State of arts on the bio-synthesis of noble metal nanoparticles and their biological application

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 bioimaging.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.

Facile synthesis of porous Pd nanoflowers with excellent catalytic activity towards CO oxidation

Microorganism-mediated, hexadecyltrimethylammonium chloride （CTAC）-directed （MCD） method was employed in this work to synthesize Pd nanoflowers （PdNFs）. Proper Pichia postoris cells （PPCs） dosage, ascorbic acid （AA）, Pd（N03）2 and CrAC concentrations were essential for the growth of the PdNFs. The size of the as- synthesized PdNFs could be tuned by adjusting the amount of Pal（N03）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 TiO2 supports to obtain bio-PdNF/Ti02 catalysts which showed excellent catalytic activity for CO oxidation, obtaining 100%; conversion at 100 ℃ and remaining stable over a period of 52 h of reaction time. @ 2015 The Chemical Industry and Engineering Sodety of China, and Chemical Industry Press. All rights reserved.

Insight into the dynamic adsorption behavior of graphene oxide multichannel architecture toward contaminants

Graphene oxide(GO) channels exhibit unique mass transport behaviors due to their flexibility, controllable thinness and extraordinary physicochemical properties, enabling them to be widely used for adsorption and membrane separation. Nevertheless, the adsorption behavior of nanosized contaminants within the channels of GO membrane has not been fully discussed. In this study, we fabricated a GO membrane(PGn, where n represents the deposition cycles of GO) with multi channels via the crosslinking of GO and multibranched poly(ethyleneimine)(PEI). Phenol was used as molecular probe to determine the correlations between dynamic adsorption behavior and structural parameters of the multilevel GO/PEI membrane. PG8 shows higher adsorption capacities and affinity, which is predominantly attributed to the multichannel structure providing a large specific surface for phenol adsorption, enhancing the accessibility of active sites for phenol molecules and the transport of phenol. Density functional theory calculations demonstrate that the adsorption mechanism of phenol within GO channel is energetically oriented by hydrogen bonds, which is dominated by oxygen-containing groups compared to amino groups. Particularly, the interfaces which facilitate strong π-π interaction and hydrogen bonds maybe the most active regions. Moreover, the as-prepared PG8 membrane showed outstanding performance for other contaminants such as methyl orange and Cr(VI). It is anticipated that this study will have implications for design of GO-related environmental materials with enhanced efficiency.

Visbreaking of heavy petroleum oil catalyzed by SO_(4)^(2-)/ZrO_(2)solid super-acid doped with Ni^(2+) or Sn^(2+)

SO_(4)^(2-)/ZrO_(2) solid super-acid catalysts(SZ)doped with Ni^(2+)or Sn^(2+)(Ni^(2+)/SZ,Sn^(2+)/SZ)were prepared for catalytic visbreaking of heavy petroleum oil from Shengli oil field.The visbreaking reactions were carried out at 240uC and 3–4 MPa for 24 h using a heavy petroleum oil to catalyst mass ratio of 100:0.05.The effect of water content on viscosity of heavy petroleum oil was also investigated.Both catalysts can promote thermolysis of heavy petroleum oil and the viscosity was reduced from 0.319 Pa·s to 0.135 Pa?s for Ni^(2+)/SZ and 0.163 Pa·s for(Sn^(2+)/SZ)with visbreaking rates of 57.7% and 48.9%,respectively.After visbreaking,the saturated hydrocarbon content increased while aromatics,resin,asphaltene,sulfur and nitrogen content decreased.The presence of water was disadvantageous to visbreaking of heavy petroleum oil.

Biosynthesized Gold/Activated Carbon Catalyst for Aerobic Glucose Oxidation： Influence of Acid Treatment on Activated Carbon

The biosynthesized gold/activated carbon catalysts for glucose oxidation were prepared with Cacumen platycladi leaves extract,and activated carbon （AC） was modified with hydrochloric acid and nitric acid to modify its surface chemistry and used as supports.The catalysts with acid-treated AC exhibited improving activity for the selective oxidation of glucose,when compared to that with untreated one.In order to investigate the influence of the acid treatment for the catalysts performance,the surface chemical properties of AC were characterized by BrunauerEmmett-Teller surface area characterization,Boehm titration,X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy,respectively.The dispersion of AuNPs on AC was observed by transmission electron microscopy and X-ray diffraction.The results indicated that the catalysts with acid treated supports showed improved dispersion than that of untreated one,which may be the result that the supports significantly increase the surface functional groups and remove the ash after acid treatment.

Effects of ancillary ligands in acceptorless benzyl alcohol dehydrogenation mediated by phosphine-free cobalt complexes

Acceptorless alcohol dehydrogenation stands out as one of the most promising strategies in hydrogen storage technologies.Among various catalytic systems for this reaction,cost-effective molecular catalysts using phosphine-free ligands have gained considerable attention.However,the central challenge for using non-precious metals is to overcome the propensity of reacting by oneelectron pathway.Herein,we synthesized a phosphine-freeη^(5)-C_(5)Me_(5)-Co complex by using the metal-ligand cooperative strategy and compared its activity with analogous catalysts toward acceptorless alcohol dehydrogenation.The catalyst showed excellent performance with a turnover number of 130.4 and a selectivity close to 100%.The improved performance among the class ofη^(5)-C_(5)Me_(5)-Co complexes could be attributed to the more accessible Co center and its cooperation with the redox-active ligand.To further study the systematic structure-activity relationship,we investigated the electronic structures ofη^(5)-C_(5)Me_(5)-Co complexes by a set of characterizations.The results showed that the redox-active ligand has a significant influence on theη^(5)-C_(5)Me_(5)-Co moiety.In the meantime,the proximal O−/OH group is beneficial for shuttling protons.For the catalytic cycle,two dehydrogenation scenarios were interrogated through density functional theory,and the result suggested that the outer-sphere pathway was preferred.The formation of a dihydrogen complex was the rate-determining step with aΔG value of 16.9 kcal∙mol‒1.The electron population demonstrated that theη^(5)-C_(5)Me_(5)ligand played a key role in stabilizing transition states during dehydrogenation steps.This work identified the roles of vital ligand components to boost catalytic performance and offered rationales for designing metal-ligand cooperative nonprecious metal complexes.