrate stabilized) Au NPs against 100 mM salt (NaCl) solution. The RCE-Au NP showed reduction ability for conversion of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). UV–vis spectrometry, transmission electron microscopy (TEM), dynamic light scattering (DLS) and zeta potential (ZT) methods were utilized to characterize the Au NPs. We demonstrated that how whole RCE (anthocyanins molecules are major component) can be used as photo-active reducing and stabilizing agents to form Au NPs in a short time under UV irradiation and strong reducing agent without additional agents.

Electrocatalytic dechlorination of chlorophenols on palladium/graphene-Nafion/titanium mesh electrode

The electrocatalytic dechlorination of 3,5-dichlorophenol (3,5-DCP) and 2,3,5-trichlorophenol (2,3,5-TCP) on palladium/graphene-Nafion/titanium mesh electrode (Pd/rGO-Nafion/Ti electrode) was studied. The preparation conditions of Pd/rGO-Nafion/Ti electrode were investigated by electrochemical workstation, and the results showed that the addition of the graphene-Nafion middle layer could improve the electrocatalytic ability. The Pd/rGO-Nafion/Ti electrode was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and X-ray photoelectron spectroscopy (XPS). The influences of dechlorination current and initial pH value of reaction solution on the conversion efficiency and the current efficiency of dechlorination on Pd/rGO-Nafion/Ti electrode were investigated. Complete dechlorination of 3,5-DCP and 2,3,5-TCP could be achieved within 90 min under initial pH of 2.3 and current of 5 mA. The dechlorination intermediate products of 3,5-DCP and 2,3,5-TCP were detected and the dechlorination pathways were inferred. The kinetics results revealed that the dechlorination of 3,5-DCP and 2,3,5-TCP followed a two-stage mixed order kinetics.

One-pot synthesis of highly luminescent and color-tunable water-soluble Mn:ZnSe/ZnS core/shell quantum dots by microwave-assisted method

In this paper, microwave-assisted method was used for rapid synthesis of highly luminescent Mn-doped ZnSe/ZnS core/shell nanocrystals in aqueous phase. A series of nanocrystals with different size was prepared in 1 h under proper condition. The as-prepared Mn-doped ZnSe/ZnS QDs exhibit the emission in the range of 565–602 nm and the highest photoluminescence quantum yield reached up to 36.3% under the optimal reaction condition. The optical properties and structure of the Mn:ZnSe/ZnS QDs have been characterized by PL spectroscopy, UV–Vis, TEM, XRD and XPS. The effects of various experimental variables, including the reaction pressure, the pH value of reaction solution, the ratio of Zn to ligand (MPA), and the post-treatment on the optical properties of the Mn:ZnSe/ZnS QDs were investigated systematically. The as-prepared MPA coated Mn-doped ZnSe/ZnS colloidal nanoparticles was utilized to ultrasensitively and selectively detect Hg2+ ions in water, the result shows that the QD-based metal ions sensor possesses high sensitivity and selectivity, and could be applied for the quantification analysis of Hg2+ ions in water.

Nanosized CoO Loaded on Copper Foam for High-Performance, Binder-Free Lithium-Ion Batteries

The synthesis of nanosized CoO anodes with unique morphologies via a hydrothermal method is investigated. By adjusting the pH values of reaction solutions, nanoflakes (CoO-NFs) and nanoflowers (CoO-FLs) are successfully located on copper foam. Compared with CoO-FLs, CoO-NFs as anodes for lithium ion batteries present ameliorated lithium storage properties, such as good rate capability, excellent cycling stability, and large reversible capacity. The initial discharge capacity is 1470 mA h g−1, while the reversible capacity is maintained at 1776 m Ah g−1 after 80 cycles at a current density of 100 mA h g−1. The excellent electrochemical performance is ascribed to enough free space and enhanced conductivity, which play crucial roles in facilitating electron transport during repetitive Li+ intercalation and extraction reaction as well as buffering the volume expansion.

PH-Dependent Syntheses, Crystal Structures and Properties of Three Low-Dimensional Iodoargentate Hybrids

By simply changing pH value of reaction solution, three low-dimensional iodoargentate hybrids, [HDABCO]2[(DABCO)2(Ag2I4)] (1), [HDABCO]0.5[(HDABCO)0.5(AgI2)] (2) and [(Me2NH2)(H2DABCO)][AgI4] (3) (DABCO = 1,4-diazabicyclo-[2.2.2]octane), have been synthesized. Noteworthy, variation in protonated degree and aggregating forms of DABCO at different pH value, the structure of inorganic moieties vary regularly from 0D [(DABCO)2(Ag2I4)]2− anion for 1 to 1D [(HDABCO)0.5(AgI2)]0.5− chain for 2 and 0D [AgI4]3− anion for 3, exhibiting unique structural directing effects. In addition, three compounds display structure-dependent semiconductor natures and thermal stabilities.

Heterogeneous Fenton oxidation of phenol in fixed-bed reactor using Fe nanoparticles embedded within ordered mesoporous carbons

Iron nanoparticles embedded within ordered mesoporous carbon catalyst (Fe-OMC) was prepared using a facile “one-pot” synthesis method. The as-synthesized catalyst was characterized by using FTIR, XRD, SEM-EDS mapping, HRTEM and XPS. The results revealed that Fe oxide nanoparticles were highly dispersed in the OMC. The prepared Fe-OMC materials as heterogeneous Fenton catalysts were specifically applied in the fixed-bed reactor which operated under continuous-flow condition, showing a promising performance in the oxidative degradation of phenol with high catalytic activity (e.g. phenol conversion nearly 100%) and stability. The effects of feed flow rate and catalyst bed height on the conversions of phenol and H2O2, the iron leaching concentration as well as pH values of reaction solutions were also systematically investigated to determine the optimal operation conditions. The experimental results showed that the Fe-OMC catalyst achieved the highest activity (>99% phenol and H2O2 conversion) with remarkable low iron leaching concentration (10–20mg/L) under continuous-flow operations. The stability and reusability evaluations of Fe-OMC catalysts indicated the phenol conversion remains above 90% during a 39h long-term evaluation. It can be finally concluded that the prepared Fe-OMC catalyst in this work shows promising potential to be an efficient heterogeneous Fenton catalyst for the degradation of hazardous phenolic aqueous solutions.

Synthesis and luminescent properties of Sr4−xSi3O8Cl4: xEu3+ red phosphor by hydrothermal method

AbstractSr4‐xSi3O8Cl4:xEu3+ (SSOC:Eu3+) phosphors were successfully synthesized by hydrothermal method. The crystallization of this phosphor was analyzed by means of X‐ray diffraction patterns. The size and morphology were recorded using SEM patterns of samples. And the PLE and PL spectra were characterized by a PL spectrophotometer. Excited by 394 nm UV light, the intense red emission is recognized in SSOC:Eu3+ phosphor and the main emission peak located at 620 nm. The influences of Eu3+ concentration, pH value of reaction solution, and charge compensator on PL spectra of SSOC:Eu3+ phosphors were investigated. The results revealed that this red phosphor had potential applications for white LEDs.

Study on the Synthesis and Performances of Ultrafine Silver Powder Used as Silicon Solar Cell Front Silver Contacts

High-performance ultrafine silver powder used as crystalline silicon solar cell front conductive paste was prepared by chemical liquid-phase reduction method using silver nitrate as metal source, ascorbic acid as reductant, and gelatin as dispersant. The effects of reducing agent concentration, doses of dispersant, PH value of reaction solution and reaction temperature on the performance of silver powder were studied. The morphology, particle size and dispersibility of silver powder were observed by scanning electron microscope (SEM). The size distribution of silver particles was characterized by laser particle size analyzer. The crystalline silicon solar cells were produced by screen-printing front conductive silver paste, made with the obtained silver powder. The photoelectric properties of the solar cells were measured by solar simulator. The processing parameters of preparation silver powder, which meets the requirement of making high conversion efficiency solar cells, were optimized.