Preliminary study on the mechanism of non- enzymatic bioreduction of gold,silver,platinum,palladium and rhodium ions by Bacillus megatherium D01 biomass has been carried out by means of TEM,XRD,XPS and FTIR methods. T...Preliminary study on the mechanism of non- enzymatic bioreduction of gold,silver,platinum,palladium and rhodium ions by Bacillus megatherium D01 biomass has been carried out by means of TEM,XRD,XPS and FTIR methods. The results showed that after contacted with D01 biomass,Au3＋ has been completely reduced to elemental,cell bound Au0 for 2h and about 45％ Rh3＋ to Rh0 for 2 d at 30℃ and pH 3.5 without biochemical or chemical cofactors; the cardinal mechanism of D01 cell accumulating metal ions was biosorption,and the primary location where biosorption occurred was the D01 cell wall; active groups such as carbonyl of amido bond and carboxyl on the cell wall may complex or chelate with the precious metal ions; and aldose and ketose,i.e.,hydrolysate of part polysaccharide on the cell wall in acidic medium,served as the election donor,and reduced soluble precious metal ions to atoms.展开更多
Some characteristics of Ag＋ biosorption and bioreduction by Lactobacillus sp. A09 biomass were reported. The optimum pH value of Ag＋ biosorption by strain A09 was 4.5. Temperature(6～ 50 ℃ ) did not affect the bios...Some characteristics of Ag＋ biosorption and bioreduction by Lactobacillus sp. A09 biomass were reported. The optimum pH value of Ag＋ biosorption by strain A09 was 4.5. Temperature(6～ 50 ℃ ) did not affect the biosorption. The biosorptive efficiency (91％ ) and biosorptive capacity(Ag＋ 125 mg· g－ 1 dry weight biomass ) were achieved under the conditions of Ag＋ 100 mg· L－ 1, biomass 800 mg· L－ 1, pH 4.5 and 30 ℃ for 24 h contact. TEM analysis indicated that A09 biomass could reduce Ag＋ to Ag0 as Ag particles on the surface of cells. IR spectroscopy showed that － CO2－ and － HN－ C=O on the surface of cells may involve in the precession for adsorbing Ag＋ .展开更多
After widely screening, a kind of bacteria was obtamed, which is casy to culture and hasstrong ability of reducing Au3+ to Au0. It was used to prepare the highly dispersive Au/a-Fe2O3catalyst by in situ reducmg the Au...After widely screening, a kind of bacteria was obtamed, which is casy to culture and hasstrong ability of reducing Au3+ to Au0. It was used to prepare the highly dispersive Au/a-Fe2O3catalyst by in situ reducmg the Au3+ ions impregnated on a-Fe2O3 supporter to Au0 particles.with a mean size of 5 nm, under the condition of 28℃ and pH 4.5. The reductive degree ofAu3+ was up to 100%. This catalyst showed good catalytic property for the oxidation of carbonmonoxide, the percent conversion of 1.5% CO, balanced withe air was up to 100% under thecondition of 25~28℃and GHSV 500mL·h-1·g-1, and the percent conversion of 100% lastedfor 75 h at 25 ℃.展开更多
In situ ATR-FTIR was used to study the interaction of bovine serum albumin（BSA） and hydroxyapatite（HA） in this work.Both on the electrochemically deposited HA and self assemblied titanate nanotubes（TNT） substrat...In situ ATR-FTIR was used to study the interaction of bovine serum albumin（BSA） and hydroxyapatite（HA） in this work.Both on the electrochemically deposited HA and self assemblied titanate nanotubes（TNT） substrates,the adsorption of BSA increases with the increase of time,and its adsorption on HA surface is much larger than that on TNT surface,implying that HA has a good biocompatibility as a biomaterial.It is indicated that Ca2+ plays an essential role in the protein absorption on the HA surface,due to that BSA is negatively charged,and it is able to combine with cation locations in HA particles by electrostatic forces.It is found that,when reacting with BSA,the phosphate band of HA in solution shifts to higher wavenumbers,indicating that PO3-4 can also be an adsorption site for BSA.The spectroscopic study on the interaction between HA and BSA will be helpful for further understanding the nano hydroxyapatite bioproperties on molecular level.展开更多
The biomass D01 was screened from the soil of mining area and it was identified as Bacillus megatherium. It is able to adsorb and reduce the noble metal ions such as Pd2+,Au3+ and Ag+ etc. at room temperature. At pH 3...The biomass D01 was screened from the soil of mining area and it was identified as Bacillus megatherium. It is able to adsorb and reduce the noble metal ions such as Pd2+,Au3+ and Ag+ etc. at room temperature. At pH 3. 5, the adsorbed ratio were 93. 2%,99. 5% and 98. 1%, respectively within 2 h. In situ TEM images showed that the Au, Ag particles adsorbed on the cell wall grew up gradually. Some of the Au particles formed polyhedron particles, while some ones broke off from the cell. The particle size can be controlled to be several nano-meters to more than a hundred nano-meters. XPS and XRD results indicated that Au3+, Ag+ and Pd2+ could be reduce to metals much faster than Rh3+ and Pt4+ by Dol. Peaks at 3 087 and 1 664 cm-1 in the IR spectra of D01 reduced gradually while interacting with metal ions, implying that metal ions were coordinated and reduced on the site of acylamide of D01. This is a promising method for preparation of metal catalysts with high dispersion and nano-meter sized metal particles.展开更多
The biosorptive interaction of Ag++ with resting cell of %Lactobacillus sp.% strain A09 has been further studied on a molecular level by means of XPS, EDX, UV-Vis and FTIR techniques. The X-ray photoelectron spectrosc...The biosorptive interaction of Ag++ with resting cell of %Lactobacillus sp.% strain A09 has been further studied on a molecular level by means of XPS, EDX, UV-Vis and FTIR techniques. The X-ray photoelectron spectroscopy(XPS) shows that the reductive ratio of the Ag++ to Ag+0 by the A09 biomass reaches to about 54^5% for 3 d. The contain of amino acid residues in dry powder of the biomass such as cysteine, methionine, arginine and lysine, being capable of reducing the Ag++ to Ag+0, are very small in quantity both cysteine and methionine are far less than 0^18%, and both arginine and lysine far less than 0^336%, %via% the analysis with quantitative energy-dispersive X-ray(EDX). The amount of the reducing sugars in the biomass is far larger than 2^71% analyzed by ultraviolet-visible spectrophotometry(UV-Vis). The chemical functional group on cell wass of the biomass such as the carboxylate anion of amino-acid residues seems to be the site for the Ag++ binding and the free aldehyde group of the hemiacetalic hydroxyl from reducing sugars, %i.e.% the hydrolysates of the polysaccharides from the cell wass, plays a protagonist in serving as the electron donor for reducing the Ag++ to Ag+0, characterized by fourier transform infrared(FTIR) spectrophotometry.展开更多
文摘Preliminary study on the mechanism of non- enzymatic bioreduction of gold,silver,platinum,palladium and rhodium ions by Bacillus megatherium D01 biomass has been carried out by means of TEM,XRD,XPS and FTIR methods. The results showed that after contacted with D01 biomass,Au3＋ has been completely reduced to elemental,cell bound Au0 for 2h and about 45％ Rh3＋ to Rh0 for 2 d at 30℃ and pH 3.5 without biochemical or chemical cofactors; the cardinal mechanism of D01 cell accumulating metal ions was biosorption,and the primary location where biosorption occurred was the D01 cell wall; active groups such as carbonyl of amido bond and carboxyl on the cell wall may complex or chelate with the precious metal ions; and aldose and ketose,i.e.,hydrolysate of part polysaccharide on the cell wall in acidic medium,served as the election donor,and reduced soluble precious metal ions to atoms.
文摘Some characteristics of Ag＋ biosorption and bioreduction by Lactobacillus sp. A09 biomass were reported. The optimum pH value of Ag＋ biosorption by strain A09 was 4.5. Temperature(6～ 50 ℃ ) did not affect the biosorption. The biosorptive efficiency (91％ ) and biosorptive capacity(Ag＋ 125 mg· g－ 1 dry weight biomass ) were achieved under the conditions of Ag＋ 100 mg· L－ 1, biomass 800 mg· L－ 1, pH 4.5 and 30 ℃ for 24 h contact. TEM analysis indicated that A09 biomass could reduce Ag＋ to Ag0 as Ag particles on the surface of cells. IR spectroscopy showed that － CO2－ and － HN－ C=O on the surface of cells may involve in the precession for adsorbing Ag＋ .
文摘After widely screening, a kind of bacteria was obtamed, which is casy to culture and hasstrong ability of reducing Au3+ to Au0. It was used to prepare the highly dispersive Au/a-Fe2O3catalyst by in situ reducmg the Au3+ ions impregnated on a-Fe2O3 supporter to Au0 particles.with a mean size of 5 nm, under the condition of 28℃ and pH 4.5. The reductive degree ofAu3+ was up to 100%. This catalyst showed good catalytic property for the oxidation of carbonmonoxide, the percent conversion of 1.5% CO, balanced withe air was up to 100% under thecondition of 25~28℃and GHSV 500mL·h-1·g-1, and the percent conversion of 100% lastedfor 75 h at 25 ℃.
文摘In situ ATR-FTIR was used to study the interaction of bovine serum albumin（BSA） and hydroxyapatite（HA） in this work.Both on the electrochemically deposited HA and self assemblied titanate nanotubes（TNT） substrates,the adsorption of BSA increases with the increase of time,and its adsorption on HA surface is much larger than that on TNT surface,implying that HA has a good biocompatibility as a biomaterial.It is indicated that Ca2+ plays an essential role in the protein absorption on the HA surface,due to that BSA is negatively charged,and it is able to combine with cation locations in HA particles by electrostatic forces.It is found that,when reacting with BSA,the phosphate band of HA in solution shifts to higher wavenumbers,indicating that PO3-4 can also be an adsorption site for BSA.The spectroscopic study on the interaction between HA and BSA will be helpful for further understanding the nano hydroxyapatite bioproperties on molecular level.
文摘The biomass D01 was screened from the soil of mining area and it was identified as Bacillus megatherium. It is able to adsorb and reduce the noble metal ions such as Pd2+,Au3+ and Ag+ etc. at room temperature. At pH 3. 5, the adsorbed ratio were 93. 2%,99. 5% and 98. 1%, respectively within 2 h. In situ TEM images showed that the Au, Ag particles adsorbed on the cell wall grew up gradually. Some of the Au particles formed polyhedron particles, while some ones broke off from the cell. The particle size can be controlled to be several nano-meters to more than a hundred nano-meters. XPS and XRD results indicated that Au3+, Ag+ and Pd2+ could be reduce to metals much faster than Rh3+ and Pt4+ by Dol. Peaks at 3 087 and 1 664 cm-1 in the IR spectra of D01 reduced gradually while interacting with metal ions, implying that metal ions were coordinated and reduced on the site of acylamide of D01. This is a promising method for preparation of metal catalysts with high dispersion and nano-meter sized metal particles.
文摘The biosorptive interaction of Ag++ with resting cell of %Lactobacillus sp.% strain A09 has been further studied on a molecular level by means of XPS, EDX, UV-Vis and FTIR techniques. The X-ray photoelectron spectroscopy(XPS) shows that the reductive ratio of the Ag++ to Ag+0 by the A09 biomass reaches to about 54^5% for 3 d. The contain of amino acid residues in dry powder of the biomass such as cysteine, methionine, arginine and lysine, being capable of reducing the Ag++ to Ag+0, are very small in quantity both cysteine and methionine are far less than 0^18%, and both arginine and lysine far less than 0^336%, %via% the analysis with quantitative energy-dispersive X-ray(EDX). The amount of the reducing sugars in the biomass is far larger than 2^71% analyzed by ultraviolet-visible spectrophotometry(UV-Vis). The chemical functional group on cell wass of the biomass such as the carboxylate anion of amino-acid residues seems to be the site for the Ag++ binding and the free aldehyde group of the hemiacetalic hydroxyl from reducing sugars, %i.e.% the hydrolysates of the polysaccharides from the cell wass, plays a protagonist in serving as the electron donor for reducing the Ag++ to Ag+0, characterized by fourier transform infrared(FTIR) spectrophotometry.
