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Attenuated total reflection infrared spectroscopy and density functional theory calculation have been employed to study the spectral properties of imidazolium-based ionic liquids (ILs) with different anions. ILs based on 1-butyl-3-methylimidazolium cation with different anions, OH(-), CF(3)CO(2)(-), HSO(4)(-), H(2)PO(4)(-), Cl(-), PF(6)(-), and BF(4)(-), are investigated in the present work. It has been shown that the C(2)-H stretching vibration of the imidazolium ring is closely related to the electron density of H-bonding between the two closest cations and anions for pure ILs. The electron density of H-bonding between cation and anion with different anions decreases in the order [OH](-)> [H(2)PO(4)](-) > [HSO(4)](-) > [CF(3)CO(2)](-) > [Cl](-) > [BF(4)](-) > [PF(6)](-). For aqueous ILs, with increasing water content, the aromatic C-H stretching vibration of the imidazolium cation showed systematic blue-shifts. Especially for BmimOH, the nu(C(2))(-H) undergoes a drastic blue-shift by 58 cm(-1), suggesting that the formation of the strong hydrogen bonds O-H...O may greatly weaken the electron density of H-bonding between the cation and anion of ILs.

Recent years have witnessed an explosion of interest in the use of DNA-nanoparticle bioconjugates for programmed nanostructures, 1D or 2D nanoparticle arrays, nanoelectronics, and biosensing and biodiagnostics. [1][2][3][4][5][6][7][8][9] DNA was chosen as a polymeric material in these studies owing mainly to the specificity of DNA base-pairing, the predictability of inter-or intramolecular interactions, its physicochemical stability, and mechanical rigidity. In addition, DNA can be manipulated and modified by a wide range of enzymes, including DNA polymerase, ligase, and restriction endonucleases. The powerful, convenient, and specific enzymatic manipulations make DNA a highly desirable building block for the construction of various nanostructures. In the current study, we set out to investigate whether we can perform rolling circle amplification (RCA) between a DNA oligonucleotide tethered to gold nanoparticles (AuNPs) as the primer and a single-stranded circular DNA as a template, catalyzed by a special DNA polymerase known as f29 DNA polymerase (f29DNAP). RCA is a powerful but simple biochemical method that can be used to generate long single-stranded DNA (ssDNA) with a repeating sequence unit. [10][11] In a typical RCA process, a DNA polymerase, such as f29DNAP, which has a strong ability to displace newly synthesized DNA strands, makes continuous nucleotide additions to a growing DNA chain over a short circular single-stranded DNA as the template under isothermal conditions. As a result, long, linear tandemly repetitive single strands of DNA are produced. As the synthesized long DNA molecules contain many repeating sequence motifs, RCA coupled with ensuing hybridization with fluorescent DNA probes has been used as an on-chip signal-amplification tool for sensitive biosensing. [12][13][14][15][16] Recently, it has been shown that long DNA molecules from RCA can be used as scaffolds for assembling nanoparticles to form 1D nanoparticle arrays. [17][18] However, to our knowledge, performing the RCA reaction on gold nanoparticles and using the resultant special DNA-AuNP assemblies to form 3D nanoparticle array have not been demonstrated. Figure 1 schematically illustrates the RCA process on gold nanoparticles and its scaffolding for 3D periodical nanoassemblies. Gold nanoparticles of 15 nm diameter were first prepared by the classical citrate reduction route. Thiolmodified DNA primers (41 nucleotides) were then functionalized onto the nanoparticles following Mirkins approach. [5] The concentration of DNA primers on the gold nanoparticles, referred to hereafter as primer-Au, was determined using UV/Vis spectroscopy by measuring the amount of DNA in solution before and after coupling; each primer-Au contained approximately 230 DNA primer strands. A 63-nucleotidelong circular DNA template was then annealed with the DNA-functionalized gold nanoparticles. The hybridization efficiency, as examined by measuring the radioactivity on the gold nanoparticles and in solution after annealing with a radiolabeled circular DNA ...

A simple method has been developed to modify the anode interface of inverted bulk-heterojunction (BHJ) polymer solar cells by spin-coating a thin layer of graphene oxide (GO) on top of the organic active layer. The device with GO exhibited a remarkable improvement in power conversion efficiency compared to devices without any interfacial layer, indicating that GO can effectively modify the BHJ/metal anode interface to facilitate efficient hole collection. The dependence of the device performance on the GO layer thickness was also investigated showing an optimum performance from a GO thickness of ∼2–3 nm.

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Reversible switching characteristics of organic nonvolatile memory transistors (ONVMTs) using chemically synthesized graphene oxide (GO) nanosheets as a charge-trapping layer are reported. The transfer curves of GO based ONVMTs showed large gate bias dependent hysteresis with threshold voltage shifts over 20 V. After writing and erasing, stored data were well maintained showing more than two orders of ON/OFF ratio (ION/IOFF=∼102) for 104 s. These results suggest that GO nanosheets are one potential candidate as the charge-trapping layer in ONVMTs.

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Single-walled carbon nanotubes can be readily wrapped in and dispersed by long single-stranded DNA molecules (ssDNAs) synthesized by rolling circle amplification.