Conventional synthesis of silver nanoparticles employs a reducing agent and a capping agent. Surfactants are effec-tive capping agents as they prevent the aggregation of nanoparticles during storage and use. However, ...Conventional synthesis of silver nanoparticles employs a reducing agent and a capping agent. Surfactants are effec-tive capping agents as they prevent the aggregation of nanoparticles during storage and use. However, the biocompatibility of several of the surfactants is questionable. In this report, the use of thiosalicylic acid as both reducing and capping agent is reported. Compared to conventional synthesis, this methodology requires higher temperature for synthesis, which then is expected to result in aggregates of larger size. The ability of three different synthesis methodologies – direct heating, photochemical and microwave dielectric treatment were evaluated and assessed on the basis of the size, size distribution and stability of the particles. Microwave irradiation was found to be most suitable for achieving particles with a hydrodynamic diameter of 10 nm. Our studies indicate that -COO- group is involved in the reduction of Ag+ and –SH group of TSA is involved in the capping of the nanoparticles.展开更多
Increasing energy cost calls for exterior coatings with high near infra-red reflectance,so as to reduce heat absorption and in turn cost of air-conditioning.While modulations of substrate,use of white metal oxides as ...Increasing energy cost calls for exterior coatings with high near infra-red reflectance,so as to reduce heat absorption and in turn cost of air-conditioning.While modulations of substrate,use of white metal oxides as pigments or under-layers has been reported in past,reports on metal oxide or doped metal oxide pigments with high NIR reflectance is scarce.We report for the first time a blue colored cobalt aluminate type pigment prepared through doping of cerium,praseodymium or neodymium.CIELAB color measurements and calculation ofDE indicated that the Nd doped sample had crystal size of(36±1)nm,bandgap value of(2.4±0.2)eV and color coordinates similar to that of cobalt aluminate.The molar ratio as estimated by EDX was found to be Al:Cu:Co:Ce:Nd:O=2:0.06:0.06:0.012:0.00012:6.18.The pigment was found to have potential applications as a cool blue colorant,owing to changes in optical properties arising out of crystal chemistry changes.Incorporation of rare earth metal ions was found to enhance the NIR reflectance by 10%,when compared to a conventional cobalt aluminate pigment.The oxide has been well characterized and its performance as a pigment evaluated.We have proposed that changes in crystal lattice when neodymium enters into Ce4+sites enhance the NIR reflectance by about 9%as against the entry of praseodymium.展开更多
文摘Conventional synthesis of silver nanoparticles employs a reducing agent and a capping agent. Surfactants are effec-tive capping agents as they prevent the aggregation of nanoparticles during storage and use. However, the biocompatibility of several of the surfactants is questionable. In this report, the use of thiosalicylic acid as both reducing and capping agent is reported. Compared to conventional synthesis, this methodology requires higher temperature for synthesis, which then is expected to result in aggregates of larger size. The ability of three different synthesis methodologies – direct heating, photochemical and microwave dielectric treatment were evaluated and assessed on the basis of the size, size distribution and stability of the particles. Microwave irradiation was found to be most suitable for achieving particles with a hydrodynamic diameter of 10 nm. Our studies indicate that -COO- group is involved in the reduction of Ag+ and –SH group of TSA is involved in the capping of the nanoparticles.
基金One of the authors(SPR)thanks the Department of Science and Technology,Government of India for the funding received under the WOS-A programFinancial assistance of the CSIR New Delhi under the XII Plan project is also acknowledged.
文摘Increasing energy cost calls for exterior coatings with high near infra-red reflectance,so as to reduce heat absorption and in turn cost of air-conditioning.While modulations of substrate,use of white metal oxides as pigments or under-layers has been reported in past,reports on metal oxide or doped metal oxide pigments with high NIR reflectance is scarce.We report for the first time a blue colored cobalt aluminate type pigment prepared through doping of cerium,praseodymium or neodymium.CIELAB color measurements and calculation ofDE indicated that the Nd doped sample had crystal size of(36±1)nm,bandgap value of(2.4±0.2)eV and color coordinates similar to that of cobalt aluminate.The molar ratio as estimated by EDX was found to be Al:Cu:Co:Ce:Nd:O=2:0.06:0.06:0.012:0.00012:6.18.The pigment was found to have potential applications as a cool blue colorant,owing to changes in optical properties arising out of crystal chemistry changes.Incorporation of rare earth metal ions was found to enhance the NIR reflectance by 10%,when compared to a conventional cobalt aluminate pigment.The oxide has been well characterized and its performance as a pigment evaluated.We have proposed that changes in crystal lattice when neodymium enters into Ce4+sites enhance the NIR reflectance by about 9%as against the entry of praseodymium.
