Spectroscopic Studies Research Articles

High-Temperature Molecular Ferroelectric [C4N2H14]2[Sb2I10] with Narrow Bandgap and Switchable Photoelectric Response.

Organic-inorganic hybrid ferroelectrics have attracted considerable attention due to their outstanding piezoelectricity, mechanical flexibility, and robust nonlinear optical properties. But the species with above room-temperature (RT) ferroelectricity, visible-light bandgap, and high photoelectric performance are still scarce. Herein, a novel organic-inorganic hybrid ferroelectric [C4N2H14]2[Sb2I10] has been synthesized hydrothermally and employed as a light-absorbing layer in organic-inorganic hybrid solar cells. A polar monoclinic structure with a space group of Pn was resolved by single-crystal XRD. A direct band gap of 1.89 eV was revealed in [C4N2H14]2[Sb2I10] by UV-vis spectroscopy and density functional theory (DFT) studies. A dramatic enhancement in photoelectric performance has been achieved by turning the ferroelectric polarization, leading to a maximum Voc ∼ 0.52 V and Jsc ∼ 15.52 μA/cm2, which are 15-fold and 29-fold higher than those of the unpoled sample, respectively. This work may open new avenues for the application of molecular ferroelectrics in optoelectronic devices.

Hydrothermally altered mineral mapping of the Malanjkhand copper mineralization in India using Landsat satellite data

ABSTRACT The study evaluates how Landsat-5 Thematic Mapper (TM), Landsat-7 Enhanced Thematic Mapper Plus (ETM+), and Landsat-8 Operational Land Imager (OLI) satellite data can be used to detect and map hydrothermally altered minerals in the Malanjkhand copper mines of Madhya Pradesh, India. By employing band ratio and principal component analysis (PCA) methods, the study generates detailed spatial distributions of hydrothermally altered rocks linked to porphyry copper mineralization in the region. The study also finds that the band ratio combinations and the PCA method effectively distinguished hydrothermally altered minerals, vegetation, and iron oxides in the satellite images. Furthermore, the research reveals that Landsat-8 OLI data outperformed Landsat-5 TM and Landsat-7 ETM+ data in detecting hydrothermally altered minerals using the PCA technique. The correlation of identified minerals with the satellite images from Landsat sensors, supported by spectroscopic and petrographic studies, underscores the comprehensive approach taken in this study to enhance the understanding of hydrothermal alteration zones and improve the efficiency of mineral exploration. In conclusion, the research emphasizes the suitability of Landsat-8 OLI data for visual interpretation of hydrothermal alteration mapping, highlighting its higher radiometric resolution and reduced interference between vegetation and altered minerals.

Ultra-Sensitive Abscisic Acid Detection Using Gold and 4-Mercaptopyridine Perovskite-Engineered Robust Nanofibers (GLAMPER-NFs) under Surface-Enhanced Raman Spectroscopy.

This study explores the development and application of gold and 4-mercaptopyridine (MPY) perovskite-engineered robust nanofibers (GLAMPER-NFs) for the ultrasensitive detection of Abscisic acid (ABA) under Raman spectroscopy, a crucial plant hormone. The GLAMPER-NFs composite material, consisting of MAPbCl3 nanofibers integrated with MPY-coated gold nanostructures, demonstrates exceptional performance in surface-enhanced Raman scattering (SERS)-based sensing. The study elucidates the material structure and properties through comprehensive characterization using scanning electron microscopy (SEM), UV-vis spectroscopy, fluorescence spectroscopy, Fourier transform infrared, and Raman spectroscopy. The SEM analysis reveals uniform nanofibers with diameter of 107.8 ± 3.06 nm, while spectroscopic studies confirm the successful synthesis and integration of the composite components. The SERS-based detection of ABA showcases remarkable sensitivity, with a linear detection range (R2 = 0.9957) spanning 7 orders of magnitude (10-14-10-7 M) and presented a limit of detection of 10-11 and enhancement factor of 1.08 × 107. This surpasses the performance of existing sensing platforms, demonstrating clear spectral responses even at femtomolar concentrations. The synergistic effects of the perovskite structure, plasmonic gold nanoparticles, and MPY linking molecules contributed exceptional sensing capabilities to the GLAMPER-NFs material. Fluorescence studies further corroborate the sensitivity and provide insights into the photophysical interactions between ABA and the composite material. This research advances the understanding of perovskite-based hybrid materials and presents a promising GLAMPER-NFs as SERS substrate for ultrasensitive plant hormone detection, with potential applications in agricultural monitoring and plant science research.

High performance Mg-Li dual metal-ion batteries based on highly pseudocapacitive hierarchical TiO2-B nanosheet assembled spheres cathodes.

Although Mg-Li dual metal-ion batteries are proposed as a superior system that unite safety of Mg-batteries and performance of Li-ion based systems, its practical implantation is limited due to the lack of reliable high performance cathodes. Herein, we report a high-performance Mg-Li dual metal-ion battery system based on highly pseudocapacitive hierarchical TiO2-B nanosheet assembled spheres (NS) cathode. This 2D cathode displayed exceptional pseudocapacitance (a maximum of 93%) specific capacity (303 mAh/g at 25 mA/g), rate performance (210 mAh/g at 1A/g), consistent cycling (retain ~100% capacity for 3000 cycles at 1A/g), coulombic efficiency (nearly 100%) and fast-charging (~12.1 min). These properties are remarkably dominant to the existing Mg-Li dual metal-ion battery cathodes. Spectroscopic and microscopic mechanistic studies confirmed negligible structural changes during charge-discharge cycles of the TiO2-B nanosheet assembled spheres electrodes. Exceptional electrochemical properties of the 2D electrode is ascribed to remarkable pseudocapacitive Mg-Li dual metal-ion diffusion via the numerous nanointerfaces of TiO2-B caused by its hierarchical microstrucrure. Large surface area, nanosheet morphology, mesoporous structure and ultrathin nature also acted as secondary factors facilitating improved electrode-electrolyte contact. Demonstrated approach of pseudocapacitive type Mg-Li dual metal-ion intercalation through hierarchical nanointerfaces may be further utilized for the designing of numerous top-notch electrode materials for futuristic Mg-Li dual metal-ion batteries&#xD.

Alkali Metal‐Induced Core‐Shell Hybrid with Mixed Ir Valence State Boosts Acidic Water Oxidation

AbstractIridium (Ir)‐based electrocatalysts have long been employed as the benchmark for the oxygen evolution reaction (OER) in acid, but further to improve their catalytic activity still facing great challenges. Herein, alkali metal K is incorporated to induce the in situ construction of a core‐shell hybrid of K‐IrOx thin skin‐wrapped metallic Ir (K‐IrOx/Ir) to boost the acidic OER. The K‐IrOx/Ir exhibits exceptional catalytic performance with a long lasting stability of 3000 h operation and a low overpotential of 199 mV to reach the 10 mA cm−2. Electrochemical and spectroscopic studies revealed that the enrichment of K in the low‐coordination IrOx shell induces a significant compressive strain, which regulates the Ir─O bond properties and further optimizes the adsorption energy of rate‐limiting intermediates, favoring of the enhanced catalytic activity. Furthermore, the surface IrOx active layer is well maintained during the OER process thanks to the mixed‐valence state and intensified electronic interaction in core‐shell hybrid that inhibit the overoxidation and dissolution of Ir, responsible for the outstanding stability. This work offers a novel strategy for developing high performance acidic OER catalysts by the design of favorable mesostructured architectures with mixed metal states to enable the intensified electronic interaction and strain effect.

Effect of Copper Substitution on Structural, Electrical, and Magnetic Properties of Nanocrystalline Cobalt Ferrites for Memory Storage Applications

Cu2+‐ion‐doped cobalt ferrites with the chemical formula Co1–xCuxFe2O4 (0 < x ≤ 0.20) are prepared using the citrate–nitrate autocombustion method. The structural properties of the synthesized samples are examined by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The XRD studies reveal the formation of a single‐phase spinel cubic structure. A slight variation in the peak position is observed with the addition of Cu2+ ions. The proposed cation distribution is supported by X‐ray relative intensity calculations. FTIR and Raman spectroscopy studies also confirm the formation of a single‐phase cubic structure. Field‐emission scanning electron microscopy (FESEM) is used to measure the surface properties of the samples. The FESEM images reveal nearly uniform‐sized grains with the addition of Cu2+ ions. The DC electrical resistivity is determined using the conventional two‐probe technique and is typically found within the range of 106 Ω cm−1. Dielectric measurements are performed using an impedance analyzer with 100 Hz–10 MHz frequency range and the variations in the dielectric properties are discussed. The magnetic properties are measured using a vibrating sample magnetometer conducted the magnetic measurements. The uneven variations in the magnetic properties are explained based on Neel's two‐sublattice model.

Probing Luminescence in the Collisions of Furan Molecules with Dihydrogen Cations Using Collision-Induced Emission Spectroscopy

Optical spectroscopic studies of furan molecules (C4H4O) impinged by dihydrogen cations (H2+) were for the first time performed employing collisioninduced emission spectroscopy at ions incident energy range of 25–1000 eV corresponding to the velocities from 49 to 311 km/s. The recorded spectra reveal strong luminescence of atomic hydrogen Balmer lines whose intensities weaken with rising principal quantum number n. The spectra also display emission bands of CH radicals excited to the first A2Δ and second B2Σ− electronic states. The emission yield curves of these excited products were additionally measured by recording resultant intensities at different projectile energies. Impact processes are unveiled based on these results.

Spin polarisation and non-isotropic effective mass in the conduction band of GdN

GdN is a ferromagnetic semiconductor which has seen increasing interest in the preceding decades particularly in the areas of spin- and superconducting- based electronics. Here we report a detailed computational and optical spectroscopy study of the electronic structure of stoichiometric and nitrogen vacancy doped GdN. Based on our calculations we provide the effective mass tensor for undoped GdN, and some indicative values for electron doped GdN. Such a property is valuable as it can affect device design, and can be measured experimentally to validate the existing computation results.

Spectroscopic study of electronic structure and vibrational properties of all-trans-retinal under solvent polarizability and high-pressure modulation

Spectroscopic study of electronic structure and vibrational properties of all-trans-retinal under solvent polarizability and high-pressure modulation

Pyrite depression by sodium metabisulfite and dextrin with xanthates: contact angle, floatability, zeta potential and IR spectroscopy studies

The individual and combined depressive action of metabisulfite and dextrin on pyrite in the presence and absence of amyl xanthate has been studied through contact angle, zeta potential, microflotation, and IR spectroscopy analyses. The combined application of depressants significantly reduces the contact angle of pyrite compared with that of galena, with this effect being enhanced when the pulp is oxygenated during conditioning with metabisulfite, facilitating pyrite surface oxidation. Zeta potential measurements demonstrate the role of the oxidation process in decreasing the magnitude of the negative electric charge on the pyrite surface. These results were further corroborated by IR spectroscopy studies, which confirmed the oxidation of the pyrite surface in the presence of metabisulfite, as well as the co-adsorption of dextrin and amyl xanthate. In microflotation experiments, pyrite and galena exhibited contrasting flotation behaviors, with pyrite being effectively depressed at pH 8 when a combination of air, metabisulfite, and dextrin was used.

The Roles of Surface Hydrogen and Hydroxyl in Alkaline Hydrogen Oxidation on Ni-Based Electrocatalysts.

One important target for anion exchange membrane fuel cells (AEMFCs) is to enable the application of anode non-precious metal hydrogen oxidation reaction (HOR) catalyst. Nickel presents a promising candidate for alkaline HOR; yet, its practical application is hampered by the intrinsically sluggish activity and poor stability. Herein, a series of Ni-based metals (Ni5Mo, Ni25Co, Ni14W and Ni) are electrodeposited as model catalysts to systematically explore the alkaline HOR by considering the role of adsorbed hydroxyl (OHad). Spectroscopic studies together with density functional theory calculations shed light on the beneficial effect of transition metal M (M=Mo, Co, W) alloying/doping on HOR by introducing the charge transfer from M to Ni and down shifting Ni 3d band center. The HOR specific activities on Ni-based catalysts reveal a volcano-type relationship with the hydrogen binding energy (HBE). The strongly adsorbed OHad is proven to induce deactivation for Ni active sites, and the deactivation potential is OHad binding energy (OHBE) dependent. This study adds new insight into the HOR mechanism and stability of Ni-based electrocatalysts, providing a new avenue for the rational design of highly efficient and robust alkaline HOR catalysts.

Single-Molecule Magnet Behavior and Spin Structure of an FeIII7 Cartwheel Cluster Revealed by Sub-Kelvin Magnetometry and Mössbauer Spectroscopy: The Final Pieces of the Puzzle.

The spin frustration and other magnetic properties of the "cartwheel" heptanuclear cluster [FeIII7O3(O2CtBu)9(Me-dea)3(H2O)3] (Me-deaH2 = N-methyldiethanolamine) have been previously investigated; we present here a Mössbauer spectroscopic study and sub-Kelvin magnetization and ac susceptibility measurements which enable a complete magnetic picture of this frustrated cluster. 57Fe Mössbauer spectra above 150 K showed three doublets in a 1:3:3 ratio, which could be assigned by their respective quadrupole splittings to the central Fe(1) and the peripheral Fe(2) and Fe(3). The field dependence of the corresponding magnetic sextets at 3 K showed that the spins on the central Fe(1) and the three peripheral Fe(2) sites with O5N coordination are oriented mutually coparallel, while these are antiparallel to the spins on the peripheral Fe(3) sites with O6 coordination, resulting in an overall S = 5/2 ground state. This provides experimental confirmation of the previously proposed spin ground state structure. Upon cooling to sub-Kelvin temperatures, a crossover to spin blocking with TB ≈ 0.21 K could be observed. This single-molecule magnet behavior had been expected but had not been observable with a conventional SQUID. The anisotropy barrier, of 3-fold symmetry, can be described in terms of the parameter D/kB = -0.47 K and a fourth-order perturbation; the latter enables thermally activated quantum tunneling through the excited sublevel mz = ± 3/2, with an activation barrier of U/kB = 1.9 K.

Brain Abnormalities During Self-Referential Task in Subthreshold Depression: A Near-Infrared Spectroscopy Study

Brain Abnormalities During Self-Referential Task in Subthreshold Depression: A Near-Infrared Spectroscopy Study

Bis(glycinium) oxalate: effect of deuteration, single crystal neutron diffraction and Raman spectroscopic studies

AbstractThe crystal structure of bis(glycinium) oxalate (BGO) is stabilized by a very strong O–H..O hydrogen bond apart from N–H…O and C-H…O hydrogen bonds. To probe the effect of deuteration on these hydrogen bonds, fully deuterated (FDBGO), C-deuterated(CDBGO), and N-deuterated bis(glycinium) oxalate (NDBGO) crystals were grown. Single crystal neutron diffraction and Raman spectroscopic studies were carried out. It was found from neutron diffraction studies that the O…O distance of the O–H…O hydrogen bond reduced on deuteration showing an inverse Ubbelohde effect. The neutron diffraction and Raman spectroscopic studies also revealed partial deuteration. The DSC studies showed no phase transition. Variation of the melting point amongst the four crystals was in a very small range from 151 to 158 °C.

Comparative Optical Properties of Amorphous and Crystalline MoO3 Films by Spectroscopic Ellipsometry Study

Comparative Optical Properties of Amorphous and Crystalline MoO₃ Films by Spectroscopic Ellipsometry Study

Effect of Anion-Directed Structural Tuning of Triazole-Containing Ag(I) Coordination Polymers for "Turn-on" Sensing of the Disulfide (-S-S-) Amino Acid over the Monosulfide (-SH) Form: Experiments and DFT Corroboration.

Identification of disulfide-peptide-bond-containing glutathione (GSSG) over the monosulfide form (GSH) remains a very challenging task because of their identical chemical properties. Although GSH detection has been well documented, selective detection of GSSG has rarely been reported. Here, four cationic Ag-based coordination polymers (Ag CPs) were synthesized using newly synthesized monotriazole linker 3-amino-5-(4H-1,2,4-triazol-4-yl)pyridine to selectively screen GSSG over GSH. The judicious choice of the counteranion in the metal salt changes the architecture, which affects the detection limit at the parts per million level. The restriction of the photoinduced electron transfer process is the driving reason for the enhancement of the fluorescence, owing to the favorable energy band gap match of the Ag CPs with GSSG over GSH. The de novo strategy for incorporating polar heteroatoms (N) into the CP network plays a pivotal role in the host-guest noncovalent interactions with donor-acceptor transfer of electrons, which was supported by X-ray photoelectron spectroscopy and density functional theory studies. The Ag CPs are thermochemically robust, recyclable, and work efficiently in a very short time (within ∼14-18 s) in different pH ranges. Additionally, detection of GSSG in serum samples was carried out with appreciable detection limits and recovery percentages (94.40-117.89%).

Effects of repetitive transcranial magnetic stimulation on prefrontal cortical activation in children with attention deficit hyperactivity disorder: a functional near-infrared spectroscopy study

BackgroundAttention deficit hyperactivity disorder (ADHD) is a prevalent neurodevelopmental disorder characterized by inattention, impulsivity, and hyperactivity. With the continuous development of neuromodulation technology, Repetitive Transcranial Magnetic Stimulation (rTMS) has emerged as a potential non-invasive treatment for ADHD. However, there is a lack of research on the mechanism of rTMS for ADHD. Functional near infrared spectroscopy (fNIRS) is an optical imaging technique that reflects the brain function by measuring changes in blood oxygen concentration in brain tissue. Consequently, this research utilized fNIRS to examine the impact of rTMS on the core symptoms and prefrontal cortex activation in children with ADHD, which provides a reference for the clinical application of rTMS in the treatment of ADHD.MethodsForty children with ADHD were chosen as research subjects and randomly assigned to two groups: a treatment group (20 subjects) and a control group (20 subjects). The control group received non-pharmacological interventions, whereas the treatment group was administered rTMS in conjunction with non-pharmacological interventions. Clinical symptom improvement was evaluated using SNAP-IV scale scores both before and after treatment. Additionally, fNIRS was utilized to monitor alterations in the relative concentrations of oxyhemoglobin (HbO2) and deoxyhemoglobin (HbR) in the prefrontal cortex during resting state and during the Go/no-go task state, both pre- and post-treatment.ResultsIn conclusion, the study comprised 17 participants in the treatment group and 18 in the control group. Initially, the SNAP-scale scores were comparable between the groups, with no significant differences observed (p > 0.05). Post-treatment, a notable reduction in SNAP-scale scores was evident (p < 0.05), with the treatment group exhibiting a more pronounced decrease (p < 0.05). Following the intervention, both groups demonstrated enhanced Resting-state functional connectivity (RSFC) in the prefrontal cortex, as indicated by a significant increase compared to pre-treatment levels (p < 0.05). Specifically, the treatment group showed superior RSFC in the left dorsolateral prefrontal cortex, right dorsolateral prefrontal cortex, left medial prefrontal cortex, and right medial prefrontal cortex compared to the control group (p < 0.05). However, no significant differences were noted in RSFC of the left and right temporal lobes between the two groups (p > 0.05). In the Go/no-go task, the treatment group recorded higher mean HbO2 concentrations in the aforementioned prefrontal cortical regions compared to the control group (p < 0.05). Conversely, no statistically significant disparities were observed in the left and right temporal lobes of both groups.ConclusionrTMS shows promise as a treatment for ADHD by modulating prefrontal cortical activation. fNIRS provides a valuable method for assessing these effects, offering insights into the neurobiological mechanisms underlying rTMS therapy.

A Molecular Catalyst-Driven Sustainable Zinc-Air Battery Assembly.

Bidirectional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts are key for molecular oxygen-centric renewable energy transduction via metal-air batteries. Here, a molecular cobalt complex is covalently tethered on a strategically functionalized silica surface that displayed both ORR and OER in alkaline media. The detailed X-ray absorbance spectroscopy (XAS) studies indicate that this catalyst retains its intrinsic molecular features while playing a central role during bidirectional electrocatalysis and demonstrating a relatively lower energy gap between O2/H2O interconversions. This robust molecular catalyst-silica composite (deposited on a porous carbon paper) is assembled along with a zinc foil and polymeric gel membrane to devise an active single-stack quasi-solid zinc-air battery (ZAB) setup. This quasi-solid ZAB assembly displayed impressive power density (60 mWcm-2@100 mAcm-2), specific capacity (818 mAh g-1@ 5mAcm-2), energy density (757 Whkg-1 @5mAcm-2), and elongated charging/discharging life (28 h). An appropriate assembly of these ZAB units is able to power practical electronic appliances, requiring ≈1.6-6.0V potential requirements.

Initial Mass Functions of Young Stellar Clusters from the Gemini Spectroscopic Survey of Nearby Galaxies. I. Young Massive Clusters in the Antennae Galaxies

The stellar initial mass function (IMF) is a key parameter to understand the star formation process and the integrated properties of stellar populations in remote galaxies. We present a spectroscopic study of young massive clusters (YMCs) in the starburst galaxies NGC 4038/9. The integrated spectra of seven YMCs obtained with GMOS-S attached to the 8.1 m Gemini South telescope reveal the spectral features associated with stellar ages and the underlying IMFs. We constrain the ages of the YMCs using the absorption lines and strong emission bands from Wolf–Rayet stars. The internal reddening is also estimated from the strength of the Na i D absorption lines. Based on these constraints, the observed spectra are matched with the synthetic spectra generated from a simple stellar population model. Several parameters of the clusters including age, reddening, cluster mass, and the underlying IMF are derived from the spectral matching. The ages of the YMCs range from 2.5 to 6.5 Myr, and these clusters contain stellar masses ranging from 1.6 × 105 M ☉ to 7.9 × 107 M ☉. The underlying IMFs appear to differ from the universal form of the Salpeter/Kroupa IMF. Interestingly, massive clusters tend to have the bottom-heavy IMFs, although the masses of some clusters are overestimated due to the crowding effect. Based on this, our results suggest that the universal form of the IMF is not always valid when analyzing integrated light from unresolved stellar systems. However, further study with a larger sample size is required to reach a definite conclusion.

Broadband cavity-enhanced Kerr Comb spectroscopy on Chip

The broad and equidistant spectrum of frequency combs has had a profound impact on spectroscopic studies. Particularly, experiments involving the coupling of frequency combs to cavities have already enabled unprecedented broadband and sensitive spectroscopy on a single-molecule level. The emergence of integrated, compact, and broadband Kerr-microcombs holds promise to bring many metrological and spectroscopic studies outside of the lab. However, performing cavity-enhanced direct frequency comb spectroscopy on-chip has remained a challenge. Here, we couple a microcomb source with a microcavity to extend the advantages of cavity-enhanced spectroscopy to photonically integrated circuits. By harnessing the coherent nature of the Kerr-comb and high-Q microcavity enhancement, we obtain a detailed dispersion landscape of the guided-wave mode and comprehensive frequency-dependent cavity lineshapes. Our microcomb-cavity coupling can facilitate photonically integrated cavity-enhanced biochemical spectroscopy by evanescently coupling analytes to the cavity’s guided mode, a mode of operation we analyze numerically and provide guidelines for its potential implementation. Demonstrated detailed dispersion measurements, overperforming state-of-the-art table-top tunable lasers in available bandwidth, show potential for integrated non-linear optics applications, as precise dispersion management is crucial for such processes. Our chip-scale comb-cavity coupled platform suggests an integrated, broadband, cost-effective, and accurate tool for the non-linear optics studies as well as for ultra-compact bio- and chemical-sensing platform.