Visible Excitation Research Articles

Optical signatures as a diagnostic tool for tracking dynamics of sedimentary dissolved organic nitrogen, phosphorus, and sulfur in an anthropogenic bay

Tracing the anthropogenic fingerprint and potential nutrient release from sediments is crucial from ecological and economic perspectives, but the lack of effective and low-cost tracking techniques poses a significant challenge. Here, we investigate the optical properties and molecular composition of sedimentary dissolved organic matter (DOM) from surface sediments (n = 41) collected along the land-sea continuum of an industrialized and urbanized bay in China. We use optical techniques (UV–visible spectroscopy and Excitation–emission matrix fluorescence spectroscopy) and Fourier-transform ion cyclotron resonance mass spectrometry for sedimentary DOM characterization. Five fluorescent components (C1-C5) are validated by Parallel Factor analysis (PARAFAC), representing diverse sources and types of sedimentary DOM, including aromatic/terrestrial, microbial, anthropogenic, and protein-like substances. Molecular analysis further reveals 14,052 unique compounds. Distinct molecular characteristics are identified for sedimentary dissolved organic nitrogen (DON), phosphorus (DOP), and sulfur (DOS). Sedimentary DOP exhibits the highest saturation, DON the highest aromaticity, and DOS the highest molecular weight. Optical parameters (e.g. fluorescence index) correlate significantly with specific molecular formulas of sedimentary DON, DOP, and DOS, suggesting that optical signatures can serve as a diagnostic tool for exploring internal nutrient release and point source pollution in aquatic ecosystems. This linkage will allow for efficient large-scale monitoring of sedimentary heteroatomic compound cycling in aquatic systems using optical techniques with robust interpretations, which has significant implications for sustainable watershed management.

Single Objective Light Sheet Microscopy allows high resolution in vivo brain imaging of Drosophila.

In vivo imaging of dynamic sub-cellular brain structures in Drosophila melanogaster is key to understanding several phenomena in neuroscience. However, a trade-off between spatial resolution, speed, photodamage, and setup complexity limits its implementation. Here, we designed and built a single objective light sheet microscope, customized for in vivo imaging of adult flies and optimized for maximum resolution. Unlike multi-objective light sheet setups, the microscope uses a single objective at the fly head interface, facilitating sample mounting and inspection, and reducing invasiveness. In contrast to two-photon microscopies, the light-sheet configuration with visible excitation offers reduced phototoxicity. We demonstrate in vivo imaging of the membrane, mitochondria, and dense-core vesicles in the axonal projections of small lateral ventral neurons. The achieved resolution was between 380 to 500 nm within a field of view of 70×50×12 μm 3 . This unique combination of easy sample mounting, high resolution, and the low-phototoxicity of light sheet illumination paves the way for new dynamic studies in the brain of living flies.

Novel Ketone Derivatives Involving Triphenylamine Electron‐Donating Group as Low Migration Photoinitiators for Visible Light Radical Polymerization and 3D Printing

AbstractGiven the ongoing advancements in photopolymerization technology, there is an imperative need to develop novel free radical photoinitiators (PIs) with long‐wavelength absorbance and low migration. To meet the demand for visible light photopolymerization, four novel ketone derivatives photoinitiators (PHMOs) were synthesized in this study via a one‐step reaction. By constructing the push‐pull structure, the maximum absorption wavelength of the new PIs was red‐shifted to the vicinity of 400 nm, satisfying the requirement of visible excitation. The one‐component photoinitiation effect of PHMOs under visible light was comparable to that of Irgacure 1173, among which the photopolymerisation performance of PHMO‐2 was significantly superior to that of 1173. The photopolymerization effect of the two‐component photoinitiaton system composed by the addition of hydrogen donor was significantly improved. PHMO‐1 was successfully used in 3D printing to produce well‐defined printed products. The photolysis mechanism of PHMOs was investigated by steady‐state photolysis and electron spin resonance test. In addition, PHMOs had good solubility, thermal stability and good biosafety. Attributed to the presence of double bonds, PHMOs had low migration. These excellent properties indicated that PHMOs had desirable potential applications in the field of visible light polymerization.

Identifying sources and distribution of organic pollutants in a Moroccan river: Characterization of dissolved organic matter by absorption, excitation–emission fluorescence and chemometric analyses

This study investigates surface water contamination of Ben-Kazza River in Morocco, fed by effluents from an adjacent lagoon-based wastewater treatment plant (WWTP) and seasonally by industrial effluents, and which occasionally serves to irrigate agricultural fields. This study has two purpose: i) to track the main sources of contamination through the evolution of dissolved organic matter (DOM) characteristics along the watercourse, and ii) to characterize the WWTP influents and effluents with a focus on the efficiency of the lagoon treatment. We characterized a total of 495 water samples across the watercourse and from the inlet and outlet of the WWTP, using UV–visible absorption and excitation–emission fluorescence coupled with chemometric analyses. Absorption indicators and fluorescence indices were calculated and compared across sampling points. Results highlight spatial shifts together with temporal changes in DOM. PARAFAC identified components that varied between protein-like, humic-like and anthropogenic-like fluorophores along the river, permitted to trace the anthropogenic components and their sources. The lagoon treatment appeared to better remove fresh organic material than humic material: fluorescence intensity decreased by 68 % for peak T1 and by 22 % for peak C. Maximum fluorescence intensities (Fmax) decreased across all PARAFAC components, leading to more than 55 % reduction of ΣFmax.

Identification of graphite with perfect rhombohedral stacking by electronic Raman scattering

Rhombohedral graphite (RG) shows strong correlations in its topological flat band and is pivotal for exploring emergent, correlated electronic phenomena. One key advantage is the enhancement of electronic interactions with the increase in the number of rhombohedrally stacked graphene layers. Increasing thickness also leads to an exponential increase in the number of stacking configurations, necessitating a precise method to identify flawless rhombohedral stackings. Overcoming this challenge is difficult because the established technique for stacking sequence identification, based on phonon originated Raman processes (e.g. the 2D peak), fails in thick RG samples. We demonstrate that the strong layer dependence of the band structure can be harnessed to identify RG without stacking faults. For thicknesses ranging from 3 to 12 layers, we show that each perfect RG structure presents distinctive peak positions in electronic Raman scattering (ERS), directly fingerprinting the flawless stacking. This measurement can be carried out using a conventional confocal Raman spectrometer at room temperature, using visible excitation wavelengths. Consequently, this overcomes the identification challenge by providing a simple and fast optical measurement technique, thereby helping to establish RG as a platform for studying strong correlations in one of the simplest crystals possible.

Unravelling the effect of oxidation/reduction sites for photocatalytic H2O2 production

Metal/semiconductor heterostructures have been widely used to drive photochemical reactions. However, understanding of the synergies between them is still limited. In this study, we discovered that under ultraviolet (UV) light, rather than visible (Vis) excitation, the redox active sites oxidize adsorbed water and reduce oxygen molecules more efficiently. In this paper, the comprehensive mechanism of Ag@TiO2 photocatalysis of H2O2 has been elucidated and confirmed their synergies in photocatalytic reactions, through in situ characterization and theoretical calculation. Our findings provide insights into the key factors that influence the difference of photoactivity in UV and Vis light, thus having important implications for the design of solar energy conversion materials as well as environmental purification materials.

Synthesis, spectroscopic characterization, electronic elucidation, chemical reactivity, topological and molecular docking investigations of cefadroxil sulfoxide

The cefadroxil sulfoxide (CDSO) para-hydroxy derivative, derived from cefadroxil, has enormous significance in pharmaceutical applications. The cefadroxil sulfoxide (CDSO) compound was synthesized and characterized by spectroscopic (FT-IR, FT-Raman, and UV–Visible) assessments. Computational investigations have been carried out concurrently with a B3LYP-6-311++G(d,p) basis set and density functional theory (DFT). The molecular vibrational assignments, chemical reactivity, electronic properties, and optical activities are calculated using gas and different solvent phases. The stable ground state configuration of the given molecular compound is investigated using PES analysis. Furthermore, the chemical behavior of the CDSO was thoroughly investigated for different solvent aspects through HOMO-LUMO, MEP, UV–Visible and electron-hole excitation analyses. The molecular occupancy, virtual occupancy, and overlapping bonding energies are investigated by TDOS, PDOS, and COOP spectrum studies. Fukui function and dual descriptor investigations extend to the chemical reactivity of individual atomic sites. The intra-molecular analysis provided a deeper understanding of the molecular interactions performed by natural bond orbitals (NBO) and non-linear optics (NLO), which provided optical activity for the title compound. Additionally, electron localization function (ELF), localized orbital locator (LOL), and reduced density gradient (RDG) analyses were also accomplished to provide insight into the delocalized orbitals in the header composite. The molecular docking was achieved, and the ligand with 4EVM protein is providing the potential antimicrobial biological activity (binding energy −7.12 kcal/mol) of the CDSO compound.

Characteristics of water dissolved organic matter in Zoige alpine wetlands, China

BackgroundDissolved organic matter (DOM) plays a significant role in the biogeochemical cycle of crucial elements in aquatic ecosystem. However, it is still not clear on the spectral characteristics of water DOM in different types of alpine wetlands, which have less anthropogenic influences and intensive ultraviolet radiation. Here, we collected 107 water samples from marsh, lake, and river wetlands in the Zoige plateau, China, and analyzed the chemical characteristics, compositions, and potential sources of chromophoric DOM by combining UV–vis spectroscopy and excitation–emission matrix fluorescence spectroscopy coupled with parallel factor analysis (EEMs-PARAFAC).ResultsUVC and UVA fulvic-like substances were the prevailing fluorescence components in water DOM, which accounted for 23.74–71.59% and 16.76–30.01% of the total fluorescence intensity, respectively. Compared with the lake and river wetlands, fluoresce intensities of UVC and UVA fulvic-like substances in DOM were higher in marsh wetland. Marsh wetlands possessed the highest SUVA254, E2/E3, E2/E4, and E4/E6 of DOM, suggesting higher humification degree, higher relative molecular nominal size, and higher aromaticity. And the E2/E4 ratios in most water samples were higher than 12, indicating water DOM was mainly derived from autochthonous sources in alpine wetlands.ConclusionsWetland types strongly affected the spectral characteristics of water DOM in Zoige plateau. These findings may be beneficial for sustainable management of alpine wetlands.Graphical

Spin Alignment of NV− Centers in 4H- and 6H-SiC Crystals Induced by IR and Visible Optical Excitation

Spin Alignment of NV− Centers in 4H- and 6H-SiC Crystals Induced by IR and Visible Optical Excitation

Trimodality applications validation of near-infrared persistent luminescence nanoparticles

Here, we introduced Cr ion, as emission center, to achieve the NIR emission for MgGa2O4, while Zn ion is used to increase oxygen vacancy to improve the emission intensity. Thus, Mg0.9Zn0.1Ga2O4: 0.006 Cr3+ (MZGC) was prepared as the optimal composite with the enhanced NIR emission at 708 nm, while the host, Mg0.9Zn0.1Ga2O4 (MZG), exhibited the afterglow emission at 425 nm under 224 nm excitation. The result from density functional theory confirmed Cr and Zn ions occupied in the octahedral coordination to improve the optical behaviors. The NIR emission of MZGC was applied for bioimaging as confirmed with mice model under both visible and NIR excitation. We proposed MZGC strategy for fingerprint imaging and recognition with their resistance to stray light interference. By applying the mixture of MZGC and MZG, we realized ratiometric temperature sensing at 35–40 °C within body temperature range. The optical mechanism clearly illustrated for tri-modality applications as bioimaging, fingerprint recognition, and temperature sensing. This work provides a reliable method for the improvement of optical properties and thus extend the applications of persistent luminescence nanoparticles.

Near UV photon upconversion in cast solid with quantum dot

Abstract CdS/ZnS core-shell semiconductor quantum dots (QDs) were hybridized with1-naphthalenecarboxylic acid, a triplet transmitter, by a ligand exchange method. UV emission peaked at 340 nm or longer was obtained by visible continuous-wave excitation at 405 nm in n-hexane solution by mixing the hybridized QD with 2,5-diphenyloxazole (PPO) as UV emitter, based on triplet-triplet annihilation upconversion (TTA-UC) mechanism. The same mixture but in tetrahydrofuran gave solid film by solution casting, and the solid showed upconversion emission in near UV spectral region (380-395 nm) by 405-nm excitation.

Characterizing Femtosecond Laser Tagging Performance With A 1030 Nm Yb:KGW Laser And Application To Continuous 50 KHz Velocimetry

This paper presents a comprehensive evaluation of unseeded Femtosecond Laser Electronic Excitation Tagging (FLEET) using a 1030 nm Yb:KGW femtosecond laser. In the first part of this work, fundamental studies were conducted in a vacuum chamber to assess the fluorescence process in dry air and nitrogen. Specifically, the effects of pressure, pulse energy, and focal length on the temporal decay of the nitrogen first and second positive band emission are quantified and reported. The results show similar trends to previous reports of FLEET emission behavior at other visible and near infra-red excitation wavelengths, indicating that the same fundamental fluorescence mechanism occurs after 1030 nm excitation. In the second part of this work, we explore the application of 1030 nm FLEET to continuous high-speed velocimetry in an under-expanded laboratory jet. Unseeded velocity measurements at 50 kHz in air were acquired at several points in the flow using burst gating of a high-speed intensifier. Frequency domain analysis of over 50,000 time-resolved measurements show strong periodic fluctuations near 8 kHz due to an acoustic resonance near the jet exit. Analysis of the streamwise velocity autocorrelation is shown to provide a means to separate uncorrelated random measurement error from true flow fluctuations. These results establish a first demonstration of continuous, high-speed FLEET measurements at 1030 nm and provides foundational data to inform future applications of this unseeded velocimetry technique in turbulent high-speed flows.

Photo-induced collective charge-density-wave dynamics in bulk 1T-VSe2

We investigated temperature (T) and excitation density dependent ultrafast near-infrared (NIR) transient reflectivity dynamics in the charge density wave (CDW) phases of bulk layered 1T-VSe2 using NIR and visible excitations. The data reveal fingerprints of conventional non-adiabatic CDW collective dynamics with rather fast electronic order parameter dynamics showing sub-picosecond suppression and recovery. The slower T-dependent 100-ps dynamics indicates rather isotropic heat transport dominated by the lattice degrees of freedom.

Methanol-to-Olefins Studied by UV Raman Spectroscopy as Compared to Visible Wavelength: Capitalization on Resonance Enhancement.

Resonance Raman spectroscopy can provide insights into complex reaction mechanisms by selectively enhancing the signals of specific molecular species. In this work, we demonstrate that, by changing the excitation wavelength, Raman bands of different intermediates in the methanol-to-hydrocarbons reactions can be identified. We show in particular how UV excitation enhances signals from short-chain olefins and cyclopentadienyl cations during the induction period, while visible excitation better detects later-stage aromatics. However, visible excitation is prone to fluorescence that can obscure Raman signals, and hence, we show how fast fluorescence rejection techniques like Kerr gating are necessary for extracting useful information from visible excitation measurements.

Yb-to-Eu Cooperative Sensitization Upconversion in a Multifunctional Molecular Nonanuclear Lanthanide Cluster in Solution.

Lanthanide metal clusters excel in combining molecular and material chemistry properties. Here, we report an efficient cooperative sensitization UC phenomenon of a Eu3+/Yb3+ nonanuclear lanthanide cluster in CD3OD. The synthesis and characterization of the heteronuclear cluster in the solid state and solution are described together with the UC phenomenon showing Eu3+ luminescence in the visible region upon 980 nm NIR excitation of Yb3+ at concentrations as low as 100 nM. Alongside being the Eu/Yb cluster to display UC (with a quantum yield value of 4.88 × 10-8 upon 1.13 W cm-2 excitation at 980 nm), the cluster exhibits downshifted light emission of Yb3+ in the NIR region upon 578 nm visible excitation of Eu3+, which is ascribed to sensitization pathways for Yb through the 5D0 energy levels of Eu3+. Additionally, a faint emission is also observed at ca. 500 nm upon 980 nm excitation, originating from the cooperative luminescence of Yb3+. The [Eu8Yb(BA)16(OH)10]Cl cluster (BA = benzoylacetonate) is also a field-induced single-molecular magnet (SMM) under 4K with a modest Ueff/kB of 8.48 K, thereby joining the coveted list of Yb-SMMs and emerging as a prototype system for next-generation devices, combining luminescence with single-molecular magnetism in a molecular cluster.

Chromium-doped zinc gallate: Impact of Sn4+ co-doping on the persistent luminescence properties at the nanoscale applied to bio-imaging

Persistent luminescence (PersL) nanoparticles emit a signal that lasts long after the excitation has ended, enabling highly sensitive bioimaging without background noise. By using UV light as the excitation source prior to injection, a strong PersL signal can be detected in vivo before disappearing within a few hours. For long-term imaging, we have shown in the past that visible LED can be used to re-excite ZnGa1.995Cr0.005O4 (ZGO:Cr3+) nanoparticles in vivo, producing a signal intensity that is, however, much lower compared to the signal obtained after the UV pre-excitation method. This lower signal intensity of the nanoprobe when using a visible LED may prevent its detection in some cases. Herein, we report an improvement in visible LED excitation efficiency using PersL Zn1.33Ga1.335Cr0.005Sn0.33O4 (ZGSO:Cr3+) nanoparticles. We fully compared ZGSO:Cr3+ and the original ZGO:Cr nanoparticles in terms of structure, optical properties and bio-imaging potential. Co-doping with tin strongly increases persistent luminescence, even at the nanoscale. In vivo imaging results showed that ZGSO:Cr3+ exhibited an approximately 3-fold signal enhancement over ZGO:Cr3+ using UV pre-excitation. More interestingly, when using LED excitation, the signal intensity of ZGSO: Cr3+ is more than 10 times higher than that of ZGO:Cr3+, making ZGSO nanoparticles much easier to detect. ZGSO:Cr nanoparticles can be surface-modified with PEG to produce nanoprobes with much longer residence time in blood. This unique comparison between the two compositions makes ZGSO:Cr3+ a more effective imaging diagnostic probe than the original ZGO:Cr3+ nanoparticles, opening up new applications for in vivo diagnostics.

UVC Up-Conversion and Vis-NIR Luminescence Examined in SrO-CaO-MgO-SiO2 Glasses Doped with Pr3.

The application of ultraviolet-C light in the field of surface treatment or photodynamic therapy is highly prospective. In this regard, the stable fluorescent silicate SrO-CaO-MgO-SiO2-Pr2O3 glasses able to effectively convert visible excitation on the ultraviolet praseodymium emission were fabricated and examined. An unusual wide-range visible-to-UVC up-conversion within 240-410 nm has been achieved in Pr3+-doped glasses, revealing their potential advantage in different sophisticated disinfection technologies. The integrated emission intensity was studied as a function of light excitation power to assess a mechanism attributed to UVC luminescence. Especially, it was revealed that the multicomponent silicate glass qualities and praseodymium 3PJ excited state peculiarities are favorable to obtaining useful broadband ultraviolet up-converted luminescence. The glass dispersion qualities were determined between 450-2300 nm. The impact of praseodymium concentration on Vis-NIR spectroscopic glass qualities was evaluated employing absorption spectra, emission spectra, and decay curves of luminescence associated with two involved praseodymium excited states. Especially, efficient interionic interactions can be inferred by investigating the decrease in 1D2 state experimental lifetime in the heavily doped samples. Examination of absorption spectra as a function of temperature implied that excitation at 445 nm should be quite effective up to T = 625 K. Contrary to this, temperature elevation gives rise to a moderate lowering of the visible praseodymium luminescence.

A novel photoelectrochemical biosensing platform utilizing dual Type-II Bi2O3/CdLa2S4/Bi2S3 ternary heterojunctions as signal transduction materials and Cu2O nanosphere as a sensitizer for CA15-3 detection

Sensitive detection of CA15-3 is important for postoperative monitoring and early diagnosis of breast cancer. In this work, a photoelectrochemical (PEC) biosensing platform was constructed of CA15-3 by using Bi2O3/CdLa2S4/Bi2S3 ternary type-II heterojunction as the photoactive transduction material for sensitive detection, and the raspberry-shaped Cu2O nanospheres were exploited as the signal sensitizing tags. On one hand, the use of Bi2S3 as a sensitizer can effectively enhance the visible light excitation of the substrate material. On the other hand, Bi2S3 and Bi2O3/CdLa2S4 have the ability to create dual type-II heterojunctions with matched energy levels, which significantly enhances the separation and migration efficiency of the photogenerated carriers and effectively suppresses the recombination of the e-/h+ pairs. Raspberry-like semiconducting Cu2O nanospheres can mediate the PEC process of the heterojunctions. An immunosensor was developed combining the signal transduction capacity of ternary heterojunction and the signal sensitizing effect of Cu2O nanospheres. The proposed PEC immunosensor showed good selectivity and stability for detecting CA15-3 (0.001 ∼ 100 U/mL) with a detection limit of 0.0003 U/mL (S/N = 3). The constructed PEC immunosensor had potential applications in the clinical detection of CA15-3, and was expected to play a great role in the early diagnosis of breast cancer in the future. Moreover, in the design engineering of photoactive materials, the improvement of visible excitation and the enhancement of carrier separation efficiency have been realized simultaneously using a single material, which provides new ideas for the design of photoactive materials.

Tailoring the Optoelectronic Properties of Soybean-Derived Nitrogen Self-Doped Carbon Dots through Composite Formation with KCl and Zeolite, Synthesized Using Autogenic Atmosphere Pyrolysis

This article investigates the environmentally friendly synthesis and characterization of carbon dots (CDs) derived from soybean biomass, in conjunction with their composites containing potassium chloride (KCl) or zeolite. By using an environmentally sustainable synthetic approach, this study sought to unlock the potential of these materials for various applications. The physicochemical properties of the CDs and composites were comprehensively analyzed using various techniques including scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. In addition, various optical properties such as UV–Vis absorption, band gap, and excitation–emission behavior were investigated. A key finding to arise from this study was that the inclusion of a doping agent such as KCl or zeolite significantly reduced the size of the resulting CDs. In this light, whereas the undoped species are associated with average sizes of 8.86 ± 0.10 nm, those doped with either zeolite or KCl were associated with average sizes of 3.09 ± 0.05 and 2.07 ± 0.05 nm, respectively. In addition, it was shown that doping with either zeolite or KCl resulted in an alteration of the elemental composition of the CDs and influenced their optical properties, especially their excitation-dependent emission. These promising results point to potential applications in environmental sensing and energy-related fields.

Luminescence properties of CdF2 single crystals co-doped with Er3+ and Y3+ ions.

The luminescence properties of erbium and yttrium co-doped cadmium difluoride with three different concentrations of yttrium were investigated. First, we synthesized single crystal samples with good optical quality using the Bridgman technique. From the optical absorption spectra, recorded at room temperature, both in the ultraviolet-visible and infrared spectral ranges, Judd-Ofelt analysis was performed based on yttrium concentrations to predict the radiative properties of Er3+ luminescent ions. For the 10% optimum concentration of yttrium, a detailed photoluminescence investigation was carried out. We mainly explored green, red, and near-infrared fluorescence under different excitation wavelengths and presented their highlight spectroscopic characteristics. The desired transitions had relatively high emission cross-sections both under visible and near-infrared excitation. Optical gain followed a similar trend. Furthermore, the dynamic fluorescence study showed a significant increase in the measured lifetime under an 800 nm infrared excitation. The upconversion process under an 800 nm excitation produced quantum efficiency greater than 100% due to the contribution of more than one energy transfer mechanism.