Highest Photoluminescence Emission Research Articles

One-pot hydrothermal synthesis of silicon, nitrogen co-doped carbon dots for enhancing enzyme activity of acid phosphatase (ACP) to dopamine and for cell imaging

Developing water-soluble nanomaterials with high photoluminescence emission and high yield for biological analysis and imaging is urgently needed. Herein, water-soluble blue emitting silicon and nitrogen co-doped carbon dots (abbreviated as Si-CDs) of a high photoluminescence quantum yield of 80 % were effectively prepared with high yield rate (59.1 %) via one-step hydrothermal treatment of N-[3-(trimethoxysilyl)propyl]ethylenediamine (DAMO) and trans-aconitic acid. Furthermore, the Si-CDs demonstrate environmental robustness, photo-stability and biocompatibility. Given the importance of the potentially abnormal levels of acid phosphatase (ACP) in cancer diagnosis, developing a reliable and sensitive ACP measurement method is of significance for clinical research. The Si-CDs unexpectedly promote the catalytic oxidation of ACP on dopamine (DA) to polydopamine under acidic conditions through the produced reactive oxygen species (ROS). Correspondingly, a fluorescence response strategy using Si-CDs as the dual functions of probes and promoting enzyme activity of ACP on catalyzing DA was constructed to sensitively determine ACP. The quantitative analysis of ACP displayed a linear range of 0.1–60 U/L with a detection limit of 0.056 U/L. The accurate detection of ACP was successfully achieved in human serum through recovery tests. As a satisfactory fluorescent probe, Si-CDs were successfully applied to fluorescent imaging of A549 cells in cytoplasmic with long-term and safe staining. The Si-CDs have the dual properties of outstanding fluorescent probes and auxiliary oxidase activity, indicating their great potential in multifunctional applications.

Advancements in the green synthesis of carbon dots for sustainable development

The use of various biomass derivatives and wastes to produce carbon dots (CDs) represents a green synthesis approach that holds great potential for commercialization by offering economically viable, abundant, and sustainable resources. The process is reliable and reproducible by producing high-quality CDs with controllable size and surface structure, high photoluminescence (PL), and narrow emission. This review highlights the potential of biomass wastes and derivatives as a valuable resource for the production of CDs, showcasing their economic viability and environmental sustainability. The discussion is focusing on optimizing the green synthesis of CDs from different biomass precursors, including small molecules (e.g., sugars, polymers, amino acids, proteins, etc.) and biomass wastes (e.g., leaves, stem, root, flower, pollen, etc.), elucidating the underlying synthetic mechanisms, and exploring various modification techniques. The pursuit of high-quality CDs materials is also realized through innovative modification strategies, such as surface passivation, precise morphology and size control, and heteroatom doping, which enable tailoring the properties of CDs according to specific requirements while minimizing waste generation. The formation mechanism and tuning of optical properties were also discussed in detail, focusing on the comparison with CDs using other precursors. We further introduced the sustainable applications of these green CDs on renewable energies, such as photocatalysis, electrocatalysis, supercapacitors, lithium-ion batteries, and photovoltaics. Finally, this review provides a perspective on the challenges, potential advancements and future directions in the field of the green CDs.

Structural and Spectroscopic properties of Eu3+ doped SiO2–TiO2 nanoparticles for photonic applications

The Eu3+-doped TiO2 nanoparticles in sol gel silicate glasses of composition (80-x)SiO2 + 20TiO2 + 0.5xEu2O3, (SiTiEu) where x = 0.0 0.5, 1.5, 2.5 and 3.5 mol%, have been prepared by sol-gel technique. The glass samples were investigated by thermos-gravimetric analysis (TGA/DTA), ATR-FTIR, XRD, SEM, TEM, EDX, optical absorption and photoluminescence emission spectroscopy at room temperature (RT). The absorption wavelength of TiO2 doped sol-gel silicate glass were red shifted due to a reduction in band gap energy with increasing annealing temperatures. According to the TEM images, all of the particles were spherical and had an average diameter is around 10 nm. The visible spectra of the Eu3+ doped TiO2 nanoparticles in sol-gel silicate glasses displayed characteristic PL emission 5D0→7FJ (J = 0, 1, 2, 3, 4, 5) transitions of Eu3+ ions at 370 nm excitation. The anatase TiO2:1.5Eu3+ nanocomposite showed high photoluminescence emission at 370 nm excitation, which was attributed to the f-f transitions of Eu3+. The hypersensitive 5D0→7F2 transition was responsible for the major red emission. From the recorded spectra, radiative parameters and Judd-Ofelt (JO) intensity parameters were computed. The Eu3+ co-doped TiO2 nanoparticles in sol-gel silicate glasses displayed emissions mostly in the red regions realized from a CIE chromaticity diagram. The results suggested that materials may be used as an optical material of technological importance such as display devices and also for optical amplifier.

Resonance photoemission in pure and Tb doped CePO4 luminescent nanowires

The resonance photoemission spectroscopy (RPES) studies on pure and Terbium doped CePO4 nanowires (NWs) are reported here with the supporting characterizations using structural, optical and morphological properties. The NWs with varying Terbium (Tb) doping concentrations were synthesized using chemical synthesis route. Photoluminescence (PL) showed high PL emission intensity in the visible wavelength range indicating strong green luminescence due to efficient Ce3+ to Tb3+ energy transfer. The PL intensity increased up to a doping concentration of 15 wt% Tb3+, beyond which it decreased due to concentration quenching or cross-relaxation effect. Based on PL studies, pure, 5 wt% (the lowest doping amount) and 15 wt% (that shows the highest PL) doped samples were chosen for RPES studies. To understand the comparative contribution of Ce3+ and Ce4+ in the valence band, RPES measurements performed around the Ce 4d →4 f resonance threshold indicated strong presence of Ce 4 f states in pure CePO4 NWs, which reduced upon 5 wt% Tb doping in CePO4 NWs. At 15 wt% Tb3+ doping, the sample did not show resonance of Ce 4 f feature, which may be because Tb3+ ions have replaced Ce3+ ions in the CePO4 lattice. The results are crucial to understand the relative participation of Ce3+ and Ce4+ oxidation states in the valence band, which is an important factor in defining the optical properties of the material that determine the PL intensity.

Photoluminescent Bi-doped CsPbX3 (X: Br, I) perovskite quantum dots for optoelectronic devices

Perovskite quantum dots (PQDs) became a hot spot in recent years due to their amazing properties, such as the high photoluminescence quantum yield, tunable emission, and narrow bandwidth being important for their application in different optoelectronic devices. In this work, Bi-doped CsPbBr3 and Bi-doped CsPbI3 PQDs were synthesized through the hot-injection method and compared with pristine CsPbBr3 and CsPbI3 to analyze the effect of Bi and the halogen on their properties. In addition, all the samples were synthesized at 130°C, 150°C, and 170°C with the aim of analyzing the effect of the temperature. The results showed a wide range of the emission wavelength from around 500 nm (Bi-doped CsPbBr3) to 630 nm (Bi-doped CsPbI3) as a consequence of the effect of the halogen in “X” position and a slight blueshift in the main photoluminescence emission band after doping the pristine quantum dots with Bi.Graphical abstractImpact statementWe believe that the work in this article represents an important advance in the application of perovskite quantum dots in optoelectronics applications, such as in LEDs or lasers. We report here the synthesis and characterization of Bi-doped CsPbX3 perovskite quantum dots (PQDs), being X: Br and I. These Bi-doped PQDs show a wide range of the emission wavelength from around 500 nm (Bi-doped CsPbBr3) to 630 nm (Bi-doped CsPbI3) as a consequence of the effect of the halogen in “X” position and a slight blueshift in the main photoluminescence emission band after doping the pristine quantum dots with Bi. Therefore, they are good candidates to fabricate optoelectronic devices such as LEDs and lasers thanks to their high photoluminescence emission and their tunable emission.

High photoluminescence and afterglow emission of nitrogen-doped graphene quantum dots/TiO2 nanocomposite for use as a photodynamic therapy photosensitizer

High photoluminescence and afterglow emission of nitrogen-doped graphene quantum dots/TiO2 nanocomposite for use as a photodynamic therapy photosensitizer

Influence of sintering temperature on structural and optical properties of Cd0.5Cu0.5CrxFe2−xO4 ferrites

Two ferrite series were synthesized. One series has nanosize samples that have been prepared by the co-precipitation method, and the second series has the corresponding bulk samples that have been sintered at 1000 °C for 6 h. X-ray diffraction has been used to estimate the cubic spinel structure of both series. The crystallite size, theoretical density, and porosity of the nanomaterials are larger than those of the bulk materials. HRTEM analysis demonstrated the aggregation of nanoscale samples, including an average particle size of 9–22.5 nm. However, bulk specimens have a limited surface area. The agglomeration of the nanoparticles was seen in TEM images, in which the mean particle size was within the limit of the crystallite size (R) result and ranged from 14 to 20 nm. The appearance of the spinel phase in the samples was validated through Raman spectroscopy. Different cation occupation ratios in either tetrahedral or octahedral sites have been identified to be associated with an observable systematic shift and asymmetric flattening in Raman spectra with a variation in Cr3+ concentration. The optical characterization was performed using the UV/Vis methodology, and the results reveal that the absorption cutoff frequency declines as the chromium content rises. It was also estimated that the optical bandgap averaged 3.6 eV for nanosamples and 4.6 eV for overall bulk materials. The highest photoluminescence emission was seen at wavelengths between λem = 415 and 460 nm. The photoluminescence emission peaks of both bulk and nanoscale materials were red-shifted. These results accurately reflect the corresponding energy gap values for almost the same ranges. Sintering leads to a rise in photoluminescence.

Optical Properties of Heterostructured ZnO/NiO Nanocomposites Synthesized via Facile Precipitation Process

The semiconductor zinc oxide/nickel oxide (ZnO/NiO) heterostructured nanocomposites have been successfully synthesized via facile and eco-friendly homogeneous precipitation process with ethanol and water as solvents. The prepared nanocomposites were studied by means of structural and optical characteristics by using X-ray diffraction, ultraviolet visible absorption and photoluminescence emission spectro-scopies. The peaks in the XRD pattern attributed to the hexagonal wurtzite structure of ZnO and face-centered cubic structure of NiO, as a result the XRD analysis further confirmed that the solvents play a powerful role in size of the crystallite of the synthesized nanocomposites. Strong UV absorption may be seen in UV-vis absorbance spectra and samples of ZnO/NiO nanocomposite materials had greater energy gap (Eg) values than those of pure NiO and ZnO materials. The synthesized materials have demonstrated high photoluminescence emission in UV-blue region in the range of 241-498 nm, it might be a valuable source for future display applications. According to the aforementioned finding, the ZnO/NiO nanocomposites showed significant promise and were a viable material for optoelectronic devices.

Ultraviolet-C AlGaN Resonant-Cavity Light-Emitting Diodes with Thermal Stability Pipe-AlGaN-Distributed Bragg Reflectors.

Ultraviolet-C AlGaN resonant-cavity light-emitting diodes with top and bottom pipe-AlGaN-distributed Bragg reflectors (DBRs) have been demonstrated. For the top/bottom DBR structures, 20 pairs of n+-AlGaN:Si/n-AlGaN:Si stack structures were transformed into the pipe-AlGaN:Si/n-AlGaN:Si DBRs through a doping-selective electrochemical wet etching process. The reflectivity of the pipe-AlGaN DBR structure was measured as 90% at 276.7 nm with a 20.9 nm flat stopband width. The anisotropic optical properties of the pipe-AlGaN DBR structure had been analyzed through the polarization-dependent reflectance spectra. For temperature-dependent reflectance spectra, the central wavelengths were slightly redshifted from 275 nm (100 K) to 281 nm (600 K) due to thermal expansion, refractive index increase, and partial strain release phenomena in the pipe-DBR structure. High photoluminescence emission intensity and line-width reducing phenomena were observed at 10 K in the UVC-LED with the resonant-cavity structure, which has potential for high-efficiency UV-C light source applications.

Narrowband emission: organic thermally-activated delayed fluorescence materials and underlying mechanisms

The underlying molecular-level insights into the structure–property relationship for narrowband emission, high photoluminescence efficiency and emission color tunability of organic MR-TADF emitters are organized both in the experiment and theory.

Eu-Doped Gd2MoB2O9 Phosphors for Latent Fingerprints Detection

The luminescent powders from rare-earth ions doped oxides have been successfully used for latent fingerprint detection due to high efficiency, high contrast and low background interface. The Gd2MoB2O9:Eu3+ phosphors with varying compositions of Eu3+ions were synthesized by solid state reaction method. These phosphors were investigated by X-ray diffraction (XRD), diffuse reflectance spectroscopy, photoluminescence (PL), and decay curves studies. Multiphoton relaxation decay rate and coupling strength was evaluated using phonon side band spectrum showing 0.4 mol% doped samples show less non radiative decay rate. The 0.40 mol% of Eu3+ ion concentration doped in the Gd2MoB2O9 host lattice show highest photoluminescence emission intensity at 613 nm, in orange red region, monitored at 394 nm excitation. The Gd2MoB2O9:Eu3+ phosphors samples were optimized to 900 °C sintering temperature and optimum milling time at 3 min in the present work. The latent fingerprints detection that developed from Gd2MoB2O9:Eu3+ phosphors in this work exhibited clearly ridge characteristics under UV illumination. The results revealed thatGd2MoB2O9:Eu3+ phosphors are potential practical forensic science applications.

Highly Enhanced Photoluminescence of Monolayer MoS2 in Plasmonic Hybrids with Double-Layer Stacked Ag Nanoparticles.

In this work, a feasible method was proposed to prepare MoS2-based plasmonic hybrid systems with high photoluminescence (PL) emission enhancement. The enhancement effect of plasmonic hybrids on the PL emission of MoS2 has been systematically studied on MoS2/Ag spherical nanoparticle (SP) hybrid systems with different architectures by changing the stacking position of Ag SPs. It is demonstrated that the sandwich-like hybrid composed of monolayer MoS2 and dielectric Al2O3 layer between two layers of Ag SPs has the highest PL enhancement. Remarkably, after adding an Al2O3 layer under MoS2, the PL intensity enhancement up to 209 times was achieved in the sandwich-like hybrid system. Compared with the hybrid with single-layer SPs, the sandwich-like hybrid system with double-layer Ag SPs exhibited an obvious blue shift as a result of the selective enhancement of the A0 exciton in MoS2. These results demonstrate that MoS2/Ag SP hybrid nanosystems have significant implications for sensing and photoelectronic devices.

Fabrication and characterization of upconversion N-doped graphene quantum dots for improving photoelectrocatalytic performance of rutile hierarchical TiO₂ nanowires under visible and near-infrared light irradiations

The development of well-organized and low-priced photoelectrocatalysts for the clean and efficient water splitting reaction is crucial. In this context, novel nitrogen-doped graphene quantum dots (N-GQDs) with high photoluminescence and upconversion emission have been synthesized as excellent light harvester. Subsequently, ordered hierarchical TiO₂ nanowires were decorated with upconversion N-GQDs as a photoanode by a simple preparation method to improve the photocatalytic performance in the visible and near-infrared (NIR) regions of solar light, not otherwise absorbable by bare TiO₂ nanostructures. Moreover, the enhancement of charge transfer efficiency and electron–hole separation according to the energy states of N-GQDs and TiO₂ are considered for the improved photocatalytic performance of water splitting. N-GQDs/TiO2 shows superior photoelectrocatalytic (PEC) performance, achieving a photocurrent density of 3.0 mA.cm−2 in 1.0 M KOH solution, which is eight times that of unmodified TiO₂ at an applied voltage of 1.23 V vs. RHE. The high stability and photoelectrocatalytic activity of oxygen evolution reaction in the presence of newly synthesized N-GQDs are confirmed by chronoamperometry, open-circuit potential measurement, and electrochemical impedance spectroscopy. The as-fabricated photoanode provides an increased solar light harvesting from UV–Vis to NIR due to the application of newly synthesized upconversion GQDs, which increase energy conversion with an appealing perspective.

Metal-Metal-to-Ligand Charge Transfer in Pt(II) Dimers Bridged by Pyridyl and Quinoline Thiols.

The investigation of two distinct species of square planar dinuclear Pt(II) dimers based on anti-[Pt(C∧N)(μ-N∧S)]2, where C∧N is either 2-phenylpyridine (ppy) or benzo(h)quinoline (bzq) and N∧S is pyridine-2-thiol (pyt), 6-methylpyridine-2-thiol (Mpyt), or 2-quinolinethiol (2QT), is presented. Each molecule was thoroughly characterized with electronic structure calculations, static UV-vis and photoluminescence (PL) spectroscopy, and cyclic voltammetry, along with transient absorbance and time-gated PL experiments. These visible absorbing chromophores feature metal-metal-to-ligand charge-transfer (MMLCT) excited states that originate from intramolecular d8-d8 metal-metal σ-interactions and are manifested in the ground- and excited-state properties of these molecules. All five molecules reported (anti-[Pt(ppy)(μ-Mpyt)]2 could not be isolated), three of which are newly conceived here, possess electronic absorptions past 500 nm and high quantum yield PL emission with spectra extending into the far red (λem > 700 nm), originating from the charge-transfer state in each instance. Each chromophore displays excited-state decay kinetics adequately modeled by single exponentials as recorded using dynamic absorption and PL experiments; each technique yields similar decay kinetics. The combined data illustrate that pyridyl and quinoline-thiolates in conjunction with select cyclometalates represent classes of MMLCT chromophores that exhibit excited-state properties suitable for promoting light-energized chemical reactions and provide a molecular platform suitable for evaluating coherence phenomena in transient metal-metal bond-forming photochemistry.

Ag-CsPbBr3 quantum dots/PMMA composite film for tunable white light emitting diodes

We demonstrated a colloidal perovskite Ag-CsPbBr3 quantum dots /PMMA (Ag-CsPbBr3 CPQDs/PMMA) composite film. Compared to the traditional CsPbBr3 CPQDs, the Ag-CsPbBr3 CPQDs exhibits two advantages: i) enhanced photoluminescence (PL) emission intensity approaching 40%; ii) up to 94% of photoluminescence quantum yield (PLQY). More importantly, the polymethylmethacrylate (PMMA) film makes the Ag-CsPbBr3 CPQDs/PMMA film still have a 56% of PLQY and high PL emission intensity at a storage time of 5 months. And through changing the ratio of CsPbI3 CPQDs in the Ag-CsPbBr3 CPQDs, the Ag-CsPbBr3 CPQDs/PMMA film can easily tune the correlated color temperature (CCT) from cold to warm light.

Photoluminescence and thermoluminescence analysis of Zn2SiO4:Dy3+ nanophosphor

This work illustrates the sol-gel synthesis of dysprosium (Dy3+)-doped zinc silicate (Zn2SiO4) nanophosphor. The studies to evaluate its properties for possible application in solid state lighting and dosimetry were done. Synthesized nanophosphors were characterized using an X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) to investigate structure and morphology. Photoluminescence (PL) properties were also investigated under ultraviolet excitation. XRD results revealed α-Zn2SiO4 crystallite phase whereas the morphology of spherical nanoparticles was observed with the sonication time of 3 h. The excitation spectrum was obtained with the main peak located at ~350 nm attributed to 6H15/2 ground state and 6P7/2 excited state of Dy3+ ions. Relatively high PL emission was observed with a sample with 2 mol% of Dy3+ ions and the spectra exhibited a broad and narrow peaks positioned at ~418 nm, 435 nm and 478 nm (blue), ~574 nm (yellow) and (red) emission at ~660 nm corresponding to optical transitions of Dy3+ ions. Thermoluminescence (TL) glow curves of the samples irradiated by a beta source revealed three peaks at ~90, 180 and 375 °C. The intensity of the signal was improving with an increase of the irradiation from 1.58 to 100.86 Gy. The TL repeatability and fading signal trend showed experimental evidence which suggests that Zn2SiO4:2 mol% Dy3+ is a promising phosphor for dosimetry application.

Band gap tailoring, structural and optical features of MgS nanoparticles: Influence of Ag+ ions

Ag+ ions incorporated MgS nanoparticles were synthesized by the co-precipitation method. X-ray diffraction (XRD) spectra revealed that the samples had a cubic structure and the transmission electron microscope (TEM) pictures confirmed the spherical shape and size of the particle. The particle size was ranged from 11 nm to 15 nm. The average size of the particles was decreased for the increase of Ag+ ions concentration. Scanning Electron Microscope (SEM) photographs disclosed the surface morphology of samples. The agglomeration of the samples was reduced in the higher doping concentration. Energy Dispersive X-ray (EDX) and Fourier Transform Infrared (FTIR) analysis were utilized to verify the presence of elements as per the stoichiometry ratio. UV–vis absorption was increased due to the incorporation of Ag+ ions and better transmittance was offered for Ag = at. 2 %. The optical band gap was blue-shifted for Ag+ ions incorporated MgS nanoparticles. High intense strong red photoluminescence (PL) emission was exhibited at 660 nm by MgS:Ag for Ag = 2 at.%. The shifting of PL peaks to higher wavelength indicates the Ag+ ions incorporation. The shallow donor defects produced PL emission in a strong red region. The red emission may also be ascribed to the electron transition in high energy levels.

Light-emitting diodes based on quaternary CdZnSeS quantum dots

Highly reproducible quaternary CdZnSeS quantum dots (QDs) have been synthesized by the hot injection method using the reactivity difference between the molar ratio of Cd/Zn and Se/S precursors. The obtained QDs exhibit characteristics of quaternary CdZnSeS QDs. The morphology of the CdZnSeS QDs was observed in the TEM. The average size of the QDs was in the range between 5.5 and 7.5 nm for reaction times between 5 and 60 min, respectively. High photoluminescence emission, in the range from 460 to 680 nm, was obtained varying the Cd to Zn and the Se to S concentrations. Varying the concentration of Zn and S, emissions of blue, green, yellow, or red, were obtained. Additionally, the CdZnSeS QDs were used as the emissive layer in light-emitting diodes (LEDs) prepared with the configuration ITO/PEDOT:PSS/PVK/CdZnSeS/Al. These devices emitted a bright single color of blue, green, or red.

Revealing photoluminescence mechanisms of single CsPbBr3/Cs4PbBr6 core/shell perovskite nanocrystals.

CsPbBr3 nanocrystals (NCs) encapsulated by Cs4PbBr6 has attracted extensive attention due to good stability and high photoluminescence (PL) emission efficiency. However, the origin of photoluminescence (PL) emission from CsPbBr3/Cs4PbBr6 composite materials has been controversial. In this work, we prepare CsPbBr3/Cs4PbBr6 core/shell nanoparticles and firstly study the mechanism of its photoluminescence (PL) at the single-particle level. Based on photoluminescence (PL) intensity trajectories and photon antibunching measurements, we have found that photoluminescence (PL) intensity trajectories of individual CsPbBr3/Cs4PbBr6 core/shell NCs vary from the uniform longer periods to multiple-step intensity behaviors with increasing excitation level. Meanwhile, second-order photon correlation functions exhibit single photon emission behaviors especially at lower excitation levels. However, the PL intensity trajectories of individual Cs4PbBr6 NCs demonstrate apparent “burst-like” behaviors with very high values of g2(0) at any excitation power. Therefore, the distinguishable emission statistics help us to elucidate whether the photoluminescence (PL) emission of CsPbBr3/Cs4PbBr6 core/shell NCs stems from band-edge exciton recombination of CsPbBr3 NCs or intrinsic Br vacancy states of Cs4PbBr6 NCs. These findings provide key information about the origin of emission in CsPbBr3/Cs4PbBr6 core/shell nanoparticles, which improves their utilization in the further optoelectronic applications.

Substrate effect on the photoluminescence of chemical vapor deposition transferred monolayer WSe2

The substrate effect is an important issue in the properties of two-dimensional transition metal dichalcogenides (2D TMDs). Quantitatively determining the dependence of the photoluminescence (PL) emission properties and the excitonic behavior of single-layer 2D materials in a specific dielectric environment would provide helpful guidance for the rational design of substrates for high performance 2D TMD PL emission devices. Here, using a WSe2 monolayer on different substrates as a model system, it is demonstrated that the PL emission intensities can drastically change depending on the substrate effect. From the analysis of the excitonic behavior, the results reveal that the spectral weight between the neutral and charged excitons in the PL spectra is significantly modified by the substrate types, and the weight factor is dependent on the laser excitation density. The charged exciton binding energy is obviously negatively related to the substrate dielectric constant. Furthermore, the change trends of the binding energy of the monolayer WSe2 on different substrates are basically the same for the increase of the excitation density. These results suggest that the choice of the substrate plays a significant role in the modulation of the PL properties and exciton states of atomically thin WSe2; hence, substrate engineering should be carefully considered in the design of future 2D devices.