ABSTRACT
We report on the improved field emission performance of graphene foam (GF) following transient exposure to hydrogen plasma. The enhanced field emission mechanism associated with hydrogenation has been investigated using Fourier transform infrared spectroscopy, plasma spectrophotometry, Raman spectroscopy, and scanning electron microscopy. The observed enhanced electron emissionhas been attributed to an increase in the areal density of lattice defects and the formation of a partially hydrogenated, graphane-like material. The treated GF emitter demonstrated a much reduced macroscopic turn-on field (2.5 V µm-1), with an increased maximum current density from 0.21 mA cm-2 (pristine) to 8.27 mA cm-2 (treated). The treated GFs vertically orientated protrusions, after plasma etching, effectively increased the local electric field resulting in a 2.2-fold reduction in the turn-on electric field. The observed enhancement is further attributed to hydrogenation and the subsequent formation of a partially hydrogenated structured 2D material, which advantageously shifts the emitter work function. Alongside augmentation of the nominal crystallite size of the graphitic superstructure, surface bound species are believed to play a key role in the enhanced emission. The hydrogen plasma treatment was also noted to increase the emission spatial uniformity, with an approximate four times reduction in the per unit area variation in emission current density. Our findings suggest that plasma treatments, and particularly hydrogen and hydrogen-containing precursors, may provide an efficient, simple, and low cost means of realizing enhanced nanocarbon-based field emission devices via the engineered degradation of the nascent lattice, and adjustment of the surface work function.
ABSTRACT
The UV-vis absorption, steady state/time resolved fluorescence spectroscopy and synchronous fluorescence, circular dichroism (CD) spectroscopy are used to investigate the interaction mechanisms of dihydroartemisinin (DHA) and 9-hydroxy-dihydroartemisinin (9-OH DHA), respectively. The UV-vis studies present that DHA and 9-OH DHA can disturb the structure of bovine hemoglobin (BHb). Steady state/time resolved and synchronous fluorescence spectroscopy reveal that the binding constant of DHA with BHb is bigger than 9-OH DHA. CD spectra indicate DHA and 9-OH DHA can change the conformation of BHb. The comparison results suggest that the binding of BHb with DHA is more stable and stronger than 9-OH DHA.
Subject(s)
Artemisinins/chemistry , Artemisinins/metabolism , Hemoglobins/metabolism , Animals , Cattle , Circular Dichroism , Hemoglobins/chemistry , Kinetics , Protein Binding , Protein Structure, Secondary , Solutions , Spectrometry, Fluorescence , Spectrophotometry, Ultraviolet , Thermodynamics , Time FactorsABSTRACT
The interaction between prodigiosin (PG) and calf thymus DNA (ct-DNA) was investigated firstly by using UV-Visible (UV-Vis), fluorescence, Fourier transform infrared (FT-IR), circular dichroism (CD) spectroscopies and viscosity measurement in Tris-HCl buffer solution (pH 6.8). The experimental results indicated that PG intercalated into the DNA helix. Upon addition of ct-DNA, PG showed hypochromic effect and slight redshift in the absorption spectra, and the melting temperature of ct-DNA was increased by from 58 to 64°C. Furthermore, FT-IR spectrum and CD spectra also suggested that the partial bases of ct-DNA react with prodigiosin. The fluorescence quenching mechanism was studied using ethidium bromide as a DNA probe, The binding constants of PG with ct-DNA in the presence of EB are 4.46×10(4) and 2.32×10(4)M(-1) at 298 and 310K, respectively, and the corresponding thermodynamic parameters ΔG, ΔH, ΔS at various temperatures were obtained.
Subject(s)
Anti-Bacterial Agents/metabolism , DNA/metabolism , Intercalating Agents/metabolism , Prodigiosin/metabolism , Animals , Cattle , Circular Dichroism , DNA/chemistry , Ethidium/chemistry , Nucleic Acid Conformation/drug effects , Protein Binding , Spectrometry, Fluorescence , Spectrophotometry, Ultraviolet , Spectroscopy, Fourier Transform InfraredABSTRACT
In this article, the interaction mechanism of prodigiosin (PG) with bovine hemoglobin (BHb) is studied in detail using various spectroscopic technologies. UV-vis absorption and fluorescence spectra demonstrate the interaction process. The Stern-Volmer plot and the time-resolved fluorescence study suggest the quenching mechanism of fluorescence of BHb by PG is a static quenching procedure, and the hydrophobic interactions play a major role in binding of PG to BHb. Furthermore, synchronous fluorescence studies, Fourier transform infrared (FTIR) and circular dichroism (CD) spectra reveal that the conformation of BHb is changed after conjugation with PG.
Subject(s)
Hemoglobins/metabolism , Prodigiosin/metabolism , Animals , Cattle , Circular Dichroism , Kinetics , Molecular Conformation , Prodigiosin/chemistry , Protein Binding , Protein Structure, Secondary , Spectrometry, Fluorescence , Spectrophotometry, Ultraviolet , Spectroscopy, Fourier Transform Infrared , Temperature , Time FactorsABSTRACT
The photoreduction of nitrobenzene (NB) on TiO(2) nanoparticles modified with asparagine (Asp), serine (Ser), phenylalanine (Phe) and tyrosine (Tyr), which were found to bind to TiO(2) via carboxyl group, have been investigated under high-pressure mercury irradiation. Modification of TiO(2) with Asp, Ser and Phe resulted in enhanced photocatalytic degradation rate of NB and high selective activity to aniline (AN) compared to using bare TiO(2). Furthermore, NB degradation followed a reductive approach over Asp, Ser, Phe-modified TiO(2) whether in additional of methanol or not. The result indicates that modification of TiO(2) with electron-donating groups is an effective way to enhance photoreduction of nitroaromatic compounds.
