Blue Shift Effect Research Articles

Facile Microwave Approach for Synthesis of Copper–Indium Sulfide Nanoparticles and Study of Their Behavior in Solar Cell

CuInS2 (CIS) nanoparticles (nps) were synthesized via a microwave approach by adding eight sulfur sources with a new copper precursor, [bis(acetylacetonato)copper(II)]; [Cu(acac)2]. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible and photoluminescence spectroscopy. Band gap of as-synthesized nps was 2.1 eV that showed about 0.55 eV blue shift in comparison to its bulk type. As observed in other semiconductor systems, the optical absorption blue shift is associated with quantum confinement effects. Thin film of CIS was prepared by doctor’s blade technique and solar cell made from indium transparent oxide/CIS/CdS/Pt layers. I–V characterization was investigated for this cell and fill factor, open-circuit voltage (V oc) and short-circuit current (I sc) were achieved.

THE IMPACT OF THE CONVECTIVE BLUESHIFT EFFECT ON SPECTROSCOPIC PLANETARY TRANSITS

We present here a small anomalous radial velocity (RV) signal expected to be present in RV curves measured during planetary transits. This signal is induced by the convective blueshift (CB) effect --- a net blueshift emanating from the stellar surface, resulting from a larger contribution of rising hot and bright gas relative to the colder and darker sinking gas. Since the CB radial component varies across the stellar surface, the light blocked by the planet during a transit will have a varying RV component, resulting in a small shift of the measured RVs. The CB-induced anomalous RV curve is different than, and independent of, the well known Rossiter-McLaughlin (RM) effect, where the latter is used for determining the sky-projected angle between the host star rotation axis and the planet's orbital angular momentum axis. The observed RV curve is the sum of the CB and RM signals, and they are both superposed on the orbital Keplerian curve. If not accounted for, the presence of the CB RV signal in the spectroscopic transit RV curve may bias the estimate of the spin-orbit angle. In addition, future very high precision RVs will allow the use of transiting planets to study the CB of their host stars.

Colloidal Germanium Nanoparticles and Nanocubes Synthesized by Chemical Liquid Deposition

In this work, both germanium colloids and nanoparticles (Ge-Coll and Ge-Nps) were synthesized by Chemical Liquid Deposition (CLD). Colloids and nanoparticles were characterized by: FTIR, HRTEM, SAED, Light Scattering and electrophoretic mobility measurements. TEM images revealed a narrow particle size distribution with values of 4.2, 5.4 and 10 nm for Ge-Nps-2-propanol, Ge-Nps-THF and Ge-Nps-acetone, respectively. UV spectra showed absorption bands of nanoparticle plasmons, blue-shift effects by quantum size effects and plasmon aggregation bands at 272 and 279 nm. Fractal aggregates growth along time was carried out by light scattering and zeta potential measurements. Electrophoretic mobility showed that nanoparticles had negative charge and FTIR spectroscopy revealed that the interaction of Ge surface with the solvent produces a double bond (Ge C), moreover varying the synthesis parameters (nucleation time and colloid concentration), Germanium nanocubes (Ge-Ncb) can be obtained. Studies on colloid stability, particles aggregation along time and thermal stability are also discussed.

NEXAFS Study of Zinc Porphyrins Intercalated into V2O5 Xerogel

For the first time the NEXAFS N1sand C1sspectra of composites on the basis of macrocyclic molecules zinc meso-tetrakis(4-pyridyl)porphyrin, zinc meso-tetrakis(N-methylpyridinium-4-yl)porphyrin tetraiodide and V2O5·nH2O xerogel were studied by a total electron yield method with using synchrotron radiation of Russian-Germany beamline at BESSY-II. These intercalation complexes are insoluble in water, stable and exhibit good electrochemical properties. The host-guest interaction leads to the great changes of NEXAFS N1sand C1s-spectra of the synthesized composites as compared with pristine compounds spectra. The studies show the 2.1 eV blue shift energy position and great increase oscillator strength of the π-resonance in the NEXAFS N1sspectra of pyridine cycle when ZnPor(Py)4 intercalated into V2O5·nH2O xerogel.

Microwave-Assisted Preparation of CdS Nanoparticles in a Halide-Free Ionic Liquid and Their Photocatalytic Activities

A microwave-assisted (4–6 min) method was used for the preparation of CdS nanoparticles in 1-ethyl-3-methylimidazolium ethyl sulfate, a halide-free room-temperature ionic liquid (RTIL). The samples were characterized by powder X-ray diffraction, energy dispersive X-ray spectroscopy, and scanning electron microscopy. Diffuse reflectance spectra showed a 1.33 eV blue shift relative to bulk CdS. The photocatalytic activities of the nanoparticles for photodegradation of methylene blue (MB) using UV and visible light were measured. The photodegradation of MB decreased with calcination temperature. First order rate constants for the reaction under visible and UV irradiations over the nanoparticles prepared in the RTIL rich media were 5.4 and 2.5 higher, respectively, than the sample prepared in water.

Mesoporous silica-coated gold nanorods: towards sensitive colorimetric sensing of ascorbic acid via target-induced silver overcoating

This article describes a nonaggregation-based colorimetric assay of ascorbic acid by tailoring the optical properties of mesoporous silica-coated gold nanorods (MS GNRs) via silver overcoating. The colorimetric measurement of ascorbic acid (AA) concentration strongly relies on the fact that the blue shift effect of localized surface plasmon resonance (LSPR) peak of MS GNRs is gradually enlarged with the increase of AA amount. The limit of detection is determined to be 49 nM, which is comparable to that of quantum dots (QDs)-based fluorimetric methods.

Label-free colorimetric detection of trace cholesterol based on molecularly imprinted photonic hydrogels

A novel colorimetric sensor for cholesterol assay was constructed by combining a molecular imprinting technique with photonic crystals. The molecularly imprinted photonic hydrogel (MIPH) film was prepared by a non-covalent, self-assembly approach using cholesterol as a template molecule, and exhibited a highly ordered three-dimensional macroporous structure characterized by scanning electron microscopy under the optimized imprinting conditions. Various factors affecting rebinding of cholesterol are discussed along with recognition specificity studies on its analogues of stigmasterol and ergosterol through estimation of UV-Vis and electrochemical impedance spectroscopy. The MIPH film generated a significantly readable optical signal directly self-reporting within less than 2 min upon binding cholesterol. The colorimetric measurement of cholesterol concentration strongly relies on the fact that the blue shift effect of the Bragg diffraction peak of the MIPH is gradually enlarged with the increase of cholesterol amounts. The detection level approached 10−13 g mL−1, which is comparable to that of fluorescence measurements. The simultaneous possession of high selectivity, high sensitivity, high stability, easy operation and being label-free enables this sensor to be potentially applicable for rapid on-site detection of trace cholesterol.

BLUE-SHIFTING HYDROGEN BONDS AND SECONDARY INTERACTIONS IN THE C3H6…HCF3, C2H4O…HCF3 AND C2H4S…HCF3 CYCLIC COMPLEXES

In this article, a theoretical study of molecular properties of small cyclic systems is presented. Through the calculations performed at the B3LYP/6-311++G(d,p) level of theory, the optimized geometries of the C3H6-HCF3, C2H4O-HCF3 and C2H4S-HCF3 hydrogen-bonded complexes were determined. By analyzing the structural parameters, it was observed a contraction of the C-H bond length of the fluoroform (HCF3). As such, the examination of the harmonic infrared spectrum accused the existence of a blue-shift effect in this bond, once its stretch frequency is displaced to upward values accompanied by a significant diminishing on the absorption intensity. In the purpose to comprehend this vibrational phenomenon, topological parameters computed at the light of the Quantum Theory of Atoms in Molecules (QTAIM) were also used. An interesting aspect is the non-linearity deviation on the hydrogen bonds (O…H) and (S…H) due to the formation of a secondary interaction (Hα…Fφ) between the fluoride (Fφ) of fluoroform and the axial hydrogen atoms (Hα) of the heterocyclic structures.

Blue shift of Tm3+ upconversion owing to Nd3+ in yttrium oxide powders pumped by pulsed red laser

Tm3+:Y2O3 powder prepared by combustion synthesis exhibits blue emission centered at λ∼450nm, corresponding to 1D2→3F4 transition of Tm3+, when the sample is irradiated by a pulsed (5ns, 10Hz) red laser operating at λ∼690nm. The blue emission band shifts to λ∼480nm, corresponding to 1G4→3H6 transition of Tm3+, when Nd3+ is added to the sample. When the laser is tuned to λ∼680nm, the blue shift effect is not observed. The shifting effect is explained based on single shot laser excitation and energy transfer mechanisms involving Tm3+ and Nd3+ ions.

Simple and low temperature preparation and characterization of CdS nanoparticles as a highly efficient photocatalyst in presence of a low-cost ionic liquid

A simple and low temperature method is proposed for preparation of CdS nanoparticles in presence of 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM] [EtSO4], a room-temperature ionic liquid (RTIL). The powder X-ray diffraction (XRD) studies display that the products are excellently crystallized in the form of cubic structure and size of the nanparticles prepared in presence of the RTIL is smaller than that prepared in water. Energy dispersive X-ray spectroscopy (EDX) investigations reveal that the products are very pure and nearly stoichiometric. The results obtained by scanning electron microscopy (SEM) demonstrate that the CdS nanoparticles prepared in presence of the RTIL have lower tendency for aggregation relative to the prepared sample in water. Diffuse reflectance spectra (DRS) of the product prepared in the neat RTIL, shows 1.52 eV blue shift relative to bulk CdS, which can be attributed to quantum confinement effect of the CdS nanoparticles. A possible formation mechanism for CdS nanoparticles in presence of the RTIL is presented. Photocatalytic activity of the CdS nanoparticles towards photodegradation of methylene blue (MB) using UV and visible lights was performed. The results demonstrate that observed firstorder rate constant for photodegradation of MB on CdS nanoparticles prepared in the neat RTIL are about 20 and 6 times greater than the prepared sample in water using visible and UV lights, respectively.

Studies on the interaction of aminocarb with calf thymus DNA by spectroscopic methods

The interaction between aminocarb and calf thymus DNA in physiological buffer (pH 7.4) was investigated by UV–vis spectrophotometry, fluorescence spectroscopy, viscosity measurements and DNA melting techniques. The absorption spectra of aminocarb with DNA showed a slight blue shift and hypochromic effect. Using ethidium bromide (EB) as a fluorescence probe, fluorescence quenching of the emission peak was seen in the DNA–EB system when aminocarb was added. The fluorescence polarization was gradually increased with increasing amounts of DNA. The value of melting temperature of DNA increased in the presence of aminocarb. Moreover, the relative viscosity of DNA increased with the addition of aminocarb. All the evidences indicated that the binding mode of aminocarb with DNA was an intercalative binding. The binding constants of aminocarb with DNA were determined. The calculated thermodynamic parameters suggested that the binding of aminocarb to DNA was driven mainly by hydrogen bond and van der Waals.

Biologically formed hollow cuprous oxide microspheres

Hollow cuprous oxide (Cu 2O) microspheres with a diameter of ca. 1.8 μm are prepared by using yeast as template. The possible mechanism for the formation of the hollow Cu 2O spheres is revealed. The biotemplated sample is investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet–visible (UV–vis) absorption spectra. The sample consists of the crystalline Cu 2O microspheres with diameters of about 59.5 nm and lattice parameter of 4.264 Å. The observed optical band gap of the product indicates that the blue–shift effect occurs, which is attributed to the hollow Cu 2O microspheres.

Simultaneous effects of laser field and hydrostatic pressure on the intersubband transitions in square and parabolic quantum wells

The intersubband transitions in square and parabolic quantum wells under simultaneous action of the hydrostatic pressure and high-frequency laser field have been investigated. We found that the laser-induced blueshift effect on the subband energy levels may be tuned by the pressure action. Our calculations revealed that the oscillator strength of the transition between the ground and the first excited levels depends on the quantum well width and shape, laser field intensity and hydrostatic pressure. This combined effect of pressure and laser field offers a new degree of freedom in the optoelectronic devices applications.

Synthesis and characterization of yellow water-borne polyurethane using a diol colorant as extender

A novel and facile method toward a series of yellow water-borne polyurethane was developed by using an intrinsically colored diol in this paper. The yellow aqueous dispersion PCLD–HENA–PU was synthesized based on isophorone diisocyanate (IPDI), polycaprolactonediol (PCLD) and 2,2-dimethylol propionic acid (DMPA) using a yellow diol N,N-bis(2-hydroxyethyl)-4-nitroaniline (HENA) as a chain extender. Due to the complete reaction of OH group in colorant HENA with NCO group in diisocyanate, a series of stable yellow polyurethanes could be obtained conveniently and easily. The structure of PCLD–HENA–PUs was confirmed by means of Fourier transform infrared spectroscopy. The UV–visible absorption analysis showed a blue shift effect of about 7 nm when HENA was blocked into polyurethane chain. The absorption intensity of PCLD–HENA–PUs increased with increasing HENA content. It was found that the tensile strength enhanced from 8.6 to 19.6 MPa with HENA content increased from 0 to 18.0%, while the extensibility decreased from 449 to 300%. The thermal gravimetric analysis presented that the initial decompose temperature began from about 250 °C, and had a little increase with increasing the HENA content.

Low temperature CO and CH4 dual selective gas sensor using SnO2 quantum dots prepared by sonochemical method

Abstract In this study, a low temperature sensor with a dual function property is fabricated by using 3–4 nm SnO 2 quantum dots (QDs) prepared by sonication-assisted precipitation. The sensor shows high selectivity to CO in the presence of methane below 375 °C. SnCl 4 aqueous solution was precipitated by ammonia under sonication, which continued for 1, 2 and 3 h. A part of the sample was then dried and calcined at 400 °C for 1.5 h and characterized by XRD and BET. UV–vis analyses were carried out for band gap measurements. The average particle size and the specific surface area of the SnO 2 QDs as well as their sensing properties were compared with the SnO 2 nano-particles prepared by conventional sol–gel method. The BET surface area of sonochemically as-prepared product after 2 h sonication and the one calcined at 400 °C after 1.5 h are 257 and 212 m 2 /g, respectively while the specific surface area for SnO 2 prepared by conventional sol–gel method is about 80 m 2 /g. XRD spectra revealed pure crystalline phase of SnO 2 is formed for both as-prepared and calcined samples of SnO 2 QDs. However, for the sample prepared by sol–gel method and calcined at 400 °C, SnO crystals are detected along with the SnO 2 crystals. Band gap measurements for the sample fabricated by sonochemical method and calcined at 400 °C indicated band gap energy of 5.7 eV which shows 2.1 eV blue-shift (shift into smaller wave lengths) from that of the bulk SnO 2 which was reported earlier by others. Quantum dots of SnO 2 show exceedingly high response to different concentrations of 100, 300 and 1000 ppm of CO in a temperature range of 25–350 °C. At about 50 °C a response of 27 was obtained for 1000 ppm CO, which increases to a maximum of 147 at 225 °C and then decreases whereas the maximum of 47.2 was detected for the SnO 2 sample prepared by the sol–gel method occurred at about 300 °C. At the same time no response to methane is observed in the whole range of temperatures for SnO 2 QDs. On the other hand the response to methane is higher than that to CO at above 375 °C.

Full-wave parallel dispersive finite-difference time-domain modeling of three-dimensional electromagnetic cloaking structures

A parallel dispersive finite-difference time-domain (FDTD) method for the modeling of three-dimensional (3-D) electromagnetic cloaking structures is presented in this paper. The permittivity and permeability of the cloak are mapped to the Drude dispersion model and taken into account in FDTD simulations using an auxiliary differential equation (ADE) method. It is shown that the correction of numerical material parameters and the slow switching-on of source are necessary to ensure stable and convergent single-frequency simulations. Numerical results from wideband simulations demonstrate that waves passing through a three-dimensional cloak experience considerable delay comparing with the free space propagations, as well as pulse broadening and blue-shift effects.

Effect of the synthesis route on the structural properties and shape of the indium oxide (In 2O 3) nano-particles

Nano-crystalline indium oxide (In 2O 3) particles have been synthesized by sol–gel and hydro-thermal techniques. A simple hydro-alcoholic solution consisting indium nitrate hydrate and citric acid (in sol–gel method) and 1, 4-butandiol (in hydro-thermal method) have been utilized. The structural properties of indium oxide nano-powders annealed at 450 °C (for both methods) have been characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and specific surface area (SSA) analysis. Structural analysis of the samples shows cubic phase in sol–gel and cubic-hexagonal phase mixture in hydro-thermally prepared particles. The nano-particles prepared by sol–gel method have nearly spherical shape, whereas hydro-thermally-made ones display wire- and needle-like shape in addition to the spherical shape. The obtained In 2O 3 nano-particles surface areas were 23.2 and 55.3 in sol–gel and hydro-thermal methods, respectively. The optical direct band gap of In 2O 3 nano-particles were determined to be ∼4.32 and ∼4.24 eV for sol–gel and hydro-thermal methods, respectively. These values exhibit ∼0.5 eV blue shift from that the bulk In 2O 3 (3.75 eV), which is related to the particle size reduction and approaching the quantum confinement limit of nano-particles.

A PBE hybrid functional study of blue-shifting and red-shifting hydrogen bonds in pi hydrocarbons

This study examines a selected group of p hydrocarbon complexes, represented by C2H4•••HCF3, C2H2•••HCF3, C2H4•••HCF3 and C2H2•••HCF3, from a theoretical point of view. From BPBE/6-311++G(d,p) calculations, the geometrical results of these complexes revealed an elongation and shortening of the H—C bond lengths of chloroform (HCCl3) and fluoroform (HCF3), respectively. In terms of the infrared spectrum, the analysis of stretch frequencies revealed that the variations in the H—C modes are essentially recognized as red and blue-shifting modes. For the purposes of understanding the two vibrational phenomena of the ? hydrocarbon complexes studied here, PBE/6-311++G(d,p) calculations were carried out and partitioning of atomic charges derived from the ChelpG algorithm were also used. A theoretical justification of red- and blue-shift effects was drawn up using charge-transfer analysis, which is manifested in the ? bonds of acetylene and ethylene to chloroform (H—CCl3) and fluoroform (H—CF3), respectively. Finally, a further debate regarding the distinct polarizability power of chloroform and fluoroform is presented, concluding that, in comparison with fluoroform, chloroform possesses the requisite features for conventional proton donors and a red-shift is therefore observed in the C2H4•••HCCl3 and C2H2•••HCCl3 complexes.

Small heterocyclics as hydrogen bond acceptors and donors: the case of the C2H3XS···NH3 complexes (X = H, F and CH3)

B3LYP/6-311++G(d,p) calculations were employed in order to examine the molecular parameters of the C2H3XS···NH3 heterocyclic hydrogen-bonded complexes with X = H, F and CH3. Intermolecular criteria were taken into account when studying the formation of these hydrogen-bonded complexes, such as geometry analysis, charge density quantification and interpretation of the harmonic vibrational spectrum, in which case the appearance of red-shift and blue-shift effects was discussed. It was assumed from the outset that many hydrogen bond types may exist in these systems, and these were investigated using the results of topological integrations from the quantum theory of atoms in molecules (QTAIM) and intermolecular charge transfer calculations using the ChelpG scheme. The proton donor/acceptor behavior of C2H3XS was interpreted in terms of hydrogen bond energies, whose values were corrected using the basis sets superposition error (BSSE) and zero point energy (ZPE).

Template-free synthesis of Cu 2O hollow nanospheres and their conversion into Cu hollow nanospheres

In this paper, Cu 2O hollow nanospheres were first generated through a template free process, and then Cu hollow nanospheres were prepared using Cu 2O hollow nanospheres as precursor and H 2 as reductant. Phase identification and morphology observation of the products were carried out by X-ray diffraction(XRD), Transmission electron microscopy (TEM) and Field scanning electron microscopy (FSEM). The results show that Cu 2O nanospheres generated at reflux are porous and hollow both in absolute alcohol and tert-butyl alcohol. It is feasible to fabricate well-dispersed Cu hollow nanospheres from Cu 2O hollow nanospheres at 170 °C. Moreover, a remarkable blue shift effect was found in the ultraviolet–visible light (UV–visible) absorption spectra for both Cu 2O and Cu hollow nanospheres.