New approach towards imaging λ-DNA using scanning tunneling microscopy/spectroscopy (STM/STS)

A new methodology to anchor λ-DNA to silanized n-Si(111) surface using Langmuir Blodget trough was developed. The n-Si (111) was silanized by treating it with low molecular weight octyltrichlorosilane in toluene. Scanning tunneling microscopy (STM) image of λ-DNA on octyltrichlorosilane deposited Si substrate shows areas exhibiting arrayed structures of 700 nm length and 40 nm spacing. Scanning tunneling spectroscopy (STS) at different stages depict a broad distribution of defect states in the bandgap region of n-Si(111) which presumably facilitates tunneling through otherwise insulating DNA layer

New approach towards imaging λ-DNA using scanning tunneling microscopy/spectroscopy (STM/STS)

Abstract. A new methodology to anchor λ-DNA to silanized n-Si(111) surface using Langmuir Blodget trough was developed. The n-Si (111) was silanized by treating it with low molecular weight octyltrichlorosilane in toluene. Scanning tunneling microscopy (STM) image of λ-DNA on octyltrichlorosilane deposited Si substrate shows areas exhibiting arrayed structures of 700 nm length and 40 nm spacing. Scanning tunneling spectroscopy (STS) at different stages depict a broad distribution of defect states in the bandgap region of nSi(111) which presumably facilitates tunneling through otherwise insulating DNA layer

Piezoresistivity of conducting polyaniline/BaTiO<SUB>3</SUB> composites

Conducting polyaniline/barium titanate (PANI/BaTiO<SUB>3</SUB>) composites exhibiting piezoresistivity properties have been synthesized by the in situ deposition technique by placing a fine grade powder of BaTiO<SUB>3</SUB> in the polymerization reaction mixture. The polyaniline was formed preferentially on the ceramic particles giving a much higher yield for PANI than in absence of the BaTiO<SUB>3</SUB> These composites exhibited piezoresistivity with the piezosensitivity being maximum at a certain composition. The current-voltage characteristics clearly revealed a nonlinear space charge controlled charge transport process. A large hysteresis in these characteristics was also observed which was dependent on the BaTiO<SUB>3</SUB> content in a composite. The various results have been explained on the basis of the charge transport mechanism in the heterogeneous conducting material having insulating domains dispersed in it

Preparation and characterisation of silver quantum dot superlattice using self-assembled monolayers of pentanedithiol

A superlattice of silver nanoclusters was prepared using sequential self-assembly of 1,5-pentanedithiol on an Au(111) substrate. The formation of highly ordered silver nanocluster arrays was confirmed using AFM and also by the longitudinal periodicity observed in the low angle X-ray diffraction pattern. In contrast to the behaviour of dithiol self-assembled monolayers (SAM) on gold substrates, which give only blocking behaviour, the superlattice exhibits interesting electrochemical properties in terms of redox accessibility of silver nanoclusters with respect to potential cycling. The room temperature emission spectrum suggests the formation of minibands in the superlattice structure as evidenced by three distinct peaks at 320, 400 and 620 nm

Evidence for second-order optical nonlinearity in γ-ray induced partially cross-linked polyacrylonitrile

The first direct evidence for second-order nonlinearity in partially cross-linked polyacrylonitrile is reported. The cross-linking in γ -ray-induced polymerized neat acrylonitrile is well supported by UV-vis spectroscopy, FTIR, and <SUP>13</SUP>C CP/MAS solid-state NMR. The second harmonic generation (SHG) powder test was employed to access the preliminary information about the occurrence of second-order nonlinear effect. The second harmonic generation is accomplished without the application of an external electric field, thus illustrating the importance of structural changes imparted by high-energy photon flux. Second-order nonlinearity in the present case is expected due to the small ? conjugation imparted by cross-linking through -C═N across polymeric chains coupled with the noncentrosymmetric molecular structure. Second harmonic intensity as high as 80% of that for powder urea has been observed

Preparation, characterization and mechanistic features of zirconia films on bare and functionalized gold surfaces

Electrochemical synthesis of microcrystalline ZrO<SUB>2</SUB> at room temperature on bare and functionalized gold surfaces is reported to illustrate the biomimetic conditions of nucleation and growth. ZrO<SUB>2</SUB> films prepared on self-assembled monolayers (SAMs) of pentane-1,5-dithiol (PDT) on polycrystalline gold surfaces reveal a high degree of orientation and a distinct cleavage face, in contrast to monoclinic films, obtained on bare gold surfaces at room temperature. Cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), impedance measurement, current-transients, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to follow the monolayer formation, Zr-attachment on the SAM-modified surface and subsequent difference in nucleation conditions of ZrO<SUB>2</SUB> formation. The role of SAMs in controlling the size and habit during crystallization of ZrO<SUB>2</SUB> is discussed in terms of a proposed reaction mechanism