Synthesis and characterization of cadmium hydroxide nanowires by arc discharge method in de-ionized water

In this study, Cd(OH)₂ nanowires have been synthesized by using arc discharge method in de-ionized water. The morphology and properties of the Cd(OH)₂ nanowires were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy, transmission electron microscopy (TEM), and UV–Vis spectroscopy. TEM observations revealed that Cd(OH)₂ nanowires were abundant morphology in synthesized nanostructures, and the diameter of the Cd(OH)₂ nanowires ranges from 5 to 40 nm with several micrometers of length. In addition, the width of nanowires is not uniform and varies throughout the nanowire. XRD analysis revealed that the Cd(OH)₂ nanowires grow along [001] direction. Furthermore, hexagonal- and irregular-shaped Cd(OH)₂ nanoplates were synthesized during arc discharge. It was obtained that required arc current is 50 A for the effective and large scale production of Cd(OH)₂ nanowires. Furthermore, the optical properties of the nanowires have been characterized by UV–Vis spectra. By the means of the optical studies, the direct band gap of Cd(OH)₂ nanowires was found to be 4.0 eV with strong quantum size effect. It is also shown that a simple and cheap method which does not require relatively expensive vacuum and laser equipment stipulates an economical alternative for the synthesis of Cd(OH)₂ nanowires.     

Experimental and computational investigation of unsymmetrical cyanine dyes: understanding torsionally responsive fluorogenic dyes

Unsymmetrical cyanine dyes are widely used in biomolecular detection due to their fluorogenic behavior, whereby fluorescence quantum yields can be very low in fluid solution but are significantly enhanced in conformationally restricted environments. Herein we describe a series of fluorinated analogues of the dye thiazole orange that exhibit improved fluorescence quantum yields and photostabilities. In addition, computational studies on these dyes revealed that twisting about the monomethine bridge beyond an interplanar angle of 60 degrees leads to a dark state that decays nonradiatively to the ground state, accounting for the observed fluorogenic behavior. The effects of position and number of fluorine substituents correlate with both observed quantum yield and calculated activation energy for twisting beyond this critical angle.     

Material binding peptides for nanotechnology

Remarkable progress has been made to date in the discovery of material binding peptides and their utilization in nanotechnology, which has brought new challenges and opportunities. Nowadays phage display is a versatile tool, important for the selection of ligands for proteins and peptides. This combinatorial approach has also been adapted over the past decade to select material-specific peptides. Screening and selection of such phage displayed material binding peptides has attracted great interest, in particular because of their use in nanotechnology. Phage display selected peptides are either synthesized independently or expressed on phage coat protein. Selected phage particles are subsequently utilized in the synthesis of nanoparticles, in the assembly of nanostructures on inorganic surfaces, and oriented protein immobilization as fusion partners of proteins. In this paper, we present an overview on the research conducted on this area. In this review we not only focus on the selection process, but also on molecular binding characterization and utilization of peptides as molecular linkers, molecular assemblers and material synthesizers.     

A comprehensive study for selective removal of Cr(VI) by asymmetric imidazolium bromide salts as environmentally-friendly extractant

The study was to determine selective removal and recovery of Cr(VI) from acidic media by solvent extraction (SX) using asymmetric imidazolium-based room temperature imidazolium bromide salts (ARTILs) as the extractants. The relevant parameters on the extraction and the stripping of Cr(VI) were investigated to identify optimum conditions. The optimum conditions were determined as equilibration time 5 minutes, acid concentration and type 0.5?mol/L H₂SO₄, stirring speed 1200?rpm, extractant concentration and type 0.5?mol/L ARTIL5, phase ratio 2.0 and stripping reagent type, and concentration 2.0?mol/L NH₃. In optimum conditions, decyl substituted ARTIL was best in extraction process about 99.7% of extraction rate, whereas moderately hydrophobic pentyl substituted ARTIL was best in stripping process about 70.0% of stripping rate. Also, the optimized process was found as so selective toward Cr(VI) in the presence of the other metal ions with an environmental-friendly liquid–liquid–based SX method.     

Assembly kinetics of nanocrystals via peptide hybridization

The assembly kinetics of colloidal semiconductor quantum dots (QDs) on solid inorganic surfaces is of fundamental importance for implementation of their solid-state devices. Herein an inorganic binding peptide, silica binding QBP1, was utilized for the self-assembly of nanocrystal quantum dots on silica surface as a smart molecular linker. The QD binding kinetics was studied comparatively in three different cases: first, QD adsorption with no functionalization of substrate or QD surface; second, QD adsorption on QBP1-modified surface; and, finally, adsorption of QBP1-functionalized QD on silica surface. The surface modification of QDs with QBP1 enabled 79.3-fold enhancement in QD binding affinity, while modification of a silica surface with QBP1 led to only 3.3-fold enhancement. The fluorescence microscopy images also supported a coherent assembly with correspondingly increased binding affinity. Decoration of QDs with inorganic peptides was shown to increase the amount of surface-bound QDs dramatically compared to the conventional methods. These results offer new opportunities for the assembly of QDs on solid surfaces for future device applications.     

Background correction by wavelength modulation using a microcomputer in atomic emission spectrometry

An Apple IIe microcomputer was employed to correct the background radiation in electrothermal atomization atomic emission spectrometry (ETA-AES). In ETA-AES, black-body radiation from the atomizer as well as any broadband molecular emission should be corrected to obtain an atomic signal alone. A quartz plate run by a G325D galvanometric motor was placed before the exit slit of a 256 mm Littrow monochromator. Improvements by a novel pulsed 3-step square waveform are demonstrated compared with the ordinatry 3-step square waveform. A soft delay was also applied in order to avoid taking data at transition stages of the quartz plate. A line and a continuum source are used to simulate offsetting of the DC component of the signal prior to the ADC. This provides a better utilization of the full dynamic range of the converter.     

High scotopic/photopic ratio white-light-emitting diodes integrated with semiconductor nanophosphors of colloidal quantum dots

We propose and demonstrate single-chip white-light-emitting diodes (WLEDs) integrated with semiconductor nanophosphors of colloidal quantum dots for high scotopic/photopic (S/P) ratio. These color conversion WLEDs achieve S/P ratios over 3.00, which exceeds the current limit of 2.50 in common lighting technologies, while sustaining sufficient levels of color rendering index.     

Broadband absorption enhancement in randomly positioned silicon nanowire arrays for solar cell applications

In this Letter, the optical properties of randomly positioned silicon nanowire arrays are studied. The result shows that position randomization with a filling ratio larger than 36% renders better absorptance over a broadband ranging from 300 to 1130 nm compared to regular structures. The ultimate efficiency of a 48% filling ratio position randomized nanowire structure is 13.4% higher compared to the optimized regularly arranged nanowire structure with the same thickness. The absorptance enhancement of random structures is attributed to lowered reflectance, more supported resonant modes, and broadening of existing resonance.