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The widely accepted viewpoint asserts that the transverse Doppler effect for plane light waves is a red shift, a purely relativistic effect caused by the time dilation or the slowing down of a moving clock. However, rigorous proof for the assertion is absent in available literature. Here, we investigated the transverse Doppler shifts for plane and spherical waves. The results show that for plane light waves, the red shift may not be a purely relativistic effect, and the true transverse Doppler effect might be a blue shift, which might mean that a moving clock can also run faster than an identical clock at rest. For spherical light waves, the transverse Doppler effect is a blue shift when a source is at the center of a rotating disk and the receiver is at its rim; on the contrary, it is a red shift. The results might not only reflect new features of special relativity but also benefit physics teaching. [ABSTRACT FROM AUTHOR]

The authors study Raman scattering and FTIR absorption spectra of pure acetylacetone and aqueous solutions of it at room temperature and atmospheric pressure. Results from experiments and calculations show that a red shift of the C=O stretching vibrational band and a blue shift of the C–H stretching vibrational band are observed when the amount of acetylacetone in a solution is reduced. The distribution of potential energy is analyzed for the monomeric molecule of the keto form of acetylacetone. The calculated and observed frequencies of vibration are in good agreement. It is shown that acetylacetone creates molecular clusters with water molecules in the form of C=O...H and C–H...O hydrogen bonds, altering the shape of the spectral bands. [ABSTRACT FROM AUTHOR]

Zinc-doped CdS nanoparticles have gained significant attention due to their tunable optical properties. Substitution of CdS with higher band gap CdxZn1-xS alloys has resulted in a reduction of the window absorption losses and an enhancement of the short circuit current. It is a potential material for solar cell applications surpassing the efficiency of pure CdS and ZnS. In our work, nanostructures of undoped and Zn-doped CdS were synthesized via the hydrothermal method with varying reaction temperatures. Structural properties were analysed using XRD patterns of the samples, which indicated the successful formation of hexagonal crystal structures of CdS nanoparticles. FESEM images further confirm these results and show the formation of CdS particles in the nano regime. Results of the optical characterization techniques, namely UV–Vis diffuse reflectance spectroscopy, suggest that in the case of Zn-doped CdS samples there is an increase in the band gap value due to the formation of CdxZn1-xS. Photoluminescence studies of the doped and undoped samples indicate a blue shift of the band edge luminescence due to Zn doping, while variation in peak positions is observed with changes in the synthesis temperatures. The intensity ratio (i.e., ratio between band edge luminescence and defect luminescence) is enhanced with an increase in synthesis temperature; this defect luminescence is attributed to the formation of CdO acceptor levels. Raman spectra of the samples show vibrational modes of the doped and undoped samples. Here, the blue shift observed is attributed to the incorporation of zinc atoms in the CdS lattice. [ABSTRACT FROM AUTHOR]

In the pursuit of creating non-absorption window (NAW) structures in high-power semiconductor laser cavities, techniques like impurity-free vacancy diffusion and rapid thermal annealing induced quantum well intermixing were employed. The challenge is to induce a desired 30 nm blue shift while safeguarding the gain-emitting region from high-temperature annealing O2− bombardment effectively inhibits quantum well mixing, as demonstrated through experiments. Epitaxial wafers subjected to this treatment exhibit just a 1 nm blue shift, compared to 32 nm without O2− bombardment. These findings provide essential insights for protecting the gain-emitting region during NAW structure fabrication. [ABSTRACT FROM AUTHOR]

In this study, the spectrophotometric studies of aqueous ethanol solution of Congo red in various buffers solutions at room temperature 25oC and at different ionic strength of 0.05, 0.1, 0.3, and 0.5 KCl mol L-1 were investigated. The acidity constants of Congo red were estimated by three different methods. The two protonation stages were observed in pH range 2 - 4 and 4 - 6 as result as protonation of amino group and azo groups. The dependence of absorption spectra of Congo red on the ionic strength of solutions which exhibited blue shift with increases ionic strength in addition the shape and intensity were varied. Therefore, the acid-base equilibria shifted toward the higher pHs with the rise in ionic strength. Also, the acidity constants were affected by the ionic strength which the acidity constants decrease with increasing ionic strength of solution because the electrostatic interaction force increased. [ABSTRACT FROM AUTHOR]

The electronic, optical and structural properties of Cs2AgXY6 (X = Bi, In; Y = Cl, Br), were investigated under external pressure (0–50 GPa) using the full potential density functional theory. In this study, the Tran–Blaha modified Becke–Johnson (TB-mBJ) functional was used to evaluate the electronic and optical properties of the double perovskites, and the GGA-PBEsol functional was used to examine the structural properties. The formation energy and tolerance factor predict the stability of these compounds. With increasing pressure, the lattice parameters and unit cell volume of these compounds decreased, resulting in a reduction in the bond length between the cations and anions. Comparatively Cs2AgInCl6 has shown a low compressibility. At zero pressure, Cs2AgInBr6 and Cs2AgInCl6 exhibit direct band gap while Cs2AgBiBr6 and Cs2AgBiCl6 has indirect band gap. Band gaps decrease with pressure. High pressure decreases peak height, shifts energy lower, and widens bandwidth in density of states. The density of states plots at zero pressure showed mixed ionic and covalent bonds, and with increasing pressure, a strengthening of covalent bonds is observed. Reflectivity/optical conductivity spectra show redshifts (Cs2AgBiBr6, Cs2AgBiCl6) and blueshifts (Cs2AgInBr6, Cs2AgInCl6). This study provides insights into double perovskite behavior under pressure, aiding material design. Additionally, our work highlights the variations in energy band gap and band structure is dependent on the choice of functional utilized. [ABSTRACT FROM AUTHOR]

Nematic chiral liquid crystals (CLCs) are characterized by a helical arrangement of nematic LC molecules. A layer of CLC typically exhibits an optical reflection band due to Bragg reflection in the helical structure. When several layers of CLC are spin-coated and polymerized on top of each other without a barrier layer in between, defect modes can form in their reflection spectrum. By comparing experimental results and simulations, we investigate the origin of the defect modes, thereby revealing details on the behavior of the materials at the interfaces during deposition. Simulations show that these defect modes can originate from the migration of chiral dopant leading to a layer with a smaller pitch or from a discontinuity in the director orientation at the interface between two layers. [ABSTRACT FROM AUTHOR]

Undoped ZnS and Ni doped ZnS with different ratios were synthesized by hydrothermal method employing ethylenediamine (EDA) as modifier. Various techniques were used to study the structural, morphological, optical, molecular and electrical properties. From X-ray diffraction (XRD), it has been confirmed that these were polycrystalline nature having cubic structures. Also from XRD, crystal size, lattice constants and growth rate enhancement with induction of Ni ions were observed. Fourier transformation infrared spectroscopy (FTIR) gave the molecular information, i.e., associated functional groups with vibration of molecules. From UV–visible spectra, we observed that the gradual increase in the optical band gap energy from 3.62 to 4.36 eV with increasing concentration of nickel dopant and the phenomena of blue shift phenomena was observed. It is evident from PL spectra that emission spectra of blue shift endured with increasing Ni concentration. Morphological image with spherical shape of nanoparticles was revealed from scanning electron microscope (SEM). Energy-dispersive X-ray analysis (EDX) confirmed the elemental Ni ratios in ZnS nanoparticles (NP). The NPs show enhanced dielectric behaviors at room temperature. The AC conductivity of ZnS NPs was studied by enhancing of Ni doping in the frequency range from 2 to 200 kHz showing semiconducting nature. [ABSTRACT FROM AUTHOR]

As an important means of modern science and technology, multiphoton fluorescence plays an essential role in high-resolution imaging, photochemistry, micro- and nano-processing and clinical diagnosis. Multiphoton fluorescence usually shares the same radiative channel as its intrinsic fluorescence. Under multiphoton excitation, except for red shift fluorescence caused by the reabsorption effect, gigantic blue shift of multiphoton fluorescence is rarely reported. In this work, metal–organic frameworks (MOFs) with 7-fold and 8-fold interpenetration are successfully synthesized. The synthesized 8-fold interpenetrated MOFs show unexpectedly giant blue-shifted (∼40 nm) two-photon–induced fluorescence compared with its fluorescence emission. Specific optical selection rules lead to different final transition states in one-photon absorption and two-photon absorption. The density functional theory (DFT) and time-dependent density functional theory (TDDFT) simulations show that, under two-photon excitation, electrons and holes can be more delocalized, and intermolecular interactions mainly govern the emission process of 8-fold interpenetrated MOFs. Highly excited electronic states of the interpenetrated MOFs are effectively excited and emitted under two-photon excitation, thus generating the inevitable blue-shifted two-photon–induced fluorescence emission. Our work provides a guide for exploring the excitation mechanism of fluorescent MOFs and offers an access to a tunable all-optical single-crystal device.

The relationship between the strength of a halogen bond (XB) and various IR and NMR spectroscopic quantities is assessed through DFT calculations. Three different Lewis acids place a Br or I atom on a phenyl ring; each is paired with a collection of N and O bases of varying electron donor power. The weakest of the XBs display a C–X bond contraction coupled with a blue shift in the associated frequency, whereas the reverse trends occur for the stronger bonds. The best correlations with the XB interaction energy are observed with the NMR shielding of the C atom directly bonded to X and the coupling constants involving the C–X bond and the C–H/F bond that lies ortho to the X substituent, but these correlations are not accurate enough for the quantitative assessment of energy. These correlations tend to improve as the Lewis acid becomes more potent, which makes for a wider range of XB strengths. [ABSTRACT FROM AUTHOR]

In this study pure and Mg, Ga, Al-doped ZnO thin films were prepared using sol–gel and spin-coating methods. The effect of dopant ion substitution on structural, morphological, optical and low temperature electrical properties of thin films were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), UV–Visible spectroscopy, spectro fluorophotometer and two probe resistivity measurement method, respectively. The XRD result confirmed the wurtzite structure of prepared thin films without the presence of any characteristic impurity peak of Mg, Ga and Al. The average crystallite size of ZnO thin film was found to be 22.17 nm which was found to decrease to 21.13 nm, 16.06 nm and 16.03 nm when Mg2+, Ga3+ and Al3+ ions substitutes Zn2+ ions, respectively. The photoluminescence study had confirmed the presence of defect states in the prepared thin films. Furthermore, the low temperature dependent electrical study had shown that Ga-doping decreased the electrical resistivity and confirmed the presence of thermally activated and hopping type conduction mechanism up to 100 K. Thus, the ability of Ga-doping to facilitate the conduction process down up to 100 K, low activation energy of 0.23 eV and high optical transmittance in Ga and Ga-Mg doped-ZnO thin films makes it a suitable transparent and conductive material for optoelectronic devices. [ABSTRACT FROM AUTHOR]

Electrostatic-spray pyrolysis of ZnSe:Eu films at different volume concentrations of europium is reported for the first time. The films were characterized for their optical, morphological and structural properties. Optical studies reveal low absorption, low reflection and high transmission within the visible region. Bandgap studies indicate a strong blue shift in comparison to bulk ZnSe. Scanning electron microscopy images of the Eu-doped zinc selenide film suggested fibre nature of ZnSe:Eu films at dopant concentration of 10%. XRD analysis shows polycrystalline nature of the ZnSe:Eu films possessing the hexagonal structure. A distortion in crystallinity was observed for high-dopant concentration (20%) for the ZnSe:Eu films. EDX analysis reveals the formation of ZnSe:Eu films. Based on the discovered properties, the ZnSe:Eu films will be appropriate for use in fibre optics communication, as an absorber for solar cell coating and also for coating optical lenses, windows and for optoelectronics applications. [ABSTRACT FROM AUTHOR]

Nematic chiral liquid crystals (CLCs) are characterized by a helical arrangement of nematic LC molecules. A layer of CLC typically exhibits an optical reflection band due to Bragg reflection in the helical structure. When several layers of CLC are spin-coated and polymerized on top of each other without a barrier layer in between, defect modes can form in their reflection spectrum. By comparing experimental results and simulations, we investigate the origin of the defect modes, thereby revealing details on the behavior of the materials at the interfaces during deposition. Simulations show that these defect modes can originate from the migration of chiral dopant leading to a layer with a smaller pitch or from a discontinuity in the director orientation at the interface between two layers.

We theoretically study the generation of attosecond XUV pulses via high-order frequency mixing (HFM) of two intense generating fields, and compare this process with the more common high-order harmonic generation (HHG) process. We calculate the macroscopic XUV signal by numerically integrating the 1D propagation equation coupled with the 3D time-dependent Schrödinger equation. We analytically find the length scales which limit the quadratic growth of the HFM macroscopic signal with propagation length. Compared to HHG these length scales are much longer for a group of HFM components, with orders defined by the frequencies of the generating fields. This results in a higher HFM macroscopic signal despite the microscopic response being lower than for HHG. In our numerical simulations in a gas target, the intensity of the HFM signal is several times higher than that for HHG, while for a plasma target the HFM generation efficiency is up to three orders of magnitude higher than for HHG. The HFM with relatively long generating pulses provides very narrow XUV lines ( $\delta \omega / \omega = 4.6 \times 10^{-4}$ ) with well-defined frequencies, thus allowing for a simple extension of optical frequency standards to the XUV range. Finally, we show that the group of HFM components effectively generated due to macroscopic effects provides a train of attosecond pulses such that the carrier-envelope phase of an individual attosecond pulse can be easily controlled by tuning the phase of one of the generating fields.

Nanocrystalline lead sulfide (PbS) thin films have been successfully deposited onto glass substrate via microwave assisted chemical bath deposition. Aqueous solutions of lead nitrate Pb(NO3) and thiourea [SC(NH2)2] were used as lead and sulfur ion sources respectively. Structural and morphological studies revealed a high synthesized nanocrystalline PbS thin films quality. Optical studies showed a significant blue shifting in the energy gap of the prepared nanocrystalline PbS thin films. Compared with bulk PbS, the prepared nanocrystalline PbS showed large energy gap, value of about 2.4 eV. This could be attributed to the confinement effect of nanocrystalline PbS thin films. The study introduced a simple and cost-effective method to further investigate other properties of nanocrystalline PbS thin films such as electrical and morphological properties.

Improving far-red light utilization could be an approach to increasing crop production under suboptimal conditions. In land plants, only a small part of far-red light can be used for photosynthesis, which is captured by the antenna proteins LHCAs of photosystem I (PSI) through the chlorophyll (Chl) pair a603 and a609. However, it is unknown how the energy level of Chls a603–a609 is fine-tuned by the local protein environment in vivo. In this study, we investigated how changing the amino acid ligand for Chl a603 in LHCA4, the most red-shifted LHCA in Arabidopsis thaliana, or one amino acid near Chl a609, affected the energy level of the resulting PSI-LHCI complexes in situ and in vitro. Substitutions of the Chl a603 ligand N99 caused a blue shift in fluorescence emission, whereas the E146Q substitution near Chl a609 expanded the emission range to the red. Purified PSI-LHCI complexes with N99 substitutions exhibited the same fluorescence emission maxima as their respective transgenic lines, while the extent of red shift in purified PSI-LHCI with the E146Q substitution was weaker than in the corresponding transgenic lines. We propose that substituting amino acids surrounding red Chls can tune their energy level higher or lower in vivo, while shifting the absorption spectrum more to the red could prove more difficult than shifting to the blue end of the spectrum. Here, we report the first in vivo exploration of changing the local protein environment on the energy level of the red Chls, providing new clues for engineering red/blue-shifted crops. [ABSTRACT FROM AUTHOR]

The sulphate radical based advanced oxidation processes (AOPs) are highly in demand these days, owing to their numerous advantages. Herein, the Fe-Mn bimetallic oxide particle was used to activate peroxymonosulphate (PMS) for Rhodamine B (RhB) degradation. Three bimetallic catalysts were synthesized via the chemical precipitation method with different concentrations of metals; Fe-Mn (1:1), Fe-Mn (1:2) and Fe-Mn (2:1). The best performance was shown by Fe-Mn (2:1) system at optimized conditions; 96% of RhB was removed at optimized conditions. Scavenging experiments displayed the clear dominance of hydroxyl radical in pH 3, while sulphate radical was present in a large amount at pH 7 and 10. The monometallic Fe and Mn oxides were also synthesized to confirm the synergistic effect that was present in the bimetallic oxide system. The application of optimized condition in real textile wastewater was conducted, which revealed the system works efficiently at high concentrations of PMS and catalyst dosage. [ABSTRACT FROM AUTHOR]

We investigated the structural and electronic energy configurations of the spinel oxide ZnGa2O4 lattice according to the crystal-phase fractions originating from substituted Eu atoms. Rietveld refinements were employed to determine the crystal structure of Eu-doped ZnGa2O4. Rietveld refinements were based on assumption of simultaneously formed three crystal phases in the normal spinel ZnGa2O4. Pure ZnGa2O4, ZnGa2O4 with Eu atoms in tetrahedral sites, and ZnGa2O4 with Eu atoms in octahedral sites were the proposed phases randomly distributed through all spinel structure. Eu atom positions in the spinel lattice were readjusted the "a" parameters from 8.3363 ± 0001 Å (for pure ZnGa2O4) to 8.3227 ± 0001 Å (for Eu atoms in tetrahedral sides) and 8.3393 ± 0001 Å (for Eu atoms in octahedral sites). Furthermore, the consequences of replacement of Eu+3 ions in octahedral side and Eu+2 ions in tetrahedral side were monitored by lowering optical emission intensity and blue shift at optical emission spectra. The blue shift was indicated by an increase in the band gap values from 4.69 ± 0.01 eV to 4.92 ± 0.01 eV. [ABSTRACT FROM AUTHOR]

A novel conjugated oligomer (Co‐imiPhenTPE) based on 4‐(1H‐imidazo[4,5‐f][1,10]phenanthroline (imiPhen) and tetraphenylethene (TPE) moieties has been synthesized. The Co‐imiPhenTPE showed Zn2+‐induced aggregation induced emission enhancement (AIEE) with high selectivity. Moreover, the Zn2+‐Co‐imiPhenTPE complex exhibited a significant blue shift from 502 nm to 393 nm (109 nm) in ethanol/water (v/v=1 : 1). The transmission electron microscopy (TEM) measurements indicated that the thin sheet porous Co‐imiPhenTPE was evenly dispersed into approximate spherical nanoparticles after the addition of Zn2+. The approach may provide insights for designing large blue‐shifted fluorescent sensors. [ABSTRACT FROM AUTHOR]

Monitoring agricultural drought via ground hyper-spectral remote sensing has always been a hot topic in the fields of agriculture and meteorology. In this study, a greenhouse experiment was conducted on wheat subjected to water stress during its different growth stages, namely tillering, jointing, and milk maturity. An instrument (HOBO ware PRO) used to continuously measure soil moisture was employed to measure the soil water content (SWC). An analytical spectral device (ASD) was utilized to obtain the spectral curve of wheat subject to different water treatment methods. The canopy temperature was obtained using thermal infrared sensors (METER SI-400). The relationships between the SWC, wheat drought stage, canopy temperature, and spectral response characteristics were elucidated. The results showed that the significant differences in spectral characteristics were due to water stress during the different growth stages of wheat. Red-edge parameters of red-valley position (RVP) and red-edge position (REP) both changed by 21 nm for the tillering-stage drought and the jointing-stage drought; however, the RVP and REP values for the milk maturity stage drought and the treatment under no water stress changed by 2 nm. Further, it was proved that the red-edge blue-shift phenomenon was affected not only by the different wheat growth processes, but also by the water stress at different growth stages. Red-edge reflectance clearly reflects wheat water stress at different growth stages. From SWC and canopy temperature analysis results, SWC and canopy temperature had a significant difference between wheat drought at different growth stages, and the canopy temperature at the jointing stage drought had the strongest change. The water index (WI) based on eleven vegetation water indexes exhibited a good performance for distinguishing wheat water stress at different growth stages. In conclusion, ground-based hyperspectral remote sensing can provide a large amount of high temporal and spectral resolution data on vegetation and its surrounding environment, making it an important technical tool for wheat drought monitoring, which has a great significance on the monitoring and early warning of wheat drought, reducing drought-related yield losses, and ensuring food security. [ABSTRACT FROM AUTHOR]

• With n-type ZnO comparison, an investigation of AlPr:123 compounds as n-type semiconductors has been reported for the first time. • Although the structure is different between AlPr:123 and ZnO, the grain and crystallite sizes are comparable with each other. • We could increase the Debye temperature, Young's modulus, q-factor, carrier density, lattice dielectric constant, energy gap, optical conductivity, and PL intensity of AlPr:123 samples to be higher than those obtained for ZnO. • These outcomes strongly recommend the AlPr:123 samples, to be better than ZnO, for plastic deformation, solar cells, light emission, supercapacitors, and high-power operation. • To best our knowledge, the present work has never been done before. With ZnO comparison, we report here an investigation of n-type semiconductors in terms of optical and photoluminescence (PL) analysis based on PrBa 2 Cu 3-3x Al 3x O y (AlPr:123) compound with (0.00 ≤ x ≤ 1.00). The structure is tetragonal of the samples with x ≤ 0.30 and changes to orthorhombic for x > 0.30, whereas it is wurtizite (hexagonal) for ZnO. As x increases to 1.00, the grain size is decreased, while the crystallite size and porosity are increased, but they are comparable with those obtained for ZnO. The Debye temperature, Young's modulus and energy gap are drastically decreased by increasing x until reach to their maximum values of 623.14 K, 952 GPa and 3.45 eV for x = 1.00 (650.39 K, 17 GPa and 3.28 eV for ZnO). The x = 0.05 has increased the carrier density to 8.06 × 10 19 (cm−3), which is about 8-times higher than of ZnO (1.07 × 10 19 (cm −3). The highest value of q-factor (3.5 × 10 5) is obtained for x = 0.00, which is about 10-tims higher than of ZnO (3 × 10 4). As x increases above 0.30, the optical conductivity is significantly increased to be greater than that of ZnO. The PL intensity of the visible emission peaks was gradually increases against x until becomes higher than that of ZnO when x = 1.00. A slight UV shift is obtained for x ≤ 0.30 samples, but it changed to blue for x ≥ 0.60, which is typically similar to ZnO. As compared to ZnO, the present samples are strongly recommended for plastic deformation, solar cell, light emission, super-capacitor and high-power operation. To the best of our knowledge, the present work has never been done elsewhere. [ABSTRACT FROM AUTHOR]

Does the weak C–H···O hydrogen bonding interaction coexist in liquid when it competes with conventional hydrogen bonding interaction? The Raman spectroscopic studies were performed for deuterated 2‐propanol/water (CD3CHOHCD3) mixture in the C‐H stretching region as a function of concentration and temperature. Combined with theoretical calculations, it is shown that both conventional O–H···O hydrogen bond and weak C–H···O hydrogen bond coexist in 2‐propanol/water solution and should be responsible for the observed C‐H blue shift in concentration‐dependent spectra. At relatively high alcohol concentrations, the O–H···O hydrogen bond plays a dominant role, whereas with the increase of water concentrations, the cooperative effect between C–H···O and O–H···O hydrogen bonds play a more significant role, responsible for continuously increased C‐H blue shift. Furthermore, the opposite temperature dependence was observed for the C‐H stretching spectra of 2‐propanol/water and methanol–water mixtures, which were explained as a result of the competition and balance between O–H···O and C–H···O hydrogen bonds at high temperature. The results not only show the role of secondary hydrogen bonds in the hydrated process of amphiphilic molecules but also demonstrate that the temperature can be used as a means of triggering and investigating weak C–H···O interaction in liquid. [ABSTRACT FROM AUTHOR]

A long persistent phosphor LiSr 4 (BO 3) 3 : Eu2+, Dy3+ shows a typical 5d–4f transition of Eu2+ under ultraviolet activation with an emission centered at 632 nm. Herein, the lattice site of Sr2+ is partially replaced with Mg2+ and Ba2+ and co-doping is performed using Eu2+ and Dy3+ to successfully synthesize several LiSr 4− x Ba x (BO 3) 3 :2% Eu2+, Dy3+ and LiSr 4− y Mg y (BO 3) 3 :2% Eu2+, Dy3+ phosphors with multicolor luminescence using a high-temperature solid-phase approach. When x or y = 0.4, the samples exhibit bright yellow or orange–red luminescence under ultraviolet (UV) excitation, with the emission spectra showing blue (611–632 nm) or red (632–648 nm) shifts, respectively. Such shifts in the peak position are ascribed to the weakened or enhanced crystal field strength. Under UV excitation, an afterglow phenomenon is also observed. The afterglow profiles can be simulated using an empirical double decay model. The LiSr 3.76 Mg 0.2 (BO 3) 3 : 2% Eu2+, Dy3+ sample exhibits the best afterglow phenomenon, which is potentially attributed to the formation of numerous electron traps with suitable trap depths after the incorporation of Mg2+ into the phosphor lattice. [ABSTRACT FROM AUTHOR]

Abstract In this work, the Cd0.9-xZn0.1BixS QDs with different compositions of Bi3+ ions (0 ≤ x ≤ 0.05) were synthesized using a facile chemical route. The prepared QDs were characterized for analyzing the structural, morphological, elemental, optical, band gap, photoluminescence and electrochemical properties. XRD results confirmed that the Cd0.9-xZn0.1BixS QDs have a cubic structure. The mean crystallite size was increased from ~ 2 to ~ 5 nm for the increase of Bi3+ ions concentration. The optical transmittance behavior was decreased with increasing Bi3+ ions. The scanning electron microscope images showed that the prepared QDs possessed agglomerated morphology and the EDAX confirmed the presence of doped elements as per stoichiometry ratio. The optical band gap was slightly blue-shifted for initial substitution (Bi3+ = 1%) of Bi3+ ions and red-shifted for further increase of Bi3+ compositions. The optical band gap was ranged between 3.76 and 4.0 eV. High intense red emission was received for Bi3+ (1%) doped Zn:CdS QDs. The red emission peaks were shifted to a higher wavelength side due to the addition of Bi3+ ions. The PL emission on UV-region was raised for Bi3+ (1%) and it was diminished. Further, a violet (422 nm) and blue (460 nm) emission were received for Bi3+ ions doping. The cyclic voltammetry analysis showed that Bi3+ (0%) possessed better electrical properties than other compositions of Bi3+ ions.

For the first time in the sixty years since the synthesis of stishovite, we report unambiguous evidence of stishovite formed in the deep Earth. A minimum pressure of about 7.5 GPa at 1000 °C is necessary for the formation of stishovite, corresponding to a depth of about 230 km. In this manuscript we report the identification of stishovite along with coesite as inclusions in mineral grains from the Waldheim granulite. This implies that the stishovite was transported upwards, probably very rapidly to a depth of about 130 km, corresponding to the highest pressure indicated by newly identified coesite in the prismatine of the Waldheim granulite, and continuing up to the depth of emplacement of the Waldheim prismatine granulite. The analysis of the Raman spectra obtained from a metastable trapped stishovite micro-crystal show that all the diagnostic Raman bands are present. However, given the metastability of the stishovite at room temperatures and pressures, this mineral breaks down step-by-step into stable polymorphs, first coesite and then quartz and cristobalite, during the Raman stimulation. The rare coesite crystals in prismatine have also resulted from the irreversible transformation from stishovite. Although the Waldheim occurrence may be unique, we suggest that Raman analysis of co-trapped crystals in similar deep-seated rocks, an area of limited previous research, may prove an important innovation in the study of mantle processes. [ABSTRACT FROM AUTHOR]

Silicon carbide nanowires (SiC NWs) were successfully synthesized using graphene and Si powder as raw materials in NaCl–NaF at 1300–1400 °C for 6 h. The synthesized SiC NWs have two crystal phases due to the presence of molten salt, which formed the 2H/3C–SiC heterojunction structure. The possible synthesis mechanism of SiC NWs is "dissolution-diffusion-reaction". Besides, photoluminescence (PL) spectra of 2H/3C–SiC heterojunction NWs show that the main emission peak has a significant blue shift, locating in 350–600 nm. The main reason is caused by the defects of 2H/3C–SiC heterojunction structure and the spontaneous polarization of 2H–SiC nano segments. [ABSTRACT FROM AUTHOR]

The blue shifting of vibrational frequencies in hydrogen bonded molecules, as observed in aqueous environments, has been attributed to local partial charge transfer from solvation. Here, we extrapolate the blue shift model to the stronger ionic interactions between hydrogen bond acceptors associated with protonation through augmented pH levels and competitive interactions with counter ion pairing. The chemical model we utilize in this work is the aqueous pyridine-pyridinium equilibrium to characterize the blue shifts observed in the pyridinium chloride ionic system. The observed agreement between observed experimental and calculated spectral shifts shows that the blue shifting model can be extrapolated to stronger interactions and accurately describe the nature of the hydrogen bond., (© 2024 Wiley-VCH GmbH.)

Incorporating coumarin nuclei into other heterocyclic scaffolds such as thienopyrimidine can significantly increase the photophysical and biological efficiency. Accordingly, we describe in this manuscript the synthesis of new heterocyclic derivatives containing combined coumarin and pyrimidine nuclei to maximize the application benefit of the target compounds. All of the synthesized derivatives were thoroughly characterized using spectral analyses such as FT‐IR, NMR, and mass spectroscopy. The photophysical properties of four compounds in solution were investigated, where the substitutions had a significant effect even when the molecule conjugation was not included. Although having similar luminescent cores, two analog compounds showed different emission colors, blue and green. Uncommonly, one derivative showed a blue shift after aggregation. DFT simulations showed that adding a terminal group can significantly alter the electronic structure or molecular packing which affected directly the luminescence behavior. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sm-doped ZnS Quantum dots was prepared using co-precipitation techniques under Ar atmosphere. • Specific capacitance was increased due to Sm-doping. • Optical transmittance and band gap was raised for Sm(2%) doped ZnS QDs. • A strong red emission was produced in IR region. Sm3+-doped ZnS quantum dots were prepared by a cost-effective, simple co-precipitation technique under an argon atmosphere. The prepared Sm3+-doped QDs exhibited a cubic structure with an average particle size of ∼ 2 nm, as confirmed through X-ray diffraction and high-resolution transmission electron microscopic investigations. The crystallite was reduced and strain produced due to the larger ionic radius of Sm3+ ions. The Sm (at. 2 %)-doped ZnS exhibited a blue shift, and the optical transmittance was enhanced. A highly intense red emission was obtained in photoluminescence investigations, and this is due to the transfer of photons from 4G 5/2 → 6H 11/2 for f-f transitions of the Sm3+ in the 4f5 configuration. The obtained photoluminescence emissions lead to red phosphor applications. The cyclic voltammogram analysis showed that adding Sm to ZnS QDs made their specific capacitance value higher and it found potential applications in supercapacitors. [ABSTRACT FROM AUTHOR]

Cylindrical whispering gallery mode (WGM) microresonators have achieved much attention in the sensing field due to high sensitivity, compatibility and integration. The excitation of spiral modes in such a resonator is unavoidable, causing the axial field distribution, and the injected analytes will undoubtedly interact with the axial mode field, resulting in unclear spectral responses. Here, these responses of the cylindrical WGM are investigated experimentally and theoretically for the first time. Using an optical fiber as the resonator, the experiment is performed by introducing the liquid into a part of the evanescent field along the axis. The perturbation is attributed to the modification of the resonator's profile, leading to an increase of the effective slope. We find the experimental demonstrations of the short-wavelength oscillations of spectral line shapes and the blue shifts of resonant wavelengths. Theoretical studies are consistent with the experimental phenomena. The research in the responses to the axial perturbation provides valuable insights into the effect of spiral modes on cylindrical WGMs and a potentially powerful tool for real-time biochemical analysis.

PbS/CdS core-shell quantum dots have been synthesized through chemical route. PbS shows polycrystalline cubic structure and CdS shows hexagonal structure. The photoluminescence study shows a blue shift of near band gap emission of core PbS when coated with shell CdS. PbS shows a band gap of 2.2 eV and CdS shows 2.7 eV whereas the PbS/CdS nanocomposite shows a reduction of band gap 1.5 eV. The observed optical properties are clearly carrying evidences of cationic exchange between the lead and cadmium ion complexes. The quantum yield of the composite is greatly enhanced implying its potential for application in optoelectronic devices.

Vision of sharks embraces various biological and ecological themes ranging from predation and adaptation to deep‐sea life. However, behavioural and genetic studies have been limited by their elusive lifestyles, repeatedly reported declines of wild populations, and their unique life‐history traits including low fecundity and enhanced longevity. Sharks have also not been actively studied on the cellular and molecular levels, because of additional difficulties in cell culture, tissue collection and genome sequencing. A recent study circumvented some of these obstacles by means of genome informatics thereby portrayed the variation of visual opsin gene repertoires among elasmobranchs (sharks and rays) and spectral shifts of the rhodopsin pigment. Comprehensive surveys in whole‐genome sequences are also revealing the repertoires of nonvisual opsins with unknown functions. This review is aimed to summarize existing studies on shark opsins with an emphasis on genomic investigation of gene repertoires and to provide insights into the better understanding of underwater ecology of marine megafauna with in vitro experimentation. [ABSTRACT FROM AUTHOR]

Facile chemical precipitation method was used to synthesize Ni (4%) doped and Co (4%): Ni (4%) co-doped CdS nanoparticles. Polyvinylpyrrolidone (PVP) was used as a surfactant to control the particles size and growth rate. The synthesized co-doped sample showed mixed structures of cubic and hexagonal which was confirmed by X-ray diffraction (XRD) study. Average crystallite size is to be 4.2 nm and 3.3 nm for Ni doped and Co:Ni co-doped CdS nanoparticles, respectively. Transmission electron microscopy (TEM) results showed spherical shape with homogeneous particle size distribution of the samples. Due to reduction the particle size, the absorption peak of co-doped CdS shows a significant blue shifting compared to the single metal ion doped CdS nanoparticles. Electron paramagnetic resonance (EPR) spectroscopy was used to study the magnetic g-factor, covalency parameter and magnetic properties of the samples. Anti-ferromagnetic magnetic signal was observed for doped and co-doped samples using Vibrating Sample Magnetometer (VSM) at room temperature. Thermal stability and lattice deformation of the samples were studied using Thermo Gravimetric–Differential Thermal Analysis (TG–DTA). The obtained room temperature based magnetic properties of CdS:Co:Ni nanoparticles demonstrate it could be suitable for spintronic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

Trichostatin A (TSA), a potential radiomitigator in pre-clinical models, inhibits the class I and II mammalian histone deacetylase (HDAC) enzyme family preferentially. In the current study, the ADME assessment of TSA was explored in terms of its binding affinity for serum protein via spectroscopic and molecular docking techniques. Fluorescence spectroscopy was used to examine changes in the protein microenvironment, and affinity was quantified in terms of binding constant and stoichiometry. Post binding conformational changes were observed using circular dichroism (CD) and UV-Visible spectroscopy. Specific binding was visualized using molecular docking to support experimental studies. UV-vis spectra demonstrated a blue shift in the interaction of TSA to BSA. The calculated binding constants ranged from 3.10 to 0.78 x 10 5 (M -1 ) and quenching constants from 2.75 to 2.15 x 10 4 (l mol-1), indicating TSA has a strong binding affinity for BSA. Based on the FRET theory, the distance between BSA (donor) and TSA (acceptor) was calculated to be 2.83 nm. The Stern-Volmer plot revealed (Ksv) static quenching. Thermodynamic parameters were calculated, and a negative ΔG value showed that the interaction is spontaneous. The CD spectra analysis further revealed a change in the protein's secondary structure, indicating TSA-BSA interaction. The molecular docking studies also indicated strong binding affinity of TSA with BSA. The results indicate that good bio-availability of TSA is possible because of the spontaneous and strong binding affinity with BSA.Communicated by Ramaswamy H. Sarma.

The surface plasmon resonance wavelength in a gold film above silver nanospheres on a silica substrate was measured using transmission absorption spectroscopy. The structure, surface morphology, and optical properties of the gold/silver nanosphere thin films were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), UV-VIS-NIR double beam spectrometry, and Raman spectroscopy, respectively. The silver nanospheres were fabricated by simple thermal annealing. A gold film with thickness ranging from 2 to 50 nm on top of the silver nanospheres exhibits a blue-shift in the resonance wavelength from 590 to 510 nm. Surface-enhanced Raman scattering (SERS) is also reported in this paper. Additionally, finite-difference time-domain (FDTD) simulations were used to describe surface plasmon resonance in the samples, and the numerical results were consistent with experimental results.

The surface of gold nanorods is chemically charged by ascorbic acid; the charging effect results in not only the blue shift on their surface plasmon bands, but also the change of the deposition rate of silver on their surfaces. The rate was prominently accelerated at room temperature, but slightly slowed down at higher temperature. The shape of gold‐silver core‐shell nanoparticles could not be obviously affected. The Fermi level of gold nanorods begins to increase under the action of charging and alters the electrical double‐layer structure of gold nanorods, resulting in the different deposition rate of silver on gold. [ABSTRACT FROM AUTHOR]

We experimentally measured the femtosecond pulse transmission through a silicon-on-insulator (SOI) nanowire waveguide under different temperatures and input pulse energy with a cross-correlation frequency-resolved optical gating (XFROG) measurement setup. The experimental results demonstrated that the temperature and pulse energy dependence of the Si photonic nanowire waveguide (SPNW) is interesting rather than just monotonous or linear, and that the suitable temperature and pulse-energy range is as suggested in this experiment, which will be valuable for analyzing the practical design of the operating regimes and the fine dispersion engineering of various ultrafast photonic applications based on the SPNWs. The research results will contribute to developing the SPNWs with photonic elements and networks compatible with mature complementary metal–oxide–semiconductors (CMOS). [ABSTRACT FROM AUTHOR]

The green InGaN/GaN micro light-emitting diode (Micro-LED) is a significant component in micro-display whereas lack of size dependence and high injected current analysis. In this letter, different size Micro-LEDs were fabricated and the electro-optical characteristics were measured. The size-dependence phenomenon for EQE “efficiency droop”, luminous flux and brightness were observed and discussed. All sizes Micro-LEDs exhibited an extremely high brightness as 37.5k and 67.6k nits at 1 A/cm2, 2.89M and 3.81M nits at 300 A/cm2 for 25 and $200~\mu \text{m}$ respectively. In addition, the elevating current densities from 160 to 6400 A/cm2 were injected into $25~\mu \text{m}$ Micro-LED and the electroluminescence (EL) spectra transformation of different current densities were depicted. The green to blue shift and secondary peak effect, which promise an opportunity to modulate the emission wavelength for higher quality and lower the barrier of mass transfer technology, were observed and analyzed through the spectra. [ABSTRACT FROM AUTHOR]

The layered van der Waals magnetic insulator chromium bromine (CrBr3) has excellent optical properties and it provides an interesting platform for investigating light–matter interactions. Here, we focused on its self‐modulated photoluminescence (PL) spectrum. We find that there are interference fringes superposed on the PL curves due to the Fabry–Perot resonance between the front and rear interfaces of CrBr3 flakes. Moreover, there is a huge Stokes shift between the PL spectrum and lowest absorption band, which can prevent reabsorption of PL and is a benefit for enhancing the resonant intensity of the PL spectrum. In addition, we investigate the PL spectrum variation under suppressing thermal vibration with decreasing temperature from 300 to 80 K, which shows the significant increase of PL intensity and blue shift of PL maximum peak. This work gives details of CrBr3 self‐modulated PL properties and creates opportunities for using CrBr3 in optical devices and lasing components in future applications. [ABSTRACT FROM AUTHOR]