Characteristics of Si(111) surface with embedded C84molecules

A monolayer of fullerene molecules on Si(111) surfaces is fabricated in an ultrahigh vacuum chamber through a controlled self-assembly process. The characteristics of self-assembled Si(111) surfaces, including supramolecular structures, electronic density of states, the quantum confinement effect, field emission features, and optoelectronical properties with embedded C84 are determined by the use of an ultrahigh vacuum scanning probe microscope. The results revealed that such a silicon surface with embedded C84 has a wide band gap of [similar]3.4 eV, high emission efficiency and low turn-on voltage, all of which are crucial to nano-electronics, optoelectronics, and the fabrication of semiconductor carbide. The measured data derived from photoluminescence emission experiments further confirm the corresponding band gap value obtained from I–V curves. The theoretical results from first-principles calculations for the field enhancement factor are compared with experimental measurements

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Probing characteristics of collagen molecules on various surfaces via atomic force microscopy

We examine, herein, specific dynamic responses of collagen molecules (i.e., observations of self-assembly and nanometric adhesion force measurements of type-I collagen molecules) as they interact with either a hydrophobic or a hydrophilic surface at two distinct temperatures, using a liquid-type atomic force microscope. We conclude that, regardless of surface hydrophobicity/hydrophilicity, assembled microfibrils eventually distribute homogeneously in accordance with changes in surface-related mechanical properties of collagen molecules at different self-assembly stages

Growth, Vibrational, Optical, Mechanical and DFT Investigations of an Organic Nonlinear Optical Material - Phenylurea

In this work, combined experimental and computational studies of an organic nonlinear optical material, phenylurea (PU), are reported. Optical quality single crystal of PU, was successfully grown by the slow evaporation method. The unit cell parameters of the grown PU crystal belong to the monoclinic system and these belong to the non-centrosymmetric (NCS), P21, space group. Morphology of the crystal was indexed and it reveals its 14 distinct faces. Vibrational modes of PU functional groups were assigned successfully using FTIR and Raman spectrum. The grown crystal exhibits low cutoff wavelength at UV region with good optical transparency and blue wavelength emission. The preliminary measurements confirmed that second harmonic generation (SHG) activity (∼7.6 KDP and ∼2.2 urea) with excellent laser induced threshold damage (LDT) having a value of 2.92 GW/cm2 (∼1.95 urea). TG/DTA analysis shows that endothermic nature of grown crystal with thermal stability up to 154 °C. The Vickers micro hardness test confirms soft material behavior of PU crystal and it was further explored by crystal void percentage calculation. Electrical properties such as dielectric and photoconductivity measurements were carried out for grown crystal. Furthermore, density functional theory (DFT) studies such as Mulliken charge distribution, frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP) map and first order hyperpolarizability (β) were determined to probe the structure-property relationship. These results suggest that PU single crystal can be a better alternate for urea in NLO applications

METHOD OF FORMING SELF-ASSEMBLED AND UNIFORM FULLERENE ARRAY ON SURFACE OF SUBSTRATE

本發明提供一種於基板表面生成自組裝且高度均勻之碳簇分子陣列的方法，其包括以下之步驟：(1)　提供一基板；(2)　在真空環境下將該基板加熱至約200℃至約1000℃；及(3)　提供一碳簇分子奈米粉末，並在該真空環境下藉由物理氣相沈積法將該碳簇分子奈米粉末沈積在該基板表面上，從而於該基板表面上形成自組裝且高度均勻之碳簇分子陣列。本發明亦提供一種由此製得之碳簇分子陣列嵌入式基板，其具有優異之場發射性能，可作為場發射器用於任何場發射顯示器(Field Emission Display；FED)中。最後，本發明亦提供一種由此製得之碳簇分子陣列嵌入式基板，其可替代碳化半導體材料，作為光電元件及高溫、高功率、抗高溫或高頻率電子元件之用

METHOD OF FORMING SELF-ASSEMBLED AND UNIFORM FULLERENE ARRAY ON SURFACE OF SUBSTRATE

本發明提供一種於基板表面生成自組裝且高度均勻之碳簇分子陣列的方法,其包括以下之步驟:(1)提供一基板;(2)在真空環境下將該基板加熱至約200℃至約1000℃;及(3)提供一碳簇分子奈米粉末,並在該真空環境下藉由物理氣相沈積法將該碳簇分子奈米粉末沈積在該基板表面上,從而於該基板表面上形成自組裝且高度均勻之碳簇分子陣列。本發明亦提供一種由此製得之碳簇分子陣列嵌入式基板,其具有優異之場發射性能,可作為場發射器用於任何場發射顯示器(Field Emission Display;FED)中。最後,本發明亦提供一種由此製得之碳簇分子陣列嵌入式基板,其可替代碳化半導體材料,作為光電元件及高溫、高功率、抗高溫或高頻率電子元件之用

VLS growth of pure and Au decorated beta-Ga2O3 nanowires for room temperature CO gas sensor and resistive memory applications

High-density single crystalline β-Ga2O3 nanowires on silicon (1 0 0) substrates were grown by vapour-liquid-solid growth method. We have characterized the pure β-Ga2O3 nanowires along with the Au-decorated β-Ga2O3 nanowires. The CO gas sensors at room temperature (RT) have been studied for pure and Au decorated nanowires with multiple-networked array and single nanowire devices. The diameter of the 1D nanostructure ranged from 127 ± 5 nm. The synthesized nanowires were studied using Field Emission Scanning Electron Microscope (FESEM), Transmission Electron Microscope (TEM), Energy Dispersive X-ray Spectroscopy (EDS), Gracing Incidence X-ray Diffraction (GI-XRD), Photoluminescence (PL), Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). Using the Focussed Ion Beam (FIB) technique, single nanowire gas sensor devices were fabricated. Single nanowire RT CO gas sensors using the proposed Au decorated β-Ga2O3 nanowire achieved remarkable sensitivity for 100 ppm CO gas at room temperature. Besides, we have compared the RT CO gas sensing properties of multiple-networked Au decorated β-Ga2O3 nanowires with single Au-decorated β-Ga2O3 nanowire and single pure β-Ga2O3 nanowire. In addition, bipolar resistive switching property is inspected for the Au/pure β-Ga2O3 nanowires/p-Si and Au/Au decorated β-Ga2O3 nanowires/p-Si structures

Impact of Cu doping on the structural, morphological and optical activity of V2O5 nanorods for photodiode fabrication and their characteristics

In this paper, we report a wet chemical precipitation method used to synthesize pure and Cu-doped V2O5 nanorods with different doping concentrations (CuxV2O5 where x = 3, 5 or 7 at%), followed by annealing at 600 °C and characterizations using several techniques. Indeed, a growth mechanism explaining the morphological evolution under the experimental conditions is also proposed. The XRD patterns revealed that all of the studied samples consist of a single V2O5 phase and are well crystallized with a preferential orientation towards the (200) direction. The presence of intrinsic defects and internal stresses in the lattice structure of the CuxV2O5 samples has been substantiated by detailed analysis of the XRD. Apart from the doping level, there was an assessment of identical tiny peaks attributed to the formation of a secondary phase of CuO. SEM images confirmed the presence of agglomerated particles on the surface; the coverage increased with Cu doping level. XPS spectral analysis showed that Cu in the V5+ matrix exists mainly in the Cu2+ state on the surface. The appearance of satellite peaks in the Cu 2p spectra, however, provided definitive evidence for the presence of Cu2+ ions in these studied samples as well. Doping-induced PL quenching was observed due to the absorption of energy from defect emission in the V5+ lattice by Cu2+ ions. We have proposed a cost-effective, less complicated but effective way of synthesizing pure and doped samples in colloidal form, deposited by the nebulizer spray technique on p-Si to establish junction diodes with enhanced optoelectronic properties

Ag-Decorated Vertically Aligned ZnO Nanorods for Non-Enzymatic Glucose Sensor Applications

The non-enzymatic glucose sensing response of pure and Ag-decorated vertically aligned ZnO nanorods grown on Si substrates was investigated. The simple low-temperature hydrothermal method was employed to synthesize the ZnO NRs on the Si substrates, and then Ag decoration was achieved by sputtering. The crystal structure and surface morphologies were characterized by X-ray diffraction, field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The Ag incorporation on the ZnO NR surfaces was confirmed using EDS mapping and spectra. Furthermore, the chemical states, the variation in oxygen vacancies, and the surface modifications of Ag@ZnO were investigated by XPS analysis. Both the glucose/ZnO/Si and glucose/Ag@ZnO/Si device structures were investigated for their non-enzymatic glucose sensing performances with different glucose concentrations. Based on EIS measurements and amperometric analysis, the Ag@ZnO-NR-based glucose sensor device exhibited a better sensing ability with excellent stability over time than pure ZnO NRs. The Ag@ZnO NR glucose sensor device recorded 2792 µA/(mM·cm2) sensitivity with a lowest detection limit of 1.29 µM