Enhancement Of Emission Intensity Research Articles

Plasma Discharge across Metal Nanoparticle Surfaces and Plasma-Driven CO2 Reduction to CO and Higher Order Hydrocarbons

: By discharging nanosecond high voltage pulses (up to 25kV) across an insulating substrate coated with metal nanoparticles (Au or Pt), significantly enhanced plasma generation is observed through local field enhancement on the surface of the nanoparticles. The structural integrity of metal nanoparticles can be maintained due to the low-temperature nature of this transient plasma. Electrostatic simulations based on high-resolution transmission electron microscope (HETEM) image of the nanoparticles demonstrate a 3-fold enhancement of the electric field near the nanoparticle surfaces. Since field emission of electrons, which initiates plasma generation, depends exponentially on electric field, this 3-fold increase in the local electric field can significantly enhance plasma generation at a given applied external voltage. Similar enhancement was also observed by discharging in a methane environment, revealing a 50X enhancement in methane upconversion to C2 and higher order hydrocarbons, presenting the exciting possibility of converting a notorious greenhouse gas into an energy dense hydrocarbon fuel. Under laser irradiation, we observe a 200-fold enhancement in the plasma emission intensity, indicating the important role that hot electrons play in the electron emission process. In addition to gas phase plasma discharge, we also demonstrate CO2 reduction to CO and higher order hydrocarbons by discharging nanosecond high votlage pulses in CO2-saturated water, as revealed by C2 Swan band emission, cryogenic NMR spectroscopy and liquid ion chromatography, which indicate clear peaks corresponding to formic acid, methanol, and acetic acid.

Bright white light emission from (Gd3+ /Dy3+) dual doped transparent lithium aluminum borate glasses for W- LED application

The improving optical and luminescence properties of Dy3+ and Gd3+ dual doped lithium aluminum borate glasses with composition 25Li2O-5.0Al2O3-2.5Gd2O3-(67.5-X)B2O3-XDy2O3 glasses were successfully developed. The as-synthesis composite used conventional melt-quenching processes. All glass samples doped with Dy2O3 show an enhanced emission intensity (photo and radioluminescence spectra) with increasing the concentration of Dy2O3 up to 1.0 mol%, and beyond that, concentration quenching has occurred for all samples. The experimental decay times calculated from the decay profiles have been gradually declined with an increase in Dy3+ ion concentration. The chromaticity coordinates (CIE 1931) were located in the white light region of the color chromaticity diagram. The Dy-doping glasses synthesized show the prevalent presence of Dy3+also, the presence of the trivalent oxidation state in the glasses series. Therefore, the results confirm that the Dy3+-doped glasses could be useable for white-LEDs applications.

Synthesis and luminescence properties of NaBaPO4:Tm3+,Dy3+ white-light emitting phosphors with enhanced brightness by Li+ co-doping

In this paper, a series of NaBaPO4:Tm3+, Dy3+, Li+ (NBPO) single-doped and co-doped phosphors were synthesized successfully by the traditional high-temperature solid state reaction method. The samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) spectra and fluorescent decay curves. The XRD results showed that samples NaBaPO4: Tm3+, Dy3+ were matched well with the standard profile NaBaPO4.White light emission can be achieved by simply adjusting the doping concentration of Tm3+ and Dy3+ ions in NaBaPO4 host. The CIE coordinates (0.3192,0.2951) of phosphor NBPO: 0.01 Tm3+, 0.04Dy3+ was closest to the coordinates of ideal white light. The enhanced emission intensity was achieved by doping Li+ ions. When the Li+ ions doping concentration was 0.01, the emission intensity reached the maximum, which was 2.2 times the emission intensity of the non-doped Li + phosphor. The results demonstrated the promising application of NaBaPO4: Tm3+, Dy3+, Li+ phosphor for near-UV white LEDs.

Colorimetric and fluorimetric detection of fluoride ion using thiazole derived receptor

Thiazole based receptor 3, was designed and synthesized by condensation reactionof5–chlorosalicylaldehyde with 4-(4-phenylthiazol-2-yl)semicarbazide for colorimetric and fluorimetric detection of fluoride ion. Receptor 3 was characterized by 1H NMR, 13C NMR, and HRMS, and shows absorption in 280–400 nm region with emission at 442 nm in tetrahydrofuran (THF). Addition of fluoride ion to the THF solution of receptor 3 results in color change from colorless to yellow with significant change in UV–Visible absorption. The receptor–anion interaction occurs via hydrogen bonding followed by deprotonation which results in large bathochromic shift in absorption spectra and naked-eye color change. The colorimetric changes show selective response for fluoride ions over other anions. Fluorescence studies exhibit remarkable enhancement in emission intensity upon addition of fluoride ion with a limit of detection (LOD) of 8.6 nM. The 1H NMR titration studies exhibit deprotonation of the –OH proton of the salicylaldimine moiety resulting significant colorimetric and fluorimetric changes.

Luminescent imaging of insulin amyloid aggregation using a sensitive ruthenium-based probe in the red region

A sensitive and selective strategy to identify insulin fibrils remains a challenge for researchers in amyloid protein research. Thus, it is critical to detect, in vitro, the species generated during amyloid aggregation, particularly the fibrillar species. Here we demonstrate that the luminescent complex cis-[Ru(phen)2(3,4Apy)2]2+ (RuApy; phen = 1,10-phenanthroline; 3,4Apy = 3,4-diaminopyridine) is a rapid, low-cost alternative to in vitro detection of fibrillar insulin, using conventional optical techniques. The RuApy complex displays emission intensity enhancement at 655 nm when associated with insulin, which enables imaging of the conformational changes of the protein's self-aggregation. The complex shows high sensitivity to fibrillar insulin with a limit of detection of 0.85 μM and binding affinity of 12.40 ± 1.84 μM which is comparable to those of Thioflavin T and Congo red, with the advantage of minimizing background fluorescence, absorption of light by biomolecules, and light scattering from physiologic salts in the medium.

White-Light-Emitting Supramolecular Polymer Gel Based on β-CD and NDI Host-Guest Inclusion Complex.

Supramolecular polymer formed by non-covalent interactions between complementary building blocks entraps solvents and develops supramolecular polymer gel. A supramolecular polymer gel was prepared by the heating-cooling cycle of β-cyclodextrin (β-CD) and naphthalenedimide (NDI) solution in N,N-dimethylformamide (DMF). The host-guest inclusion complex of β-CD and NDI 1 containing dodecyl amine forms the supramolecular polymer and gel in DMF. However, β-CD and NDI 2, having glutamic acid, fail to form the supramolecular polymer and gel under the same condition. X-ray crystallography shows that the alkyl chains of NDI 1 are complementary to the hydrophobic cavity of the two β-CD units. From rheology, the storage modulus was approximately 1.5 orders of magnitude larger than the loss modulus, which indicates the physical crosslink and elastic nature of the thermo-responsive gel. FE-SEM images of the supramolecular polymer gel exhibit flake-like morphology and a dense flake network. The flakes developed from the assembly of smaller rods. Photophysical studies show that the host-guest complex formation and gelation have significantly enhanced emission intensity with a new hump at 550 nm. Upon excitation by a 366 nm UV-light, NDI 1 and β-CD gel in DMF shows white light emission. The gel has the potential for the fabrication of organic electronic devices.

Polymorph acceptor-based triads with photoinduced TADF for UV sensing

In contrast to many donor–acceptor type organic luminophores exhibiting thermally activated delayed fluorescence (TADF), two deep blue TADF emitters designed in this work contain only typical electron accepting moieties with different electron accepting abilities. Derivatives of benzophenone and diphenylsulfone substituted with phenothiazine-5,5-dioxide donor moieties were synthesized and studied. In addition to the TADF, green to blue emission color switching and strong fluorescence intensity enhancement by more than 60 times was detected for THF solution of the derivative of phenothiazine-5,5-dioxide and benzophenone under increase of UV excitation dose. We proved by a variety of experimental and theoretical studies that the unusual photophysical properties of the derivative of benzophenone are mainly related to the formation of different conformers. The photostimulated intensity enhancement of the compound is due to the rise of the quantity of triplet states and their further crossing to singlet states. To our knowledge, this is the first observation of a combination of photoinduced color switching and triplet-dependent emission intensity enhancement. These properties are shown to be useful for UV sensing with very low detection limits (less than 10 μW/cm2 for the toluene solution). Under gradual increase of UV excitation dose, the DMF solution demonstrated a green → blue color swishing from (0.34; 0.44) to (0.17; 0.18) of CIE coordinates that can be detected by naked eye.

Emission Intensity Enhancement for Iridium(III) Complex in Dimethyl Sulfoxide under Photoirradiation.

We found emission intensity enhancement for fac-Ir(ppy)3 (ppy = 2-(2'-phenyl)pyridine) in aerated dimethyl sulfoxide (DMSO) during photoirradiation for the first time. This phenomenon was concluded to be responsible for the consumption of 3O2 dissolved in DMSO through dimethyl sulfone production by photosensitized reaction using fac-Ir(ppy)3. A 3O2 adduct of DMSO molecule was detected by UV absorption measurement and theoretical calculation. We proposed a mechanism for the emission enhancement reaction including 1,3O2 molecules and 1,3O2-DMSO adducts and validated it through a simulation of emission intensity change using an ordinary differential equation solver.

Luminescence properties and energy transfer mechanism of La2ZnTiO6:Mn4+/Er3+ far-red/green dual-emitting phosphors for plant lighting

A new far-red/green dual-emitting phosphor La2ZnTiO6:Mn4+/Er3+ (LZT:Mn4+/Er3+) was successfully synthesized by the sol-gel method. Under 381 ​nm excitation, LZT:Mn4+/Er3+ phosphor shows the strong far-red emission peak of 709 ​nm (Mn4+: 2Eg→4A2g) and weak green emission peak of 523/548 ​nm (Er3+: 2H11/2/4S3/2 ​→ ​4I15/2), which consistent with the requirement of plant growth for far-red and green light. A 1.5-fold enhancement of far-red emission intensity is found in LZT:Mn4+/Er3+ phosphor compared with the Mn4+ singly-doped counterparts. Moreover, the relative emission intensity of far-red and green can be easily controlled by changing temperature. Utilizing the optimal LZT:0.2%Mn4+/2%Er3+ phosphor as plant lighting, a prototype near-UV-pumped LED device was fabricated. Upon 120 ​mA driving current, it demonstrated far-red/green dual emission. All the results indicated that the LZT:Mn4+/Er3+ phosphor is a potential material for plant growth illumination with far-red/green light.

A carbon-based fluorescent probe (N-CDs) encapsulated in a zeolite matrix (NaFZ) for ultrasensitive detection of Hg (II) in fish

In this work, a novel strategy was addressed to fabricate new sensing probe (N-CDs@NaFZ) from nitrogen doped carbon dots (N-CDs) confined in Al-free ferrisilicates zeolite (NaFZ) by hydrothermal/solvothermal method. The probe was systematically characterized by HR-TEM, FTIR, energy dispersive X-ray (EDX), powder X-ray diffraction, and UV–Vis absorption and fluorescence spectrophotometers. Characterization of the designed nanocomposite template N-CDs@NaFZ by fluorescence spectrum demonstrates a variety of important conducts as stability improvements, reasonable dispersibility in water, highly emission intensity enhancement at 435 nm when excited at 340 nm, excitation independent fluorescence behaviors, great quantum yield percentage of 91.2%, and narrow size distribution 12 nm, as a nano-space confinement effect of zeolite effectively increase the rigidity of N-CDs. Based on the fluorescence quenching mechanism, the designed approach exhibits an excellent selectivity and good sensitive response to the presence of Hg(II) ions under ambient temperature, with a wide linear range of 0.1–1500 nM and lower detection limits of 5.5 pM. Influences of variables pH and incubation time were optimized. The N-CDs@NaFZ sensor was effectively applied for the detection of Hg(II) ions in the farmed and wild rainbow trout fishes, and the results are in reasonable agreement when compared with that obtained by the cold vapor atomic absorption method.

Coupling of a single tin-vacancy center to a photonic crystal cavity in diamond

We demonstrate optical coupling between a single tin-vacancy (SnV) center in diamond and a free-standing photonic crystal nanobeam cavity. The cavities are fabricated using quasi-isotropic etching and feature experimentally measured quality factors as high as ∼11 000. We investigate the dependence of a single SnV center's emission by controlling the cavity wavelength using a laser-induced gas desorption technique. Under resonance conditions, we observe an intensity enhancement of the SnV emission by a factor of 12 and a 16-fold reduction of the SnV lifetime. Based on the large enhancement of the SnV emission rate inside the cavity, we estimate the Purcell factor for the SnV zero-phonon line to be 37 and the coupling efficiency of the SnV center to the cavity, the β factor, to be 95%. Our work paves the way for the realization of quantum photonic devices and systems based on efficient photonic interfaces using the SnV color center in diamond.

Self‐assembled CoSe2 Microspheres with Intrinsic Peroxidase Mimicking Activity for Efficient Degradation of Variety of Dyes

AbstractIn this investigation, we report a new and greener self‐assembly of CoSe2 microsphere (CoSe2 MS) without assistance of harmful reducing and structure‐directing agents (SDA). Intrinsic peroxidase mimicking activity of synthesized CoSe2 MS was evaluated for 3,3,5,5′‐tetramethylbenzidine as a substrate by monitoring the absorbance of oxidized product at 653 nm. The smaller Michalis Menten constant (Km) for CoSe2 MS catalyzed reaction (0.371 mM), than the natural Horse Radish Peroxidase (HRP) enzyme, signifies the high substrate affinity of CoSe2 MS than HRP. Further, intrinsic peroxidase activity was assessed using emission intensity enhancement of terephthalic acid (TA) in presence of CoSe2 MS and H2O2 with time due to the production of .OH radicals and subsequent hydroxylation of TA. CoSe2 MS was further employed for organic dyes degradation in presence of H2O2, where cationic and anionic dyes degraded within 120 min with the highest degradation efficiency of 99.45 % for malachite green.

LIBS technique combined with blow gas and vacuum suction to remove particle cloud and enhance emission intensity during characterization of powder samples

The present study reports developing a bench-top Laser-Induced Breakdown Spectroscopy (LIBS) set up for the online analysis of powder samples without sample preparation. The powder particle blow-off during pulsed laser ablation was mitigated by adding a blow gas (an inert gas blown across the ablation surface) and a suction unit (for extraction of the blow gas and blown-off particle cloud) to the existing LIBS setup. The influence of a blow-gas combined with a suction unit on LIBS emission intensity from coal powder and flyash particles is studied in the present work. The effect of the blow gas flow rate and the suction pressure was studied on the LI-BS emission intensity and removal of the laser blown-off particle cloud. The combination gas flow at 2 lpm (liter per minute) flow rate and suction at 925 mbar (absolute) show an increase in the LIBS emission intensity and effective particle removal. The ratio of LIBS emission intensity of the powder sample and solid-target (pellet) sample improved from 0.25 without the Ar gas flow and the suction unit to 0.85, which is by a factor of 3.4 times with the proposed approach.

A Double-Pulse Energy Injection Converter With Reduced Switching Frequency for MHz WPT System

Class-E inverter is widely used in the wireless power transmission (WPT) system due to its high efficiency. Generally, its switching frequency should be in accordance with the resonant frequency. In a weak-coupling case, the maintenance of high transmission efficiency requires a higher resonant frequency, which would restrict its application due to the corresponding high switching frequency. To solve the issue, this article proposes a Class-E-based inverter with the phase shift control strategy, which enables the operation frequency of the inverter much lower than the resonant frequency. Besides, the transmitting coil accepts power injection twice during each period, which greatly enhances emission intensity. In addition, the proposed phase shift control strategy avoids the weakness of an extremely low duty cycle. Hence, it contributes to the MHz middle power WPT system. Then, simulations and experiments are implemented to verify that the WPT system with the proposed inverter maintains a high efficiency within the middle range and realizes nearly 50% transmission efficiency even in a very weak-coupling coefficient ( k=0.08). Finally, it is proved that the proposed converter and its control strategy are available.

Phase and luminescence behaviour of Ce-doped zirconia nanopowders for latent fingerprint visualisation

Present work focuses on the phase evolution, emission behaviour of Ce-doped zirconia nanopowders, calcined under air and argon atmosphere and its application in latent fingerprint visualisation. The different concentration of Ce-doped ZrO2 nanoparticles were prepared via precipitation method using sodium borohydride and calcined at 600 °C under air and argon atmosphere. The tetragonal phase of zirconia was detected for all samples under air atmosphere. However, the crystalline phase of tetragonal zirconia was observed for above 1 mol% Ce-doped ZrO2 samples, calcined under argon atmosphere. A broad photoluminescence emission was observed in the UV and visible range for all samples due to 5D3/2 →7FJ transitions (J = 7/2 and 5/2) of Ce3+ ions. The increase of Ce-concentration causes more distortion in the tetragonal structure of zirconia, and provides an enhanced emission intensity under air atmosphere. However, the emission intensity was found to be similar under argon atmospheric condition due to lower crystallinity of t-zirconia. Further, all the samples lie in the violet-bluish region of the CIE-diagram. The latent fingerprint visualisation was explored using Ce-doped ZrO2 nanopowders on both non-porous and porous surface, and the obtained results validate its use in the forensic applications.

A colorimetric and fluorescence sensor based on biphenolic-dansyl derivative for specific fluoride ion detection

ABSTRACT 2ʹ-(2-((4-(methylthio)phenyl)amino)-2-oxoethoxy)-[1,1ʹ-biphenyl]-2-yl 5(dimethyl amino)naphthalene-1-sulphonate (1) was synthesised and used as a F− ion sensor. The selectivity of sensor 1 with various anions (F−, Cl−, Br−, CH3COO−, C6H5COO− and H2PO4 −) in DMSO was evaluated by 1H NMR, UV-visible and fluorescence study. For 1H NMR, an amide proton of sensor 1 disappeared due to the deprotonation reaction upon addition of F− ion. On the contrary, the proton signal of HF2 − emerged at 16.11 ppm. Upon addition of F− ion, sensor 1 showed a new absorption band at 300 nm and the solution turned colourless. For fluorescence response, sensor 1 exhibited the enhancement of emission intensity at 434 nm with slight blue shift when titrated with F− ion. These results suggest that sensor 1 possessed high sensitivity and selectivity towards F− ion detection. In addition, the sensor 1 test strip coated on TLC plates and filter papers were demonstrated for specific detection F− ion.

Exploitation of the Second Coordination Sphere to Promote Significant Increase of Room-Temperature Luminescence Lifetime and Anion Sensing in Ruthenium–Terpyridine Complexes

This paper deals with the synthesis, characterization, and photophysical behaviors of three Ru(II)-terpyridine complexes derived from a terpyridyl-imidazole ligand (tpy-HImzPh3Me2), wherein a terpyridine moiety has been coupled with a dimethylbenzil unit through a phenylimidazole spacer. The three complexes display strong emission at RT having excited-state lifetimes in the range of 2.3-43.7 ns, depending upon the co-ligand present and the solvents used. Temperature-dependent emission spectral measurements have demonstrated that the energy separation between emitting metal-to-ligand charge transfer state and non-emitting metal-centered state is increased relative to that of [Ru(tpy)2]2+. In contrast to our previously studied Ru(II) complexes containing similar terpyridyl-imidazole motif but differing by peripheral methyl groups, significant enhancement of RT emission intensity and quantum yield and remarkable increase of emission lifetime occur for the present complexes upon protonation of the imidazole nitrogen(s) with perchloric acid. Additionally, by exploiting imidazole NH motif(s), we have examined their anion recognition behaviors in organic and aqueous media. Interestingly, the complexes are capable of visually recognizing cyanide ions in aqueous medium up to the concentration limit of 10-8 M. Computational studies involving density functional theory (DFT) and time-dependent DFT methods have been carried out to obtain insights into their electronic structures and to help with the assignment of absorption and emission bands.

Influence of doping with Sb3+, In3+, and Bi3+ ions on the structural, optical and dielectric properties of ZnS nanoparticles synthesized by ultrasonication process

Doped-ZnS nanoparticles (NPs) with various trivalent elements ions (Sb3+, In3+, and Bi3+) were synthesized using the sonochemical method. X-ray diffraction patterns proved the formation of the ZnS cubic phase without any phase separation with the doping process. The dependence of the crystallite size and the internal micro-strain on the dopant type was demonstrated. Optical absorption spectra of doped ZnS NPs revealed a decrease in the optical band gap due to the formation of extended defect states below the conduction band. Photoluminescence spectra of the doped samples revealed the enhancement of visible light emission intensity compared with the as-prepared ZnS NPs. The AC electrical properties of the trivalent elements doped ZnS NPs were studied at room temperature in the frequency range from 2 kHz to 1 MHz, where In-doped ZnS NPs had the lowest dielectric constant and largest conductivity compared with the other samples.

Remarkable enhancement of upconversion emissions by thermal stimulation in Er-doped Yb2Mo3O12 microcrystals

Lanthanide-doped luminescent materials have drawn great attention due to their lighting, display, and sensing applications. However, their emission intensity usually decreases with increasing temperature, leading to a weaken performance. In this work, the Er3+-doped Yb2Mo3O12 microcrystals with optical temperature sensing properties have been synthesized by a solid-phase sintering route. Under the excitation of a 980 nm laser, the sample shows enhanced upconversion emissions as temperature rises, which is attributed to the negative thermal expansion in the crystal structure and enhanced crystal field strength. At the same time, based on the luminous intensity ratio of two thermally coupled energy levels (Er3+:2H11/2,4S3/2), the temperature sensing properties of the prepared microcrystals were studied. This work achieves high SR (1207.4/T) in the range from 313 to 573 K, and it is accompanied by a 21-fold enhancement of the upconversion emission intensity. As a whole, this is an excellent material that can be used for optical temperature sensing with highly sensitive and enhanced upconversion emission.

Fabrication of Nd3+ and Yb3+ doped NIR emitting nano fluorescent probe: A candidate for bioimaging applications

The intentional design of rare earth doped luminescent architecture exhibits unique optical properties and it can be considered as a promising and potential probe for optical imaging applications. Calcium fluoride (CaF2) nanoparticles doped with optimum concentration of Nd3+ and Yb3+ as sensitizer and activator, respectively, were synthesized by wet precipitation method and characterized by x-ray diffraction (XRD) and photoluminescence. In spite of the fact that the energy transfer takes place from Nd3+ to Yb3+, the luminescence intensity was found to be weak due to the lattice defects generated from the doping of trivalent cations (Nd3+ and Yb3+) for divalent host cations (Ca2+). These defect centres were tailored via charge compensation approach by co-doping Na+ ion and by optimizing its concentration and heat treatment duration. CaF2 doped with 5 mol% Nd3+, 3 mol% Yb3+ and 4 mol% Na+ after heat treatment for 2 h exhibited significantly enhanced emission intensity and life time. The ex vivo fluorescence imaging experiment was done at various thickness of chicken breast tissue. The maximum theoretical depth penetration of the NIR light was calculated and the value is 14 mm. The fabricated phosphor can serve as contrast agent for deep tissue near infrared (NIR) light imaging.