Near-infrared Absorption Spectra Research Articles

Physical, optical and spectral properties of Sm3+ and Eu3+ ions doped zinc boro-phosphate glass

This study focuses on the synthesis of Sm³⁺ and Eu³⁺ rare earth ions doped zinc boro-phosphate glasses and their physical, optical and spectral characterization. Photoluminescence was carried out through both steady-state and time-domain luminescence measurements. The glasses were prepared via the melt quenching technique, and they exhibit impressive mechanical strength and transparency. Judd-Ofelt analysis of the near-infrared absorption spectra revealed parameters Ω₂, Ω₄, and Ω₆, indicating low covalency and reduced site asymmetry for the rare earth ions compared to those in silicate-based glasses. When excited with violet light, the Sm³⁺-doped samples emitted bright orange luminescence, resulting from radiative relaxation from the ⁴G₅/₂ state to lower energy levels. The calculated branching ratios correspond well with the observed emission peak ratios. However, increasing the Sm³⁺ ion concentration resulted in reduced luminescence intensity and shorter fluorescence lifetimes, due to cross-relaxation effects. In the Sm³⁺/Eu³⁺ co-doped glasses, energy transfer from Sm³⁺ to Eu³⁺ ions was detected upon selective excitation of Sm³⁺ ions. This energy transfer efficiency was found to increase with higher concentrations of Eu³⁺ ions.

Determination of leaf nitrogen content in apple and jujube by near-infrared spectroscopy

The nitrogen content of apple leaves and jujube leaves is an important index to judge the growth and development of apple trees and jujube trees to a certain extent. The prediction performance of the two samples was compared between different models for leaf nitrogen content, respectively. The near-infrared absorption spectra of 287 apple leaf samples and 192 jujube leaf samples were collected. After eliminating the outliers by Mahalanobis distance method, the remaining spectral data were processed by six different preprocessing methods. BP neural network (BP), random forest regression (RF), least partial squares (PLS), K-Nearest Neighbor (KNN), and support vector regression (SVR) were compared to establish prediction models of nitrogen content in apple leaves and jujube leaves. The results showed that the determination coefficient (R2), root mean square error (RMSE) and residual prediction deviation (RPD) of the models established by different combined pretreatment methods were compared among the five methods. Compared with the performance of the other four models, the modeling method of SG + SD + CARS + RF was suitable for the prediction of nitrogen content in apple leaves, and its modeling set R2 was 0.85408, RMSE was 0.082188, and RPD was 2.5864. The validation set R2 is 0.75527, RMSE is 0.099028, RPD is 2.1956. The modeling method of FD + CARS + PLS was suitable for the prediction of nitrogen content in jujube leaves. The modeling set R2 was 0.7954, RMSE was 0.14558, and RPD was 2.4264; the validation set R2 is 0.81348, RMSE is 0.089217, and RPD is 2.4552.In the prediction modeling of apple leaf nitrogen content in the characteristic band, the model quality of RF was better than the other four prediction models. The model quality of PLS in predictive modeling of nitrogen content of jujube leaves in characteristic bands is superior to the other four predictive models, These results provide a reference for the use of near-infrared spectroscopy to determine whether apple trees and jujube trees are deficient in nutrients.

Photoelectric properties of the semiconductor Bi2YbO4Cl with broad spectral response

Bi2YbO4Cl with a fluorite layer structure belongs to the family of the bismuth rare-earth oxyhalides Bi2REO4X (X=Cl, Br, I). However, the synthesis and photoelectric properties of Bi2YbO4Cl have almost not been reported. In this work, Bi2YbO4Cl was synthesized using the solid-state method and the solvothermal method. Yb3+ ions show a strong characteristic absorption peak at 980 nm, which was measured by ultraviolet–visible–near-infrared absorption spectra. The transient photoconductivity of Bi2YbO4Cl was obtained by time-resolved terahertz spectroscopy system under 400 and 800 nm laser excitations, respectively. The frequency-dependent transient photoconductivity analysis reveals the Drude-Smith behavior in Bi2YbO4Cl. Under photoexcitation, the hot charge carriers with a long relaxation lifetime and a carrier mobility of 48 cm2/(V·s) are obtained. The synthesis of Bi2YbO4Cl is of great significance for the development of novel photocatalytic and photoharvesting materials with broad spectral response.

Deciphering the Nd3+ environment and energy-transfer mechanisms in thermally stable novel calcium aluminate glasses: elucidation of broadband high-gain performance for laser applications

Rare-earth-doped barium calcium aluminate (BCA) glasses, having extended infrared (IR) transmission (6 μm), are attractive materials for near IR (NIR) photonic applications. Nd2O3-doped BCA glasses display broadband emission at 1.07 µm, but they are limited, with poor glass-forming ability (GFA) and low emission cross sections. In the present study, four different barium zinc calcium aluminate (BZCA) glasses are synthesized with varied ZnO concentrations (from 9.5 to 24.5 mol%) and doped with 0.5 mol% Nd2O3 to decipher the effect on GFA and spectroscopic properties. The addition of ZnO enhances the GFA, and the NdBZCA20 glass shows the maximum GFA. Ultraviolet (UV)–visible (Vis)–NIR absorption spectra reveal a decreasing trend in the nephelauxetic effect, while J–O parameters, emission, and gain properties lead to no significant alteration with increasing ZnO, and the structure–properties correlation is established accordingly. However, the emission cross sections for all ZnO concentrations are found ∼4.5 × 10−20 cm2 accompanied by broadband emission (Δλ eff ∼ 40 nm), which ensures the potentiality of these glasses for low-threshold high-gain laser applications as well as ultrashort pulse laser applications. Furthermore, a thorough analysis of 1.06 µm emission as a function of Nd concentration in the BZCA20 glass is reported here. The emission spectra and decay time indicate that 0.5 mol% is the optimized doping concentration. Inokuti–Hirayama and Burshtein equations are adopted to study the decay kinetics and energy-transfer mechanisms, which confirm that the energy-transfer process due to cross-relaxation is dominant up to 0.5 mol% concentration, whereas, beyond that concentration, excitation energy migration via the hopping mechanism supersedes.

Development of near-infrared spectroscopy (NIRS) for estimating organic matter, total carbon, and total nitrogen in agricultural soil

The analysis of soil organic matter (OM), total carbon (TC), and total nitrogen (TN) using traditional methods is quite time-consuming and involves the use of hazardous chemical reagents. Absorbance spectroscopy, especially near-infrared (NIR), is becoming more popular for soil analysis. This method requires little sample preparation, no chemicals, and a single spectral analysis to evaluate soil properties. Thus, this research aimed to develop an NIR spectroscopy method for the analysis of OM, TC, and TN in agricultural soils. These findings can provide a good concept of using PLS regression with NIR techniques. The method is as follows:•Topsoil (0–20 cm) samples were collected from various agricultural fields. OM, TC, and TN were analyzed using traditional methods and NIR spectroscopy.•NIR spectra were obtained using an FT-NIR spectrometer, original spectral including with Savitzky–Golay smoothing, standard normal variate (SNV) and multiplicative scatter correction (MSC) preprocessing method were used to create a predicted model through Partial Least Squares (PLS) regression with 65 % calibration, and the rest 35 % for validation.•The results showed significant relationships between measured soil properties (SOM and TC) and NIR absorbance spectra in agricultural soil (R2 of calibration and validation higher than 0.80).

DC-driven subatmospheric glow discharges in the infrared-stimulated

This paper presents a conceptual framework for experimental research combined with numerical analysis on direct current (DC) glow discharges in microscale planar gas discharge-semiconductor systems (GDSS). In the experimental section, several structural and elemental analyses, including SEM, EDAX, AFM, and near-infrared absorption spectra measurements were carried out for compound semiconductor zinc selenide (ZnSe) cathode sample. Argon (Ar) was charged into the plasma reactor cell of GDSS at pressures of 100 Torr subatmospheric and 760 Torr atmospheric, respectively, by a vacuum pump- gas filling station. Glow discharge light emissions from plasma, excited under three different intensity levels (dark, weak, strong) of infrared beam illumination on ZnSe cathode electrode, were measured by using a phomultiplier tube that is sensitive to UV–Visible wavelengths. In the numerical analysis section, simulation studies were carried out on the two-dimensional gas discharge-semiconductor microplasma system (GDSµPS) cell models using the finite-element method (FEM) solver COMSOL Multiphysics DC plasma program. Calculations and predictions were based on mixture-averaged diffusion drift theory and Maxwellian electron energy distribution function. GDSµPS cell was modeled in a square chamber with planar anode/cathode electrode pair coupled at a 50 μm discharge gap. Single side of ZnSe cathode was finely micro-digitated to increase the effective surface area for enhanced electron emission to the gas discharge cell. The electrical equivalent circuit (EEC) of the proposed model was driven by 1.0 kV DC voltage source. Binary Ar/H2 gas medium in a mixture of 3:2 molar ratio was introduced to the gas discharge chamber at constant 200 Torr subatmospheric pressure. Simulations were run for normal glow discharges to exhibit the electrical fast transient glow discharge behaviours from electron field emission state to self-sustained normal glow discharge state by numerically solving the electron density (ED), electron current density (ECD) and electric potential distribution (EPD) parameters.It is figured out that binary Ar/H2 gas discharge model can undertake a major role in shaping and controlling the spatiotemporal response to transient electro-optical behavior of microplasma-based artificial electromagnetic materials configured for high-efficiency infrared-to-visible wavelength conversion applications.

Near-infrared spectroscopy of low-transmittance samples by a high-power time-stretch spectrometer using an arrayed waveguide grating (AWG)

Although time-stretch spectroscopy is an emerging ultrafast spectroscopic technique, the applications in industrial fields have been limited due to the low output power caused by undesirable nonlinear effects occurred in a long optical fiber used for pulse chirping. Here, we developed a high-power time-stretch near infrared (NIR) spectrometer utilizing arrayed waveguide gratings (AWGs). The combination of AWGs and short optical fibers allowed large amounts of chromatic dispersion to be applied to broadband supercontinuum pulses without the power limitation imposed by employing the long optical fiber. With the proposed configuration, we achieved chirped pulses with the output power of 60 mW in the 900–1300 nm wavelength region, which is about 10 times higher than conventional time-stretch spectrometers using long optical fibers. With the developed spectrometer, the NIR absorption spectra of a standard material and liquid samples were observed with high accuracy and precision within sub-millisecond measurement time even with four orders of magnitude optical attenuation by a neutral density filter. We also confirmed the quantitative spectral analysis capability of the developed spectrometer for highly scattering samples of an oil emulsion. The qualitative comparison of the measurement precision between the developed spectrometer and the previous time-stretch spectrometer was also conducted.

Spectroscopic investigations of Tm3+ doped CdF2 single crystals and infrared laser potentialities

By use of standard Bridgman technique, CdF2 single crystals doped with Tm3+ have been obtained with good optical quality. XRD analysis has been performed confirming the cubic structure. An ordered sequence of spectroscopic measurements (including absorption, excitation, emission and fluorescence dynamics) was carried out at room temperature. By exploiting both UV–Visible and near-infrared absorption spectra, the JO phenomenological parameters are determined by taking into account the complete refractive index dispersion, which allowed us to compute the probabilities of all transitions. Under 355 nm wavelength excitation, the Stokes emission spectrum exhibits mainly an intense blue emission line around 450 nm which is associated to 1D2→3F4 excited state transition. Whereas, the anti-Stokes blue emission around 480 nm associated to 1G4→3H6 transition is obtained under infrared excitation according to a two photon absorption mechanism. For both blue emissions, the CIE chromaticity coordinates of CdF2:Tm3+ are located in the blue region.As trivalent Tm3+ ions are known for their emissions in the near- and mid-infrared spectral ranges suitable for efficient laser operation, we have systematically studied the fluorescence behavior of the eye safe emission (pointed at ∼1.8 μm) and associated to the 3F4 → 3H6 transition. Such transition exhibit a relatively high emission cross-section (σem = 0.22 × 10−20 cm2) and a positive gain cross-section at low pumping threshold with a metastable fluorescence lifetime decay.

Characterization, Preparation, and Promotion of Plant Growth of 1,3-Diphenylurea/β-Cyclodextrin Derivatives Inclusion Complexes.

The study aimed to prepare inclusion complexes of 1,3-diphenylurea (DPU) with β-cyclodextrin (βCD) and 2-hydroxypropyl-β-cyclodextrin (HP-βCD) using a three-dimensional ground mixture (3DGM). Their physicochemical properties, intermolecular interactions, solubilities, and plant growth-promoting activities were investigated on broccoli sprouts. Phase-solubility diagrams indicated the stability constant (Ks) and complexation efficiency (CE) of βCD/DPU were found to be K1/1 = 250 M-1, CE = 2.48× 10-3. The Ks and CEs of HP-βCD/DPU were found to be K1/1 = 427 M-1, CE = 3.93 × 10-3 and K2/1 = 196 M-1, CE = 1.93 × 10-3 respectively. The powder X-ray diffraction results of 3DGM (βCD/DPU = 2/1, HP-βCD/DPU = 2/1) showed that the diffraction peaks originating from the DPU and βCD disappeared, indicating a halo pattern. Differential scanning calorimetry results showed an endothermic peak at 244 °C derived from the melting point of DPU, but the endothermic peak disappeared in the 3DGM (βCD/DPU = 2/1, HP-βCD/DPU = 2/1). Near-infrared absorption spectra showed peak shifts in 3DGM (βCD/DPU and HP-βCD/DPU) at the -CH and -NH groups of DPU and the -OH groups of βCDs and free water. In the dissolution test (after 5 min), the concentration of intact DPU was 0.083 μg/mL. However, the dissolution concentrations of DPU in the 3DGM (βCD/DPU = 1/1), 3DGM (βCD/DPU = 2/1), 3DGM (HP-βCD/DPU = 1/1), and 3DGM (HP-βCD/DPU = 2/1) were 3.27, 3.64, 5.70, and 7.03 μg/mL, respectively, indicating higher solubility than that of the intact DPU. Further, 1H-1H NOESY NMR spectroscopic measurements showed cross-peaks between H-A (7.32 ppm) and H-B (7.12 ppm) of DPU and H-6 (3.79 ppm) in the βCD cavity of the 3DGM (βCD/DPU = 2/1). A cross-peak was also observed among DPU H-A (7.32 ppm), H-B (7.11 ppm), and H-6 (3.78 ppm) in the βCD cavity. The results of the broccoli sprout cultivation experiment showed that 3DGM (βCD/DPU = 1/1), 3DGM (βCD/DPU = 2/1), 3DGM (HP-βCD/DPU = 1/1), and 3DGM (HP-βCD/DPU = 2/1) increased the stem thickness compared with that of the control group (DPU). These results indicated that the βCD/DPU and HP-βCD/DPU inclusion complexes were formed by the three-dimensional mixing and milling method, which enhanced the solubility and plant growth-promoting effects.

In situ measurement of circulation composition of refrigerant mixture in heat pump system with NIR absorption spectroscopy

Near-infrared absorption spectra of difluoromethane (R32) and 2,3,3,3-tetrafluoropropene (R1234yf) were experimentally measured for superheated gas and subcooled liquid under different temperature and pressure conditions. Molar attenuation coefficients at wavelengths of 1.59, 1.64, 1.70 and 1.78 μm were obtained using 1.5 μm wavelength data as a reference spectrum. Attenuation coefficient of the gas phase R32 refrigerant showed significant variation depending on the operating conditions, where liquid phase showed relatively constant absorption characteristics at different pressures and temperatures. Furthermore, the attenuation coefficients were distinctive between R32 and R1234yf and absorption peaks and intensities were identical. The estimation model of absorption characteristic for refrigerant mixture was then constructed using the liquid phase spectra of the pure refrigerants at each wavelength with validation using the experiment data of upward flow with circulation compositions of R32 : R1234yf = 30 : 70, 50 : 50 and 70 : 30 mass%. The estimated data qualitatively showed good agreement with the measured spectra in point of dependency on composition ratio. However, up to 15% deviation was found in the 1.59 μm spectra where R1234yf has relatively strong absorption. Further investigation, spectra dependency of refrigerant mixture on molecular interactions and of pure refrigerant on broader range of conditions, including pressure near critical point, are considered to be necessary to improve the estimation model.

Aqueous ionic effects on near-infrared absorption spectra and chemical imaging

Aqueous ionic effects on near-infrared absorption spectra and chemical imaging

Towards obtaining the optimum physical, optical and nuclear radiation attenuation behaviours of tellurite–germanate glasses through Eu2O3 reinforcement: Glass synthesis, experimental and theoretical characterisation study

We report the physical, optical and nuclear radiation attenuation behaviours of tellurite–germanate (TeO2–GeO2–PbO) glasses reinforced with varying amounts of Eu2O3. The samples were synthesised using the conventional melt-quenching method and had the following composition (in wt.%): 33.34TeO2 - 33.33GeO2 - 33.33PbO (TGP). Different concentrations of Eu2O3 (in wt.%) were added to the glass composition, labelled TGP1, TGP2 and TGP3. The physical, optical and nuclear radiation attenuation properties were measured using both experimental and theoretical methods. At room temperature, the visible to near-infrared optical absorption spectrum ranged from 400 to 900 nm. The TGP1 sample with 1 wt% The Eu2O3 additive exhibited the lowest absorbance and the highest transparency. The TGP1 sample also exhibited the highest nuclear radiation absorption properties. The gamma-ray absorption capabilities of TGP1 were demonstrably superior to those of various types of glass shields and other old- and new-generation concrete-shielding materials. Thus, adding 1 wt% Eu2O3 to tellurite–germanate glasses would ‘improve nuclear radiation absorption and optical properties. It can also be concluded that expanded scientific community investigations in this area would be a significant step toward gaining a deeper understanding of these glass structures and determining what other optimisation tasks the addition of 1 wt% Eu2O3 can accomplish.

Retrievals of XCO2, XCH4 and XCO from portable, near-infrared Fourier transform spectrometer solar observations in Antarctica

Abstract. The COllaborative Carbon Column Observing Network (COCCON) uses low-resolution, portable EM27/SUN Fourier transform spectrometers (FTSs) to make retrievals of column-averaged dry-air mole fractions (DMFs, represented as Xgas) of CO2, CH4, CO and H2O from near-infrared solar absorption spectra. The COCCON has developed rapidly over recent years and complements the Total Carbon Column Observing Network (TCCON). In this work, we provide details of the first seasonal time series of near-infrared XCO2, XCH4 and XCO retrievals from measurements made in Antarctica during the deployment of an EM27/SUN to the Arrival Heights laboratory on Ross Island over the austral summer of 2019–2020 under the auspices of the COCCON. The DMFs of all three species were lower in Antarctica than at mid-latitude, and for XCO2 and XCO, the retrieved values were less variable. For XCH4 however, the variability was significantly greater and it was found that this was strongly correlated to the proximity of the polar vortex. In order to ensure the stability of the instrument and the traceability of the retrievals, side-by-side comparisons to the TCCON station at Lauder, New Zealand and retrievals of the instrument line shape (ILS) were made before and after the measurements in Antarctica. These indicate that, over the course of the deployment, the instrument stability was such that the change in retrieved XCO2 was well below 0.1 %. The value of these data for satellite validation is demonstrated by making comparisons with the TROPOspheric Monitoring Instrument (TROPOMI) on the Sentinel-5 precursor (S5P) satellite. The dataset is available from the COCCON central facility hosted by the ESA Atmospheric Validation Data Centre (EVDC) https://doi.org/10.48477/coccon.pf10.arrivalheights.R02 (Pollard, 2021).

(INVITED)Judd-Ofelt analysis, visible to NIR photoluminescence emission under 450 nm and 976 nm excitations and energy transfer of barium fluorotellurite glasses doping with Ho3+, Yb3+, Ho3+:Yb3+

Barium fluorotellurite glasses doping with Ho3+, Yb3+, and Ho3+:Yb3 were fabricated using the conventional melt and quenching method, and their optical properties were studied using different optical spectroscopic techniques. The FITR absorption band at 3000 cm−1 was used to investigate OH- concentrations of the prepared glasses, which increased with Yb3+ content. However, it decreased by substituting a portion of BaF2 content with Ba2CO3 concentration. The electric dipole line strengths and Judd-Ofelt parameters were estimated using UV–visible near-infrared (NIR) optical absorption spectra to gain information on the rare earth ions doped glasses for laser applications. The various radiative parameters such as line strengths, optical intensity, and radiative rates from the higher energy levels, including 5F4+5S2, 5F5, 5I4,5I5,5I6 and 5I7, to the ground state, 5I8 have been reported and discussed. The influence of the Yb3+ and Ba2CO3 concentrations on the upconversion and downconversion photoluminescence emission intensities of the glasses prepared have been investigated by pumping with 450 nm and 976 nm excitation sources. Under 450 nm and 976 nm, the NIR photoluminescence emissions reveal a band ranging from 980 nm to 1220 nm attributing to an overlap between Yb3+ and Ho3+ transitions. The influence of Yb3+ concentration on photoluminescence lifetime at the 2F5/2→2F7/2, 5F4+5S2 →5I8 and 5I6 →5I8 transitions under 976 nm laser excitation has been studied and reported. The results indicate that lifetime decreases with increasing Yb3+ concentration attributing to an efficient energy transfer from Yb3+ to Ho3+ ions. The energy transfer efficiency from Yb3+ → Ho3+ has been examined, which rises from 30% to 47% upon increasing Yb3+ content. Nevertheless, it decreases with the mixing of BaF2 and Ba2CO3 lattice modifier contents. The results demonstrated that the 1200 nm (5I6 →5I8 transition) has remarkable potential for developing fiber lasers.

Atomic and microstructural origin of banded colours in purple-blue variety of agate from Yozgat Province, Turkey

Agates from Yozgat province are appreciated on the gem market for their white and purple-blue banded colours. In this study, we present a detailed investigation aimed at the identification of the atomic and structural origin of this peculiar colouration of chalcedony. X-ray diffraction and Raman spectroscopy revealed the presence of fine grains of quartz and moganite with a preferential accumulation of the latter in the blue bands. Near-infrared diffuse absorption spectra show overtones of hydroxyls vibrations at 1425, 1900, and 2250 nm. In the visible, the broad absorption at about 500 nm, as well as its behaviour at low temperatures, is compatible with the optical activity of iron impurities in quartz matrices, such as that observed in amethysts. Peak intensities and shapes are very similar for spectra collected in blue and white bands. Accordingly, trace-element composition from laser ablation inductively coupled mass spectrometry confirmed that the two regions have similar Fe content. The perceived changes in band colours are indeed originated by differences in microstructural arrangement and size of the grains visualised through scanning electron microscopy. White and blue stripes have grains of about 5 µm and 300 nm in size, respectively, resulting in an accentuated scattering component for the white bands. Therefore, the unique purple-blue shades typical of Yozgat agates are a combination of iron-related colour centres and scattering effect.

Integration of near-infrared spectroscopy and aquaphotomics for discrimination of cultured cancerous cells using phenol red

Presently, mammalian cell lines are the most utilized hosts for the production of biopharmaceuticals. Optical spectroscopy is extensively used for the physical or physiological measurements of cellular features to study the diagnosis, prognosis, and treatment of different cancers. Near-infrared (NIR) spectroscopy and aquaphotomics are ubiquitous techniques increasingly used for nondestructive assessment. The key objective of this study is to evaluate the feasibility of absorbance spectra in the NIR region (700–1100 ​nm) coupled with aquaphotomics analysis to classify the different cancerous cell lines. Human cervix adenocarcinoma cells (HeLa) and human prostate carcinoma (DU145) were the cancerous cell lines, while normal mouse skin fibroblast (L929 ​cell line) was used as a reference for the assessment. The NIR absorbance spectra for 50 ​000 to 275 ​000 ​cells of L929, DU145, and HeLa cell lines in culture media prepared with and without phenol red (PhR) were subjected to principal component analysis (PCA) and soft independent modeling of class analogies (SIMCA) models. The PCA of the spectral absorbance data revealed a clear discrimination between the three cell lines, with subgroups detected based on the presence or absence of PhR in the culture medium. The SIMCA method showed a high accuracy of classification, where larger class distances were obtained among the non-stained cells.

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe 2 Co} Coordination Polymers via Metal-to-Metal Charge Transfer

Ligand Modified and Light Switched On/Off Single-Chain Magnets of {Fe ₂ Co} Coordination Polymers via Metal-to-Metal Charge Transfer

A C 54 B 2 Polycyclic π-System with Bilayer Assembly and Multi-Redox Activity

A C ₅₄ B ₂ Polycyclic π-System with Bilayer Assembly and Multi-Redox Activity

Near-Infrared Absorption Properties of Neutral Bis(1,2-dithiolene) Platinum(II) Complexes Using Density Functional Theory.

Small metal complexes are highly interesting for bioimaging because of their excellent near-infrared (NIR) absorption properties. In this study, neutral complexes of platinum(II) connected to two monoreduced 1,3-diisopropylimidazoline-2,4,5-trithione ligands—namely, [Pt(iPr2timdt)2]—were investigated. Theoretical studies using the density functional theory (DFT) and GW-BSE approximation verified the effects of the geometry of the isopropyl moieties on the NIR absorption spectra. The calculated absorption spectra showed excellent correspondence with the experimental results. The geometry of the isopropyl groups considerably influenced the electronic structures of the metal complexes, which altered the absorption profiles of the respective geometries, as demonstrated in this research.

Croconic Acid Doped Triglycine Sulfate: Crystal Structure, UV-Vis, FTIR, Raman, Photoluminescence Spectroscopy, and Dielectric Properties

Triglycine sulfate (TGS) single crystals doped with croconic acid (CA) were grown by evaporation from aqueous solutions. X-ray diffraction analysis shows a slight reduction in unit cell volume in TGS:CA compared to pure TGS crystals. The polarized Raman and near-infrared absorption spectra show that the positions of most lines resulting from inter- and intramolecular vibrations are in good agreement with those in spectra of undoped TGS crystals. The inclusion of CA in TGS is confirmed by the presence of bands characteristic of CA in the infrared-Fourier transform spectra. The ultraviolet-visible absorption spectra of TGS:CA are characterized by the presence of additional absorption bands (compared to the spectra of pure TGS) located in the transparent region of pure TGS. In the photon energy region 1.6–3.6 eV, a strong “green” luminescence band is present in TGS:CA upon excitation at λ = 325 nm. The position of the emission band depends on the wavelength of the exciting light. Doping of TGS with CA causes pinning of domain walls, which is accompanied by a decrease in amplitude and frequency dispersion of the dielectric anomaly at the phase transition, a decrease in the switchable polarization and an increase in the coercive field of hysteresis loops.