Changes In Absorption Spectra Research Articles

Development of Neutral Red as a pH/pCO2 Luminescent Sensor for Biological Systems

Neutral Red (NR), a eurhodin dye, is often used for staining living cells, but we demonstrated for the first time that NR can also serve as a CO2 sensor, because of NR’s unique optical properties, which change with dissolved carbon dioxide (dCO2) concentrations. In the present study, optical sensitivity of NR was quantified as a function of changes in absorption and emission spectra to dCO2 in a pH 7.3 buffer medium at eight dCO2 concentrations. NR exhibited a response time of two minutes for equilibration in pure N2 to 100% CO2 with an ~200% percent change (%∆) in emission intensity and >400%∆ in absorbance, with full reversibility. Important to its application to biological systems, NR exhibited zero sensitivity to dissolved oxygen, which has routinely caused interference for CO2 measurements. NR exhibited pH sensitive emission and excitation energies with dual excitation wavelengths at 455 nm and 540 nm, and a single emission at 640 nm. The CO2 sensing properties of NR were benchmarked by a comparison to pyranine (8-hydroxypyrene-1, 3,6-trisulfonic acid trisodium salt) (HPTS). Future studies will evaluate the feasibility of NR as an intracellular in vivo pCO2 sensor in aquatic organisms critically impacted by increasing global CO2 levels.

High-field soft-x-ray dichroism of a hard ferrimagnet with easy-plane anisotropy

We performed soft x-ray spectroscopic studies of the ferrimagnet ${\mathrm{TbFe}}_{5}{\mathrm{Al}}_{7}$ with strong easy-plane anisotropy in pulsed magnetic fields up to 29 T along with bulk magnetization and magnetostriction measurements. We observed pronounced amplitude changes of x-ray magnetic circular dichroism and x-ray absorption spectra at the field-induced magnetic transition. This microscopically evidences the simultaneous rotation of the Tb $4f$ and Fe $3d$ magnetic moments from a collinear ferrimagnetic order along the [100] axis to a state with the moments close to [010], the other easy-axis direction of the tetragonal lattice in magnetic fields applied along the [100] axis. We determined the magnetic-anisotropy constant of ${\mathrm{TbFe}}_{5}{\mathrm{Al}}_{7}$ by simulating the high-field macro- and microscopic magnetization process using a two-sublattice model.

Expression and characterization of rainbow trout Oncorhynchus mykiss recombinant myoglobin

Recombinant expression system was established for rainbow trout myoglobin (Mb) considering its unique primary structure of having one unusual deletion and two cysteine residues in contrast to the other fish Mbs. The obtained recombinant Mb without His-tag showed non-cooperative thermal denaturation profile. The presence of free cysteine residue(s) in rainbow trout Mb was demonstrated by reacting with a sulfhydryl agent, 4, 4´-dithiodipyridine, which ultimately resulted in the oxidation of Mb with characteristic changes in visible absorption spectra. Besides, the recombinant Mb displayed steady peroxidase reactivity indicating in vivo roles of Mb as a reactive oxygen species scavenger. The findings of the present study indicate that the solitary rainbow trout Mb, which ultimately manifest typical secondary structure pattern and corroborate characteristic functionality, can be over expressed in recombinant system devoid of fusion tag.

Assigning Optical Absorption Transitions with Light-Induced Crystal Structures: Case Study of a Single-Crystal Nanooptomechanical Transducer

UV/vis absorption spectroscopy affords indirect structural information about the photochemistry and photophysics of molecules by inferring types of electronic transitions from spectral features. Direct structural information would become available, though, if light-induced crystal structures could be mapped against changes in optical absorption spectra as a photochemical process evolves. We present a series of light-induced crystal structures that track real-time changes in solid-state optical absorption spectra of a crystalline nanooptomechanical transducer, while the transduction process unfolds within its crystal lattice at 100 K. Results afford a combined structural and spectral mapping of its solid-state optical absorption, from which the operational mechanism of nanooptomechanical transduction is revealed. Metal-to-ligand and metal-centered charge-transfer bands are assigned to optical absorption peaks directly from their three-dimensional (3D) light-induced crystal structures. This approach could be used to characterize many solid-state optoelectronic materials.

Amelioration of disulfonated Acid Red and hexavalent chromium phytotoxic effects on Triticum aestivum using bioremediating and plant growth-promoting Klebsiella pneumoniae SK1

Bacterial strain identified as Klebsiella pneumoniae SK1, based on 16S rDNA sequence study, was isolated from a textile mill discharge point at Dada Nagar industrial area in Kanpur, India in media containing 100 µg/ml each of disulfonated azo dye Acid Red 249 (AR) and hexavalent chromium [Cr(VI)]. SK1 is efficient in the concomitant decolorization and reduction of 100 µg/ml toxic AR and Cr(VI) respectively in 48 h under microaerophilic conditions. The efficacy of AR decolorization was found to be preeminent in static conditions, 37°C, 2-4% salinity and 7-9 pH range. 99% decolorization for initial AR concentration of 100 µg/ml in 48 h, and 91% for 250 µg/ml and 77% for 500 µg/ml was recorded in 72 h respectively in the presence of 100 µg/ml Cr(VI). Significant reductive changes in spectroscopic absorption spectra were observed for SK1 treated AR+Cr(VI) amended media with respect to controls. FITR spectroscopy was used to ascertain the breakage of the azo dye bond and the formation of biodegradative metabolites. Additionally, SK1 was found to be positive for indole acetic acid, ammonia, phosphate and potassium solubilization and biofilm formation. In plant bioassay, in vitro SK1 treated AR+Cr(VI) TSB media was used to treat Triticum aestivum in the soil environment. In comparison to untreated control, plants treated with bioremediation media shows increased percent germination, root and shoot length with a complete reversal of phytotoxic effects of the AR+Cr(VI) treated plants. In this study, environmental K. pneumoniae SK1 shows concomitant azo dye and Cr(VI) remediation with plant growth-promoting activity.

A protoberberine alkaloid based ratiometric pH-responsive probe for the detection of diabetic ketoacidosis

Herein we report a ratiometric naturally occurring fluorescent pH probe, berberrubine (BBn) for the direct detection of diabetic ketoacidosis (DKA) conditions of patients having type I diabetes mellitus. The photophysical properties of the probe during pH titrations showed remarkable changes in absorption spectra where two absorption bands at 377 and 326 nm have disappeared followed by the emergence of an absorption maxima at 346 nm in highly acidic conditions. In addition, a fluorescence enhancement effect was observed in the alkaline pH, with a bathochromic shift of 33 nm. Moreover, the solution switches the color from light yellow to light pink with the change of pH from acidic to basic. A pKa value of 7.57 and a good linearity between pH 5.0–9.0 indicate that the probe can be used efficiently for the DKA condition, where pH variations are in the range of 6–7. The excellent water solubility, photostability, reversibility, and selectivity of BBn make it a potential pH sensing agent for acidic microenvironments. The reversible sensing of pH variations during DKA could be effective in primary detection and diagnosis which can assist in avoiding further complications of acidosis.

Kinetic and mechanism investigation on the gamma irradiation induced degradation of quizalofop-p-ethyl

ABSTRACT An efficient gamma radiolytic decomposition of one of the extensively used herbicides in the world quizalofo-p-ethyl (QPE) was explored under different experimental conditions. Aqueous solutions of QPE were irradiated by gamma rays emitted by a Cobalt 60 source. QPE aqueous solutions were irradiated at doses of 0.5–3 kGy with 26.31 Gy min−1 dose rate. Obtained results indicated that removal efficiency of 98.5% and 73% of QPE were obtained, respectively, in absence and in presence of dissolved oxygen. Change of absorption spectra, pH effect and Total Organic Carbon (TOC) were carried out and studied. It was found that all absorption bands decreased with increasing irradiation dose and disappear totally after 3 kGy applied dose. Three pH conditions (pH = 10, pH = 6.2 and pH = 3) were applied in radiolytic degradation of QPE showing that the best removal efficiency has been found for neutral pH. Interestingly, the % TOC removal reaches 98% at 3 kGy indicated practically total mineralization. Furthermore, spectrophotometric analyses argued in favour of a pseudo-first-order kinetic of QPE degradation. The resulting apparent rate constant value is approximately k app = (0.012 ± 0.001) min−1. Finally, several by-products such as 6-chloroquinoxalin -2-ol, 2-(4-hydroxy-phenyoxy) propionate, 1,4-hydroquinone, quinone, 4-chlorobenzene-1,2diol and 1,2,4-benzenetriol were identified by gas chromatography–mass spectrometry (GC/MS) evidencing that radiation process starting with the fragmentation of the molecule involving the hydroxyl radical, which is generated by the radiolysis of water. Based on the identification intermediates, a degradation mechanistic schema of QPE has been proposed.

Core electron spectroscopic studies for 11 iron-based superconductors

Using density functional theory (DFT)-based first principal calculations we have investigated the electron energy loss near edge spectra (ELNES) of two different iron-based superconducting material from 11 family (FeSe and FeTe). The origin of spectral features in Fe K-edge absorption spectra are thoroughly described in light of Fe/Se/Te atom projected partial density of states (PDOS). When include the “core–hole effect”, we found drastic change in absorption spectra. Our theoretically calculated results including core–hole effect agrees well with experimentally observed X-ray Absorption Near Edge Structure (XANES) data available in literature.

Publisher’s Note

Abstract Vanadium dioxide can exist in several polymorphs and among these the layered polymorph VO2 (B) with monoclinic symmetry has numerous applications. In this work, VO2 (B) phase thin film was prepared on quartz substrate via sputtering technique and its temperature dependent structural, electrical, and electronic properties were investigated. We have witnessed a broader structural phase transition around 220 K; which encounter significant changes in the lattice constants yet the monoclinic symmetry is retained over a temperature range from 100 K to 380 K. Temperature dependent resistance measurement also exhibited a semi-metal to insulator like transition near 220K displaying over 2 order of magnitude change in resistance across the transition. Small changes in the oxygen K-edge x-ray absorption spectrum were seen with change in temperature. At low temperature, an additional peak (d|| band) has emerged in the XAS spectra at energy higher than the σ* peak. The appearance of d|| band density of states is associated with the enhanced electron correlation effects driven by the localization of V–V pair's interactions at low temperature.

Role of Oxygen Vacancy Sites on the Temperature-Dependent Photoluminescence of SnO2 Nanowires

The role of oxygen vacancies in temperature-dependent photoluminescence of SnO2 nanowires was investigated by X-ray absorption spectroscopy. Two types of oxygen vacancies are present in the nanowires: at out-of-plane sites and at in-plane sites; both play crucial roles in the temperature dependence of the photoluminescence. Oxygen vacancies at in-plane sites participate in photon emission at low temperature, whereas those at out-of-plane sites result in photoluminescence at room temperature. Accordingly, the luminescence color changes from orange (630 nm, 1.93 eV) to green (515 nm, 2.4 eV) at 100 K. The color change is accompanied with a notable change in the oxygen K-edge X-ray absorption spectra. The scanning transmission X-ray microscopy results indicate that more oxygen vacancies at in-plane sites are present in the surface region than in the bulk region, whereas more oxygen vacancies at out-of-plane sites are present in the bulk region than in the surface region. Overall, the results demonstrate that oxygen-vacancy-mediated fluorescence properties of SnO2 nanowires are temperature-dependent; i.e., the photoluminescence mechanisms of the nanowires are mediated by oxygen vacancies at different sites, and the bicolor fluorescence originates from charge transfer between the states.

Dual-Responsive Thermally Activated Delayed Fluorescence of Spiropyran Derivatives

Dual-Responsive Thermally Activated Delayed Fluorescence of Spiropyran Derivatives

Controlled Fabrication and Characterization of Coronene Diimide-Based Insoluble Thin Films Produced by Photoinduced Cyclization.

An insoluble thin film of a coronene diimide (CDI) derivative was fabricated from a soluble precursor of perylene diimide (PDI) by photoirradiation. We prepared a 1,7-diarylated PDI (TP-PDI) that can be converted into a coronene diimide (TP-CDI) derivative via a Scholl-type photocyclization reaction. This reaction was accompanied by structural changes from a twisted structure to a π-extended planar molecule. It was found that this photoconversion reaction occurs for both solution-based and thin-film-based reactants investigated by the changes of UV-vis absorption spectra and 1 H NMR spectra. The photocyclization reactions were found to proceed smoothly in polar solvents. In the thin-film state, the solvent vapor annealing method is a key process for achieving photoconversion reaction. Additionally, the fabrication of multi-layered thin films was achieved without undesirable dissolution of the underlying layers because of different solubilities of TP-PDI and TP-CDI.

Beta-Substituent and Metal Effect on Their Structures and Electrochemical Properties

Three-dimensional π-conjugated molecules have received extensive attention in many chemical research areas due to their interesting structure and unique characteristics. In particular, twisted π-conjugated systems have been focused on for potential applications to solution processible organic materials. To date, numerous twisted organic molecules such as twistacenes have been synthesized. Under these situations, we found that oxidation of beta-amino substituted porphyrins provided highly twisted porphyrin dimers in excellent yield. Sequential use of amination and oxidation of 5,10,15,20-tetramesitylporphyrins afforded highly twisted porphyrin oligomers. The structures of the dimers proved dependent on substituents at porphyrin periphery. This time, we succeeded in the synthesis of beta-substituted porphyrin oligomers by using the oxidative dimerization protocol. Introduction of more bulky substituents at meso-positions on oxidation process provided the corresponding twisted porphyrin dimers with larger twisted angles. As a result, beta-substituents induced more distortion of porphyrin oligomers. In addition, electrochemical analysis revealed the distortion caused reduction of electronic communications between each porphyrin unit. We also found beta-methyl substituted porphyrin oligomer exhibited solvent-dependent and temperature dependent optical property. Theoretical calculations as well as electrochemical measurements suggested that conformational change by solvent and temperature caused change of absorption spectrum of the tetramer. Such conformational change dependent on solvent is quite rare for porphyrin oligomers and that should lead to novel stimuli-responsive porphyrin oligomers.Secondly, we also investigated the central metal effect on the electrochemical properties and structures of the dimers. The central Ni(II) metal can be readily removed by treatment of concentrated sulfonic acid. Insertion of Zn(II) and Cu(II) metals induced planarization of porphyrin planes, resulting in smaller twisting angle of the corresponding dimers. In the case of the Cu(II) complex, the presence of magnetic interactions between two porphyrin units were revealed by temperature dependent magnetic susceptibility measurements. In this presentation, we will disclose the structural characterizations of these dimers and would like to show the relationship between electrochemical properties and the conformations of porphyrin dimers. Figure 1

Efficient N2- and O2-Sensing Properties of PtSe2 With Proper Intrinsic Defects.

Developing efficient N2 and O2 gas sensors is of great importance to our daily life and industrial technology. In this work, first-principles calculations are performed to study the N2 and O2 gas-sensing properties of pure and defected PtSe2. It is found that both N2 and O2 adsorb weakly on pure PtSe2, and adsorption of the molecules induces negligible changes in the electrical and optical properties. Whereas the Pt@Se anti-site defect significantly improves the N2 adsorption capacity of PtSe2 and induces notable changes in the electrical property. Similar results are also observed for the Pt and Se vacancies and Pt@Se anti-site defects when examining O2 adsorption. In addition, notable changes in the optical absorption spectra of the PtSe2 with Pt@Se defect are induced upon N2 adsorption, which also occurs for PtSe2 with Pt and Se vacancies and Pt@Se anti-site defects upon O2 adsorption. These results demonstrate that PtSe2 with the corresponding defects can be both excellent electrical and optical sensors for detecting N2 and O2 gases. Our work offers a new avenue for preparing efficient gas sensors.

Dimeric Corrole Analogs of Chlorophyll Special Pairs.

Chlorophyll special pairs in photosynthetic reaction centers function as both exciton acceptors and primary electron donors. Although the macrocyclic natural pigments contain Mg(II), the central metal in most synthetic analogs is Zn(II). Here we report that insertion of either Al(III) or Ga(III) into an imidazole-substituted corrole affords an exceptionally robust photoactive dimer. Notably, attractive electronic interactions between dimer subunits are relatively strong, as documented by signature changes in NMR and electronic absorption spectra, as well as by cyclic voltammetry, where two well-separated reversible redox couples were observed. EPR spectra of one-electron oxidized dimers closely mimic those of native special pairs, and strong through-space interactions between corrole subunits inferred from spectroscopic and electrochemical data are further supported by crystal structure analyses (3 Å interplanar distances, 5 Å lateral shifts, and 6 Å metal to metal distances).

Reversible Isomerization of Metal Nanoclusters Induced by Intermolecular Interaction

Most inorganic nanoparticles are directly surface-terminated (and -stabilized) by protecting ligands, which could greatly affect the atomic packing and physical/chemical properties of their inorganic cores. Here, we show that the intermolecular interactions between the adsorbed molecules and surface ligands can also affect the core structure of inorganic nanoparticles. Through the coupling/decoupling of cationic surfactants (cetyltrimethylammonium cations, CTA+) and anionic surface ligands (para-mercaptobenzoic acid, p-MBA) in the aqueous phase, we have achieved a reversible transformation between two isomers of [Au25(p-MBA)18]− nanoclusters. The interconversion process between the two isomers shows the characteristics of a reversible nanocluster isomerization process, with a measured forward and backward activation barrier of 1.16 and 1.17 eV, respectively. One of the isomers has the structure similar to the single-crystal data of [Au25(SR)18]− known since 2008. The other isomer features a distinctly different optical absorption spectrum and color change (i.e., reddish brown to dark green) in the solution phase, and its structure is identified to be the one recently predicted and observed in gas phase through density functional theory (DFT) calculations. The two isomers are topologically connected via a simple rotation of the gold core without breaking any Au-S bonds at the metal-ligand interface. Molecular dynamics simulations suggest that the adsorbed CTA+ cations would interact with the p-MBA layer through the CH∙∙∙π interaction and stabilize the more open ligand shell of the new isomer in the forward isomerization process. Interestingly, this principle can also be extended to organic phases by using organo-soluble cations to stimulate the surface interactions. Our research proposes a new approach to control the structure of inorganic nanoparticles, which helps to customize their electronic and optical properties in the solution phase without changing their surface ligands.

A chromo-fluorogenic HMT sensor for Ag+ and the resultant HMT-Ag complex turn-off probe for F− in DMSO: experimental and theoretical studies

The photophysical properties of Hexamethylenetetramine (HMT) were investigated through physical methods and spectroscopically in dimethyl sulfoxide (DMSO) at ambient temperature. Evidently, HMT turned out as a sensor, selective and sensitive to silver ion (Ag+) only, among other cations, through colorimetric and fluorometric activities (observable by naked eye) and spectrally, both by UV-Vis and fluorescence spectroscopy. The resulting complex pedant (HMT-Ag) is highly responsive to the presence of fluoride ion (F−) in aqueous soluble DMSO, evidenced by changes in absorption spectra as well as fluorescence quenching, upon addition of the respective ions. Consequently, spectral changes induced by the addition of these ions, were consistently concomitant with colour changes, from colourless to light brown (HMT-Ag) to dark brown (HMT-Ag-F) in daylight condition, while bright light blue colour (HMT) to dark blue brownish (HMT-Ag) under UV-light conditions. The experimental results were complimented by theoretical studies, which are well within agreement of one another.

A Covalent Organic Framework Film for Three-State Near-Infrared Electrochromism and a Molecular Logic Gate.

A Kagome structure covalent organic framework (COF) film with three-state NIR electrochromic properties was designed and synthesized. The COFTPDA-PDA film is composed of hexagonal nanosheets with high crystallinity and has three reversible color states at different applied potentials. It has high absorption spectra changes in the NIR region, ascribed to the strong intervalence charge transfer (IVCT) interaction of the Class III mixed-valence systems of the conjugated triphenylamine species. The film showed sub-second response time (1.3 s for coloring and 0.7 s for bleaching at 1050 nm) and long retention time in the NIR region. COFTPDA-PDA film shows superior NIR electrochromic properties in term of response time and stability, attributed to the highly ordered porous structure and the π-π stacking structure of the COFTPDA-PDA architecture. The COFTPDA-PDA film was applied in mimicking a flip-flop logic gate with optical memory function.

A Covalent Organic Framework Film for Three‐State Near‐Infrared Electrochromism and a Molecular Logic Gate

AbstractA Kagome structure covalent organic framework (COF) film with three‐state NIR electrochromic properties was designed and synthesized. The COFTPDA‐PDA film is composed of hexagonal nanosheets with high crystallinity and has three reversible color states at different applied potentials. It has high absorption spectra changes in the NIR region, ascribed to the strong intervalence charge transfer (IVCT) interaction of the Class III mixed‐valence systems of the conjugated triphenylamine species. The film showed sub‐second response time (1.3 s for coloring and 0.7 s for bleaching at 1050 nm) and long retention time in the NIR region. COFTPDA‐PDA film shows superior NIR electrochromic properties in term of response time and stability, attributed to the highly ordered porous structure and the π–π stacking structure of the COFTPDA‐PDA architecture. The COFTPDA‐PDA film was applied in mimicking a flip‐flop logic gate with optical memory function.

Methods, principles and applications of optical detection of metal ios

• The optical detection methods of 12 common metal ions are reviewed. • The main principles and experimental phenomena of optical detection are summarized. • The development and advantages of optical detection methods are summarized. • The applications of optical detection method are summarized. • The future development and main challenges of optical detection are discussed. Heavy metal elements were widely used in alloy manufacturing, medical treatment, food additive, military industry and other fields, which were harmful to human body. Optical detection was a non-contact nondestructive detection method, which had the advantages of high selectivity, high sensitivity and low cost, and had important applications and prospects in environmental monitoring and biological science. In this paper, the optical detection methods, detection principles and detection methods of 12 kinds of metal ions (Ag + , Al 3+ , Cd 2+ , Co 2+ , Cr 3+ , Cu 2+ , Fe 2+ , Fe 3+ ,Hg 2+ ,Pb 2+ , Pd 2+ ,Zn 2+ ) were reviewed. Fluorescence, colorimetry and spectral change were the main detection methods. Fluorescence detection methods mainly included fluorescence quenching, fluorescence enhancement and fluorescence spectrum changes; The colorimetric method included the change of color and the change of ultraviolet absorption spectrum; The spectral changes mainly included circular dichroism, phosphorescence and surface enhanced Raman scattering, etc. Photoinduced electron transfer, intramolecular charge transfer and fluorescence resonance energy transfer were the primary principles of optical detection. The application prospect and main challenges of optical detection were discussed.