Enhancement Of Emission Intensity Research Articles

Photoluminescence Study of Undoped and Eu-Doped Alkali-Niobate Aluminosilicate Glasses and Glass-Ceramics

In this study, the photoluminescence (PL) behavior of two aluminosilicate glass series containing alkali-niobates ranging from 0.4 to 20 mol% was investigated. The glasses exhibit an intense visible emission centered at ~18,400 cm−1 for the peralkaline series and at higher energies (~19,300 cm−1) for the metaluminous glasses. However, the photoluminescence emission intensity varies significantly with the niobate content and the bulk chemistry. PL and fluorescence lifetime measurements indicate that the broad emission bands result from the overlap of different niobate populations, whose distribution changes with niobate content. The distinct PL behavior in the two glass series was related to the structural evolution of the niobate units upon niobium addition. An enhancement of the visible emission was observed for a higher fraction of distorted [NbO6] units. Eu-doping was carried out as a structural probe of the glass network, and also to determine if these glasses could be used as potential rare earth element (REE) activators. The crystal field strength around Eu ions is strongly dependent on the bulk chemistry and the niobate content. Furthermore, the peralkaline series showed energy transfer from the host [NbO6] to Eu3+, confirming the feasibility of exploring niobate glasses and glass-ceramics as lanthanide ion-activated luminescent materials. In addition, glass-ceramics (GCs) containing alkali-niobate phases with a perovskite-like structure were developed and studied to verify the optical performance of these materials. It was verified that the bulk chemistry influences crystallization behavior, and also the photoluminescence response. The transparent GC from the metaluminous series exhibits a quenching of the Eu3+ emission, whereas an enhanced emission intensity is observed for the peralkaline GC. The latter shows a strong excitation-dependent PL emission, suggesting energy transfer and migration of electronic excitation from one Eu population to another. Additionally, Eu3+ emissions arising from the D15 and D25 excited states were observed, highlighting the low phonon energy achievable in niobo-aluminosilicate hosts.

Excitonic Thermalization Bottleneck in Twisted TMD Heterostructures.

Twisted van der Waals heterostructures show intriguing interface exciton physics, including hybridization effects and emergence of moiré potentials. Recent experiments have revealed that moiré-trapped excitons exhibit remarkable dynamics, where excited states show lifetimes that are several orders of magnitude longer than in monolayers. The origin of this behavior is still under debate. Based on a microscopic many-particle approach, we investigate the phonon-driven relaxation cascade of nonequilibrium moiré excitons in the exemplary MoSe2-WSe2 heterostructure. We track exciton relaxation pathways across different moiré mini-bands and identify the phonon-scattering channels assisting the spatial redistribution of excitons into low-energy pockets of the moiré potential. We unravel a phonon bottleneck in the flat band structure at low twist angles preventing excitons from fully thermalizing into the lowest state, explaining the measured enhanced emission intensity and lifetime of excited moiré excitons. Overall, our work provides important insights into exciton relaxation dynamics in flat-band exciton materials.

Magnetic emission intensity enhancement for amorphous alloys by constructing a multi-phase structure with α-Fe nanocrystals

Magnetic emission intensity enhancement for amorphous alloys by constructing a multi-phase structure with α-Fe nanocrystals

From Fluorescence-Transfer-Lightening-Printing-Assisted Conductive Adhesive Nanocomposite Hydrogels toward Wearable Interactive Optical Information-Electronic Strain Sensors.

The interactive flexible device, which monitors the human motion in optical and electrical synergistic modes, has attracted growing attention recently. The incorporation of information attribute within the optical signal is deemed advantageous for improving the interactive efficiency. Therefore, the development of wearable optical information-electronic strain sensors holds substantial promise, but integrating and synergizing various functions and realizing strain-mediated information transformation keep challenging. Herein, an amylopectin-modified nanoclay/polyacrylamide-based nanocomposite hydrogel and an aggregation-induced-emission-active ink are fabricated. Through the fluorescence-transfer printing of the ink onto the hydrogel film in different strains with nested multiple symbolic information, a wearable interactive fluorescent information-electronic strain sensor is developed. In the sensor, the nanoclay plays a synergistic "one-stone-three-birds" role, contributing to "lightening" fluorescence (∼80 times emission intensity enhancement), ionic conductivity, and excellent stretchability (> 1000%). The sensor has high biocompatibility, resilience (elastic recovery ratio: 97.8%), and strain sensitivity (gauge factor: 10.9). Additionally, the amylopectin endows the sensor with skin adhesiveness. The sensor can achieve electrical monitoring of human joint movements while displaying interactive fluorescent information transformation. This research poses an efficient strategy to develop multi-functional materials and provides a general platform for achieving next-generation interactive devices with prospective applications in wearable devices, human-machine interfaces, and artificial intelligence. This article is protected by copyright. All rights reserved.

Benzocoumarin‐Fused Triskelions Exhibit AIEE Due to Inhibited Molecular Inversion

AbstractDeveloping aggregation‐induced emission luminogens (AIEgens) is a unique strategy for alleviating concentration quenching of π‐conjugated organic compounds. This AIE behaviour can be induced not only in organic dyes with rotors but also in invertible π‐conjugated systems. Herein, intramolecular Ullmann coupling was used to synthesize π‐twisted triskelion‐shaped AIEgens (2F, 2G, and 2H), in which benzo[f], [g], and [h] coumarins were fused into the benzene core to form a helical propeller shape. These structural isomers had unique molecular thicknesses and planarities depending on the fusion mode of the benzocoumarin. The racemic crystals, PPP and MMM, had different overlapping molecular configurations because of their twisted molecular frameworks. Compounds 2F, 2G and 2H demonstrated weak fluorescence emission in diluted solutions resulting from molecular motions caused by the isomerization process during molecular inversion. By comparison, aggregates exhibited enhanced emission intensity. These π‐twisted triskelions exhibited the characteristics of AIEgens.

EMM EMUS Observations of Hot Oxygen Corona at Mars: Radial Distribution and Temporal Variability

AbstractWe present the first observations of the dayside coronal oxygen emission in far ultraviolet (FUV) measured by the Emirates Mars Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM). The high sensitivity of EMUS is providing an opportunity to observe the tenuous oxygen corona in FUV, which is otherwise difficult to observe. Oxygen resonance fluorescence emission at 130.4 nm provides a measurement of the upper atmospheric and exospheric oxygen. More than 500 oxygen corona profiles are constructed using the long–exposure time cross–exospheric mode (OS4) of EMUS observations. These profiles range from ∼200 km altitude up to several Mars radii (>6 RM) across all seasons and for two Mars years. Our analysis shows that OI 130.4 nm is highly correlated with solar irradiance (solar photoionizing and 130.4 nm illuminating irradiances) as well as changes in the Sun–Mars distance. The prominent short term periodicity in oxygen corona brightness is consistent with the solar rotation period (quasi–27–day). A comparison between the perihelion seasons of Mars Year (MY) 36 and MY 37 shows interannual variability with enhanced emission intensities during MY 37, due to the rise of Solar Cycle 25. These observations show a highly variable oxygen corona, which has significant implications on constraining the photochemical escape of atomic oxygen from Mars.

Luminescent characteristics at ∼2.9 μm in Lu3+ modified Dy3+/Tm3+ co-doped LiYF4 single crystal

The single crystals specimens comprising 0.3 mol% Dy3+, 0.5 mol% Tm3+ and γ mol% Lu3+ doped LiYF4 (γ = 0, 0.3, 0.5, and 1.5) were meticulously synthesized using the Bridgman method, with the specific aim of catering to applications in the ∼2.9 μm laser domain. The microstructure of the obtained single crystal was investigated by conducting X-ray diffraction (XRD) measurements. The Judd-Ofelt (J-O) intensity parameters of the Dy3+ ion and the impacts of Lu3+ doping on fluorescence characteristics of the 6H13/2 (Dy3+) level were studied. The Dy3+/Tm3+ doped LiYF4 single crystal exhibits ∼52 % enhancement in emission intensity at ∼2.9 μm (Dy3+: 6H13/2→6H15/2) through a favorable introduction of Lu3+ ions into the single crystal at 808 nm LD excitation. The Tm3+/Dy3+/Lu3+ triply doped single crystal exhibited a maximum emission cross section of 2.480 × 10−20 cm2 at 2904 nm. The fluorescent lifetimes of the Dy3+: 6H13/2 level in the single crystals were determined to be located in the range of 2.78 ms–3.33 ms. The microscopic mechanism of energy transfer (ET) between Tm3+ and Dy3+ ions were investigated and the ET coefficients from 3H4 level of Tm3+ ion to 6F5/2 of Dy3+ ion (ET1) and 3F4 of Tm3+ to 6H11/2 of Dy3+ (ET2) in the triply doped single crystal were calculated, yielding values of 3.422 × 10−39 cm6/s and 5.768 × 10−39 cm6/s, separately. The results clearly demonstrated that the mid-infrared luminescence at ∼2.9 μm from Dy3+ ions can be significantly enhanced by the strategic incorporation of appropriate Lu3+ ions into Tm3+/Dy3+: LiYF4 single crystal.

Enhanced TNT vapor sensing through a PMMA-mediated AIPE-active monocyclometalated iridium(III) complex: a leap towards real-time monitoring.

Based on the explosive nature and harmful effects of nitro-based explosive materials on living beings and the environment, it is extremely important to develop luminescence-based probe molecules for their detection with excellent selectivity and sensitivity. Two AIPE (aggregation-induced phosphorescence emission)-active iridium(III) complexes (M1 and M2) were developed for the sensitive detection of TNT in both contact and non-contact modes. The aggregate solutions of both complexes (M1 and M2 in THF/H2O, 1/9 by volume) detected TNT at the pico-molar (pM) level. These complexes showed greatly enhanced emission intensity while embedded in a PMMA(polymethyl methacrylate) matrix film. The amplified quantum efficiency, improved phosphorescence lifetime, and enhanced porous network of M2-PMMA composite helps to improve the sesitivity of TNT vapor detection. Interestingly, the sensitivity of the detection of TNT by the M2 complex was significantly improved (5-fold) in a PMMA-incorporated complex (CP) with an observed limit of detection (LOD) of 12.8 ppb. From the BET analysis of CP, it was observed that the mesoporous network of CP has an average pore diameter of 8.52 nm and a surface area of 2.03 m2 g-1. The porous network of CP assists in trapping TNT vapor in a polymeric network containing an electron-rich probe (iridium(III) complex, M2), which helps to effectively trap TNT, thus enhancing electronic communication. As a result, significant emission quenching was observed.

Highly intense NIR emissive Cu4Pt2 bimetallic clusters featuring Pt(i)–Cu4–Pt(i) sandwich kernel

NIR phosphorescent Cu–Pt bimetallic clusters have been synthesized with solid-state quantum yield (QY) of up to 36.7%. Ligand effects enhances emission intensity and modulates emission wavelength via intra- and inter-molecular interactions.

Impact of nitridation on the up-conversion luminescence property of Yb3Al5O12: Er3+ phosphors upon 980 nm excitation

In this work, the nitriding method was used to improve the up-conversion (UC) luminescence intensity and temperature sensing sensitivity of phosphor materials. Yb3Al5O12: Er3+ and partially nitrided Yb3Al5O12-1.50xNx: Er3+ phosphors by using AlN as nitrogen source were prepared via solid-state reaction method. The influence of nitridation on the UC luminescence and temperature sensing properties of Yb3Al5O12: Er3+ phosphors upon 980 nm excitation were discussed. Almost pure red UC emission was obtained, and the intensity of the red UC emission of the samples was enhanced by 25 % after nitridation. Meanwhile, the absolute temperature sensitivity respectively derived from the intensity ratios of the green and red emissions increased by 5 % and 50 % after nitridation. Judd-Ofelt theory was utilized to analyze the change of the crystal field environment around Er3+ and confirmed that the introduction of N3– reduced the symmetry around Er3+ and strengthened the covalence between Er3+ and ligands, which may result in the enhancement of UC emission intensity and temperature sensing sensitivity. The experiment proved that Yb3Al5O12: Er3+ red UC phosphors had potential application in luminescence imaging and temperature sensors.

Overcoming the cyan gap for full‐spectrum lighting using cation‐substitution‐induced rigid Ca2YZr2Al3O12:Ce3+

AbstractMixing multicolor phosphors for simulating the full spectrum of sunlight illumination is a popular solution to obtain high‐quality white light. However, there is still a need to overcome the cyan gap in the emission spectrum. In this work, a series of garnet Ca2Y0.94–xLuxZr2–yHfyAl3O12:6%Ce3+ (abbreviated as CY0.94–xLuxZr2–yHfyA:Ce3+) cyan phosphors are designed and prepared by substituting Y3+ and Zr4+ in Ca2YZr2Al3O12:6%Ce3+ with Lu3+ and Hf4+ with smaller ionic radius and larger mass. Under 405 nm violet light excitation, the optimized Ca2Y0.88Lu0.06Hf2Al3O12:6%Ce3+ (CY0.88Lu0.06Hf2A:Ce3+) shows a bright cyan emission band in the range of 430–750 nm with the peak at 477 nm. Importantly, the emission intensity and thermal stability properties of CY0.88Lu0.06Hf2A:Ce3+ were significantly improved by 58% and 47% compared to those of pure Ca2YZr2Al3O12:Ce3+. Small and heavy cation substitution could induce highly stable rigid structure, thus enhancing emission intensity and stability. The color rendering index increases from 84.5 to 92.0 after supplementing CY0.88Lu0.06Hf2A:Ce3+ phosphor in white light‐emitting diode devices combining commercial red, green, and blue phosphors with a violet chip, indicating its practical application in full‐spectrum lighting. The present study provides promising strategies for the design and development of efficient cyan materials for high‐quality full visible spectrum light‐emitting diode lighting.

High-contrast multicolour photoswitching based on dithienylethene Schiff base with a hydrazinylquinoline moiety

A new asymmetrical photochromic diarylethene DTE-HQo composed of a 2-hydrazinoquinoline moiety as the binding unit for ions and dithenylethene as a photoswitching trigger was reported. DTE-HQo displayed favourable photochromism upon irradiation with UV/vis light. Its fluorescent behaviour could be efficiently modulated by light, Zn2+, Cd2+ and HSO4−. The binding of Zn2+ induced a strong fluorescence peak at 510 nm in DTE-HQo due to the formation of a 1:2 complex [Zn2+ + 2DTE-HQo], resulting in a notable colour change from dark to intense white emission. Triggered by Cd2+, DTE-HQo formed a 1:1 complex [Cd2+ + DTE-HQo], leading to an enhanced emission intensity by 21-fold with an emission peak red-shifted from 461 nm to 514 nm. Unexpectedly, [Zn2+ + 2DTE-HQo] underwent hydrolysis when stimulated with water, generating a yellow-emitting complex [Zn2+ + DTE-HQo]. This color change easily distinguishes it from Cd2+ complex. Additionally, DTE-HQo showed high selectivity towards HSO4− and exhibited distinct “turn-on” fluorescence with a colour change from dark to bright blue upon stimulation. Moreover, the strong emission complexes of DTE-HQo with Zn2+, Cd2+ and HSO4− could be effectively quenched during the photocyclization process. Therefore, DTE-HQo can serve as an unimolecular multicolour photoswitching chemosensor, offering potential applications as a multifunctional probe for detecting Zn2+, Cd2+ and HSO4−.

A reversible Schiff base chemosensor for the spectroscopic and colorimetric sensing of Eu3+ ions in solution and solid-state

Herein, the metal sensing properties of a previously reported aluminium sensor (E)-N’-((2-hydroxynapthalene-1-yl)thiophene-2-Carbohydrazide) (L) have been further explored in selective sensing of lanthanide ions. Among many tested lanthanide ions sensor L showed the selective colorimetric response for only Eu3+ ions. The presence of Eu3+ ions caused electronic transitions in the visible region with a color change from colorless to yellow in aqueous acetonitrile media. A red-shift in the absorption band and enhancement in emission intensity is investigated only for the addition of Eu3+ ions to L, without any interference of other existing ions. This chemosensor binds the Eu3+ ions in 1:1 stoichiometric ratio and works upto a detection limits, 2.179 × 10-8 M (LOD for Eu3+ at 415 nm from UV–Visible), 3.443 × 10-8 M (LOD for Eu3+ at 477 nm from fluorescence) with a binding constant of 8.691 × 103 M−1 for the L-Eu3+ binding. However, the developed sensor is used as a paper, cotton-based test kit assay and solid state colorimetric sensing of Eu3+ ions. The reversibility of sensor L is checked by colorimetric observation with the addition of sodium salt ethylenediaminetetraacetic acid (EDTA) and found it reversible up to three cycles.

Exploring luminescent color tunability and efficient energy transfer mechanism of a single-phased hexagonal nanophosphor for white light emitting diodes (WLEDs) application

Nowadays, NUV-triggered phosphor-converted white light-emitting diodes (pc-WLEDs) have gained prominence as substantial alternatives to conventional incandescent and fluorescent lamps as a source of illumination. In this study, we have successfully developed a Tm3+ codoped La2O3:Sm3+ nanophosphor and investigated its potential suitability for application in white light-emitting diodes (WLEDs). X-ray diffraction (XRD) analysis was conducted to examine the phase impurity and structural characteristics of the synthesized nanophosphor. The analysis confirmed the formation of a single-phase La2O3 nanophosphor with a hexagonal crystal structure. The FT-IR spectrum of the synthesized nanophosphor exhibited distinct peaks associated with the vibrational frequencies of La-O bonds. The peaks observed in the fingerprint region of the spectrum, indicate the presence of La-O atoms in the nanophosphor. However, the HR-TEM analysis confirmed that the prepared nanophosphor had a polycrystalline nature and the observed particle sizes lay within the nanoscale range. The incorporation of Tm3+ ions into the host matrix led to a reduction in the optical band gap, leading to enhanced emission intensity. The photoluminescence (PL) study reveals that the Tm3+ ion exhibited blue emission upon excitation at 360 nm, whereas the Sm3+ ion emits reddish-orange light when excited at 379 nm and 408 nm, respectively. However, under 325 nm excitation, the nanophosphor exhibited a white emission color that resulted from the blending of colors emitted by both Tm3+ and Sm3+ ions. This unique finding suggests that this nanophosphor has the potential to generate white light specifically under this particular excitation wavelength. The efficient energy transfer between Tm3+ and Sm3+ ions was attributed to the electric multipolar interaction between the nearest neighbor ions, leading to a quenching phenomenon. Furthermore, the photometric analysis revealed that the correlated color temperatures (CCTs) associated with the emitted white light were found to be higher than 4000 K. Thus, based on these characteristics, it can be inferred that the prepared nanophosphor has the potential to be utilized as a cool white-emitting nanophosphor for single-phased WLEDs application.

Synthesis, cadmium sensing ability and biological activities of a pyrrole-based macrocyclic Schiff base fluorescent ligand: DFT studies

A novel turn-on fluorescent sensor was designed for cadmium detection and synthesized by the condensation reaction of a prepared dialdehyde with diethylenetriamine, and characterized by FT-IR, UV–visible, 1HNMR, Mass spectra, and elemental analyses. According to the fluorescent findings, an approximately 3-fold enhancement of the emission intensity of L toward Cd2+ ions was observed at 430 nm, while 18 other metal ions did not make significant changes (LOD=2.7×10−9 M). DFT calculations confirmed the experimental results. Lowering the band gap (Eg) and increasing the electrophilicity index (ω) indicated that charge transfer is responsible for the enhancement of emission intensity of L when binding to Cd2+. The sensor (L) and its complexes exhibited significant antioxidant potency. Furthermore, [CdL] demonstrated much more extensive antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, among other evaluated compounds.

Energy transfer in Bi3+-Sm3+ co-doped phosphors for temperature sensing and imaging

Optical thermometry has the distinct superiority of non-invasive, non-contact, and high spatial resolution. However, the simultaneous improvement of temperature sensitivity and resolution remains challenging. Herein, the tunable emission colors can be realized via energy transfer in Bi3+-Sm3+ co-doped La3Ta0.8Sb0.2O7, which further applied for fluorescence temperature sensing and imaging. With the partial substitution of Sb5+ with Ta5+, the emission peak of La3SbO7:0.04Bi3+ shiftes from 530 nm to 460 nm, together with a 2.1-fold enhancement of emission intensity. The emission shifted from bright blue to purple under 365 nm excitation based on the energy transfer. The energy transfer efficiency from Bi3+ to Sm3+ can reach 41.6 % via dipole–dipole interaction. The La3Ta0.8Sb0.2O7:(0.04Bi3+,0.005Sm3+) phosphors exhibit maximum relative sensitivity (Sr) of 1.32 %K−1 (@498 K) and absolute sensitivity (Sa) of 0.059 K−1 (@417 K), which have excellent temperature resolution and repeatability. Thus, the energy transfer in co-coped phosphors can simultaneously improve the temperature sensitivity and resolution for fluorescence temperature sensing. Besides, the phosphor/PDMS films can exhibit obvious thermochromic imaging.

Microscopic and luminescence characteristics of Dy3+ doped KSrVO4 nanophosphors as energy efficient photoluminescent material with potential application in white light-emitting diodes.

Nanotechnology has drawn an enormous amount of attention by providing various measures to reduce energy consumption. Phosphor-converted white-light emitting diodes (pc-w-LEDs), which are used in lighting applications, are gaining popularity. These materials are affordable, effective, and safe for the environment. Therefore, the main objective of the current study is to synthesize an economical phosphor which consumes low energy and is less harmful to the environment. In this study, Dysprosium (Dy3+) doped Potassium Strontium Vanadate (KSrVO4) nanopowders synthesized via the combustion process and using X-ray diffraction, FESEM, EDAX, HRTEM, UV-Vis spectroscopy, and photoluminescence spectroscopy techniques, we have examined its various structural, spectroscopic, optical, and morphological characteristics. The crystallite size was estimated using the XRD patterns and was found to be 25.724 nm. The functional groups contained in synthesized phosphor were identified using FTIR spectrum measurements. Using HRTEM, a particle size of 36.33 nm was predicted, which is consistent with the XRD results. The Kubelka-Munk approximation is used to determine the band gap energy of the produced nanophosphors. Three major peaks that correspond to the transitions of 4F9/2 → 6HJ (J = 15/2, 13/2, and 11/2) were discovered at 476 nm, 578 nm, and 669 nm, respectively, under the excitation of 390 nm near UV light. We investigated the impact of Dy3+ doping, the enhancement of emission intensity and the mechanism of concentration quenching on the photoluminescence spectra of the KSrVO4 host. KSrVO4:Dy3+ also demonstrated a suitable CCT (3745 K), enhanced color purity and high quantum yield in this work, indicating that this phosphor has potential applications in w-LED devices.

Near-infrared optical nanothermometry via upconversion of Ho3+-sensitized nanoparticles

Recently, materials revealing the upconversion (UC) phenomenon, which is a conversion of low-energy photons to higher-energy ones, have attracted considerable attention in luminescence thermometry due to the possibility of precise and remote optical thermal sensing. The most widely studied type of luminescent thermometry uses a ratiometric approach based on changes in the UC luminescence intensity, mainly of lanthanide ions’ thermally coupled energy levels. In this work, NaYF4:Ho3+@NaYF4, and NaYF4:Ho3+, Er3+@NaYF4 nanoparticles (NPs) were synthesized by the controlled reaction in oleic acid and octadecene at 573 K. The obtained nanoparticles had hexagonal structures, oval shapes, and average sizes of 22.5 ± 2.2 nm and 22.2 ± 2.0 nm, respectively. The spectroscopic properties of the products were investigated by measurements of the UC emission under 1151 nm laser excitation in the temperature range between 295 to 378 K. The sample doped with Ho3+ and Er3+ ions showed unique behavior of enhancing emission intensity with the temperature. The relative sensitivity determined for the NPs containing Ho3+ and Er3+ ions, reached the maximum value of 1.80%/K at 378 K. Here, we prove that the NaYF4:Ho3+, Er3+@NaYF4 system presents unique and excellent optical temperature sensing properties based on the luminescence intensity ratios of the near-infrared bands of both Ho3+ and Er3+ ions.

Influence of Thermionic Emission on He Ionization and Plasma Enhancement in Thermionic Energy Conversion

In this paper, the influence of thermionic emission on He ionization and plasma enhancement in thermionic energy conversion (TEC) are studied by experiment and numerical simulation. A 1D unsteady plasma TEC model, which includes a He ionization model, plasma conservation equations, and a thermionic emission formula for the wall, is developed. A He plasma thermionic energy conversion device composed of a barium–tungsten cathode and a tungsten anode is established. The volt–ampere curves of the He plasma TEC device are measured at 1050 K, 1150 K, 1250 K, 1300 K, and 1350 K temperatures. Both important cathode parameters, work function and emission area, are estimated. Based on the modelling simulation and the experiment, the He ionization mechanism in plasma TEC is discovered. The effects of cathode temperature on several distributions of plasma reaction rates, particle number density, and potential in He plasma TEC are described. Some important parameters, including electron mobility, resistivity, and plasma equilibrium are analyzed. The relationship of thermionic emission on plasma enhancement to the output power of plasma TEC is presented. The output powers of plasma TEC and vacuum TEC are compared at various cathode temperatures. A dimensionless analyzing method concerning thermionic emission intensity and plasma enhancement power is proposed. A brief dimensionless relationship is deduced regarding thermionic emission intensity and the plasma enhancement contribution of TEC. The principles and methods for quantitative calculations concerning the output power of plasma TEC under the action of thermionic emission are established. It is possible to do quantitative research on the effects of thermionic emission on plasma-enhanced TEC.

The emission intensity enhancement and improved limit of detection of Cu, Ag, and Au using electric field assisted LIBS

Conventional LIBS suffers from several challenges including high detection limit and low sensitivity. The current approaches include electric field-assisted laser-induced breakdown spectroscopy (EF-LIBS) to study the laser ablation process and characterize the effectiveness of this method on several parameters such as plasma temperature, electron number density, intensity enhancement, and limits of detection. The purpose of the present study is to analyze the improvement in the signal intensity and limits of detection of Copper (Cu), Silver (Ag), and Gold (Au) using EF-LIBS. The laser plasma is generated by focusing a high-power laser beam on gold alloy samples. The intensities of Cu and Ag lines were normalized using the Au line to reduce the statistical errors. Calibration curves were drawn for each element to determine the limit of detection (LOD). The detection sensitivity was enhanced using an external electric field to the axial direction of plasma. The effect of the electric field on plasma parameters, limits of detection, and signal intensities has been studied. It was observed that LODs of Cu and Ag were improved from 14.3 ppm to 4.6 ppm–1.7 ppm and 2.06 ppm respectively with significant enhancement in the emission intensity. The present study demonstrates that EF-LIBS can be utilized for the better detection of precious elements in geological mineralogical and alloy samples. In addition, results showed that the single-shot EF-LIBS is a better choice for precious samples because of a smaller mass ablation against standard LIBS and it is a low-cost setup as compared to other analytical techniques.