Hexagonal and triangular Au microplates extending over an area of~12,000μm^(2) with thickness in the range 30-1000 nm have been synthesized using a single step thermolysis of(AuCl_(4))^(-)-tetraoctylammonium bromide ...Hexagonal and triangular Au microplates extending over an area of~12,000μm^(2) with thickness in the range 30-1000 nm have been synthesized using a single step thermolysis of(AuCl_(4))^(-)-tetraoctylammonium bromide complex in air.The microplates are self-supporting and can be easily manipulated using a sharp pin,a property which enables them to serve as substrates for living cells.The microplate surface is non-toxic to living cells and can enhance the fluorescence signal from fluorophores residing within the cell by an order of magnitude.In addition,the microplates are smooth and single-crystalline,and ideal as microscopy substrates and molecular electrodes.The growth of the microplates in the initial stages is interesting in that they seem to grow perpendicular to the substrate,as evidenced by in situ microscopy.展开更多
Working with a biased atomic force microscope(AFM)tip in the tapping mode under ambient atmosphere,attoliter(10^(-18) L)water droplet patterns have been generated on a patterned carbonaceous surface.This is essentiall...Working with a biased atomic force microscope(AFM)tip in the tapping mode under ambient atmosphere,attoliter(10^(-18) L)water droplet patterns have been generated on a patterned carbonaceous surface.This is essentially electrocondensation of water leading to charged droplets,as evidenced from electrostatic force microscopy measurements.The droplets are unusual in that they exhibit a highly corrugated surface and evaporate rather slowly,taking several tens of minutes.展开更多
A simple,inexpensive direct micromolding method for patterning Au nanocrystal superlattices using a polydimethylsiloxane(PDMS)stamp has been developed.The method involves in situ synthesis of Au(I)dodecanethiolate and...A simple,inexpensive direct micromolding method for patterning Au nanocrystal superlattices using a polydimethylsiloxane(PDMS)stamp has been developed.The method involves in situ synthesis of Au(I)dodecanethiolate and its decomposition leading to Au nanocrystals in the microchannels of the stamp which order themselves to form patterned superlattice stripes,in conformity with the stamp geometry.Owing to its insolubility in common solvents,the dodecanethiolate was made by reacting Au(PPh3)Cl and dodecanethiol in situ inside the microchannels,by injecting first the former solution in toluene at room temperature followed by the thiol solution at 120°C.Annealing the reaction mixture at 250°C,resulted in formation of nanocrystals(with a mean diameter of 7.5 nm)and hexagonal ordering.By using an external pressure while molding,parallel stripes with sub-100 nm widths were obtained.The choice of parameters such as injection temperature of the thiol and concentrations is shown to be important if an ordered superlattice is to be obtained.In addition,these parameters can be varied as a means to control the nanocrystal size.展开更多
基金B.Radha thanks the Council of Scientific and Industrial Research,India for financial assistance.
文摘Hexagonal and triangular Au microplates extending over an area of~12,000μm^(2) with thickness in the range 30-1000 nm have been synthesized using a single step thermolysis of(AuCl_(4))^(-)-tetraoctylammonium bromide complex in air.The microplates are self-supporting and can be easily manipulated using a sharp pin,a property which enables them to serve as substrates for living cells.The microplate surface is non-toxic to living cells and can enhance the fluorescence signal from fluorophores residing within the cell by an order of magnitude.In addition,the microplates are smooth and single-crystalline,and ideal as microscopy substrates and molecular electrodes.The growth of the microplates in the initial stages is interesting in that they seem to grow perpendicular to the substrate,as evidenced by in situ microscopy.
基金The authors thank Professor C.N.R.Rao,Fellow of Royal Society(FRS)for his encouragement.Support from the Department of Science and Technology,Government of India is gratefully acknowledged.N.K.acknowledges Council of Scientific and Industrial Research(CSIR)for funding.N.K.acknowledges Ritu for reading the manuscript.The authors thank Veeco India Nano-technology Laboratory at Jawaharlal Nehru Centre for Advanced Scientific Research(JNCASR)for the AFM facility.A.S.acknowledges INDO-US Science&Technology Forum(IUSSTF)for funding.
文摘Working with a biased atomic force microscope(AFM)tip in the tapping mode under ambient atmosphere,attoliter(10^(-18) L)water droplet patterns have been generated on a patterned carbonaceous surface.This is essentially electrocondensation of water leading to charged droplets,as evidenced from electrostatic force microscopy measurements.The droplets are unusual in that they exhibit a highly corrugated surface and evaporate rather slowly,taking several tens of minutes.
基金Support from the Department of Science and Technology,India is gratefully acknowledgedB.R.thanks council for Scientific and Industrial Research(CSIR),India for financial assistance.
文摘A simple,inexpensive direct micromolding method for patterning Au nanocrystal superlattices using a polydimethylsiloxane(PDMS)stamp has been developed.The method involves in situ synthesis of Au(I)dodecanethiolate and its decomposition leading to Au nanocrystals in the microchannels of the stamp which order themselves to form patterned superlattice stripes,in conformity with the stamp geometry.Owing to its insolubility in common solvents,the dodecanethiolate was made by reacting Au(PPh3)Cl and dodecanethiol in situ inside the microchannels,by injecting first the former solution in toluene at room temperature followed by the thiol solution at 120°C.Annealing the reaction mixture at 250°C,resulted in formation of nanocrystals(with a mean diameter of 7.5 nm)and hexagonal ordering.By using an external pressure while molding,parallel stripes with sub-100 nm widths were obtained.The choice of parameters such as injection temperature of the thiol and concentrations is shown to be important if an ordered superlattice is to be obtained.In addition,these parameters can be varied as a means to control the nanocrystal size.
