Search

We report a facile synthesis method of CuO/Co3O4 heterostructural catalysts with remarkable benzene catalytic oxidation capability.

Nanomaterials are materials in which at least one of the dimensions of the particles is 100 nm and below. There are many types of nanomaterials, but noble metal nanoparticles are of interest due to their uniquely large surface-to-volume ratio, high surface area, optical and electronic properties, high stability, easy synthesis, and tunable surface functionalization. More importantly, noble metal nanoparticles are known to have excellent compatibility with bio-materials, which is why they are widely used in biological applications. The synthesis method of noble metal nanoparticles conventionally involves the reduction of the noble metal salt precursor by toxic reaction agents such as NaBH4, hydrazine, and formaldehyde. This is a major drawback for researchers involved in biological application researches. Hence, the bio-synthesis of noble metal nanoparticles (NPs) by bio-materials via bio-reduction provides an alternative method to synthesize noble metal nanoparticles which are potentially non-toxic and safer for biological application. In this review, the bio-synthesis of noble metal nanoparticle including gold nanoparticle (AuNPs), silver nanoparticle (AgNPs), platinum nanoparticle (PtNPs), and palladium nanoparticle (PdNPs) are first discussed. This is followed by a discussion of these biosynthesized noble metal in biological applications including antimicrobial, wound healing, anticancer drug, and bio-imaging. Based on these, it can be concluded that the study on bio-synthesized noble metal nanoparticles will expand further involving bio-reduction by unexplored bio-materials. However, many questions remain on the feasibility of bio-synthesized noble metal nanoparticles to replace existing methods on various biological applications. Nevertheless, the current development of the biological application by bio-synthesized noble metal NPs is still intensively ongoing, and will eventually reach the goal of full commercialization.

Volatile organic compounds (VOCs) are a great threat to the health of human beings, and developing catalysts with prominent activity and stability to eliminate them are highly desired. In this work...

Shrimp waste (SW) was calcified to CaCO3 and CaO with variant morphologies by simple calcination in air and used as efficient support for Pd NPs (

Directly using natural materials as supporting material and reducing agent to obtain supported catalysts is significance along with the research of green and sustainable technologies. Herein, diato...

This work reports the template-free synthesis of diverse Carbon, self-doped Zinc oxide (C-doped ZnOSPs) superstructures through synergy between Cinnamomum camphora leaf extract and NaOH assisted by freeze-drying and annealing at desired temperatures. The high-activity and cost-effective porous supports with improved reducibility and charge transport act as catalyst support for ultra fine Pd NPs in the gas-phase selective remediation of the volatile organic compounds (VOCs) benzene. Uv–vis spectroscopy, XRD, XPS, SEM and TEM and photoluminescence studies, were used to characterize and verify the nature of the ZnOSPs. XPS analyses reveal that C-doping is introduced into the lattice of the as-produced ZnOSPs and the extent varied with leaf extract amount used. FTIR-analysis and simulation experiments showed flavones, polyphenols, and proteins were responsible for the formation of the ZnOSPs. Moreover, ultrafine Pd NPs sizes 1˜3 nm can be anchored on the exterior surfaces of ZnOSPs to form diverse surface contact boundaries for enhanced low-temperature benzene oxidation. Pd/ZnOSP-3 catalyst with the least crystallite size 17.4 nm and largest surface contact boundary 3.2 nm presented the best performance. The superior activity of Pd/ZnOSPs over commercial Pd/ZnO-C is attributed to its carbon modification, the high porous framework; defects incorporation which causes smaller optical energy gap, improved reducibility, enhanced mechanical responses and high charge transport to promote the benzene oxidation reaction.

The search for efficient and durable catalysts for volatile organic compounds oxidation is essential for environmental remediation. Herein, porous coral-like cobalt–manganese oxide (CoMnOx) catalyst was synthesized through annealing Co–Mn–1,3-propanediol precursors at 300 °C in air and applied for the catalytic oxidation of benzene. The as-prepared CoMnOx exhibited uniform porous coral-like structure, with an improved benzene catalytic abatement performance as compared to those of Mn3O4 and Co3O4 samples prepared by the same method, respectively. According to BET, H2-TPR, O2-TPD, and XPS analysis, the as-obtained CoMnOx catalyst showed the highest BET surface area, better low-reducibility temperature, and high content of absorbed oxygen groups when compared to Mn3O4 and Co3O4, which makes significant contribution to its catalytic benzene oxidation activity. Moreover, a plausible surface reaction mechanism for benzene oxidation over CoMnOx catalyst was also proposed through the in situ DRIFTS study.

Highly dispersed Au catalysts supported on amorphous titanosilicate supports with three-dimensional wormhole-like mesoporosity were prepared by deposition–precipitation method, which show excellent performance in propylene epoxidation with H2 and O2. The best catalytic performance, propylene conversion of 12.8%, propylene oxide selectivity of 76.2% and PO space-time yield of 160.9 gpo/Kgcat/h, was obtained at the reaction temperature of 300 °C. The Ti/Si molar ratio of the supports and some experimental parameters, such as the urea amount, loading temperature and Au loading on the as-produced catalyst are optimized. In addition, with the assistance of in-situ Fourier transform infrared spectroscopy (In-situ FT-IR), adsorption and desorption of PO, propylene and the reaction mixture on the catalyst are conducted to further explore the deactivation mechanism. It suggests that propylene and PO can be irreversibly and strongly adsorbed on the catalyst surface and finally transform to carbonate adsorbed on the active sites Ti-OH, resulting in catalyst deactivation.

In this study, an efficient Bi6O6(OH)3(NO3)3·1.5H2O/BiOCl heterojunction was prepared by a facile hydrothermal method, Bi6O6(OH)3(NO)3·1.5H2O nanoparticles with an average size of approximately 10 nm were grown uniformly in situ on the plates of BiOCl. The modification of Bi6O6(OH)3(NO3)3·1.5H2O effectively improves the photocatalytic activity of BiOCl for the degradation of rhodamine B (RhB). The enhancement of the photocatalytic activity could be attributed to the increased light harvesting ability, decreased charge resistance, and suppressed recombination of photoinduced electron–hole pairs in Bi6O6(OH)3(NO3)3·1.5H2O/BiOCl heterojunction.

Experimental work on benzene oxidation over C, N doped-MnxOy species showed that the oscillation formation and utilization of sub-surface O2 species from the catalyst was the rate-determining factor for activity. The MnxOy species were synthesized using the biosynthesis method. Characterizations from XRD, XPS, H2-TPR, and In-situ DRIFT were employed to study their catalytic properties. The MnxOy@300 catalyst with low activation energy (Ea = 62 kJ/mol) and TOF of 0.035 h−1 showed the best performance. The kinetic and mathematical model was proposed based on the current results, and those from previous works. The Ea, heat of vaporization, and temperature included in the kinetic model, increased its efficiency. The parameters of the kinetic study were regressed and verified by experimental data and the oxidation route was simulated. The kinetic model was extended into a mathematical model to predict which parameters had the most effect on the C6H6 oxidation process.

Bimetallic Pd-Pt nanoflowers (Pd-Pt NFs) of varying sizes (20–60 nm) were synthesized through the concurrent reduction of Pd(NO3)2 and K2PtCl4 using Cinnamomum camphora (C. camphora) leaf extract assisted by ascorbic acid (AA). C.Camphora acted as both a co-reducing agent and a green template in the synthesis protocol providing a fast, simple, green and cost-effective means of producing the Pd-Pt NFs. Characterization techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to confirm the Pd-Pt NFs formation. FT-IR analysis showed that biomolecules such as polyphenols and flavonoids were responsible for the reduction while stretching vibration bands from C H, C C , O H, and C O O acted as capping agents. The as-formed Pd-Pt NFs showed excellent performance and stability in the electro-oxidation of ethanol in alkaline media. Electro-catalytic performance increased with Pt content, while addition of Pd increased stability. The PdPt3 NFs presented the best performance with a mass activity of 1.43 A mg−1metal, 5.72, 4.93, 2.27, 1.27, 11 and 4.6% higher than the Pd, Pt, Pd3Pt, and PdPt NFs, and commercial Pt and Pd-black respectively. However, it was more prone to poisoning, with an If/Ir value of 0.78 compared to 1.37 for Pd3Pt NFs.

We report the green synthesis of ZnO supported Ni-Pd alloy nanoparticles for the gas-phase selective hydrogenation of 1, 3- butadiene. The supported catalysts were synthesized through a simple bio-reduction route using Cinnamomum Camphora leaf extract. X-ray diffraction, scanning and transmission electron microscopy and energy dispersed X-ray were used to characterize and verify the nature of the catalysts. The results showed that the Ni-Pd alloy particles were 3.2 ± 0.7, 3.4 ± 0.3 and 3.8 ± 0.6 nm for Ni1Pd1, Ni1Pd3 and Ni3Pd1 respectively. FTIR analysis revealed that stretching vibration bands such as C-H,-C=C-, O-H, -C-O- O remained on the surface acting as stabilizer. The influence of some reaction variables, such as type of S-Pd bimetallic catalyst, type of metal oxide support and reaction temperature, on the hydrogenation activity and selectivity towards total butene (trans-2-butene, 1-butene and cis-2-butene) is investigated. The bioreduction supported catalysts showed excellent catalytic activity and selectivity to butene in the selective hydrogenation of 1,3 butadiene. The calculated total butene selectivity was above 80% for all supported S1-Pd1 catalyst compared to 46.92 % for monometallic Pd/ZnO catalyst. In addition, the Ni1-Pd1/ZnO catalyst presented the best butene yield 88.90 % which was 1.9 times that of Pd/ZnO catalyst. Moreover, it maintained stability over a 10 h durability experiment.

Well-defined Au/Pd/Ag nanowires (NWs) that are difficult to synthesize via pure chemical reduction method are fabricated using a facile one-pot microorganism-mediated method in the presence of hexadecyltrimethylammonium bromide (CTAB). The result showed that the formation of Au/Pd/Ag NWs were strongly dependent on the mass of Pichia pastoris cells (PPCs) and CTAB concentration of the reaction solution. The PPCs acted as templates in the formation of Au/Pd/Ag NWs, and an appropriate concentration of CTAB was favor of anisotropic growth during the NWs formation procedure. This work exhibits a novel method to fabricate multi-metallic nanostructures by combining a surfactant and microorganisms.

Flower-like Copper Oxide microstructures (CuOMFs) are fabricated through a simple bioreduction route using Cinnamomum Camphora ( C. camphora ) leaf extract at room temperature without the addition of any templates and additives. X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), and energy dispersed X-ray were used to characterized and verify the nature of the CuOMFs. The results showed that the CuOMFs of average size 1.3±2.0 µm consisted of several 2D nanorods. The plant extract acted as both reducing and stabilizing agent.

Because of the huge demand for energy materials, it is paramount to develop practical, low-cost, and renewable energy systems. Until now, batteries made of green materials have either been costly or of limited use. Herein, this paper reports the pioneer utilization of fish waste, doped with Pd nanoparticles (Pd NPs) by incipient wetness impregnation to form Pd/Fish-Collagen. The Pd/Fish-Collagen was first used as a catalyst to abate benzene, and then utilized as anode material in three different rechargeable battery systems; Li-, Na-, and Mg- ion batteries. XRD patterns confirmed that the Fish-Collagen (CaS and CaCO3) was amorphous, while the Pd/Fish-Collagen sample exhibited broad peaks assigned to a mixture of Pd and PdO NPs coexisting with the amorphous Fish-Collagen. TEM and HRTEM images confirmed that the Fish-Collagen and the Pd NPs had average particle sizes of about 70 and 5 nm respectively. The electrochemical properties of the Pd/Fish-Collagen as an anode material in Li, Na, and Mg-based cells showed reversible capacities of 270, 120, and 105 mA h g−1, respectively. The CV and ex-situ XRD tests suggested a pseudocapacitance reaction occurred in Li and Na storage, while the Mg-based cells presented a conversion reaction. This new strategy to generate electrodes from renewable sources is cost-effective and with optimization, millions of tons of this remaining waste can find potential applications in such energy storage systems.

We report a simple but efficient biological route based on the hydrolysis of cellulose to synthesize Ag–Pd alloy nanoparticles (NPs) under hydrothermal conditions. X-ray powder diffraction, ultraviolet-visible spectroscopy and scanning transmission electron microscopy-energy dispersive X-ray analyses were used to study and demonstrate the alloy nature. The microscopy results showed that well-defined Ag–Pd alloy NPs of about 59.7 nm in size can be biosynthesized at 200 °C for 10 h. Fourier transform infrared spectroscopy indicated that, triggered by silver sulfate, cellulose was hydrolyzed into saccharides or aldehydes, which served as both reductants and stabilizers, and accounted for the formation of the well-defined Ag–Pd NPs. Moreover, the as-synthesized Ag–Pd nanoalloy showed high activity in the catalytic reduction of 4-nitrophenol by NaBH4.

Synthesis and applications of one dimensional (1D) metal nanostructures have attracted much attention. However, one-step synthesis of bimetallic nanowires (NWs) has remained challenging. In this work, we developed a microorganism-mediated, hexadecyltrimethylammonium bromide (CTAB)-directed (MCD) approach to synthesize closely packed and long Au-Ag NWs with the assistance of a continuous injection pump. Characterization results confirmed that the branched Au-Ag alloy NWs was polycrystalline. And the Au-Ag NWs exhibited a strong absorbance at around 1950 nm in the near-infrared (NIR) region, which can find potential application in NIR absorption. In addition, the Au-Ag NWs showed excellent surface-enhanced Raman scattering (SERS) enhancement when 4-mercaptobenzoic acid (MBA) and rhodamine 6G (R6G) were used as probe molecules.

A double hydrolysis approach is first adopted to prepare yttrium aluminum garnet (YAG) powders using Y(NO3)3 · 6H2O and NaAlO2 as raw materials. A variety of techniques, such as thermogravimetry/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are employed to characterize the as-synthesized samples. The results show that pure-phase YAG powders are accurately available at 900 °C and above. Among these, the YAG powders, produced at 1100°C, are elliptic in shape, with an average particle size of ~44 nm. Pellets of pressed YAG powders are sintered in vacuum at 1700°C for 8 h, resulting in a dense and nearly pore-free microstructure with an average grain size of ~7 μm.

Microorganism-mediated, hexadecyltrimethylammonium chloride (CTAC)-directed (MCD) method was employed in this work to synthesize Pd nanoflowers (PdNFs). Proper Pichia pastoris cells (PPCs) dosage, ascorbic acid (AA), Pd(NO 3 ) 2 and CTAC concentrations were essential for the growth of the PdNFs. The size of the as-synthesized PdNFs could be tuned by adjusting the amount of Pd(NO 3 ) 2 solution and dosage of PPCs used. Characterization techniques such as X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to verify the nature of the PdNFs. Finally the PdNF/PPC nanocomposites were immobilized onto TiO 2 supports to obtain bio-PdNF/TiO 2 catalysts which showed excellent catalytic activity for CO oxidation, obtaining 100% conversion at 100 °C and remaining stable over a period of 52 h of reaction time.

BACKGROUND The synthesis and application of novel zinc micro/nanostructures are of increasing importance in modern nanotechnology. RESULTS This paper reports the large scale synthesis of zinc oxide micro-flowers (ZnOMFs) using precipitation assisted by Cinnamomum camphora leaf extract (C. camphora) at relatively low temperatures ≤ 80°C. The results showed that the ZnOMFs consisted of several nanoplates connecting together in the presence of the leaf extract which acted as a modifying, capping and stabilizing agent. X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM), energy dispersed X-ray and photoluminescence studies were used to characterize and verify the nature of the ZnOMFs. Varying the leaf extract amount (5 to 20 mL) fine-tuned the morphology of the as-formed zinc oxide microstructures (ZnOMS). The as-formed ZnOMFs showed high photocatalytic activity for the degradation of methyl orange dye under ultraviolet (UV) irradiation, achieving 100% degradation after 45 min of reaction. CONCLUSION The use of leaf extract as a bio-template and capping agent provided an effective, cheaper and more environmentally benign way of controlling and directing the shape of as-formed ZnO microstructure. © 2015 Society of Chemical Industry

In this paper, we report a microwave-assisted biosynthesis method with Cinnamomum camphora (CC) leaf extract for the green and rapid synthesis of Ag nanoparticles (NPs). The as-produced Ag nanoparticles were immobilized onto CeO 2 as supported Ag/CeO 2 catalyst, which proved to be efficient for carbon monoxide (CO) oxidation. Active components in the plant extract were identified by FTIR analysis and later on validated through simulated experiments. The results revealed that polyphenols and proteins were the reducing and protecting agents, respectively. The optimum preparation conditions for the catalyst were irradiation time of 140 s, Ag loadings of 5 wt.%, CC extract concentration of 25 g L −1 and sintering temperature of 300 °C. Since biomolecules adsorbed over the surface of catalyst was detrimental to its catalytic activity, calcination to remove the biomolecules was critical to the enhanced activity. Considering the trade-off between particle size and biomass removal extent, the optimum calcination temperature was determined to be 300 °C.

Pt catalysts and Co doped Pt catalysts with TiO2 as the support were prepared by the sol immobilization method based on biological synthesis process, whereby Pt nanoparticles (PtNPs) were reduced from Na2PtCl4 using Cacumen Platycladi extract (CPE). The catalytic performance of the catalysts was studied using hydrogenation of cinnamaldehyde as the model reaction. For comparison, Co doped Pt/catalysts were also prepared by traditional impregnation method, TEM observation, and XRD measurement were carried out to characterize the catalysts. The effects of different Pt loadings and Co doping amounts were investigated. The results showed that the PtNPs could be well dispersed onto the TiO2 support with narrow size distribution between 4 and 6 nm. 1.0% was observed as the optimal Pt loading amount in our experiments showing a cinnamaldehyde conversion of 73.3% with 68.8% selectivity to cinnamyl alcohol. A proper Co doping amount was also essential to the catalytic performance of the prepared Pt/catalysts as wel...

Yttrium aluminum garnet (YAG) precursor precipitates, which were produced through bubbling ammonia gas approach, were solvothermally treated in alcoholic solution to synthesize monodispersed YAG powders in this paper. A variety of techniques, such as thermogravimetry/differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the as-synthesized YAG precursor and powders. The results showed that the crystallization temperature of the YAG phase was largely dependent on the ethanol. Increasing the ethanol content in the solvent could decrease the YAG crystallization temperature. When the ratio of ethanol to water was 3:1, single-phase YAG was accurately available at a relatively lower temperature of 320 °C. Moreover, the obtained YAG powders were well-defined monodispersed spheres with mean particle size of about 274 nm, and showed excellent sinterability.

In this paper, a microorganism-mediated, cetyltrimethylammonium bromide (CTAB)-directed (MCD) aggregation of Au nanostructures around Escherichia coli cells (ECCs) for enhanced Au recovery, from aqueous HAuCl 4 is demonstrated for the first time. Owing to the coordination of cell-CTAB–ascorbic acid (AA), one dimensional Au nanostructures grew around the ECCs, inducing the rapid aggregation of Au and the ECCs. The concentrations of CTAB and AA had insignificant effect on the precipitation if the ECC dosage and HAuCl 4 concentration were matched. The Au recovery efficiency decreased with increasing CTAB concentration, while a minimum AA concentration was required for higher Au recovery efficiency. The ECC-binding Au ions were reduced to form Au nuclei over the cell surface that provided preferential nucleation sites. Meanwhile, the free ligand-substituted anions in the solution were reduced to Au atoms that served as Au source for growing the Au nanostructures around the ECCs. This work exemplifies a new avenue to enhance the efficiency of recovering Au through the engineering of Au nanostructures.

A simple method is developed for synthesizing nanopowder of neodymium-doped yttrium aluminum garnet (Nd:YAG) by coprecipitation with flushing (bubbling) by ammonia. Different methods are used to study the specimens obtained, such as thermogravimetry/differential scanning calorimetry, X-ray powder diffraction, infrared spectroscopy based on a Fourier transform, scanning electron microscopy. Results show that stoichiometric Nd:YAG powders may be prepared by calcination of a precursor at 900°C for 2 h. In addition, it is detected that a slow ammonia supply rate (5 – 10 ml/min) is favorable for forming Nd:YAG powders with a good structure and with an average particle size of ~70 nm. The technology developed by us does not use manual titration for synthesizing multibasic oxides, as a result of which this technology may be readily used on an industrial scale.

Ordered mesoporous carbon (Fe-CMK-3) with iron magnetic nanoparticles was prepared by a casting process via SBA-15 silica as template and anthracene as carbon source, was used as a magnetic adsorbent for the removal of anionic dye Orange II (O II) and cationic dye methylene blue (MB) from aqueous solution. TEM and magnetometer images showed that the iron magnetic nanoparticles were successfully embedded in the interior of the mesoporous carbon. The effect of various process parameters such as temperature (25-45°C), initial concentration (100-500 mg L(-1)) and pH (2-12) were performed. Equilibrium adsorption isotherms and kinetics were also studied. The equilibrium experimental data were analyzed by the Langmuir, Freundlich, Temkin and Redlich-Peterson model. The equilibrium data for two dyes adsorption was fitted to the Langmuir, and the maximum monolayer adsorption capacity for O II and MB dyes were 269 and 316 mg g(-1), respectively. Pseudo-first-order and pseudo-second-order kinetic and intraparticle diffusion model were used to evaluate the adsorption kinetic data. The kinetic data of two dyes could be better described by the pseudo second-order model. Thermodynamic data of the adsorption process were also obtained. It was found that the adsorption process of the two dyes were spontaneous and exothermic.

A series of Au/TiO2 catalysts for CO oxidation with same Au loading but different Au nanoparticles (NPs) sizes were prepared by varying the calcination temperatures and biomass concentration via a biosynthetic approach. The resulting catalysts were characterized by DRUV–vis, TEM, and TG techniques. The experimental results showed that the activity of the gold catalysts for CO oxidation was very sensitive to the particle size. Among the tested catalysts, the one with mean size of 3.8 nm was the most active. As determined by TEM, the contact boundary between the Au NPs and the TiO2 support was related to the size of the Au NPs. For the most active catalyst, hemispherical Au NPs (3.8 ± 0.6 nm) had the best contact boundary with the TiO2 support, yielding the longest perimeter interface, suggesting that the contact boundary was the most critical factor for the CO oxidation. The in-situ FTIR study of CO adsorption on the catalysts showed that CO was not adsorbed on the Au surface. This might be due to the modi...

national Nature Science Foundation of China (NSFC) [21036004]; State Key Laboratory of Advanced Technologies for Comprehensive Utilization of Platinum Metals [SKL-SPM-201210]

BACKGROUND The synthesis and application of novel Au nanostructures are of increasing importance in modern nanotechnology. RESULTS Closely packed and chemically difficult-to-synthesize Au nanohorns (AuNHs) were synthesized in the presence of Escherichia coli cells (ECCs) and hexadecyltrimethylammonium chloride (CTAC) by a microorganism-mediated, CTAC-directed (MCD) approach. A proper ECC dosage, ascorbic acid (AA) and CTAC concentrations were essential for the growth of the AuNHs. In the formation mechanism of the AuNHs the ECCs surface acted as a platform for preferential nucleation and initial anisotropic growth of Au nanocrystals. As a result, some of the adjacent nanoparticles over the cell surface connected together via linear fusion to form dendritic nanostructures. Meanwhile, secondary nucleation in the solution gave rise to smaller nanoparticles that were consumed later on via Ostwald ripening during the formation of the AuNHs. Eventually, the two-dimensional film-like nanostructures between adjacent cells easily connected to form well-defined AuNHs with three-dimensional nanostructures. Interestingly, the AuNH/ECC composites can be used directly as sensitive surface-enhanced Raman spectroscopy (SERS) substrates for effective detection of 4-mercaptobenzoic acid (MBA). CONCLUSION The MCD strategy was an effective approach to novel AuNHs and AuNH/microorganism nanocomposites as SERS substrate. © 2014 Society of Chemical Industry

Reactive kinetics coupled with population balance model (PBM) and computational fluid dynamics (CFD) was implemented to simulate silver nanoparticles (AgNPs) formation in a microtubular reactor. The quadrature method of moments, multiphase model theory, and kinetic theory of granular flow were employed to solve the model, and the particle size distributions (PSD) were calculated. The simulation results were validated by synthesizing AgNPs experimentally in an actual microtubular reactor for comparison with the PSD. The results confirmed the effectiveness of the model and its applicability in predicting AgNPs formation and its PSD evolution in the microtubular system. Finally, benefiting from its superiority, in that the influence of reactive kinetics and fluid dynamics on particle evolution could be considered separately, the model was employed to verify predictions and inferred conclusions in our previous works, which were difficult to verify through experiment.

Au/TS-1 catalysts prepared by an eco-friendly and economical bioreduction method were used for the liquid phase epoxidation of styrene to styrene oxide (SO) using aqueous hydrogen peroxide (H2O2) as oxidant. The catalysts were characterized by a variety of techniques including FT-IR, DRUV–Vis, UV–Vis, N2 physisorption, XRD, XPS, TG–DTG and TEM. The influence of various parameters (Au loading, calcination, solvents, oxidants, reaction temperature, reaction time and catalyst amount) on the catalytic performance was systematically investigated. The results showed that both the conversion of styrene and selectivity to SO were improved and enhanced when catalyzed by biosynthesized gold nanoparticles (GNPs) supported on TS-1. However, decomposing the Cacumen Platycladi (CP) biomass properly through calcinations can enhance the catalytic performance though it acted as reductant and protective agents during the catalysts preparation. Besides, the optimum catalytic activity and stability of bioreduction Au/TS-1 catalysts were obtained under operational conditions of Au loading of 1.0 wt.%, CP extract (10 g L−1) as reductant, calcined at 723 K for 2 h, reaction time of 10 h, reaction temperature of 333 K, catalyst amount of 500 mg, aqueous H2O2 (30 wt.%) as oxidant and N,N-dimethylformamide as solvent. Under the optimal condition, styrene conversion of 92.7% and SO selectivity of 90.4% was achieved, which were comparable or even superior to those reported in the literatures. The catalyst was reused five times, without significant decrease in both the styrene conversion and SO selectivity.

The activity of supported Pd catalyst as a result of metal oxide support (zinc, titanium, copper and manganese) is explored in the abatement of C6H6 in the gas-phase. The high-activity and cost-effective catalysts were synthesized utilizing impregnation assisted biosynthesis (IB) method. NH3-TPD, XRD, H2-TPR, TEM, XPS, O2 and Benzene-TPD, SEM and in situ DRIFT were done to probe their physicochemical characteristics and predict the plausible oxidation mechanism. Pd particle size and dispersion, and support active acid sites were the determining factors for activity. These factors markedly affected the catalyst ability to generate surface active O2 species from the metal oxides lattice station and controlled the benzene absorption/desorption rates. The as-synthesized Pd/Mn3O4-O with small crystallite size, good Pd dispersion, improved acid sites, and low activation energy (Ea = 45.3 kJ/mol) showed commendable O2 transportability and activity as low as 140 °C, GHSV of 120,000 mLg−1 h−1. Its T100 at 240 °C was similar to Pd supported on TiO2 but was 20, 40 and 60 °C better than Pd/Mn3O4-C, Pd/ZnO and Pd/CuO. In situ DRIFT studies showed that the main intermediate species benzoquinone are oxidized to CO2 and H2O through the alkoxide and acid sites. Moreover, it was stable and highly resistant to H2O vapor.

BACKGROUND Biosynthesis of Ag nanoparticles (AgNPs) utilizing renewable materials and nontoxic chemicals has become highly desirable and is currently receiving tremendous attention. In this study, a facile and cellulose-based approach was developed to biosynthesize AgNPs through tandem hydrolysis of silver sulfate and cellulose under hydrothermal conditions. RESULTS Well-defined AgNPs of about 72.0 nm in size were biosynthesized with 0.30 g of cellulose at 200°C for 10 h. The particle sizes of the as-synthesized AgNPs were positively affected by the reaction temperature and time, but on the contrary were negatively affected by the amount of cellulose employed. The results from Fourier transform infrared spectroscopy showed that the cellulose-hydrolyzed products (saccharides or aldehydes) were accountable for the bioreduction of the Ag ions, and the C = O (C–O) groups in the aldehydes or saccharides played critical roles in capping the AgNPs. Additionally, in the presence of the as-synthesized AgNPs, enhanced surface fluorescence of methyl orange was achieved. CONCLUSION A biological and maneuverable strategy was successfully developed for the synthesis of AgNPs by a hydrothermal route through tandem hydrolysis of silver sulfate and cellulose. Thus, this environmentally friendly method is anticipated to be utilized for the biosynthesis of AgNPs and opens up avenues to prepare other metal nanoparticles from metal sulfates. © 2013 Society of Chemical Industry

BACKGROUND The facile use of microorganisms as green templates for shape-control of Au nanostructures can not only utilize their characteristic nanoscale dimensions and versatility, but also bridge the gap between bulk materials and Au nanostructures for technical applications. RESULTS Using Escherichia coli cells (ECCs), closely packed, hierarchically branched, chemically difficult-to-synthesize and stable Au nanowires (AuNWs) were fabricated through a seedless microorganism-mediated, hexadecyltrimethylammonium bromides (CTAB)-directed method. The ECCs played dual roles in the biosorption of Au ions and acted as preferential nucleation sites for Au nanocrystals in the formation of the AuNWs. In addition, proper CTAB concentration and just a little excessive ascorbic acid were essential to the formation of the AuNWs. The preferential nucleation sites that were simultaneously mediated by adjacent cells favored branched growth. Random growth of the same nanowire with multiple branched points gave rise to hierarchically branched AuNWs. Interestingly, the AuNW/ECC nanocomposites exhibited a noticeable absorbance at around 1900 nm in the near-infrared (NIR) region. CONCLUSION This study verifies the general strategy by combining a microorganism and CTAB for the fabrication of functional AuNW/microorganism nanocomposites. © 2013 Society of Chemical Industry

Yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG) precursor was synthesized by the co-precipitation method with ammonium hydrogen carbonate as the precipitant. The influence of aging and calcination temperature on the precursor composition and transformation temperature of the YAG phase was investigated. On that basis, a two-step sintering (TSS) method (heating the sample up to 1800 °C followed by holding it at 1600 °C for 8 h) was used to fabricate bulk transparent YAG ceramics in vacuum (10 −3 Pa) in this communication. A variety of techniques, such as X-ray powder diffraction, infrared spectra, scanning electron microscopy and UV–vis–NIR spectrophotometry were adopted to characterize the resulting YAG powders and ceramics. The results showed that aging had a dramatic effect on the precursor composition, which in turn influenced the transformation temperature of the YAG phase. Loosely agglomerated YAG powders with a mean particle size of 50 nm were obtained by calcinating the precursor without aging at 1000 °C. Finally, a transparent YAG ceramic specimen, achieving the in-line transmittance of 41% in the visible wavelength region and a nearly pore-free microstructure with uniform grains of about 4 μm, was produced via the TSS technique.

The synthesis and applications of anisotropic nanostructures have attracted much attention in modern nanotechnology. Recently, biosynthesis has been demonstrated to be a viable green alternative to traditional chemical and physical methods for synthesizing metal nanostructures. Herein, we developed a new, green one-pot synthetic protocol in which silver nanoflowers (Ag NFs) with three-dimensional structures were synthesized by Canarium album foliar broths in the presence of trisodium citrate (TSC) at room temperature. The effects of silver nitrate, TSC, and foliar broths on these synthesis processes were investigated to determine the optimum synthesis conditions. Further exploration of the formation mechanism of Ag NFs showed that both the biomolecules and TSC played very important roles. The improved insight into the specific roles of the bioprotective components and the controlled synthesizing ability are expected to help explain the formation mechanism of this interesting nanostructure that exhibited a...

Herein, a microfluidic biosynthesis of Au–Ag bimetallic nanoparticle (NP) in a tubular microreactor, based on simultaneous reduction of HAuCl4 and AgNO3 precursors in the presence of Cacumen Platycladi (C. Platycladi) extract was studied. The flow velocity profile was numerically analyzed with computational fluid dynamics. Au–Ag bimetallic NPs with Ag/Au molar ratios of 1:1 and 2:1 were synthesized, respectively. The alloy formation, morphology, structure, and size were investigated by UV–Vis spectra analysis, transmission electron microscopy (TEM), high resolution TEM, scanning TEM, and energy-dispersive X-ray analysis. In addition, the effects of volumetric flow rate, reaction temperature, and concentration of C. Platycladi extract and NaOH on the properties of the as-synthesized Au–Ag bimetallic NPs were investigated. The results indicated that these factors could not only affect the molar ratios of the two elements in the Au–Ag bimetallic NPs, but also affect particle size which can be adjusted from 3.3 to 5.6 nm. The process was very rapid and green, since a microreactor was employed with no additional synthetic reagents used. This work is anticipated to provide useful parameters for continuous-flow biosynthesis of bimetallic NPs in microreactors.

Based on rapid adsorption and incomplete reduction in Pd (II) ions by yeast, Pichia pastoris (P. pastoris) GS115, the effects of pretreatment on adsorption and reduction of Pd (II) ions and the catalytic properties of Pd NP/P. pastoris catalysts were studied. Interestingly, the results showed that the adsorption ability of the cells for Pd (II) ions was greatly enhanced after they were pretreated with aqueous HCl, aqueous NaOH and methylation of amino group. For the reduction in the adsorbed Pd (II) ions, more slow reduction rates by pretreated P. pastoris cells were displayed compared with the cells without pretreatment. Using the reduction of 4-nitrophenol as a model reaction, the Pd NP/P. pastoris catalysts based on the cells after pretreatment with aqueous HCl, aqueous NaOH and methylation of amino group exhibited higher stability than the unpretreated cells. The enhanced stability of the Pd catalysts can be attributed to smaller Pd NPs, better dispersion of the Pd NPs, and stronger binding forces of the pretreated P. pastoris for preparing the Pd NPs. This work exemplifies enhancing the stability of Pd catalysts through pretreatments.

The effects of different biomolecules in Artocarpus heterophyllus Lam leaf extract on the morphology of obtained gold nanoparticles were investigated in this study. The results indicated that reducing sugars, flavones, and polyphenols consisting of about 79.8 % dry weight of the leaf extract were mainly involved in providing the dual function of reduction and the size/shape control during the biosynthesis. The gold nanoparticles present included 64 ± 10 nm nanospheres, 131 ± 18 nm nanoflowers, and 347 ± 136 nm (edge length) nanoplates and they were synthesized using the main content of reducing sugars, flavones, and polyphenols, respectively, after they were desorbed by the AB-8 macroporous adsorption resin column. Particularly, flower-like and triangular/hexagonal gold nanoparticles with a yield more than 80 % were obtained. Possible shape-directed agents for the nucleation and growth were characterized by FTIR, it can be seen that ketones were bound on the surface of the spherical and flower-like GNPs, while both the ketones and carbonyls bound on the Au {111} plane this may have favored the formation of the twin defects, which are very essential for nanoplates’ formation.

Pt nanoparticles (PtNPs) were biologically synthesized by reducing Na2PtCl4 with Cacumen Platycladi Extract (CPE). The effects of reaction temperature, initial Pt(II) concentration, and CPE percentage on Pt(II) conversion and the size distribution of the PtNPs were studied. The results showed that the Pt(II) conversion rate reached 95.9% and that PtNPs measuring 2.4±0.8nm were obtained under the following conditions: reaction temperature, 90°C; CPE percentage, 70%; initial Pt(II) concentration, 0.5mM; reaction time, 25h. In addition, the bioreduction of Pt(II) was attributed to reducing sugars and flavonoids rather than proteins. The elucidation of bioreductive mechanism of Pt(II) ions was achieved by investigating the changes that occurred in the reducing sugar, flavonoid and protein concentrations in the plant extract, leading to a good insight into the formation mechanism of such biosynthesized PtNPs.

Closely packed, size-controllable and stable Au nanohorns (AuNHs) that are difficult to synthesize through pure chemical reduction are facilely synthesized using a microorganism-mediated method in the presence of hexadecyltrimethylammonium chloride (CTAC). The results showed that the size of the as-synthesized AuNHs could be tuned by adjusting the dosage of the Pichia pastoris cells (PPCs). The initial concentrations of CTAC, ascorbic acid (AA) and tetrachloroaurate trihydrate (HAuCl4·3H2O) significantly affected the formation of the AuNHs. Increasing the diameters of AuNHs led to a red shift of the absorbance bands around 700 nm in their UV-vis-NIR spectra. Interestingly, the AuNH/PPC composites exhibited excellent Raman enhancement such that rhodamine 6G with concentration as low as (10(-9) M) could be effectively detected. The formation process of the AuNHs involved the initial binding of the Au ions onto the PPCs with subsequent reduction by AA to form supported Au nanoparticles (AuNPs) based on preferential nucleation and initial anisotropic growth on the platform of the PPCs. The anisotropic growth of these AuNPs, which was influenced by CTAC and PPCs, resulted in the formation of growing AuNHs, while the secondary nucleation beyond the PPCs produced small AuNPs that were subsequently consumed through Ostwald ripening during the aging of the AuNHs. This work exemplifies the fabrication of novel gold nanostructures and stable bio-Au nanocomposites with excellent optical properties by combining microorganisms and a surfactant.

Synthesis of metal nanoparticles (NPs) is in the limelight in modern nanotechnology. In this present study, bimetallic Au/Pd NP/Pichia pastoris composites were successfully fabricated through a one-pot microbial reduction of aqueous HAuCl4 and PdCl2 in the presence of H2 as an electron donor. Interestingly, flower-like alloy Au/Pd NP/Pichia pastoris composites were obtained under the following conditions, NaCl concentration 0.9% (w/v), molar ratio of Au/Pd (1:2) and the time for pre-adsorption of Au(III) and Pd(II) ions 15 min, through fresh yeast reduction. The mapping results from scanning transmission electron microscopy (STEM) with a high-angle annular dark field detector confirmed that the Au/Pd NPs on the surface of the yeast were indeed alloy. Furthermore, the energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) measurements showed that the composition of the bimetallic NPs were consistent with the initial molar ratio of the precursors.