Obvious Spectral Changes Research Articles

Passively Q-switched modulation based on antimonene in erbium-doped fiber laser with a long term stability

Antimonene, as a novel two-dimensional material, has received extensive attention in recent years. It has similar properties to most semiconductor materials and has many other materials unmatched characteristics. Herein, we prepare antimonene nanosheets by the liquid-phase exfoliation method, and fabricate antimonene-based saturable absorbers (SA) according to their saturable absorption characteristics and successfully apply them in fiber lasers to achieve stable passively Q-switched output with a center wavelength of 1558 nm. The saturation intensity of antimonene-based SA is 1.52 MW/cm 2 , and the modulation depth is 11.63% in our experiment. The pulse duration is varied from 5.10 μs to 1.42 μs, and the repetition frequency is changed from 25.6 kHz to 124.1 kHz, with the pump power from 81 mW to 445 mW in the passively Q-switched operation. The experimental results fully reveal the huge potential and nonlinear optical properties of antimonene used in pulsed fiber lasers and expand the scope of new optical applications. • Successfully employed Sb-SA in erbium-doped fiber lasers based on its saturated absorption characteristics. • The Q-switched pulse with a center wavelength of 1558 nm and pulse duration of 1.42 μs was realized. • The Q-switched output pulse has long-term stability without obvious spectral changes and intensity fluctuations.

An amphiphilic B,O-chelated aza-BODIPY dye: synthesis, pH-sensitivity, and aggregation behaviour in a H2O/DMSO mixed solvent.

A novel amphiphilic B,O-chelated azadipyrromethene (aza-BODIPY) dye, containing hydrophobic dodecyloxy groups and hydrophilic tetraethylene glycol (TEG) chains, was synthesized and characterized by NMR, HRMS, Vis/NIR absorption and fluorescence spectroscopy. The B,O-chelated dye 1 exhibited largely bathochromically shifted NIR absorption and fluorescence spectra in comparison with common BF2-chelated aza-BODIPY dyes. Upon gradual addition of trifluoroacetic acid (TFA) to the dye 1 solution, obvious spectral changes were observed in Vis/NIR absorption and fluorescence spectroscopy measurements. Meanwhile, the colour change of the dye 1 solution from pink to blue was noticeable by the naked eye, indicating the pH-sensitivity of dye 1. The pH-sensitivity of dye 1 under acidic conditions could be ascribed to the formation of dye species 2·H+. Furthermore, owing to the amphiphilic feature of dye 1, it self-assembled into J-type aggregates in a mixed solvent of water/DMSO (2/8, v/v). Temperature-dependent Vis/NIR spectroscopic studies revealed a cooperative aggregation process of dye 1 and a nanowire-like morphology of the nanoaggregates was observed by AFM.

Transition-metal redox evolution and its effect on thermal stability of LiNi Co Mn O2 based on synchrotron soft X-ray absorption spectroscopy

The correlations between electronic structure evolution and thermal stability of layered LiNi x Co y Mn z O 2 cathodes are investigated systematically based on the synchrotron soft X-ray absorption spectroscopy and micro-calorimetry. Based on the synchrotron soft X-ray absorption spectroscopy experiments, the fundamental electronic structures of layered LiNi x Co y Mn z O 2 (NCM) are investigated systematically and the data of transition-metal (TM) L - and O K -edges spectra are collected. Distribution of Ni ions under different oxidation states is evaluated according to linear combination fit. It is found that the ratio of Ni 4+ expands with the increase of Ni since it dominates in charge compensation during charging, and that the existence of Ni 3+ is nearly negligible in delithiated NCM. The valence state of Co also strongly depends on Ni content, the perceptible position shift of Co L 3 -edge absorption peak towards higher energy in Ni-rich material agrees well with the small voltage plateau at around 4.2 V. The stability of Mn is verified as no obvious spectral change with the Mn L -edge is observed. Moreover, as Ni content rises, the O 2 p holes near the Femi level increases with higher oxidation state of Ni, indicating the enhanced hybridization of O 2 p -TM 3 d . Delithiated NCMs with higher Ni content are prior to lose electron existing in highly hybridized Ni 3 d -O 2 p bands upon heating, which accounts for the pronounced O 2 release in phase transitions and the deterioration in thermal stability. These detailed observation of the electronic structure evolution is one of the key ingredients to improving the electrochemical and thermal performance of NCM.

A reaction-based sensing scheme for volatile organic amine reagents with the chromophoric-fluorogenic dual mode.

In this study, we present the classical Michael's addition reaction-based sensing scheme for volatile organic amine reagents such as ethylenediamine, N, N-dimethylethylenediamine and diethylenetriamine using a near-infrared fluorescent dye TCF1. Obvious spectral changes in the UV-vis absorption and fluorescence spectra of TCF1 were observed upon addition of these amine reagents with an effective catalyst DBU, resulting in significant and fast color changes detectable by the naked-eye. TCF1 showed an efficient response to these amine reagents with a low detection limit, especially for diethylenetriamine. NMR and MS spectral analysis proved that the mechanism of the detection was based on the classical Michael addition, which was also verified by the theoretical calculations. In addition, a portable test paper incorporated with TCF1 had also successfully realized the detection of a low concentration of these amine reagents.

The In Situ Tryptophan Analogue Probes the Conformational Dynamics in Asparaginase Isozymes

Dynamic water solvation is crucial to protein conformational reorganization and hence to protein structure and functionality. We report here the characterization of water dynamics on the L-asparaginase structural homology isozymes L-asparaginases I (AnsA) and II (AnsB), which are shown via fluorescence spectroscopy and dynamics in combination with molecular dynamics simulation to have distinct catalytic activity. By use of the tryptophan (Trp) analog probe 2,7-diaza-tryptophan ((2,7-aza)Trp), which exhibits unique water-catalyzed proton-transfer properties, AnsA and AnsB are shown to have drastically different local water environments surrounding the single Trp. In AnsA, (2,7-aza)Trp exhibits prominent green N(7)-H emission resulting from water-catalyzed excited-state proton transfer. In stark contrast, the N(7)-H emission is virtually absent in AnsB, which supports a water-accessible and a water-scant environment in the proximity of Trp for AnsA and AnsB, respectively. In addition, careful analysis of the emission spectra and corresponding relaxation dynamics, together with the results of molecular dynamics simulations, led us to propose two structural states associated with the rearrangement of the hydrogen-bond network in the vicinity of Trp for the two Ans. The water molecules revealed in the proximity of the Trp residue have semiquantitative correlation with the observed emission spectral variations of (2,7-aza)Trp between AnsA and AnsB. Titration of aspartate, a competitive inhibitor of Ans, revealed an increase in N(7)-H emission intensity in AnsA but no obvious spectral changes in AnsB. The changes in the emission profiles reflect the modulation of structural states by locally confined environment and trapped-water collective motions.

Supramolecular assembly and nanostructures of a series of luminol derivatives with aromatic/alkyl substituted groups in Langmuir-Blodgett films.

A series of functional luminol derivatives with aromatic and alkyl substituted groups has been designed and synthesized from the reaction of the corresponding chloride precursors with luminol. These compounds can be spread on water surface to form stable Langmuir films at the air-water interface. It has been found that UV and IR spectra confirmed the characteristic aromatic segment, imide group, and aromatic/alkyl substituted groups. In addition, for the interfacial assembly process of compounds with alkyl substituted groups, there are obvious spectral changes for the alkyl chains. AFM results indicated that various different aggregated domains may be fabricated in the transferred LB films. For all cases, the substituted groups in molecular structures have an important effect in regulating the aggregation mode and spectral changes in organized molecular films. The present results showed that the modified luminol derivatives may have potential application in functional material fields such as ECL sensor, which may give some insight to study the relationship between the molecular structures and supramolecular aggregation of amphiphiles in organized molecular films.

Research on LB Films of Two Schiff Base Compounds with Alkyl Chains and Different Azobenzene Substituted Groups

In order to investigate the supramolecular assembly and interfacial coordination of special amphiphile, two Schiff Base compounds with alkyl chains and different azobenzene substituted groups were designed and synthesized, and their supramolecular assembly and interfacial properties were investigated by spectral and morphological measurements. It was found that the Schiff base compounds can be spread on water surface to form stable monolayer. When on the Cu(II) ions subphase, an in situ coordination can occur for all ligands. In addition, for the coordination process of C16SB-Me-Azo with Cu(II), there are obvious spectral changes for the alkyl chains. For all process, the headgroups in all amphiphiles have predominant effect in regulating the aggregation mode and spectral changes in organized molecular films.

New applications of ruthenium solar cell sensitizers N3 and N719 as luminescence turn-on anion sensors

Optical sensing of F −, Cl −, Br −, I −, OAc −, H 2 PO 4 - , NO 3 - , and ClO 4 - by cis-dithiocyanatobis(2,2′-bipyridyl-4,4′-dicarboxylic acid)ruthenium(II) ( N3) and bis(tetrabutylammonium) cis-dithiocyanatobis(2,2′-bipyridine-4-COOH,4′-COO −)ruthenium(II) ( N719) have been investigated in dimethyl sulfoxide (DMSO), by means of UV–Vis absorption and emission spectrophotometric titrations. Additions of F −, OAc −, and H 2 PO 4 - in DMSO solution caused obvious UV–Vis spectral changes with appearance of several isosbestic points, and remarkable emission enhancements along with large blue shifts in emission bands. The values of F −-induced emission intensity enhancement factor (emission quantum yield enhancement factor), I/ I 0 ( φ/ φ 0), were found to be 40 (86) and 38 (58) for N3 and N719, respectively. No obvious spectral changes were observed upon addition of Cl −, Br −, I −, NO 3 - and ClO 4 - in DMSO solutions. Luminescent F − sensing in DMSO/H 2O (4:1, v/v) has also been demonstrated to be operative with a luminescence enhancement factor of 12, indicating that N3 is very potential for practical application as fluorescent anion sensor in aqueous solution. An interaction mechanism of anion-induced deprotonation of N3 and N719 was confirmed, and the deprotonation reaction equilibrium constants of N3 and N719 were derived as well.

PLANETARY NEBULAE IN FACE-ON SPIRAL GALAXIES. II. PLANETARY NEBULA SPECTROSCOPY

As the second step in our investigation of the mass-to-light ratio of spiral disks, we present the results of a spectroscopic survey of planetary nebulae (PNe) in five nearby, low-inclination galaxies: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), and M101 (NGC 5457). Using 50 setups of the WIYN/Hydra and Blanco/Hydra spectrographs, and 25 observations with the Hobby-Eberly Telescope's Medium Resolution Spectrograph, we determine the radial velocities of 99, 102, 162, 127, and 48 PNe, respectively, to a precision better than 15 km/s. Although the main purpose of this data set is to facilitate dynamical mass measurements throughout the inner and outer disks of large spiral galaxies, our spectroscopy has other uses as well. Here, we co-add these spectra to show that to first order, the [O III] and Balmer line ratios of planetary nebulae vary little over the top ~1.5 mag of the planetary nebula luminosity function. The only obvious spectral change occurs with [N II], which increases in strength as one proceeds down the luminosity function. We also show that typical [O III]-bright planetaries have E(B-V) ~ 0.2 of circumstellar extinction, and that this value is virtually independent of [O III] luminosity. We discuss the implications this has for understanding the population of PN progenitors.

Functionalized Rhenium(I) Complexes with Crown Ether Pendants Derived from 1,10-Phenanthroline: Selective Sensing for Metal Ions

A series of rhenium(I) tricarbonyl diimine complexes with crown ether pendants has been synthesized and characterized. The complexes showed selective and specific binding properties for various metal ions of different sizes and degrees of hardness and softness by variation of the cavity size and donor atoms of the crown ether. Upon binding of metal ions, obvious spectral changes were observed in the UV−vis spectra of the complexes and the emission intensity was found to be strongly enhanced. The X-ray crystal structure of one of the complexes has also been determined.

Diffuse reflectance spectroscopy of tetravalent neptunium and plutonium ions in ThO 2

Near infrared (4000–12 000 cm −1) absorption spectra of Pu 4+ and Np 4+ dilutely incorporated in air-fired polycrystalline ThO 2 were collected at ambient temperature and showed several well-defined absorption bands having widths of a few hundred cm −1. These bands are ascribed to f–f single-ion electronic transitions and increase in intensity with Np and Pu concentration up to 0.03 formula units (f.u.). Reheating samples in H 2/N 2 atmosphere at 1400 °C did not produce obvious spectral change for Np-doped ThO 2 and therefore no evidence of the formation of Np 3+. However, the spectral lines attributed to Pu 4+ decreased by approximately a factor of six in intensity, which implies reduction of Pu 4+ to Pu 3+.

Classification of normal and malignant human gastric mucosa tissue with confocal Raman microspectroscopy and wavelet analysis

Thirty-two samples from the human gastric mucosa tissue, including 13 normal and 19 malignant tissue samples were measured by confocal Raman microspectroscopy. The low signal-to-background ratio spectra from human gastric mucosa tissues were obtained by this technique without any sample preparation. Raman spectral interferences include a broad featureless sloping background due to fluorescence and noise. They mask most Raman spectral feature and lead to problems with precision and quantitation of the original spectral information. A preprocessed algorithm based on wavelet analysis was used to reduce noise and eliminate background/baseline of Raman spectra. Comparing preprocessed spectra of malignant gastric mucosa tissues with those of counterpart normal ones, there were obvious spectral changes, including intensity increase at ∼1156 cm −1 and intensity decrease at ∼1587 cm −1. The quantitative criterion based upon the intensity ratio of the ∼1156 and ∼1587 cm −1 was extracted for classification of the normal and malignant gastric mucosa tissue samples. This could result in a new diagnostic method, which would assist the early diagnosis of gastric cancer.

Screening of gastric carcinoma cells in the human malignant gastric mucosa by confocal Raman microspectroscopy

Confocal Raman microspectroscopy was used to characterize gastric carcinoma cell in both cultured cells and human gastric mucosa tissues. Based on the spectra of single cultured cell, gastric carcinoma cells were screened out in the malignant gastric mucosa successfully and the positive ratio is about 58.06%. The high SNR (signal-to-noise) spectra from human gastric mucosa tissues and cells were obtained by this technique without any sample preparation and the time of detection required less than 3 min. Comparing spectra of malignant gastric mucosa tissues with those of counterpart normal ones, there were obvious spectral changes, including intensity decrease at ∼1587 cm −1 and alteration of peak shape at ∼1660 cm −1 with malignancy. Additionally, spectral features of single cell also differed from those of stomach tissues at ∼1525 and ∼1156 cm −1 where these two bands were assigned to carotenoids. These results demonstrate the possibility of a rapid clinical diagnosis of gastric carcinoma with Raman microspectroscopy in combination with a remote optical probe.

Absorption and emission of ErNbO4 powder

Abstract Visible and near infrared absorption and emission (488 nm excitation) characteristics of ErNbO4 powder, which were prepared by calcining the Er2O3 (50 mol%) and Nb2O5 (50 mol%) powder mixture at 1100 and 1600 °C for different durations, have been investigated at room temperature. The absorption and emission characteristics of these calcined ErNbO4 powder were summarized and discussed in comparison with those of Er2O3. Weak emission of Er2O3 relative to the calcined ErNbO4 is mainly conducted with absorption difference at the excitation wavelength 488 nm. The obvious spectral changes from Er2O3 to calcined ErNbO4 samples are related to an elevated-temperature-assisted phase transformation according to the solid-state chemical reaction equation: Er2O3 + Nb2O5 ⇌ 2ErNbO4, which results in the changes of the ion environment of Er3+ and hence changes of the Stark levels of Er3+. The further spectral change as the strengthened calcination results from the improvement of ErNbO4 purity in the calcined mixture. The borders between two green transitions and between two near infrared transitions in the emission spectra of both calcined samples and Er2O3 were tentatively identified by referencing earlier reported emission spectra of the precipitated Z-cut VTE Er(2.0 mol%):LiNbO3 crystal and the match relation between absorption and emission spectra of the ErNbO4 powder. A comparison was performed on the spectra of calcined ErNbO4 powder and those of VTE Er(2.0 mol%):LiNbO3 crystals. The results allow to preliminarily deem the contribution of ErNbO4 precipitates, generated inside these crystals by the VTE procedure, to the spectra of these crystals.

In-situ spectrocyclic voltammetry investigations of the formation of a water oxidation catalyst [(bpy) 2(H 2O)RuORu(H 2O)(bpy) 2] 4+ at a Nafion®-coated electrode

The monomeric ruthenium complex cis-[Ru(bpy) 2(H 2O) 2] 2+ was adsorbed into a Nafion® film coated onto an indium tin oxide (ITO) electrode. In-situ spectrocyclic voltammetric investigations under different pH conditions showed that the monomeric complex in the Nafion film dimerizes upon oxidation, with obvious spectral changes, to yield the corresponding oxo-bridged complex [(bpy) 2(H 2O)RuORu(H 2O)(bpy) 2] 4+ which is a water oxidation catalyst. The reversible formation of the dimer and monomer during oxidation and reduction of the corresponding complexes at appropriate potentials was established by in-situ spectrocyclic voltammetry at a Nafion-film-coated ITO electrode.

The reaction of ethanol with an aluminum oxide surface studied by inelastic electron tunneling spectroscopy

Inelastic electron tunneling spectroscopy (IETS) has been employed to study the vibrational structure of ethanol reacting with a clean alumina surface as a function of temperature from 295 to 575 K. The spectra for the surface species up to approximately 450 K correspond to infrared spectra of aluminum ethoxide, Al(OC2H5)3. Between 450 and 475 K the structure changes from an ethoxide to an acetate, the most obvious spectral change being the appearance of a new peak at approximately 1585 cm−1 (197 meV) which is characteristic of the asymmetric OCO stretching mode of various inorganic acetates. No further changes are observed above 475 K. Above 370 K, there is also a significant increase in the total concentration of adsorbed species. This is due to a partial dehydration or dehydroxylation of the surface, thus freeing active sites which had previously been blocked by water or hydroxyl groups formed during the initial stages of ethanol adsorption. This dehydration or dehydroxylation of the surface is simultaneously accompanied by a transformation of the bulk aluminum oxide to aluminum hydroxide. While IETS has been applied successfully in the past to study a wide variety of adsorbate–adsorbent systems, here tunneling spectroscopy is demonstrated explicitly to be effective in monitoring quantitatively the structural changes occurring in a reacting system at low pressures as a function of temperature.