UV Excitation Research Articles

Rapid and facile detection of largemouth bass ranavirus with CRISPR/Cas13a

Largemouth bass ranavirus (LMBV) is an epidemic disease that seriously jeopardizes the culture of largemouth bass（Micropterus salmoides）, and it has a very high incidence in largemouth bass. Once an outbreak occurs, it may directly lead to the failure of the culture, resulting in substantial economic losses, but there is no effective vaccine or special effective drug yet. Consequently, it is important to establish an accurate, sensitive, convenient and specific detection approach for preventing LMBV infection. The recombinant enzyme-assisted amplification (RAA) technology was used in combination with clustered regularly interspaced short palindromic repeats (CRISPR), and associated protein 13a (CRISPR/Cas13a) to detect LMBV. We designed RAA primers and CRISPR RNA (crRNA) that targeted the conserved region in the LMBV main capsid protein (MCP) gene, amplified sample nucleic acids using the RAA technology, performed CRISPR/Cas13a fluorescence detection and evaluated the sensitivity and specificity of the established method with qPCR as a control method. This technique was able to determine the results by collecting fluorescence signals, visualizing fluorescence by UV excitation and combining with lateral flow strips (LFS). The sensitivity and specificity of the established method were consistent with the qPCR method. Besides, it was performed at a constant temperature of 37 °C and the sensitivity of the reaction system was 3.1 × 101 copies/μL, with no cross-reactivity with other common aquatic pathogens. Further, the positive detection rate of the proposed method in 32 clinical samples was consistent with that of qPCR. In conclusion, our established RAA-CRISPR/Cas13 method for detecting LMBV is sensitive, simple and specific, which is applicable in the rapid on-site detection and epidemiological monitoring of LMBV.

Enhancing light output of WSLED with microlens array fabricated on Tb³⁺/Sm³⁺ co-doped fluorophosphate glass via hot embossing

In this study, Tb3+/Sm3+ co-doped NaPO3–BaF2–AlF3–CaF2 glasses were synthesized using the melt quenching method. These glasses exhibit a glass transition temperature below 380 °C and maintain optical transparency close to 90% within the visible spectrum. Furthermore, under UV excitation, the emission shows a wide spectrum and varies with the rare-earth doping ratio or excitation wavelength. Hence, this glass was introduced into the wide-spectrum light-emitting diode (WSLED) application. Moreover, a microlens array was fabricated on the glass surface using the hot embossing technique. In fact, the microlens array enhanced the light output power of the WSLED by 5% at a driving current of 150 mA.

UV- and X-ray-activated broadband NIR garnet-type Ca3Ga2Sn3O12:Fe3+ phosphors with efficient persistent luminescence

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are compact light sources of great interest for NIR spectroscopy applications. Beyond typical Cr3+-activated NIR-emitting phosphors, there exists a strong demand for Cr3+-free alternatives with high efficiency and broadband emission to rich the landscape of NIR luminescent materials and extend their range of application fields. Here, we report a series of Fe3+-activated Ca3Ga2Sn3O12 garnet-type phosphors exhibiting broadband NIR emission in the 650–1000 nm range attributed to 4T1(G) → 6A1(S) transition, with a maximum at 754 nm and a FWHM of 89 nm upon UV excitation. The spectroscopic results were analyzed according to the Tanabe-Sugano theory from which the crystal field parameter Dq and Racah parameters B and C were obtained for the octahedrally coordinated Fe3+ ion. Notably, the NIR persistent luminescence lasting over 1 h was detected following UV or X-ray irradiation. The possible mechanism involving electron traps was proposed to explain the observed persistent luminescence. Furthermore, a NIR pc-LED was fabricated by coating synthesized phosphor on a UV chip, and its performance was evaluated to assess its potential suitability as a NIR light source. Our discovery of novel type of nontoxic Fe3+-activated broadband NIR luminescence phosphors with efficient NIR persistent luminescence paves the way for discovering Cr3+-free multifunctional NIR luminescence materials, thereby expanding their application possibilities.

Novel Defluorination Pathways of Perfluoroether Compounds (GenX): α-Fe2O3 Nanoparticle Layer Retains Higher Concentrations of Effective Hydrated Electrons.

The development of efficient defluorination technology is an important issue because the kind of emerging pollutant of hexafluoropropylene oxide dimer acid (GenX) as an alternative to perfluorooctanoic acid (PFOA) has the higher environmental risks. In the UV/bisulfite system, we first developed a hydrophobic confined α-Fe2O3 nanoparticle layer rich in oxygen vacancies, which accelerated the enrichment of HSO3- and GenX on the surface and pores through electrostatic attraction and hydrophobic interaction, retaining more hydrated electrons (eaq-) and rapidly destroying GenX under UV excitation. Especially, under anaerobic and aerobic conditions, the degradation percentage of GenX obtain nearly 100%, defluorination of GenX to 88 and 57% respectively. It was amazed to find that the three parallel H/F exchange pathways triggered by the rapid reactions of eaq- and GenX, which were unique to anaerobic conditions, improved the efficiency of fluoride removal and weaken the interference of dissolved oxygen and H+. Therefore, this study provided an available material and mechanism for sustainable fluoride removal from wastewater in aerobic and anaerobic conditions.

Tuning Optical Properties of Carbon Dots by Co‐doping Strategy for Versatile Applications

AbstractCarbon dots (CDs) with tunable photoluminescence was successfully prepared via selective co‐doping of three elements, including nitrogen, phosphorus and sulfur element by green one‐step hydrothermal method. Nitrogen‐sulfur‐doped CDs (red NS‐CDs), which emitted red fluorescence under UV excitation, were used to detect iron ions in the linear range 1–50 μM, yielding detectable limits as low as 94 nM. The nitrogen‐phosphorus‐doped CDs (blue NP‐CDs) exhibited blue fluorescence with quantum yields up to 34.5 %. When the concentration is 800 μg/mL, it showed excellent anticancer effect in vitro. The nitrogen‐sulfur‐phosphorus‐doped CDs (green NPS‐CDs) emitting green fluorescence showed a low cytotoxicity at a high concentration of 800 μg/mL and were used for intracelluar imaging of NCl−H292 cells. This study demonstrated the photoluminescent characteristics of carbon dots (CDs) and highlighted the ability to modify their peak fluorescence emission wavelengths through the flexible combination of specific reagents under comparable hydrothermal conditions. Additionally, it provided valuable insights into the efficient methodologies for synthesizing CDs suitable for various application scenarios.

Fluorescence Microscopy with Deep UV, Near UV, and Visible Excitation for In Situ Detection of Microorganisms.

We report a simple, inexpensive design of a fluorescence microscope with light-emitting diode (LED) excitation for detection of labeled and unlabeled microorganisms in mineral substrates. The use of deep UV (DUV) excitation with visible emission requires no specialized optics or slides and can be implemented easily and inexpensively using an oblique illumination geometry. DUV excitation (<280 nm) is preferable to near UV (365 nm) for avoidance of mineral autofluorescence. When excited with DUV, unpigmented bacteria show two emission peaks: one in the near UV ∼320 nm, corresponding to proteins, and another peak in the blue to green range, corresponding to flavins and/or reduced nicotinamide adenine dinucleotide (NADH). Many commonly used dyes also show secondary excitation peaks in the DUV, with identical emission spectra and quantum yields as their primary peak. However, DUV fails to excite key biosignature molecules, especially chlorophyll in cyanobacteria. Visible excitation (violet to blue) also results in less mineral autofluorescence than near UV, and most autofluorescence in the minerals seen here is green, so that red dyes and red autofluorescence of chlorophyll and porphyrins are readily distinguished. The pairing of DUV and near UV or visible excitation, with emission across the visible, represents the most thorough approach to detection of labeled and unlabeled bacteria in soil and rock.

The effects of delayed annealing on the luminescent activity of heavy metal cadmium zinc phosphate glasses activated by: Er3+ and Tb3+ ions

The luminescent spectra of the RE2O3-doped P2O5–CdO–ZnO glasses (RE = Er, and Tb) were investigated to separate the effects of two studied rare-earth elements and the annealing regime on the emission performance of the prepared glasses. The glasses undergo a series of collective measurements including UV–visible absorption, luminescence, thermal expansion, XRD, TEM, and FTIR. The optical UV–visible spectra of the two doped glasses reveal a UV band due to undoped glass beside and extra extended 11 peaks with the Er3+ ions with high distinct features while the Tb3+ ions samples exhibit peaks within the visible region. These peaks are correlated with transitions from the ground state in each case to specific energy transitions. The overall optical data indicate that the two rare earth ions are present in a stable trivalent state. Under UV excitation, both Er3+ and Tb3+ emit a characteristic green light corresponding to 4S3/2 → 4I15/2 and 5D4 → 7F5 transitions, respectively. The performance of the green light was identified to be enhanced by increasing the concentration of rare earth and the effect of annealing temperature. Moreover, the intensity of the infrared emission of Er3+ at 1532 nm corresponds to the (4I13/2 → 4I15/2) transition which is assumed to be developed with the effect of heating. The resultant IR spectra show distinct vibrational peaks due to phosphate groups that undergo only minor modifications when doped with rare earth elements or over-annealed.

Enhancement of Luminescence from Lanthanide Metal–Organic Frameworks by Ytterbium and Calcium Doping: Application to Photonic Barcodes and Fingerprint Detection

AbstractEmission from metal–organic frameworks (MOFs) made from Eu3+ and 1,3,5‐benzenetricarboxylic acid (BTC) is enhanced eightfold by doping with Y3+ and Ca2+ ions. The Ca2+ ions are shown to substitute into the MOFs, and the MOFs structure is shown to be retained at high Y3+ doping levels. The emission enhancement is shown to be associated with variations in the local electric field at the Eu3+ centers in the MOFs. Calculations indicate that the HOMO and LUMO levels vary considerably with both Y3+ doping and with low‐level Ca2+ doping. These then modulates Eu3+ concentration quenching, ligand‐metal energy transfer processes, and the local electric field at the Eu3+ centers, qualitatively accounting for the primary observed features. For UV excitation (250, 295, and 393 nm, respectively), the greatest emission enhancement comes from the doped MOFs with 10% Eu3+, 89% Y3+, and 1% Ca2+. In a photonic barcode application, the doped MOFs are shown to facilitate increased information storage density, and in a fingerprinting application, they are displayed to lead to higher photostability and reduced materials demand.

Photophysical properties of DAPI in PVA films. Possibility of room temperature phosphorescence

We studied the spectral properties of 4′-6-diamidino-2-phenylindole (DAPI) in poly (vinyl alcohol) (PVA) films. Absorption and fluorescence spectra, emission and excitation spectra, quantum yield, and fluorescence lifetime have been characterized. An efficient room temperature phosphorescence (RTP) of DAPI has been observed with UV and blue light excitations. A few hundred millisecond phosphorescence lifetime enables a gated detection with sufficient background reduction. We found the phosphorescent Quantum Yield of DAPI in PVA Film to be 0.0009.

Growth and performance of CsCu(Br, Cl)3 single crystals

This paper presents the growth of large-sized CsCu(Br, Cl)3 crystals using the aqueous solution evaporation method. The structure and the components of the crystals were analyzed. It was found that CsCuBr3 is a direct bandgap material, while CsCuCl3 is an indirect bandgap material, and the band gap of CsCu(Br, Cl)3 halides can be adjusted in the range of 2.63–3.63 eV (PBE) by changing the ratio of Br-/Cl-. Besides CsCuCl3, which has an absorption valley at 654 nm, the other CsCu(Br, Cl)3 crystals show high absorption in the range of 200–1000 nm. Under UV excitation, the PL spectra show that CsCu(Br, Cl)3 crystals exhibit red and blue emission.

Unraveling the mechanism of photo-induced surface enhanced Raman scattering on ZnO/Au thin films

Surface-enhanced Raman scattering (SERS) is a powerful technique for detecting pollutants. Recent studies have shown that the sensitivity of SERS can be further improved by using appropriate light excitation before or during Raman measurements, a phenomenon known as photo-induced enhanced Raman scattering (PIERS). In this study, we developed a highly sensitive SERS substrate by fabricating a ZnO/Au thin film using radio frequency magnetron sputtering and post-annealing processes. The resulting substrate exhibited high crystallinity and high sensitivity for pollutant detection. The study found that in situ UV excitation significantly enhanced the Raman signal, up to 5.5 times more efficiently than the traditional SERS technique. The excitation process was reversible, leading to a quick recovery of the Raman intensity to its initial level when the UV excitation was turned off. This relaxation process is attributed to the recombination of electrons and holes. The investigation shows that ZnO/Au thin films was able to detect fungicide thiram with a limit of detection of 10−8 M. PIER also helps to lower the detection threshold down to 10−9 M.

Crystal structure and optical properties of Eu3+–doped and undoped complex sulfate KSc(SO4)2 produced by facile and efficient crystallization process

Both pristine and Eu3+-doped scandium-potassium complex sulfate KSc(SO4)2 has been obtained with 99% yield via crystallization from solutions. The high-temperature XRPD and thermal studies revealed an enantiotropic first-order phase transition at 700–725 K and standard pressure. In the temperature region 724–754 K, the low-temperature stable monoclinic polymorph, β-KSc(SO4)2 (sp.gr. С2/m), coexists with the high-temperature trigonal modification, α-KSc(SO4)2 (sp.gr. P321), with decomposition at ∼1120 K. DFT calculations confirmed this rank of polymorphs and a low hospitality of their Sc-sublattices for Eu3+ cations. Under UV excitation, the KSc0.98Eu0.02(SO4)2 sample exhibits Eu3+ luminescence at 570−720 nm. Heating of the sample from 298 K to 423 K leads to a luminescence fading of 13% and to its a sharp decline at elevated temperatures. Kinetic studies have shown that the lifetime depends on the chosen excitation wavelength and temperature. An Х-band resonance in the sample of KSc(SO4)2:Eu3+ has been detected in the temperature range of 299–500 K. The EPR spectra are interpreted assuming the presence of sulfate radicals.

Multi-color luminescent material with Mn2+/Mn4+ non-stoichiometric ratio doped octahedra and its anti-counterfeiting applications

Mn ions in different valence states can emit light of different colors in an octahedral coordination environment, which is conducive to the development of a single matrix with multi-color luminescence and applications in the field of anti-counterfeiting. The dual mode multi-color luminescent material CaSb2O6: Mn has been successfully synthesized using a single Mn source in the atmosphere. The CaSb2O6 matrix itself can also absorb 285 nm UV light, emit blue light, and show a long afterglow phenomenon. Both Mn4+ and Mn2+ ions will appear in the [SbO6] octahedra, whether the Mn source adopts MnCO3 or MnO2. The Mn4+ ion exhibits red emission upon UV excitation at 347 nm. The Mn2+ ion can emit a bright green light at 285 nm excitation while exhibiting a long afterglow phenomenon. In this study, the Mn2+ doped octahedron showed unique green emission and broadens the range of its photoluminescence (PL) wavelength. The performance of the material's long afterglow properties on the digital codes demonstrates its potential for dynamic anti-counterfeiting.

Signatures of Conical Intersections in Extreme Ultraviolet Photoelectron Spectra of Furan Measured with 15 fs Time Resolution.

Ultrafast internal conversion of furan upon deep UV excitation at 200 nm is studied by using extreme ultraviolet time-resolved photoelectron spectroscopy with a time resolution of 15 fs. Ballistic nuclear wavepacket motion from the 1B2(ππ*) state to the ground state is fully observed using 21.7 eV probe pulses. Through the performance of a comparison with the results of electronic structure calculations at the MS(3)-CASPT2(10,10)/cc-pVTZ level of theory, the photoelectron signals from the conical intersection regions are identified.

Monitoring the Evolution of Relative Product Populations at Early Times during a Photochemical Reaction.

Identifying multiple rival reaction products and transient species formed during ultrafast photochemical reactions and determining their time-evolving relative populations are key steps toward understanding and predicting photochemical outcomes. Yet, most contemporary ultrafast studies struggle with clearly identifying and quantifying competing molecular structures/species among the emerging reaction products. Here, we show that mega-electronvolt ultrafast electron diffraction in combination with ab initio molecular dynamics calculations offer a powerful route to determining time-resolved populations of the various isomeric products formed after UV (266 nm) excitation of the five-membered heterocyclic molecule 2(5H)-thiophenone. This strategy provides experimental validation of the predicted high (∼50%) yield of an episulfide isomer containing a strained three-membered ring within ∼1 ps of photoexcitation and highlights the rapidity of interconversion between the rival highly vibrationally excited photoproducts in their ground electronic state.

High-quality dense ZnO thin films: work function and photo/electrochemical properties

Compact ZnO (wurtzite) thin films are prepared on four different substrates by (i) spray pyrolysis or (ii) pulsed reactive magnetron sputtering combined with a radio frequency electron cyclotron wave resonance plasma. Films are characterized by AFM, XRD, Kelvin probe, cyclic voltammetry, electrochemical impedance spectroscopy, and UV photoelectrochemistry. Film morphologies, defect concentrations, crystallite size, and orientation provided specific fingerprints for the electronic structure of ZnO close to the conduction band minimum. Fabricated films are referenced, if relevant, to a model system based on a wurtzite single crystal with either Zn-face or O-face termination. Kelvin probe measurements of the ZnO/air interface distinguished effects of annealing and UV excitation, which are attributed to removal of oxygen vacancies close to the surface. In turn, the work function, at the electrochemical interface, specifically addressed the growth protocol of the ZnO electrodes but not the effects of crystallinity and annealing. Finally, high photocurrents of water oxidation are observed exclusively on virgin films. This effect is then discussed in terms of photocorrosion, and work function changes due to UV light.Graphical

Neuropathological Applications of Microscopy with Ultraviolet Surface Excitation (MUSE): A Concordance Study of Human Primary and Metastatic Brain Tumors.

Whereas traditional histology and light microscopy require multiple steps of formalin fixation, paraffin embedding, and sectioning to generate images for pathologic diagnosis, Microscopy using Ultraviolet Surface Excitation (MUSE) operates through UV excitation on the cut surface of tissue, generating images of high resolution without the need to fix or section tissue and allowing for potential use for downstream molecular tests. Here, we present the first study of the use and suitability of MUSE microscopy for neuropathological samples. MUSE images were generated from surgical biopsy samples of primary and metastatic brain tumor biopsy samples (n = 27), and blinded assessments of diagnoses, tumor grades, and cellular features were compared to corresponding hematoxylin and eosin (H&E) images. A set of MUSE-treated samples subsequently underwent exome and targeted sequencing, and quality metrics were compared to those from fresh frozen specimens. Diagnostic accuracy was relatively high, and DNA and RNA integrity appeared to be preserved for this cohort. This suggests that MUSE may be a reliable method of generating high-quality diagnostic-grade histologic images for neuropathology on a rapid and sample-sparing basis and for subsequent molecular analysis of DNA and RNA.

Effect of neodymium ions on the photosensitivity of photo-thermo-refractive glass

Neodymium doping of photo-thermo-refractive (PTR) glass leads to a fast non-radiative depopulation of excited states of cerium ions, which are responsible for the glass photosensitivity. The non-radiative energy transfer from cerium to neodymium ions results in a decrease in the efficiency of photoelectron generation under UV irradiation. Emission spectra and fluorescence decay curves of cerium ions under UV excitation were investigated. Absorption spectra of the glasses were obtained as well to distinguish the reabsorption processes and the non-radiative energy transfer mechanisms. It was found that as Nd2O3 concentration increases from 0 to 2 mol%, cerium ions average lifetime decreases from 44.5 to 28 ns, while the energy transfer efficiency reaches 37 %. It was also found that Förster resonance energy transfer may compete with other relaxation mechanisms and the Förster distance for the Ce3+-Nd3+ pair in PTR glass is ∼0.33 nm. This study has important implications for future research; it informs future studies on optimizing the photosensitivity of the PTR glass and choosing rare-earth activators.

Triplet Excimer Formation in a DNA Duplex with Silver Ion-Mediated Base Pairs.

The dynamics of excited electronic states in self-assembled structures formed between silver(I) ions and cytosine-containing DNA strands or monomeric cytosine derivatives were investigated by time-resolved infrared (TRIR) spectroscopy and quantum mechanical calculations. The steady-state and time-resolved spectra depend sensitively on the underlying structures, which change with pH and the nucleobase and silver ion concentrations. At pH ∼ 4 and low dC20 strand concentration, an intramolecularly folded i-motif is observed, in which protons, and not silver ions, mediate C-C base pairing. However, at the higher strand concentrations used in the TRIR measurements, dC20 strands associate pairwise to yield duplex structures containing C-Ag+-C base pairs with a high degree of propeller twisting. UV excitation of the silver ion-mediated duplex produces a long-lived excited state, which we assign to a triplet excimer state localized on a pair of stacked cytosines. The computational results indicate that the propeller-twisted motifs induced by metal-ion binding are responsible for the enhanced intersystem crossing that populates the triplet state and not a generic heavy atom effect. Although triplet excimer states have been discussed frequently as intermediates in the formation of cyclobutane pyrimidine dimers, we find neither computational nor experimental evidence for cytosine-cytosine photoproduct formation in the systems studied. These findings provide a rare demonstration of a long-lived triplet excited state that is formed in a significant yield in a DNA duplex, demonstrating that supramolecular structural changes induced by metal ion binding profoundly affect DNA photophysics.

Solid‐State Organic Fluorophore for Latent Fingerprint Detection and Anti‐Counterfeiting Applications

AbstractA highly fluorescent material exhibiting solid‐state fluorescence is particularly important in detecting latent fingerprints (LFPs) and anti‐counterfeiting applications. Herein, we have synthesized a coumarin‐benzothiazole moiety 3‐(benzo[d]thiazol‐2‐yl)‐2H‐chromen‐2‐one (3‐BTC) to inspect its capability to visualize LFPs and work as an anti‐counterfeiting ink. The compound showed yellow‐greenish emission under UV excitation and good covertness under visible light conditions. With the help of the powder dusting method, the latent fingerprints were coated with 3‐BTC powder and images of the LFPs developed over various substrates including plastic, steel, aluminium plate, rubber, etc. under UV 365 nm light displayed good resolution be able to discern the patterns of all the levels 1–3. Apart from fresh fingerprints (taken within 10 seconds), aged (over 60 days) and incomplete eccrine LFPs were successfully visualized using 3‐BTC powder. Anti‐counterfeiting ink prepared using 3‐BTC also proved to be a promising candidate as an anti‐counterfeiting ink. Various types of paper materials, including tissue paper, printing paper, newspaper, etc. were used for evaluating 3‐BTC as a satisfactory anti‐counterfeiting ink.