Poly N-isopropyl acrylamide (abbreviated as PNIPA) as a kind of thermally sensitive hydrogel is utilized to concentrate Bovin Serum Albumin (BSA) solution. In order to decrease its surface adsorption to BSA in aqueous...Poly N-isopropyl acrylamide (abbreviated as PNIPA) as a kind of thermally sensitive hydrogel is utilized to concentrate Bovin Serum Albumin (BSA) solution. In order to decrease its surface adsorption to BSA in aqueous solution, surface layer grafting of the gels by radiation technology was carried out. The results showed that hydroxyl propyl methacrylate (HPMA) grained gel exhibited a low level of BSA adsorption and still kept the original thermally sensitive properties of PNIPA hydrogels.展开更多
A novel soluble π-conjugated polymer, poly [（3-acetylpyrrole-2, 5-diyl） p-（N, N-dimethylamino） azobenzylidene] （PAPDMAABE）, was synthesized by condensation of 3-acetylpyrrole with 4-aldehyde-4＇-dimethylaminoaz...A novel soluble π-conjugated polymer, poly [（3-acetylpyrrole-2, 5-diyl） p-（N, N-dimethylamino） azobenzylidene] （PAPDMAABE）, was synthesized by condensation of 3-acetylpyrrole with 4-aldehyde-4＇-dimethylaminoazobenzene （ADMAA）. The chemical structure of PAPDMAABE was characterized by Fourier transform infrared spectroscopy （FTIR）, ^1H-NMR, and UV-Vis-NIR spectra. Transmission electron microscope （TEM） analysis for PAPDMAABE indicates that part of PAPDMAABE is in crystal state, due to the short-range order of the polymer. Thermogravimetric analysis （TGA） curve shows that the polymer has good thermal stability and its decomposition temperature is 248℃. The optical band gap of PAPDMAABE obtained from the optical absorption spectrum is about 1.73 eV. The resonant third-order nonlinear optical property of PAPDMAABE at 532 nm was studied using degenerate four-wave mixing （DFWM） technique. The resonant third-order nonlinear optical susceptibility of the polymer is about 7.48×10^-8 esu.展开更多
Poly （acrylic acid） （PAA） chains are grafted on one side of a microcantilever by the self-assembled method and the deflections of the microcantilever are detected as a function of medium pH from 3 to 11. It is fou...Poly （acrylic acid） （PAA） chains are grafted on one side of a microcantilever by the self-assembled method and the deflections of the microcantilever are detected as a function of medium pH from 3 to 11. It is found that when the pH varies, the microcantilever deflects because of the changing surface stress. By analysing the electrostatic repulsive effect, the surface stress change is related to the conformation transition of PAA from a collapse state to a swelling state. This method offers the interaction information among the polymer chains during the conformational transition and affords an alternative way to study conformational change of polymers.展开更多
A novel soluble π-conjugated polymer, poly[(3-octanoylpyrrole-2,5-diyl)-p-(N,N-dimethylamino)benzylidene](POPDMABE), was synthesized firstly by the condensation of 3-octanoylpyrrole with para-dimethylaminobenzaldehyd...A novel soluble π-conjugated polymer, poly[(3-octanoylpyrrole-2,5-diyl)-p-(N,N-dimethylamino)benzylidene](POPDMABE), was synthesized firstly by the condensation of 3-octanoylpyrrole with para-dimethylaminobenzaldehyde. The chemical structure of the polymer was characterized by FTIR and 1H NMR spectrometries. The polymer is a potential nonlinear optical(NLO) material. According to the function of optical forbidden band gap(E_g) and photon energy(hν), the optical forbidden band gaps of the polymer before and after ion implantation were calculated. The resonant third-order nonlinear optical properties of POPDMABE before and after ion implantation were also studied by using the degenerate four-wave mixing(DFWM) technique at 532 nm. When the energy is 25 keV and the dose is 2.2×10 17 ions/cm 2, the {polymer′s} optical forbidden band gap is about 1.63 eV which is smaller than that of the non-implanted sample(1.98 eV) and the resonant third-order NLO susceptibility of POPDMABE is about 4.3×10 -7 esu, 1 order of magnitude higher than that of the non-implanted sample(4.1×10 -8 esu). The results show that nitrogen ion implantation is an effective method to improve the resonant third-order NLO property of the polymer.展开更多
Temperature-sensitive hydrogel—poly(N-isopropyl acrylamide) (PNIPA) was prepared and applied to protein refolding. PNIPA gel disks and gel particles were synthesized by the solution polymerization and inverse suspens...Temperature-sensitive hydrogel—poly(N-isopropyl acrylamide) (PNIPA) was prepared and applied to protein refolding. PNIPA gel disks and gel particles were synthesized by the solution polymerization and inverse suspension polymerization respectively. The swelling kinetics of the gels was also studied. With these prepared PNIPA gels, the model protein lysozyme was renatured. Within 24h, PNIPA gel disks improved the yield of lysozyme activity by 49.3% from 3375.2U·mg^-1 to 5038.8U·mg^-1. With the addition of faster response PNIPA gel beads, the total lysozyme activity recovery was about 68.98% in 3h, as compared with 42.03% by simple batch dilution. The novel refolding system with PNIPA enables efficient refolding especially at high protein concentrations. Discussion about the mechanism revealed that when PNIPA gels were added into the refolding buffer, the hydrophobic interactions between denatured proteins and polymer gels could prevent the aggregation of refolding intermediates, thus enhanced the protein renaturation.展开更多
Poly (N-vinylacetatnide) ( PNVA) was synthesized by free radical polymerization in ethanol solution, in which alpha, alpha'-azobisisobutyronitrile was used as an initiator. Tb(III)-PNVA polymer was prepared and ch...Poly (N-vinylacetatnide) ( PNVA) was synthesized by free radical polymerization in ethanol solution, in which alpha, alpha'-azobisisobutyronitrile was used as an initiator. Tb(III)-PNVA polymer was prepared and characterized by ultraviolet-visual (UV), fourier transform infrared (FIF-IR), X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. The experimental results of UV, FT-IR and XPS show that the Tb (III)-PNVA electrovalent complex is formed by electrostatic interaction between terbium (III) cation and complexible atoms of acylamino group in the pendant chain of the polymer. The fluorescence spectrum of the complex exhibits intensive characteristic emission of terbium at 490, 545 and 584 run, which are assigned to D-5(4)->F-7(6), D-5(6)->F-5(6) and D-5(4)->F-7(3) transition, indicating that there exists an efficient intermolecular energy transfer from the polymer ligand to the central rare earth ion. The emission intensity of the complex is increased with the increasing concentration of Tb (III) ion until the weight ratio of Tb (III) on to PNVA is 1.5% (mass fraction), and decreased with the further increasing concentration of Tb (III) ion, which is a typical concentration quenching behavior.展开更多
Novel amphiphilic fluorescent graft copolymer （PVP-PyAHy） was successfully synthesized by the free radical copolymerization of hydrophobic monomer N-（1-pyrenebutyryl）-N＇-acryloyl hydrazide （PyAHy） with hydrophi...Novel amphiphilic fluorescent graft copolymer （PVP-PyAHy） was successfully synthesized by the free radical copolymerization of hydrophobic monomer N-（1-pyrenebutyryl）-N＇-acryloyl hydrazide （PyAHy） with hydrophilic precursor polymers of vinyl-functionalized poly（N-vinylpyrrolidone） （PVP） in DMF. The copolymer is amphiphilic and has intrinsic fluorescence. FT-IR, ^1H-NMR, TEM, gel permeation chromatography-multi-angle laser light scattering, UV-Vis spectroscopy and fluorescence spectroscopy were used to characterize this copolymer. The TEM observation shows that the copolymer PVP-PyAHy forms micelles in aqueous solution. Results of fluorometric measurements illustrate that the critical micelle concentration （CMC） value of PVP-PyAHy in aqueous solution is about 0.90 mg/mL. To examine the encapsulation ability of the copolymer in aqueous media, methyl yellow was employed as a model hydrophobic agent. The loading level of the polymer to methyl yellow is 8.8 mg/g. The cytotoxicity assays for Madin Darby Canine Kidney （MDCK） cells shows good biocompatibility of PVP-PyAHy in vitro. These results suggest the potential of this copolymer PVP-PyAHy as drugs delivery carrier and fluorescent tracer.展开更多
Novel Y-shaped block copolymers of poly（ethylene glycol） and poly（N-isopropylacrylamide）, PEG-b-（PNIPAM）2, were successfully synthesized through atom transfer radical polymerization （ATRP）. A difunctional macr...Novel Y-shaped block copolymers of poly（ethylene glycol） and poly（N-isopropylacrylamide）, PEG-b-（PNIPAM）2, were successfully synthesized through atom transfer radical polymerization （ATRP）. A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly（ethylene glycol） monomethyl ether （PEG）. The copolymers were obtained via the ATRP ofN-isopropylacrylamide （NIPAM） at 30℃ with CuCl/Me6TREN as a catalyst system and DMF/H2O （v/v = 3：1） mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography （GPC） and ^1H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions （PDI 〈 1.15）. Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry （DSC）. As a result, the phase transition temperature of PEG45-b-（PNIPAM55）2 is higher than that of PNIPAM, however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular composition and architecture on the phase transition.展开更多
As a potential solution to the crises of energy and resources, forward osmosis(FO) has been limited by the development of draw agents. An ideal draw agent should be able to generate high osmotic pressure and can be ea...As a potential solution to the crises of energy and resources, forward osmosis(FO) has been limited by the development of draw agents. An ideal draw agent should be able to generate high osmotic pressure and can be easily recovered. In this study, a thermo-sensitive polyelectrolyte of poly(N-isopropylacrylamide-co-acrylic acid)(PNA)is developed as an efficient draw agent, and two easy and simple methods are proposed to effectively recover the polyelectrolytes. After adjusting the pH value of polyelectrolyte solutions to around 6.0, the polyelectrolyte can generate relatively high osmotic pressure, and induce average water fluxes of 2.09 and 2.95 L·m^(-2)·h^(-1) during12 h FO processes when the polyelectrolyte concentrations are 0.20 and 0.38 g·ml^(-1) respectively. After acidifying and heating to 70 °C, the PNA-10 polyelectrolyte can aggregate together because of hydrophobic association and separate from water, so it can be easily recovered by either simple centrifugation or gravitational sedimentation. The recovery ratios of PNA-10 polyelectrolyte in both methods are as high as 89%, and the recovered polyelectrolytes can be reused with almost the same FO performance as fresh ones. The results in this study provide valuable guidance for designing efficient and easily recoverable draw agents for FO processes.展开更多
The effect of graft yield on both the thermo-responsive hydraulic permeability and the thermo-respousive diffusional permeability through porous membranes with plasma-grafted poly(N-isopropylacrylamide) (PNIPAM)gates ...The effect of graft yield on both the thermo-responsive hydraulic permeability and the thermo-respousive diffusional permeability through porous membranes with plasma-grafted poly(N-isopropylacrylamide) (PNIPAM)gates was investigated. Both thermo-respousive flat membranes and core-shell microcapsule membranes with a wide range of graft yield of PNIPAM were prepared using a plasma-graft pore-filling polymerization method. The grafted PNIPAM was formed homogeneously throughout the entire thickness of both the fiat polyethylene membranes andthe microcapsule polyamide membranes. Both the hydraulic permeability and the diffusional permeability were heavily dependent on the PNIPAM graft yield. With increasing the graft yield, the hydraulic permeability (water flux) decreases rapidly at 25℃ because of the decrease of the pore size; however, the water flux at 40℃ increases firstly to a peak because of the increase of hydrophobicity of the pore surface, and then decreases and finally tends to zero because of the pore size becoming smaller and smaller. For the diffusional permeability, the temperature shows different effects on the diffusional permeability coefficients of solutes across the membranes. When the graft yield was low, the diffusional coefficient of solute across the membrane was higher at temperature above the lower critical solution temperature (LCST) than that below the LCST; however, when the graft yield was high, the diffusional coefficient was lower at temperature above the LCST than that below the LCST. It is very important to choose or design a proper graft yield of PNIPAM for obtaining a desired thermo-respousive 'on/off' hydraulic or ditfusional permeability.展开更多
Stable and well-dispersed poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium colloidal clusters wereprepaxed via the reduction of ruthenium(III) chloride by refluxing with low boiling point alcohols. Investigation...Stable and well-dispersed poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium colloidal clusters wereprepaxed via the reduction of ruthenium(III) chloride by refluxing with low boiling point alcohols. Investigation of the size ofRu colloids by transmission electron microscopy (TEM) indicated that the average diametes could be controlled in the rangeof 1.2-1.6 nm with relative standard deviations of less than 0.33 by changing the molar ratio of PVP to Ru. The X-rayphotoelectron spectroscopy (XPS) characterization verified the formation of elemental ruthenium colloids.展开更多
基金This project is sponsored by the National Natural Science Foundation of China.
文摘Poly N-isopropyl acrylamide (abbreviated as PNIPA) as a kind of thermally sensitive hydrogel is utilized to concentrate Bovin Serum Albumin (BSA) solution. In order to decrease its surface adsorption to BSA in aqueous solution, surface layer grafting of the gels by radiation technology was carried out. The results showed that hydroxyl propyl methacrylate (HPMA) grained gel exhibited a low level of BSA adsorption and still kept the original thermally sensitive properties of PNIPA hydrogels.
基金the National Natural Science Foundation of China for financial support of this work(No.60277002).
文摘A novel soluble π-conjugated polymer, poly [（3-acetylpyrrole-2, 5-diyl） p-（N, N-dimethylamino） azobenzylidene] （PAPDMAABE）, was synthesized by condensation of 3-acetylpyrrole with 4-aldehyde-4＇-dimethylaminoazobenzene （ADMAA）. The chemical structure of PAPDMAABE was characterized by Fourier transform infrared spectroscopy （FTIR）, ^1H-NMR, and UV-Vis-NIR spectra. Transmission electron microscope （TEM） analysis for PAPDMAABE indicates that part of PAPDMAABE is in crystal state, due to the short-range order of the polymer. Thermogravimetric analysis （TGA） curve shows that the polymer has good thermal stability and its decomposition temperature is 248℃. The optical band gap of PAPDMAABE obtained from the optical absorption spectrum is about 1.73 eV. The resonant third-order nonlinear optical property of PAPDMAABE at 532 nm was studied using degenerate four-wave mixing （DFWM） technique. The resonant third-order nonlinear optical susceptibility of the polymer is about 7.48×10^-8 esu.
基金Supported by the National Natural Science Foundation of China under Grant Nos 20674078, 10627201, 10472111 and 10472112, and the Doctorial Programme of the Ministry of Education of China under Grant No 20040358027.
文摘Poly （acrylic acid） （PAA） chains are grafted on one side of a microcantilever by the self-assembled method and the deflections of the microcantilever are detected as a function of medium pH from 3 to 11. It is found that when the pH varies, the microcantilever deflects because of the changing surface stress. By analysing the electrostatic repulsive effect, the surface stress change is related to the conformation transition of PAA from a collapse state to a swelling state. This method offers the interaction information among the polymer chains during the conformational transition and affords an alternative way to study conformational change of polymers.
文摘A novel soluble π-conjugated polymer, poly[(3-octanoylpyrrole-2,5-diyl)-p-(N,N-dimethylamino)benzylidene](POPDMABE), was synthesized firstly by the condensation of 3-octanoylpyrrole with para-dimethylaminobenzaldehyde. The chemical structure of the polymer was characterized by FTIR and 1H NMR spectrometries. The polymer is a potential nonlinear optical(NLO) material. According to the function of optical forbidden band gap(E_g) and photon energy(hν), the optical forbidden band gaps of the polymer before and after ion implantation were calculated. The resonant third-order nonlinear optical properties of POPDMABE before and after ion implantation were also studied by using the degenerate four-wave mixing(DFWM) technique at 532 nm. When the energy is 25 keV and the dose is 2.2×10 17 ions/cm 2, the {polymer′s} optical forbidden band gap is about 1.63 eV which is smaller than that of the non-implanted sample(1.98 eV) and the resonant third-order NLO susceptibility of POPDMABE is about 4.3×10 -7 esu, 1 order of magnitude higher than that of the non-implanted sample(4.1×10 -8 esu). The results show that nitrogen ion implantation is an effective method to improve the resonant third-order NLO property of the polymer.
基金the National Natural Science Foundation of China (No. 20276065).
文摘Temperature-sensitive hydrogel—poly(N-isopropyl acrylamide) (PNIPA) was prepared and applied to protein refolding. PNIPA gel disks and gel particles were synthesized by the solution polymerization and inverse suspension polymerization respectively. The swelling kinetics of the gels was also studied. With these prepared PNIPA gels, the model protein lysozyme was renatured. Within 24h, PNIPA gel disks improved the yield of lysozyme activity by 49.3% from 3375.2U·mg^-1 to 5038.8U·mg^-1. With the addition of faster response PNIPA gel beads, the total lysozyme activity recovery was about 68.98% in 3h, as compared with 42.03% by simple batch dilution. The novel refolding system with PNIPA enables efficient refolding especially at high protein concentrations. Discussion about the mechanism revealed that when PNIPA gels were added into the refolding buffer, the hydrophobic interactions between denatured proteins and polymer gels could prevent the aggregation of refolding intermediates, thus enhanced the protein renaturation.
文摘Poly (N-vinylacetatnide) ( PNVA) was synthesized by free radical polymerization in ethanol solution, in which alpha, alpha'-azobisisobutyronitrile was used as an initiator. Tb(III)-PNVA polymer was prepared and characterized by ultraviolet-visual (UV), fourier transform infrared (FIF-IR), X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. The experimental results of UV, FT-IR and XPS show that the Tb (III)-PNVA electrovalent complex is formed by electrostatic interaction between terbium (III) cation and complexible atoms of acylamino group in the pendant chain of the polymer. The fluorescence spectrum of the complex exhibits intensive characteristic emission of terbium at 490, 545 and 584 run, which are assigned to D-5(4)->F-7(6), D-5(6)->F-5(6) and D-5(4)->F-7(3) transition, indicating that there exists an efficient intermolecular energy transfer from the polymer ligand to the central rare earth ion. The emission intensity of the complex is increased with the increasing concentration of Tb (III) ion until the weight ratio of Tb (III) on to PNVA is 1.5% (mass fraction), and decreased with the further increasing concentration of Tb (III) ion, which is a typical concentration quenching behavior.
基金This work was supported by the National Natural Science Foundation of China (No. 20474044).
文摘Novel amphiphilic fluorescent graft copolymer （PVP-PyAHy） was successfully synthesized by the free radical copolymerization of hydrophobic monomer N-（1-pyrenebutyryl）-N＇-acryloyl hydrazide （PyAHy） with hydrophilic precursor polymers of vinyl-functionalized poly（N-vinylpyrrolidone） （PVP） in DMF. The copolymer is amphiphilic and has intrinsic fluorescence. FT-IR, ^1H-NMR, TEM, gel permeation chromatography-multi-angle laser light scattering, UV-Vis spectroscopy and fluorescence spectroscopy were used to characterize this copolymer. The TEM observation shows that the copolymer PVP-PyAHy forms micelles in aqueous solution. Results of fluorometric measurements illustrate that the critical micelle concentration （CMC） value of PVP-PyAHy in aqueous solution is about 0.90 mg/mL. To examine the encapsulation ability of the copolymer in aqueous media, methyl yellow was employed as a model hydrophobic agent. The loading level of the polymer to methyl yellow is 8.8 mg/g. The cytotoxicity assays for Madin Darby Canine Kidney （MDCK） cells shows good biocompatibility of PVP-PyAHy in vitro. These results suggest the potential of this copolymer PVP-PyAHy as drugs delivery carrier and fluorescent tracer.
基金support from the National Natural Science Foundation of China(No. 20134020)the Visiting Scholar Project of Shandong Province of China(No.20081001)the Science Research Fund of Shandong Jiaotong University of China(No.Z200802)
文摘Novel Y-shaped block copolymers of poly（ethylene glycol） and poly（N-isopropylacrylamide）, PEG-b-（PNIPAM）2, were successfully synthesized through atom transfer radical polymerization （ATRP）. A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly（ethylene glycol） monomethyl ether （PEG）. The copolymers were obtained via the ATRP ofN-isopropylacrylamide （NIPAM） at 30℃ with CuCl/Me6TREN as a catalyst system and DMF/H2O （v/v = 3：1） mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography （GPC） and ^1H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions （PDI 〈 1.15）. Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry （DSC）. As a result, the phase transition temperature of PEG45-b-（PNIPAM55）2 is higher than that of PNIPAM, however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular composition and architecture on the phase transition.
基金Supported by the National Natural Science Foundation of China(21276162)the Program for Yangtse River Scholars and Innovative Research Team in Universities(IRT1163)
文摘As a potential solution to the crises of energy and resources, forward osmosis(FO) has been limited by the development of draw agents. An ideal draw agent should be able to generate high osmotic pressure and can be easily recovered. In this study, a thermo-sensitive polyelectrolyte of poly(N-isopropylacrylamide-co-acrylic acid)(PNA)is developed as an efficient draw agent, and two easy and simple methods are proposed to effectively recover the polyelectrolytes. After adjusting the pH value of polyelectrolyte solutions to around 6.0, the polyelectrolyte can generate relatively high osmotic pressure, and induce average water fluxes of 2.09 and 2.95 L·m^(-2)·h^(-1) during12 h FO processes when the polyelectrolyte concentrations are 0.20 and 0.38 g·ml^(-1) respectively. After acidifying and heating to 70 °C, the PNA-10 polyelectrolyte can aggregate together because of hydrophobic association and separate from water, so it can be easily recovered by either simple centrifugation or gravitational sedimentation. The recovery ratios of PNA-10 polyelectrolyte in both methods are as high as 89%, and the recovered polyelectrolytes can be reused with almost the same FO performance as fresh ones. The results in this study provide valuable guidance for designing efficient and easily recoverable draw agents for FO processes.
基金Supported by the National Natural Science Foundation of China(No.29876022).
文摘The effect of graft yield on both the thermo-responsive hydraulic permeability and the thermo-respousive diffusional permeability through porous membranes with plasma-grafted poly(N-isopropylacrylamide) (PNIPAM)gates was investigated. Both thermo-respousive flat membranes and core-shell microcapsule membranes with a wide range of graft yield of PNIPAM were prepared using a plasma-graft pore-filling polymerization method. The grafted PNIPAM was formed homogeneously throughout the entire thickness of both the fiat polyethylene membranes andthe microcapsule polyamide membranes. Both the hydraulic permeability and the diffusional permeability were heavily dependent on the PNIPAM graft yield. With increasing the graft yield, the hydraulic permeability (water flux) decreases rapidly at 25℃ because of the decrease of the pore size; however, the water flux at 40℃ increases firstly to a peak because of the increase of hydrophobicity of the pore surface, and then decreases and finally tends to zero because of the pore size becoming smaller and smaller. For the diffusional permeability, the temperature shows different effects on the diffusional permeability coefficients of solutes across the membranes. When the graft yield was low, the diffusional coefficient of solute across the membrane was higher at temperature above the lower critical solution temperature (LCST) than that below the LCST; however, when the graft yield was high, the diffusional coefficient was lower at temperature above the LCST than that below the LCST. It is very important to choose or design a proper graft yield of PNIPAM for obtaining a desired thermo-respousive 'on/off' hydraulic or ditfusional permeability.
基金This work was supported by the National Natural Science Foundation of China (No. 29873058).
文摘Stable and well-dispersed poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium colloidal clusters wereprepaxed via the reduction of ruthenium(III) chloride by refluxing with low boiling point alcohols. Investigation of the size ofRu colloids by transmission electron microscopy (TEM) indicated that the average diametes could be controlled in the rangeof 1.2-1.6 nm with relative standard deviations of less than 0.33 by changing the molar ratio of PVP to Ru. The X-rayphotoelectron spectroscopy (XPS) characterization verified the formation of elemental ruthenium colloids.
