Low Luminescence Research Articles

The Urges

The Urges Deborah Allbritain (bio) Stored in mason jars, lining the window ledge.Blue sulks unruly, demands salt or elsea pleading syrup. Ochre whispers Italian,Loneliness is a hole nothing lives in.Carmine, like finger notes poured from the ram.Let’s pretend. You be the happy bear,sugar-coaxed, sipping this sherry pinkedaniline. And sarcoline, the colorof our limbs, calms any grief, ghost-stockingscaught in trees. Flaming a hole in your skull,the double jar, perilous, a deep red falu—unscrewed then askew, your tender-wet futurea low luminescence, a crave like whine,the oldest urge, specifically mine. [End Page 85] Deborah Allbritain deborah allbritain’s poetry appears or is forthcoming in Beloit Poetry Journal, Potomac Review, the MacGuffin, Salamander, the Laurel Review, Sugar House Review, the Greensboro Review, and B O D Y Literature. She received the Patricia Dobler Poetry Prize in 2017. * Copyright © 2021 University of North Carolina Wilmington

Enhanced emission from CH3NH3PbBr3 perovskite films by graphene quantum dot modification

Organic-inorganic hybrid perovskites have emerged as promising emitters with the benefits of low cost and high color purity, but their low luminescence efficiency is a drawback for practical application on light emitting devices. Here we show that by incorporating proper amount of graphene quantum dots (GQDs) into perovskite precursor, dense CH3NH3PbBr3 films with reduced grain size and well passivated grain boundaries could be obtained. This gives rise to enhanced emission from GQD modified perovskite films. Our work thus provides a viable way to prepare highly luminescent perovskite films for optoelectronic applications.

Разнолигандные комплексные соединения европия (III) с o-метоксибензойной кислотой и фосфорсодержащими нейтральными лигандами

The luminescent coordination multi-ligand compounds of europium (III) with o-methoxybenzoic acid and island-containing phosphorus-containing neutral ligands of the composition Eu (MOBA) 3 • 3Н2О and Eu (MOBA) 3 • L, where MOBA is o-methoxybenzoic acid, D is hmpa (D hexamethylphosphoric triamide), tppo (triphenylphosphine oxide), Et6pa (hexaethylphosphotriamide). The composition, structure, and thermal properties of complex multi-ligand compounds of europium (III) were studied. It was shown that during thermolysis, detachment of a neutral ligand molecule occurs in one stage with an endothermic effect, complex compounds are stable up to 280 С.Based on the data of IR spectroscopy, it was found that in the europium (III) o-methoxybenzoates, the o-methoxybenzoic acid is coordinated to the europium (III) o-methoxybenzoic ion in a bidentate manner. The low luminescence intensity of multi-ligand europium (III) compounds is explained by the inefficient transfer of electronic excitation energy from o-methoxybenzoic acid and phosphorus-containing neutral ligands to the europium ion.

Highly Efficient Organic Afterglow from a 2D Layered Lead-Free Metal Halide in Both Crystals and Thin Films under an Air Atmosphere.

Organic afterglow materials (OAMs) with a lifetime longer than 0.1 s have recently received much attention for their fascinating properties meeting the critical requirements of applications in newly emerged technologies. However, the development of OAMs lags behind for their low luminescence efficiency. Usually, enhancing the phosphorescence efficiency of organic materials causes a short lifetime. Here, we report two kinds of OAMs, two-dimensional (2D) layered organic-inorganic hybrid zinc bromides (PEZB-NTA and PEZB-BPA), obtained in an environmentally friendly ethanol solvent by a low-temperature solution method. They display highly efficient and persistent luminescence in air in both crystals and thin films with phosphorescence quantum yields up to 42% in crystals and 27% in films. For OAMs, the two quantum yields are the highest values ever reported for crystals and films. Due to the excellent crystalline and film-forming ability, PEZB-NTA and PEZB-BPA in ethanol can be used as inks to construct patterns on various rigid and flexible substrates, including paper, iron, plastic, marble, tin foil, and cloth. Consequently, the novel OAMs show great application prospects in the fields of anti-counterfeiting and information storage because of their economic synthesis, solution processing, and easy operation.

The enhancement mechanism of Yb3+/Tm3+/12CaO·7Al2O3 via Li+ incorporation and temperature sensing applications

The manipulation of enhancing the upconversion emission and temperature sensing for obtaining new bifunctional materials is significant. However, the application of upconversion materials suffers from low luminescence efficiency and low temperature sensitivity. Herein, the enhancement of upconversion luminescence and high-temperature sensing in the Yb3+/Tm3+/12CaO·7Al2O3 system (the host material can work at temperatures greater than 1000 °C with high melting points and strong mechanical properties) have been achieved with Li+ ions doped via the solid-state reaction method. The blue upconversion emission was increased ∼43 times with Li+ ion doping, mostly due to the distorted crystal field (replacing Ca2+ site, occupying interstitial space and oxygen vacancy) and the reduction of quenched ions. And the energy transfer efficiency increase from ∼37.6% to ∼70.5% with the doping of Li+ ions. Furthermore, a high Sa of 2.33 10−3 K−1 was obtained. These results provided a new platform for the design of a blue light visible laser and optical temperature sensor.

Plasma effect：A simple method for improving the persistent luminescence and light response range of persistent luminescent materials

The persistent luminescent materials are important energy-saving and environmentally friendly materials used in wide application range, but the application scale is relatively small. In order to overcome the problems of narrow light response range and low persistent luminescence performance, the Ag/Sr2MgSi2O7:Eu2+,Dy3+ structure was firstly shaped by a photoreduction deposition method. The persistent luminescence performance and the photo response range are greatly improved via the plasmon resonance after the deposition of Ag on the surface of Sr2MgSi2O7:Eu2+,Dy3+. The initial brightness can be increased by a factor of 9, while the range and intensity of absorbed light are greatly changed, indicating that the plasmon resonance of Ag can be applied to persistent luminescent material, which can efficiently increase the number of photogenerated electrons and holes which will be captured and released, thereby effectively improving the afterglow performance. The influence mechanism of Ag on the generation of photogenerated electrons and holes, the number and depth of traps, and the transfer-capture-release-luminescence mechanism of photogenerated electrons and holes, namely the persistent luminescence enhancement mechanism, are revealed. The development of this research can promote the application of Sr2MgSi2O7:Eu2+,Dy3+, and meanwhile provide an effective method for improving the persistent luminescence of various persistent luminescent materials.

A Strategy of NIR Dual-Excitation Upconversion for Ratiometric Intracellular Detection.

Intracellular detection is highly desirable for biological research and clinical diagnosis, yet its quantitative analysis with noninvasivity, sensitivity, and accuracy remains challenging. Herein, a near‐infrared (NIR) dual‐excitation strategy is reported for ratiometric intracellular detection through the design of dye‐sensitized upconversion probes and employment of a purpose‐built NIR dual‐laser confocal microscope. NIR dye IR808, a recognizer of intracellular analyte hypochlorite, is introduced as energy donor and Yb,Er‐doped NaGdF4 upconversion nanoparticles are adopted as energy acceptor in the as‐designed nanoprobes. The efficient analyte‐dependent energy transfer and low background luminescence endow the nanoprobes with ultrahigh sensitivity. In addition, with the nonanalyte‐dependent upconversion luminescence (UCL) excited by 980 nm as a self‐calibrated signal, the interference from environmental fluctuation can be alleviated. Furthermore, the dual 808/980 nm excited ratiometric UCL is demonstrated for the quantification of the level of intracellular hypochlorite. Particularly, the intrinsic hypochlorite with only nanomolar concentration in live MCF‐7 cells in the absence of exogenous stimuli is determined. Such an NIR dual‐excitation ratiometric strategy based on dye‐sensitized UCL probes can be easily extended to detect various intracellular analytes through tailoring the reactive NIR dyes, which provides a promising tool for probing biochemical processes in live cells and diagnosing diseases.

Intensive measures of luminescence in GaN/InGaN heterostructures.

The intensive measures of luminescence in a GaN/InGaN multiple quantum well system are used to examine the thermodynamics and phenomenological structure. The radiative /nonradiative transitions along with absorbed or emitted phonons that occur between the different quantum states of the electrons and holes associated with these processes make the quantum efficiency of a semiconductor nanosystem in an equilibrium state an extensive property. It has long been recognized that tuning of the indium (In) composition in InGaN interlayers gives the potential to obtain a spectrum in the near-infrared to near-ultraviolet spectral range. The thermodynamic intensive properties, including the Debye temperature, carrier temperature, and junction temperature, are the most appropriate metrics to describe the optical-related interactions inherent in a given heterostructure and so can be used as the state variables for understanding the quantum exchange behaviors. The energetic features of the quantum processes are characterized based on analysis of the intensive parameters as determined by means of electroluminescence (EL) and photoluminescence (PL) spectroscopy and current-voltage measurement and then correlated with the designed InGaN/GaN microstructures. According to the McCumber-Sturge theory, the EL and PL Debye temperatures obtained experimentally signal the strength of the electron-phonon and photon-phonon interaction, respectively, while the EL and PL carrier/junction temperatures correspond to the carrier localization. Higher EL Debye temperatures and lower EL carrier/junction temperatures reflect significantly higher luminescence quantum yields, indicative of electron-phonon coupling in the transfer of thermal energy between the confined electrons and the enhancement by excited phonons of heat-assisted emissions. On the other hand, the observation of low luminescence efficiency, corresponding to the lower PL Debye temperatures and higher PL carrier/junction temperatures, is attributed to photon-phonon coupling. These findings are in good accordance to the dependence of the EL and PL quantum efficiency on the In-content of the InGaN/GaN barriers, suggesting that the characteristic Debye and carrier/junction temperatures are intensive parameters useful for assessing the optical properties of a nano-engineered semiconductor heterostructure.

Structure and Photoluminescence Properties of Hybrid Nanocomposites on the Base of PP/PbS/CdS

In given paper, were studied optical properties of nanocomposites obtained on base of PP + PbS/CdS with different concentration. The UV–Vis spectral analysis indicated that the optical band gap of the system was decreases with increasing of concentration of semiconductor nanoparticles inside the polymer. This can be explained by increasing of size of nanoparticles due to agglomeration of nanoparticles with increasing of concentration. SEM analysis of PP + PbS/CdS based nanocomposites showed that particle size in PP + 3% PbS/CdS, PP + 5% PbS/CdS, and PP + 15% PbS/CdS nanocomposites was the range of 5–10 nm, 12–18 nm, and 18–34 nm in respectively. At the same time, were investigated luminescence spectra of nanocomposites with different concentrations obtained on the base of PP + PbS/CdS. It has been established that the highest luminescence intensity is observed in nanocomposites PP + 3% PbS/CdS. This can be explained by the fact that in this concentration the luminescent centers are more active and more optimal structures are formed. At the same time, low luminescence intensity in PP + 15% PbS/CdS nanocomposites can be explained by reduction of the luminescence surface and weakening of activity of centers due to the growing size of particles by agglomerating with increasing of concentration.

(Invited) Large Photoluminescence Enhancement of Monolayer Molybdenum Disulfide Via Molecular Treatment

Molecular interaction is an essential process in various fields such as chemistry, biology and materials science. The interaction of molecules includes: 1) the local electron transfer process, 2) local chemical bonding and 3) assembling to form a structure. All three occur essentially from each molecule’s “recognition” ability. We are trying to extend the molecular interaction system onto inorganic electronic materials to harness the highest-performance of inorganic systems. In this presentation, I will present our recent results of molecular interaction on a semiconducting 2D material, transition metal dichalcogenides (TMDCs).1,2,3 TMDCs are constructed by stacking atomically-thin layers (thickness ~0.7 nm) with van der Waals interaction, and they are expected to generate tiny optoelectronic devices due to their thin nature. Since monolayer TMDC has a direct bandgap, it is a good platform for realizing atomically thin optoelectronic devices. However, an issue is their low luminescence brightness. For example, a representative TMDC, MoS­2, shows photoluminescence (PL) quantum yield of ~1% or less. In this presentation, I will show our recent results of improving the brightness of monolayer MoS2 dramatically (more than 100 times enhancement from the original) via molecular treatments. One method is using a superacid (bis(trifluoromethane)sulfonimide; TFSI) molecule.3 The superacid molecular treatment onto a monolayer MoS2 changes the PL quantum yield of MoS2 from 1% to near-unity. I will discuss the PL enhancement factor in the TFSI treatment on MoS2. The second method is using a redox-active molecule, fluoranil. The fluoranil molecule can reduce the electron concentration of monolayer MoS2, resulting in enhancement of the PL intensity.4 Furthermore, we found that the solvent used for the fluoranil treatment is critical to obtain bright monolayer MoS2. Solvent molecules would screen the charges on fluoranil molecules, as a result, which stabilizes the electron transfer-interaction between fluoranil and MoS2. Keywords: Superacid, redox-active molecules, Transition metal dichalcogenides, Photoluminescence, Transistors

Greatly enhanced luminescence efficiency of CdS nanoparticles in aqueous solution

A simple shell-creating technique for the synthesis of CdS nanoparticles covered by ZnS is presented, which also contributes to the understanding of their low quantum yield and luminescence intensity in water, which is usually below 0.01%. The CdS nanoparticles with about 0.8 nm thick ZnS shell were synthesized in a colloidal aqueous solution and stabilized by EDTA. The CdS carrier lifetime and the quantum efficiency is greatly increased. For the latter, values up to 2.7% were achieved. A mechanism for the CdS nanoparticle luminescence in the aqueous solution is proposed, which is based on radiative recombination of charge carriers with structural defects. It was found that the synthesis of CdS in air leads to the inclusion of oxygen atoms in the structure of nanoparticles, which strongly effects the luminescence spectrum. These results show that most of the CdS luminescence centers are localized inside the nanoparticle.

Energy Loss Mechanism of Upconversion Core/Shell Nanocrystals

Small-sized upconversion nanocrystals (<10 nm) show a quite low luminescence efficiency. Even if these nanocrystals are coated by a 2 nm thick inert shell, the core/shell nanocrystals still exhibit...

Luminescent Properties of Europium(III) Compounds with Quinolinic Acid and Phosphorus-Containing Neutral Ligands

Luminescent mixed-ligand europium(III) complexes with quinolinic acid and phosphorus-containing neutral ligands with a dimeric structure of the composition Eu2(QA)3 · 3Н2О, Eu2(QA)3 · D · 2Н2О, where QA is quinolinic acid and D is hmpa (hexamethylphosphortriamide), tppo (triphenylphosphinoxide), (hmpa), or Et6pa (hexaethylphosphortriamide), are synthesized. The thermal and spectral-luminescent properties of the synthesized complex mixed-ligand europium(III) compounds are studied. It is shown that the detachment of water and neutral ligand molecules during thermolysis occurs in two stages with endothermic effects and that the complex compounds are stable at temperatures up to 320°С. It is found by IR spectroscopy that quinolinic acid coordinates to the europium(III) ion by two carboxylate ions. The low luminescence intensity of mixed-ligand europium(III) quinolinates is explained by inefficient electronic excitation energy transfer from quinolinic acid and phosphorus-containing neutral ligands to europium ions.

A 14-bp functional deletion within the CMTM2 gene is significantly associated with litter size in goat

CKLF-like MARVEL transmembrane domain-containing 2 (CMTM2) plays an important role in animal reproduction, and abnormal CMTM2 expression leads to spermatogenesis disorders. This study was conducted to assess the role of CMTM2 in goat reproduction by investigating an insertion/deletion (indel) variation and its effect on litter size, and to reveal its functional mechanism. A 14-base pair (bp) indel was found at position −861 to −848 nt of the CMTM2 promoter in 1131 female Shaanbei white cashmere goats. Association analyses revealed that the 14-bp indel in dams was significantly correlated with the size of the first litter (P = 0.013), with the 14-bp deletion significantly decreasing litter size. Moreover, litter size at first kidding was significantly correlated with genotype frequencies (P = 0.019). Expression of the goat CMTM2 gene was detected in testes and ovaries. In male, CMTM2 was increased after the initiation of meiosis in the developing testis. In female, CMTM2 expression was higher in ovary from multiple prolific goats at first kidding compared to non-prolific goats. Moreover, both in testis after initiation of meiosis and in ovary, the homozygous 14-bp inserted genotype II was associated with increased CMTM2 expression compared to the heterozygous genotype ID (P < 0.05). To further explore whether the 14-bp indel was located in the core promoter activity region of the CMTM2 promoter, the five recombinant plasmids pGL3-pro1 (−1756 to +83), pGL3-pro2 (−1200 to +83), pGL3-pro3 (−763 to +83), pGL3-pro4 (−496 to +83), and pGL3-pro5 (−205 to +83) were co-transfected with pRL-TK into HEK293T and GC-1 cells. A luciferase reporter assay showed that the pGL3-pro2 and pGL3-pro5 vectors produced significantly stronger luminescence than the other vectors. Interestingly, the 14-bp indel locus was included in the pGL3-pro2 plasmid, suggesting that the indel was functional. Subsequently, the two recombinant plasmids pGL3-pro2-inserted-allele and pGL3-pro2-deleted-allele were co-transfected with pRL-TK into HEK293T and GC-1 cells, respectively. The luciferase reporter assay demonstrated that the deleted allele of CMTM2 showed significantly lower luminescence activity than the inserted allele (P < 0.05), which corresponded to a decrease in litter size in the deletion-deletion genotype. Therefore, our results suggest that a 14-bp deletion in the promoter region of CMTM2 is significantly correlated with litter size in goats; this marker seems promising for breeding selection for improving economically important traits in goats.

Highly efficient silica-coated Eu3+ and Mn2+ doped CsPbCl3 perovskite quantum dots for application in light-emitting diodes

Perovskite quantum dots (PQDs) are potential luminescent materials for display and LED illumination, whereas CsPbCl3 quantum dots (QDs) exhibit low luminescence quantum yields (QYs), limiting their wide application. In this work, Mn2+ and Eu3+ doped all-inorganic CsPbCl3 QDs were prepared, which were encapsulated into SiO2 film to form ultra-stable and highly luminescent CsPbCl3/SiO2 composites. Through silica coating, surface defects of the composites were reduced effectively, the luminescence QYs of the Eu3+ doped CsPbCl3 PQDs increased from 3.52% to 49.00%, and those of the Mn2+ doped CsPbCl3 PQDs increased from 21.01% to 50.84%. Using these composites, LEDs were prepared, exhibiting good stability and high luminescent efficiency for lighting applications.

Defect Engineering in 2D Perovskite by Mn(II) Doping for Light-Emitting Applications

Summary Low-dimensional perovskites are considered good candidates for light-emitting applications given their high exciton binding energy. Yet, single-layered two-dimensional (2D) perovskites are strongly limited by trap-assisted recombination and suffer from low luminescence yields, hampering their application in electroluminescence devices. Here, we use synthetic and defect engineering strategies to overcome such issues. We employ metallic doping (Mn2+ and Eu3+) to introduce luminescent impurities in the 2D perovskite NMA2PbX4 (NMA = 1-naphtylmethylammonium). By means of temperature-dependent and time-resolved spectroscopy, we demonstrate efficient energy transfer to Mn2+ centers. This avoids funneling of photo-excited species in inefficient recombination channels, enhancing photoluminescence and giving a quantum yield surpassing 20% in doped films. Eventually, we embody Mn-doped NMA2PbBr4 in a light-emitting diode architecture and show electroluminescence from the Mn2+ 4T1 → 6A1 transition. This proof-of-concept demonstration shows the potential of doping in layered perovskites and prompts the study of a wider range of host-guest structures.

Visible-Light Photocatalysts of ZrO2/AgCl:Eu3+ Nanoparticles

This paper reports the visible-light photocatalysts and luminescence quenching of ZrO2/AgCl:Eu3+ nanoparticles synthesized by the co-precipitation method as a function of AgCl concentration. XRD analysis indicated the presence of crystalline tetragonal ZrO2 and an AgCl phase. The synthesized ZrO2/AgCl:Eu3+ nanoparticles were observed to have a spherical morphology with diameters of ∼ 20 nm. The photocatalyst with 2.5% mole fractions of AgCl showed effective degradation of methylene blue under visible light with the decolorization percentage reaching ∼ 95% in 180 min. The red emission of Eu3+ in the ZrO2/AgCl:Eu3+ nanoparticles decreased with increasing AgCl mole fraction. Visible-light photocatalysts of ZrO2/AgCl:Eu3+ nanoparticles can be attributed to the presence of AgCl resulting in higher photoexcited charges separation, which can be confirmed by lower luminescence intensity.

Preparation of ZnSe Quantum Dots by Hydrothermal Method Assisted by Ammonia

ZnSe quantum dots (QDs) with high intrinsic fluorescence quantum efficiency (QY) and low defect luminescence were prepared by hydrothermal method assisted with ammonia, in which the selenium powder and zinc acetate were used as Se and Zn source, and the mercaptopropionic acid (MPA) was used as ligand. Effect of ammonia amount, Zn/Se ratio, Zn/MPA ratio, and reaction time was investigated in detail in this study. The as-prepared ZnSe QDs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-visible absorption spectrum (UV-Vis), fluorescence spectrum (PL). ZnSe QDs assisted with ammonia were sphalerite, and with emission peak in the range of 380~405nm. The optimal condition was following: Zn/Se ratio was 5, Zn/MPA ration was 0.25, reaction temperature was 110 °C and reaction time was 6 h. Under the optimal condition, ZnSe QDs with intrinsic emission QY of 47% and diameter of 3.8±0.3 nm can be obtained. The ZnSe QDs prepared in this study were expected to replace toxic Cd-related QDs in biomarkers, violet and blue light solid luminescent devices, and provide excellent parent materials for the doped ZnSe QDs system.

Investigations on the interaction of water-soluble semiconductor polymer with thioglycolic acid (TGA) capped CdTe quantum dots

Studies of nanocomposites produced by the association of quantum dots (QDs) and polymers, in general, use the nanocrystals as the energy's donor and the polymer's molecules as acceptors. The production of nanocomposites in which a water-soluble polymer is the energy donor species and the quantum dots the acceptors species is particularly difficult due to low luminescence quantum yield and low fluorescence lifetimes of these molecules when compared to the QDs. In this work, we associated colloidal CdTe QDs stabilized with thioglycolic acid (TGA) with water-soluble semiconductor luminescent polymer Poly{[2,5-bis(2-(N,N-diethylamino)ethoxy)-1,4-phenylene]-alt-1,4-phenylene} (PPE-DBE) to produce nanocomposites that favors the polymers as donors and QDs as acceptors. We characterized the composites by absorption, static fluorescence, and dynamic fluorescence. Our results showed the intensification of the QDs emission and its quantum yield on the nanocomposite and the decrease of the polymer lifetime. Thus, we verified the occurrence of energy transfer from the polymer to the quantum dots, especially for samples which the ratio of PPP-DBE monomers per number of QDs in solution is approximately 465, achieving an increase of 11.34% on the QDs' fluorescence quantum yield.

Tailored emission to boost open-circuit voltage in solar cells

Recently, a lot of research focus has been on how to make solar cells more efficient. One direction is to enhance the open-circuit voltage V oc by optimizing the emission of photons in the cell, where emission is a necessary loss process due to the reciprocity between absorption and emission of light. Here, we performed a Shockley-Queisser detailed balance analysis to predict the benefit of managing emitted photons in a single-junction solar cell. First, at low internal luminescence efficiency η int, non-radiative recombination dominates, and management of emitted photons plays negligible role for V oc. Similarly, for an external luminescence efficiency η ext < 10%, externally emitted photons play negligible role, and V oc is set either by non-radiative recombination; or parasitic absorption of internally emitted photons. For higher η ext, the V oc can be boosted, maximally by 15%, by restricting the external emission to match the incidence cone of the AM1.5D sun light spectrum. Such emission restriction corresponds to lower escape probability of internally emitted photons, enhances photon recycling, drops η ext, and actually makes the solar cell into a worse LED. Finally, for partly diffuse incident light, by restricting the angular emission for photons in a 130 nm wavelength range around the bandgap, we predict a maximum 14% relative boost in solar cell efficiency. The results of this paper are intended to serve as a general guideline on how to utilize emission-tuning possibilities to develop highly efficient photovoltaic devices.