Resonance Absorption Spectra Research Articles

Study on preparation and performance of TiN modified vertically aligned carbon fiber evaporator

The application of solar photothermal conversion is currently one of the main ways to utilize solar energy, therefore it is crucial to find effective materials for photothermal conversion. In this study, carbon fiber evaporators (C-EVAP and R-EVAP) with vertically aligned carbon fiber structure were prepared from ramie and cotton using fiber bundling and carbonization, and then TiN-C-EVAP and TiN-R-EVAP were further obtained by modifying with TiN. The effects of precursor materials and TiN modification on the performance of the evaporators were discussed. The vertically aligned carbon fiber structure facilitates rapid moisture transport similar to the tree stem, enhances the internal reflection of light and improves light absorption. Compared to the short carbon fibers of cotton evaporators, ramie evaporators (R-EVAP and TiN-R-EVAP) with the long vertically aligned carbon fibers and multi-stage hollow structure have better photothermal conversion efficiency. Owing to the wide plasma resonance absorption spectrum and high absorbance of TiN, the TiN modification improves photothermal conversion efficiency of the carbon evaporators. The combination of long vertically aligned carbon fiber structure and TiN modification gives the ramie evaporator efficient photothermal conversion performance. The prepared TiN-R-EVAP has the best photothermal conversion efficiency with an evaporation rate of 1.96 kg·m−2h−1 and an evaporation efficiency of 91.29 % under 1 sunlight. It also has seawater desalination capability and excellent cycling stability, and the typical ion content of the TiN-R-EVAP desalinated condensate can meet the World Health Organization (WHO) standard for usable freshwater salinity. The vertically aligned ramie evaporators similar to the tree stem can be applied to the fields of photothermal conversion and seawater desalination.

Employing molecular dynamics simulations and DFT calculations to elucidate the energetic, structural, and spectroscopic attributes of (poly)valines in water solution

In this study, we explored how the growth of peptide chains containing valines impacts nuclear magnetic resonance (NMR) and optical absorption spectra. Results stem from equilibrated configurations in water, reflecting solvent influence and valine vibration. Utilizing fully atomistic molecular dynamics (MD), simulations, and density functional theory (DFT) including TD-DFT, we observe a notable shift in optical absorption towards longer wavelengths with increased valine count. Additionally, carbon atom magnetic signatures unveil distinct peptide bond characteristics. This work sheds light on the spectroscopic behavior of valine-rich peptide chains, crucial for understanding structural and functional properties, particularly in biomolecular contexts.

Polymer‐Protected Gold Nanoparticles for Photothermal Treatment of Ehrlich Adenocarcinoma: In Vitro and In Vivo Studies

AbstractPhotothermal therapy (PTT) is recognized as an effective tool for the treatment of cancer and it has attracted considerable attention of scientists. In this work, gold nanospheres (AuNSs) and gold nanorods (AuNRs) stabilized using poly(N‐vinylpyrrolidone) (PVP), pristine gellan gum (PGG), and poly(2‐ethyl‐2‐oxazoline)‐grafted gellan gum (GG‐g‐PEtOx) are synthesized and evaluated as PTT agents in Ehrlich cancer cells. The physicochemical characteristics of these AuNSs and AuNRs, including their surface plasmon resonance absorption spectra, size, zeta potential, and aspect ratio are studied using UV–vis‐spectroscopy, dynamic light scattering, zeta potential, transmission electron microscopy, and optical microscopy techniques. The polymer‐protected AuNSs exhibit light‐to‐heat conversion, raising the temperature from 37 to 43 °C when irradiated using a visible light source. In the case of AuNSs, considerable damage to Ehrlich cancer cells is observed following irradiation and 40 days of examination. However, with regard to AuNSs, the damage to Ehrlich cancer cells is slightly lower than observed in AuNRs. In vivo experiments demonstrate that laser irradiation of tumors in mice after injecting AuNSs leads to a statistically significant decrease in tumor size as compared to those not irradiated and the control samples.

Enhancement of spin to charge conversion efficiency at the topological surface state by inserting normal metal spacer layer in the topological insulator based heterostructure

In this study, we report efficient spin to charge conversion (SCC) in the topological insulator (TI) based heterostructure (BiSbTe1.5Se1.5/Cu/Ni80Fe20) by using spin-pumping technique, where BiSbTe1.5Se1.5 is the TI and Ni80Fe20 is the ferromagnetic (FM) layer. The SCC, characterized by inverse Edelstein effect length (λIEE) in the TI material, gets altered with an intervening Copper (Cu) layer, and it depends on the interlayer thickness. The introduction of Cu layer at the interface of TI and FM metal provides a new degree of freedom for tuning the SCC efficiency of the topological surface states. The significant enhancement of the measured spin-pumping voltage and the increased linewidth of ferromagnetic resonance absorption spectra due to the insertion of Cu layer at the interface indicate a reduction in spin memory loss at the interface that resulted from the presence of exchange coupling between the surface states of TI and the local moments of FM metal. The temperature dependence (from 8 to 300 K) of the evaluated λIEE data for all the trilayer systems, TI/Cu/FM with different Cu thicknesses, confirms the effect of exchange coupling between the TI and FM layer on the SCC efficiency of the topological surface state. This study offers promising ways for designing more efficient spin-charge conversion devices of the TI-based heterostructure by controlling the interface effects.

Enhanced the energy storage performance in AgNbO3‑based antiferroelectric ceramics via manipulation of oxygen vacancy

The applications of silver niobate (AgNbO3)-based antiferroelectric (AFE) ceramics for potential energy storage are limited by the introduction of oxygen vacancies (OVs). The inevitable OVs narrow the band gap and promote grain growth, resulting in poor breakdown strength and low recoverable energy density (Wrec). Here, we report a significant energy density performance of (Ag1-2xSrx)(Nb0.78Ta0.22)O3 AFE ceramics designed by restraining OVs. Electron paramagnetic resonance (EPR) and UVvis absorption spectra experiments demonstrate that the OV content gradually decreases and the band gap increases with increasing Sr content. Donor doping of Sr leads to the generation of silver ion vacancies, thus, the OV concentration decreases to maintain the electrical neutrality of the system. As a result, a high Wrec of ~5.6 J/cm3 together with an energy efficiency of 70.1% at 300 kV/cm is achieved in the (Ag0.92Sr0.04)(Nb0.78Ta0.22)O3 ceramic. This work offers a novel strategy for improving the energy storage properties of AgNbO3-based AFE ceramics.

An ultrahigh-resolution multicolor sensing platform via target-induced etching of gold nanorods for multi-colorimetric analysis of trace silver ions

Heavy metal ion pollution is a pressing global concern with detrimental effects on the environment and human health. To address this issue, we have developed an ultrahigh-resolution multicolor sensing platform for the specific detection of silver ions (Ag(I)). The method employs the nanozyme of platinum nanoparticles (PtNPs) as a link to control the etching of gold nanorods (AuNRs). Through specific binding with Ag(I), the PtNPs hinder the catalase-like activity responsible for hydrogen peroxide (H2O2) decomposition. This inhibition enables the Fenton reaction between H2O2 and ferrous ions, generating highly oxidizing hydroxyl free radicals (·OH). The resulting etching of AuNRs induces a blue-shift in their local surface plasmon resonance (LSPR) absorption spectra. The degree of blue-shift is directly proportional to the Ag(I) concentration, facilitating trace-level detection. Furthermore, the aspect ratio change of the AuNRs yields distinguishable colors. In contrast to common multicolor sensors relying on nanozyme horseradish peroxidase (HRP) activity, which exhibits an inverse relationship between AuNR etching and target concentration, our approach demonstrates a proportional response. This unique characteristic enables ultrahigh-resolution multicolor detection of Ag(I) visible to the naked eye. We anticipate that this innovative sensing platform will pave the way for nanosensor development in environmental monitoring and food safety detection.

Synthesis and Characterization of Schiff Base Ligands and Their Palladium(II) Complexes

Abstract: This paper is concerned with the preparation and characterization of Schiff base ligands derived from the condensation of salicylaldehyde with three different diamines, namely, ethylenediamine, o-phenylenediamine, and trans-1,2-diaminocyclohexane. The Schiff base ligands were characterized by elemental analysis, melting point, FTIR, UV-Vis, 1H-NMR and 13C-NMR. The Schiff base ligands are reacted with palladium(II) ion via direct reaction or using a template method. Identical complexes were obtained from the two methods with the same percentage yields. The formulas obtained for the complexes are PdC16H16N2O2Cl2, [PdL1]Cl2; PdC16H16N2O2Br2, [PdL1]Br2; PdC16H16N2O2.(BF4)2, [PdL1](BF4)2; PdC20H16N2O2Cl2, [PdL2Cl]Cl; PdC20H16N2O2Br2, [PdL2]Br2; PdC20H15N2O2.BF4, [PdL2]BF4; PdC20H22N2O2Cl2, [PdL3]Cl2; PdC20H22N2O2Br2, [PdL3]Br2; PdC20H20N2O2.2H2O, [PdL3].2H2O. The isolated compounds were characterized based on their melting points, elemental analyses, conductivity measurements, nuclear magnetic resonance, FTIR and electronic absorption spectra.

Magnetization enhanced the multiple magnetic domain-dominated resonance modes in stripe domain films

FeCoHf films with different Hf contents and thicknesses were deposited by composition-gradient sputtering. The results showed that the stripe domain (SD) structure emerges when the film thickness exceeds a critical thickness (220–330 nm), but the increase in introduced Hf leads to a decrease in magnetization, and in turn, the stripe phase weakens and eventually disappears. Dynamic measurements revealed magnetic domain-dependent resonant absorption spectra with up to seven resonance peaks, which have rarely been observed in magnetic film with an established SD structure. The number of resonant peaks can be controlled by the saturation magnetization of the film. Micromagnetic simulations indicate that multiple magnetic domain resonance modes can be attributed to the enhanced magnetization, which induces an increase in the magnetic domain wall volume. These results emphasize the pivotal role of magnetic domain dynamics in the framework of spintronic and microwave devices.

Resonant perfect absorption of molybdenum disulfide beyond the bandgap

Light absorption and radiation are fundamental processes in optical science and engineering. Materials with perfect absorption properties play an important role in numerous optical applications. Following the meteoric rise of MoS2 material, global opportunities and challenges coexist due to its extremely weak light–matter interaction capability beyond its energy band. In this work, we designed a kind of sandwich resonance structure and investigated MoS2 as a perfect absorber in the infrared spectrum that should be transparent according to the optical band theory. The infrared absorption properties of W or Au/MoS2/Au models at 800 nm–2400 nm were systematic simulated. By optimizing the structural parameters, the resonant wavelength of perfect absorption can be modulated from 830 nm to 1700 nm with angle insensitivity and polar independence. Moreover, we discovered that the bandwidth of absorption exceeding 50% of the W-top model reaches 500 nm, while that of the Au-top model is less than 100 nm, indicating that the top metal material has a great influence on the resonance absorption spectrum. Our work provides a practical route for enhancing and manipulating the light–matter interactions of low-dimensional materials beyond their own band gaps, which will be critical in the future design and implementation of optoelectronic devices and systems.

Modulated excited state geometry and Electron-Phonon coupling of lutein by temperature and solvent polarizability

Resonance Raman spectroscopy is one of the spectroscopic methods often chosen for studying linear polyene molecules because the Raman intensities of their υ1 (C = C) and υ2 (C-C) stretching vibrations are sensitive to electron–phonon coupling and the π-electron energy gap. Here, the resonance Raman and absorption spectra of lutein were studied as a function of solvent polarizabilities and of temperature in the CS2 solvent. For lutein in CS2, as the temperature decreased and CS solidified, the Raman scattering cross-section (RSCS) and the electron–phonon coupling constant had opposite dependence trends on temperature. The wavenumber of the lutein 0–0 electronic transition showed a marked shift to lower wavenumbers when the polarizability of the solvents decreased, and the Huang-Rhys (HR) factors and electron–phonon coupling also decreased. This work helps explore the influence of the external environment (e.g., temperature and solvent) on the excited state geometry of linear polyene molecules.

Resonance Raman scattering on graded-composition WxMo1–xS2 alloy with tunable excitons

Exciton–phonon interactions strongly affect photocarrier dynamics in two-dimensional materials. Here we report on resonant Raman experiments based on a graded composition WxMo1–xS2 alloy with tunable exciton energy without changing the energy of excitation laser. The intensities of the four most pronounced Raman features in the alloy are dramatically enhanced due to the resonance derived from the energy of B exciton shifting to the vicinity of the energy of excitation laser with an increase in W composition x. Specifically, through the resonance peak shift, absorption spectra and PL emission spectra under different excitation power, we conclude the resonance Raman is related to the exciton emission process. Our study extends the resonant Raman study of two-dimensional materials, which is expected to obtain deeper understanding of the excitonic effects in two-dimensional semiconductor materials.

Light luminescence and trapping in polydimethylsiloxane foils with low concentration of gold nanoparticles

Light trapping and luminescence have been observed in polydimethylsiloxane (PDMS) foils containing about 0.1–0.2 wt% gold nanoparticles (AuNPs). The so-prepared PDMSs have been physically characterized using SEM microscopy, UV–Vis, FTIR and Raman spectroscopies. The used AuNPs have been controlled by means of the surface plasmon resonance absorption spectra. In the AuNPs–PDMS foils, a luminescence peak at about 425 nm has been induced by an exciting light at 280 nm. The light injection with an optical fiber is trapped inside the polymer-containing NPs and illuminates all the polymer volume. The measurements of scattered light show an increment in the light intensity due to the presence of AuNPs and air bubbles inducing diffractions, reflections and Mie scattering. Further investigations have been conducted irradiating the PDMS with AuNPs in vacuum with 2.9 MeV proton beams producing luminescence in the blue region. The mechanisms of light trapping and luminescence and the possible applications of the prepared material are presented and discussed.

Elucidation of hole transport mechanism in efficient energy cascade organic photovoltaics using triple donor system

Recently, the energy cascade structure using multiple light-absorbing layers has been considered as a novel device architecture to overcome the inherent limitations of small-molecule organic photovoltaics (OPVs). The light-absorbing layers in the energy cascade OPVs should have a large overlap between the emission spectrum of a Förster resonance energy transfer (FRET) donor and absorption spectrum of a FRET acceptor. An equally important requirement is efficient charge transport across the organic layers by the formation of a suitable energy-level alignment. 5,10,15,20-tetraphenylbisbenz[5,6]indeno[1,2,3-cd:1′,2′,3′-lm]perylene (DBP)/5,6,11,12-tetraphenyltetracene (RUB)/5,12-diphenyltetracene (DPT) layers are representative donor systems, which exhibited a high power conversion efficiency in energy cascade OPVs. However, the detailed hole-transport mechanism has not been understood. In this study, the energy level alignment of C60/DBP/RUB/DPT/poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) layers was investigated via in-situ ultraviolet photoelectron spectroscopy and inverse photoelectron spectroscopy. The highest-occupied molecular orbital levels of DBP/RUB/DPT were almost perfectly aligned after their contact, indicating an efficient hole transport toward the anode without hindrance of energy barrier after exciton dissociation. This is owing to the formation of an interface dipole that aligns the charge neutrality levels of the organic layers.

Gamma Radiosynthesis of Colloidal Silver Nanoparticles Stabilized in ι-Carrageenan Under Atmospheric Gases: A Surface Plasmon Resonance Based Study

ι-Carrageenan is a biodegradable and biocompatible biomaterial which potentially stabilizes colloidal silver nanoparticles (AgNPs). The present study explored gamma radiosynthesis of AgNPs at varied concentration of ι-carrageenan solutions. The reaction system contained 1.0 mM silver precursor from silver nitrate salt. Gamma irradiation was conducted at doses up to 20 kGy under simple condition, i.e., atmospheric gases and without addition of hydroxyl radical scavenger. The behavior of AgNPs in suspension was characterized based on their surface plasmon resonance (SPR) absorption spectra which were measured using UV-vis spectrophotometer. The results show that colloidal AgNPs were successfully radiosynthesized due to dual stabilizing/reducing activity of ι-carrageenan. The degradation product of ι-carrageenan shows antioxidant activities, which increase the reducing condition of the reaction system. TEM micrograph reveals that the nanoparticles are spheroid in shape and monodisperse with an average particle size of below 10 nm. The SPR spectra indicate that the highest AgNPs concentration is found for irradiation at a dose of 10 kGy and ι-carrageenan concentration of 1.0 % (w/v). However, instability of AgNPs occurred a day after radiosynthesis due to oxidative dissolution and agglomeration. Further works on pH adjustment and optimization on irradiation dose and ι-carrageenan concentration are critical to improve the stability of colloidal AgNPs. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";}

A narrowband dual-polarization filter based on photonic crystal fiber with Au-Ag double-layer films

A narrowband dual-polarization filter based on photonic crystal fiber (PCF) with Au-Ag double-layer films is proposed. The cladding of PCF is composed of three layers of air holes, and Au-Ag double-layer films are coated on two symmetrical air holes to excite surface plasmon resonance (SPR) effect. The special mechanism of the Au-Ag double-layer films takes advantage of the narrower full width at half maximum (FWHM) of silver. On the other hand, gold is used to protect the silver from oxidation and improve the stability of the filter, and can also enhance SPR effect. The simulation results show that the dual-polarization filter with double-layer metal films has higher resonance absorption and better spectra than that with the single-layer metal film. When the thickness of the double-layer metal films is 22.5 nm (the thickness of silver film is 18 nm), the confinement loss of dual-polarization filter at 1430 nm is achieved to 64.08 dB/cm (y-pol core mode) and at 1530 nm is achieved to 37.26 dB/cm (x-pol core mode). The wavelength range of crosstalk (CT) greater than 20 dB and less than −20 dB are 1410–1450 nm and 1510–1550 nm for the device length of 10 mm, respectively. The CT is achieved 555.07 dB and −321.54 dB at the wavelength of 1430 nm and 1530 nm, respectively. These characteristics show that the filter has excellent performance, and will become a suitable candidate for a narrowband polarization filter.

Recent advances of the ionic chiral selectors for chiral resolution by chromatography, spectroscopy and electrochemistry.

Ionic chiral selectors have been received much attention in the field of asymmetric catalysis, chiral recognition, and preparative separation. It has been shown that the addition of ionic chiral selectors can enhance the recognition efficiency dramatically due to the presence of multiple intermolecular interactions, including hydrogen bond, π-π interaction, van der Waals force, electrostatic ion-pairing interaction, and ionic-hydrogen bond. In the initial research stage of the ionic chiral selectors, most of work center on the application in chromatographic separation (capillary electrophoresis, high-performance liquid chromatography, and gas chromatography). Differently, more and more attention has been paid on the spectroscopy (nuclear magnetic resonance, fluorescence, ultraviolet and visible absorption spectrum, and circular dichroism spectrum) and electrochemistry in recent years. In this tutorial review as regards the ionic chiral selectors, we discuss in detail the structural features, properties, and their application in chromatography, spectroscopy, and electrochemistry.

Ultra-narrowband absorption filter based on a multilayer waveguide structure.

We propose a six-layer waveguide structure embedded in a single-layer grating based on guided-mode resonance (GMR), which can realize ultra-narrowband filtering with a tunable resonance wavelength. The filtering characteristics were analyzed and calculated by rigorous coupled-wave analysis (RCWA) and COMSOL Multiphysics. The narrowband resonance wavelength and absorption are tuned by changing the geometry and physical parameters of the structure such as the grating period and width, layer thickness, and materials. We designed and calculated the full width at half maximum (FWHM) and resonance absorption spectra in detail under different polarization states of electromagnetic waves. We obtained an absorption FWHM of 8.51e-5 nm for the transverse electric (TE) mode and 0.023 nm for the transverse magnetic (TM) mode, with the absorption coefficients having a value over 99.2%. The GMR filtering structure shows a good sensitivity and figure of merit (FOM) for refractive index sensing. For instance, a very high FOM of 17782.6/RIU for TM incidence is observed. These structures can have possible applications in optical information devices and sensors.

Pseudo-optical fluid of continuous power flow from plasmonic coupling

A significant challenge for plasmonics as an enabling technology for energy harvesting and conversion processing is the active control of light on the nanoscale. By exploiting the resonant absorption spectra of silver nanoparticle dimer array, the theoretical results show that the resonant transverse mode and longitudinal mode is defined by the direction of dipole moment. Both of this two kind of plasmonic coupling mode induces continuous power flow around the nanoparticle, namely an analogy of pseudo-optical fluid. The direction of the circulating optical energy is governed by the spatial phase reversal of the Poynting vector. Based on the hydrodynamic theory, the negative pressure of photon is proposed to describe the intensely accumulated energy within a nanoscale volume, and the significant energy density satisfies the forming condition of pseudo-optical fluid. The analytical assumptions build the bridge for the electrodynamics and hydrodynamics to achieve dynamically-tunable and switchable vortex-operated plasmonic nanodevice for subwavelength waveguides, high-energy batteries and laser light sources.

Plasma resonance ultraviolet absorption spectroscopy of gold nanorods

Au nanorods were prepared by seed growth method. Based on the local surface plasmon resonance (SPR) absorption spectra of gold nanoparticles, the formation and growth kinetics of gold nanorods were observed and studied in real time. The effects of temperature and reaction time on the growth process of gold nanorods were emphatically investigated. It was found that the shift of SPR UV-vis absorption peak was closely related to the experimental conditions The influence factors and mechanism of SPR absorption peak shift are discussed. It is concluded that the moving direction of SPR peak is the result of the competition of particle size and charge transfer.

Effect of phonons on the electron spin resonance absorption spectrum

The unavoidable presence of vibrations in solid-state devices can drastically modify the expected electron spin resonance (ESR) absorption spectrum in magnetically active systems. In this work, we model the effect of phonons and temperature on the ESR signal in molecular systems with strong E ⊗ e Jahn–Teller (JT) effect and an electronic spin-1/2. Our microscopic model considers the linear JT interaction with a continuum of phonon modes, the spin–orbit coupling, the Zeeman effect, and the response of the system under a weak oscillating magnetic field. We derive a Lindblad master equation for the orbital and spin degrees of freedom, where one- and two-phonon processes are considered for the phonon-induced relaxation, and the thermal dependence of Ham reduction factors is calculated. We find that the suppression of ESR signals is due to phonon broadening but not based on the common assumption of orbital quenching. Our results can be applied to explain the experimentally observed absence of the ESR signal in color centers in diamond, such as the neutral nitrogen-vacancy and negatively charged silicon-vacancy color centers in diamond.