Photoluminescence Enhancement Research Articles

Strong photoluminescence enhancement from a WS2 atomic layer integrated on a metallic nanogroove array with intermediate plasmon–exciton coupling

The coupling between surface plasmons and excitons in transition metal dichalcogenides (TMDs) plays crucial roles in light emission, nonlinear optics, and quantum information processing. However, the intermediate plasmon–exciton coupling has not been reported in the TMD-integrated metallic nanoarray. Herein, we demonstrate the intermediate coupling behavior between surface plasmons in the silver nanogroove array and excitons in 2D layered tungsten disulfide (WS2). The results show that the reflection spectra of the silver nanogroove array possess an obvious reflection dip at the wavelength of ∼630 nm due to the generation of surface plasmons. The experiment results are well consistent with the numerical simulations. When the silver nanoarray is integrated with a trilayer WS2, there exists a distinct coupling between surface plasmons and A excitons in WS2. The temporal coupled-mode theory analysis shows that the plasmon–exciton coupling locates in the intermediate plasmon–exciton coupling region. The intermediate coupling can give rise to the strong photoluminescence (PL) enhancement of 48-fold in WS2. The wavelength of the PL peak presents a red shift with the increase of the temperature. This work paves a new pathway for the generation of plasmon–exciton coupling and the PL enhancement in atomic-layer TMDs.

Synergistic enhancement of photoluminescence and advanced deep learning model through YOLOv8x in combined effects of carbon dots and Sr₉Al₆O₁₈:Sm³⁺ phosphors

A series of orange-red-emitting Sr₉Al₆O₁₈:Sm³⁺ (1–11 mol %) phosphors are synthesized using the combustion method, while carbon dots (CDs) are produced from urea and citric acid. The incorporation of CDs into the Sr₉Al₆O₁₈:Sm³⁺ (SAO:Sm3+) matrix reduced both negative and positive defects, enhancing the crystallinity of the phosphor. A significant spectral overlap is observed between the emission of CDs and the absorption of SAO:Sm³⁺. An 11.9-folds enhancement in luminescence intensity is detected from the 5 wt% CDs@SAO:Sm³⁺ composite, along with an extended fluorescence lifetime. The energy transfer between CDs and Sm³⁺ is demonstrated, with the increased PL intensity attributed to the Förster Resonance Energy Transfer (FRET) mechanism. The CDs@SAO:Sm³⁺ composites demonstrated excellent selectivity and high contrast when developing latent fingerprints (LFPs). Level I–III structural characteristics of LFPs are easily recognized under ulta violet (UV) light. Furthermore, YOLOv8x, an effective deep learning model, has been modified for the important forensic science task of LFPs recognition. YOLOv8x is able to precisely locate LFPs in complex backgrounds by employing the real-time object detection capabilities of the architecture. With this adjusting, detection speed and accuracy are much increased, making it an effective tool for forensic analysis and law enforcement applications. The optimized orange-red-emitting CDs@SAO:Sm³⁺ composites is synthesized with soluble polyvinyl alcohol (PVA) to produce a transparent anti-counterfeiting ink. The resulting film exhibited excellent flexibility, foldability, and superior thermal and optical properties. In summary, the highly efficient CDs@SAO:Sm³⁺ composite is a versatile luminescent material with multifunctional capabilities, making it ideal for flexible films, LFPs detection, and white light-emitting diodes (w-LEDs) applications.

Giant Photoluminescence Enhancement of Ga-Doped ZnO Microwires by X-Ray Irradiation.

Ga-doped zinc oxide (ZnO) microwires hold great promise for developing highly efficient light sources because of the wide bandgap with proper exciton binding energy. However, most microwires grown from one mainstream approach, i.e., chemical vapor deposition (CVD), are morphologically and crystallographically defective, exhibiting limited photoluminescence performances. Herein, a simple and effective X-ray irradiation strategy is demonstrated for enhancing the photoluminescence of Ga-doped ZnO microwire in ambient conditions. Under moderate doses (≤ 150Gy), the photoluminescence monotonically rockets up with X-ray dose increment and achieves nine-fold enhancement at a dose of ≈150Gy, recording high photoluminescence improvement of ZnO microwires to date. The elemental characteristics under different controlled irradiation atmospheres suggest the elimination of surface oxygen vacancy and the cross-section transmission electron microscope reveals prominent lattice relaxations after mild X-ray irradiation. In addition, the X-ray irradiated microwires further exhibit elevated electroluminescence by over three times. The enhanced photoluminescence and electroluminescence as well as long-term stability enable us to imagine the super-rapid applications of ZnO microwires in modern optoelectronic devices.

An overview on plasmon-enhanced photoluminescence via metallic nanoantennas

Abstract In the realm of nanotechnology, the integration of quantum emitters with plasmonic nanostructures has emerged as an innovative pathway for applications in quantum technologies, sensing, and imaging. This research paper provides a comprehensive exploration of the photoluminescence enhancement induced by the interaction between quantum emitters and tailored nanostructure configurations. Four canonical nanoantennas (spheres, rods, disks, and crescents) are systematically investigated theoretically in three distinct configurations (single, gap, and nanoparticle-on-mirror nanoantennas), as a representative selection of the most fundamental and commonly studied structures and arrangements. A detailed analysis reveals that the rod gap nanoantenna configuration achieves the largest photoluminescence enhancement factor, of up to three orders of magnitude. The study presented here provides insights for the strategic design of plasmonic nanoantennas in the visible and near-IR spectral range, offering a roadmap for these structures to meet specific requirements in plasmon-enhanced fluorescence. Key properties such as the excitation rate, the quantum yield, the enhanced emitted power, or the directionality of the emission are thoroughly reviewed. The results of this overview contribute not only to the fundamental understanding of plasmon-enhanced emission of quantum emitters but also set the basis for the development of advanced nanophotonic devices with enhanced functionalities.

Engineering Photocarrier Redistributions in Graphene/III-V Quantum Dot Mixed-Dimensional Heterostructures for Radiative Recombination Enhancements.

Integration of graphene and quantum dots (QD) is a promising route to improved material and device functionalities. Underlying the improved properties are alterations in carrier dynamics within the graphene/QD heterostructure. In this study, it is shown that graphene functions as a carrier redistribution and supply channel when integrated with InAs QDs. Photoluminescence (PL) spectroscopy provides evidence that graphene modifies the redistribution, escape, and recombination dynamics of carriers in the InAs QD ensemble, which ultimately leads to enhanced radiative recombinations at all temperatures and excitation densities probed. It is also shown that the PL enhancement from the graphene/InAs QD heterostructure is greatest with a thin GaAs cap and at higher temperatures where devices operate. This study advances the understanding of graphene/QD heterostructures and can aid the design of mixed-dimensional optoelectronic devices.

Surface Plasmon Polariton Photoluminescence Enhancement of Single InP Nanowires with InAsP Quantum Wells

A significant (up to 4 times) photoluminescence enhancement of single InP/InAsP/InP nanowires transferred onto a silicon oxide‐covered silver layer on silicon substrate with a metal surface roughness level of less than 1 nm and a dielectric thickness of 5 nm has been demonstrated. This phenomenon is explained by the interaction of electron–hole pairs in the semiconductor with surface plasmon polaritons. The photoluminescence kinetics and results of modeling confirm the indicated enhancement mechanism.

Plasmon-enhanced NIR-II photoluminescence of rare-earth oxide nanoprobes for high-sensitivity optical temperature sensing.

With ongoing advancements in photothermal therapy, achieving efficient tumor cell eradication while minimizing damage to healthy tissues necessitates a highly effective and non-invasive real-time temperature monitoring technique for human tissues. Herein, we report a near-infrared (NIR)-II optical temperature sensing nanoprobe featuring rare-earth-doped gadolinium oxide nanocrystals (RENCs) attached to the dumbbell mesoporous silica-coated gold nanorods (AuNRs). The composite nanoprobe presents an intense absorption in the NIR region, and NIR-II photoluminescence (PL) increases by 97.2 to 102-fold compared to pure RENCs upon 980 nm irradiation. The localized electric field generated through surface plasmon resonance effects of AuNRs demonstrated a dumbbell-shaped distribution that aligns with the structure of nanoprobes, maximizing the PL enhancement of RENCs. Moreover, the NIR-II emissions are changed with the rising temperature, with an exceptional relative sensitivity of 7.25% K-1 at 338 K based on PL lifetime, indicating the nanoprobe is highly potential for optical temperature sensing.

Enhancing negative thermal quenching in green-emitting perovskite microspheres via shallow trap state modulation

AbstractFor luminescent materials, negative thermal quenching (NTQ), characterized by an increase in the luminescent intensity with temperature, has a large potential in lighting and display technologies. However, leveraging NTQ in metal halide perovskites is challenging, and the mechanism is not well understood. Herein, by utilizing low-temperature photoluminescence, persistent luminescence and thermoluminescence, the origins of NTQ in CsPbBr3 microspheres are systematically studied, which pertain to the liberation of carriers from shallow trap states. Experimental and theoretical investigations reveal that the energy of these shallow defect states is approximately 0.135 eV beneath the conduction band. A rapid thermal treatment increases the density of these shallow traps and amplifies the NTQ effect, resulting in an enhancement of room-temperature photoluminescence by more than 60% compared to that at 150 K. The process also reduces the threshold for amplified spontaneous emission to about 45 W/cm2. Our findings not only provide a deeper understanding of the NTQ phenomenon in CsPbBr3 microspheres but also open new avenues for enhancing the performance of perovskite optoelectronic devices through energy state regulation.

Effect of silver nanoparticles on the photostability and aging of CsPbBr3 nanocrystals

Abstract Perovskite nanocrystals may become a promising replacement for current phosphors in light-emitting diodes (LEDs) and screens, but the question of the stability of their optical properties remains open. One way to solve this problem could be to use plasmonic nanoparticles. In this work, we investigate the combination of all-inorganic perovskite nanocrystals synthesized by the hot-injection method with spherical Ag nanoparticles (mean diameter 53 nm). 3-fold enhancement of photoluminescence (PL) has been implemented in hybrid ‘silver-CsPbBr3-polymethyl methacrylate’ structures. The presence of silver nanoparticles reduces the likelihood of Auger processes and forms a possible silver bromide barrier layer which prevents photoinduced ion migration in the perovskite-polymer film. Plasmonic enhancement of PL partially presents during long-term samples storage within 75 days. This work may be useful in the creation of perovskite LEDs using remote phosphor technology.

Surface plasmon-mediated photoluminescence boost in graphene-covered CsPbBr3 quantum dots

The optical properties of graphene (Gr)-covered CsPbBr3 quantum dots (QDs) were investigated using micro-photoluminescence spectroscopy, revealing a remarkable three orders of magnitude enhancement in photoluminescence (PL) intensity compared to bare CsPbBr3 QDs. To elucidate the underlying mechanisms, we combined experimental techniques with density functional theory (DFT) calculations. DFT simulations showed that the graphene layer generates interfacial electrostatic potential barriers when in contact with the CsPbBr3 surface, impeding carrier leakage from perovskite to graphene and enhancing radiative recombination. Additionally, graphene passivates CsPbBr3 surface defect states, suppressing nonradiative recombination of photo-generated carriers. Our study also revealed that graphene becomes n-doped upon contact with CsPbBr3 QDs, activating its plasmon mode. This mode resonantly couples with photo-generated excitons in the perovskite. The momentum mismatch between graphene plasmons and free-space photons is resolved through plasmon scattering at Gr/CsPbBr3 interface corrugations, facilitating the observed super-bright emission. These findings highlight the critical role of graphene as a top contact in dramatically enhancing CsPbBr3 QDs’ PL. Our work advances the understanding of graphene-perovskite interfaces and opens new avenues for designing high-efficiency optoelectronic devices. The multifaceted enhancement mechanisms uncovered provide valuable insights for future research in nanophotonics and materials science, potentially leading to breakthroughs in light-emitting technologies.

Improvement of photoluminescence efficiency and photoelectricity performances of InP quantum dots through the passivation of surface defects

At present, InP quantum dot-sensitized solar cells (QDSSCs) still show moderate power conversion efficiency (PCE), because of charge recombination on the surface defects. Herein, we report a method to reduce the surface defects of InP quantum dots by Ga-doped and ZnS shell coating, which improves the performance of InP QDSSCs. Simultaneous enhancement of photoluminescence (PL) and photo-electricity performance of Ga doped InP (Ga:InP) quantum dots (QDs), Ga:InP/ZnS core/shell QDs were achieved. The maximum PL quantum yield of Ga:InP QDs and Ga:InP/ZnS QDs reached 14.9% and 76%, respectively. The maximum PCE value of Ga:InP and Ga:InP/ZnS QDSSCs reached 3.0% and 4.5% under 1 sun illumination (AM 1.5 G, 100 mW/cm2), respectively. The J-V curve revealed that Ga doping and ZnS shell coating reduced the surface recombination and increased the cell efficiency and stability. These results provided a new approach to obtaining quantum dot materials with high luminescence properties or good solar cell performances.

Interface induced photoluminescence enhancement from heterojunction BaMoO4/HEAs phosphors: Experiment, theory and anti-counterfeiting application

The BaMoO4/FeCoNiCrMo (BMO/HEA(Mo)), BMO/FeCoNiCrTi (HEA(Ti)) and BMO/FeCoNiCrTiAl (HEA(Al)) phosphors were synthesized by an integrated technology. The structural characterization showed that except the main lattice phase, only the characteristic peak of high-entropy alloys (HEAs) appeared in BMO/HEAs phosphors and the existence of lattice distortion for [MoO4]2- in BMO. The microstructure analysis confirmed that there is a special interface contact between BMO and HEAs, which makes the metal in HEAs easy to have a certain connection with BMO, which causes the lattice distortion of [MoO4]2- to intensify, thus accelerating the recombination rate of charge carriers in BMO/HEAs phosphors. The BMO/HEAs phosphors have a strong emission peak at 445 nm under the excitation wavelength of 285 nm. Theoretical calculations and experiments confirmed that the luminescence of BMO/HEAs phosphor is caused by the lattice distortion of [MoO4]2-, the interface defect of BMO/HEAs and the recombination of charge carriers. The Mo in HEA(Mo) can accelerate the recombination rate of charge carriers between BMO and HEAs, thus enhancing the luminescence performance of BMO/HEA(Mo) phosphor and exhibit dynamic fluorescence anti-counterfeiting applications. However, the Ti in HEA(Ti) and Al in HEA(Al) can easily separate the charge carriers between BMO and HEAs, thus reducing the luminescence of BMO/HEA(Ti) and BMO/HEA(Al) phosphors.

Red-shift of the photoluminescent emission and enhancement of the internal quantum efficiency by co-doping Gd3+ in Tb3Al5O12: Ce3+ phosphors for warm WLEDs

White Light Emitting Diodes (WLEDs) are widely used in our lives as the fourth generation of solid-state lighting sources. However, the phosphors in the WLEDs device lack a red component, resulting in a cool white light, which affects the quality of lighting while damaging the user's eyesight. In this work, the Tb3Al5O12: Ce3+ (TAG: Ce3+) and Tb3Al5O12: Ce3+, Gd3+ (TAG: Ce3+, Gd3+) phosphors were synthesized by sol-gel method. Powder X-ray diffraction analysis confirmed the successful substitution of Ce3+ and Gd3+ in the system, as evidenced by the quantifiable expansion of the unit cell volume when Tb3+ was replaced with Ce3+ and Gd3+. As the increasing of Gd3+ doping concentration in the TAG: 0.025Ce3+, yGd3+ phosphors, the emission peak of Ce3+ (arises from the 5d→4f transition) shifted from 565 nm to 580 nm. The photoluminescence emission intensity of TAG: 0.025Ce3+, 0.6Gd3+ phosphor can be increased by about 192 % compared to TAG: 0.025Ce3+ phosphor (y = 0). The Gd3+-to-Ce3+ energy transfer is robustly supported by the prolonged lifetime of Ce3+ with an increase in Gd3+ content in TAG: 0.025Ce3+, yGd3+. Notably, the energy transfer process from Gd3+ to Ce3+ effectively enhanced the internal quantum efficiency (IQE) of the TAG: 0.025Ce3+, yGd3+ phosphors, up to 70.14 %. Variable-temperature emission spectra indicates that TAG: Ce3+, Gd3+ phosphors prepared by the sol-gel method have excellent luminescent thermal stability. Ultimately, the WLEDs devices assembled with TAG: Ce3+, Gd3+ phosphors can produce warm white light, which indicates that TAG: Ce3+, Gd3+ phosphors are a potential material for warm WLEDs.

Modulation of photoluminescence properties of transition metal dichalcogenides through temperature and Au/Ag nanoparticles

Abstract Transition metal dichalcogenides (TMDCs) attract significant attention because of their remarkable optical properties. Nowadays, the light emission efficiency of TMDCs is still inferior. Temperature and plasma resonance effects can be important approaches in the modulation of their luminescence performance. Here, multilayer WSe2 and monolayer MoSe2 were synthesized. Under the temperature control system, two photoluminescence (PL) peaks are observed from multilayer WSe2. The higher-energy PL peak results from K-Γ indirect band gap transition, which is then demonstrated by the first principle calculation. Otherwise, PL enhancement is realized on monolayer MoSe2 decorated with Au nanoparticles. The PL of WS2 is inhibited by hybridization with Ag nanoparticles.

Deterministic Assembly of Single-Emitter Plasmonic Antenna for Ultrahigh Photoluminescence Enhancement.

Single-emitter nanoantennas play a crucial role in the fabrication of nanosensors and integrated sources. Since the coupling of single emitter to nanoantennas is largely based on stochastic methods, low qualified rate still hinders a massive deployment. Here, we proposed a deterministic, optical-force-driven method to achieve gap-plasmonic photoluminescence enhancement. Two deterministic steps are carried out in sequence: a composite nanoemitter is first synthesized by linking quantum dots to a silica-rapped gold nanoparticle, followed by an optical delivery of the nanoparticle into a nanoaperture in a gold film. We reason that the nanoparticle-in-nanoaperture (NPiNA) structure efficiently couples out-of-plane excitation light into a gap-plasmon via a transverse electromagnetic mode (TEM)-like transmission mode. An in situ photoluminescence measurement demonstrates a 3× brightness as compared to the nanoparticle-on-mirror (NPoM). This approach paves the way toward deterministic positioning of individual nanoparticles for a wide range of applications on nanophotonics structures on-a-chip.

The influence of ultrafast laser processing on morphology and optical properties of Au-GaAs composite structure

The results of direct femtosecond laser structuring of GaAs wafer coated with continuous semitransparent gold (Au) film are presented. The obtained structures demonstrate a combination of different features, namely laser-induced periodic surface structures (LIPSS) on semiconductor and metal film, nanoparticles, Au islands, and fragments of exfoliated Au film. The properties of Au-GaAs samples are studied with scanning electron microscopy (SEM), Raman scattering, and photoluminescence (PL) spectroscopy. The behaviour of phonon modes and enhancement of band-edge PL of Au-GaAs composite sample are discussed. The Raman spectra of Au-GaAs sample processed at different levels of irradiation pulse energy reveal forbidden TO and allowed LO phonon modes for selected geometry of experiment, as well as the manifestation of GaAs surface oxidation and amorphization. A 12-fold increase of PL intensity for Au-GaAs sample with LIPSS compared to initial GaAs surface is observed. The detected PL enhancement is caused by an increase of absorption in GaAs due to the light field enhancement near the Au nanoislands and a decrease of nonradiative surface recombination. The blue shift of PL band is caused by the quantum size effect in GaAs nano-sized features at laser processed surface. The combination of GaAs substrate with surface micro- and nanostructures with Au nanoparticles can be useful for photovoltaic and sensorics applications.

Coloring Tetrahedral Semiconductors: Synthesis and Photoluminescence Enhancement of Ternary II-III2-VI4 Colloidal Nanocrystals.

Ternary tetrahedral II-III2-VI4 semiconductors, where II is Zn or Cd, III In or Ga, and VI S, Se, or Te, are of interest in UV radiation detectors in medicine and space physics as well as CO2 photoreduction under visible light. We synthesize colloidal II-III2-VI4 semiconductor nanocrystals from readily available precursors and ascertain their ternary nature by structural and spectroscopic methods, including 77Se solid-state NMR spectroscopy. The pyramidally shaped nanocrystals range between 2 and 12 nm and exhibit optical gaps of 2-3.9 eV. In the presence of excess anions on the particle surface, treatment with Lewis acidic, Z-type ligands results in better passivation and enhanced photoluminescence. Electronic structure calculations reveal the most stable, lowest energy polymorphs and coloring patterns. This work will pave the way toward more environmentally friendly, ternary semiconductors for optoelectronics and electrocatalysis.

Ratiometric Imaging Detection of Amyloid-β Fibrils by a Dual-Emissive Tris-Heteroleptic Ruthenium Complex.

Two dual fluorescent/phosphorescent tris-heteroleptic mononuclear Ru(ΙΙ) complexes (2 and 3) were designed and applied in amyloid-β (Aβ) sensing. These complexes have a general formula of [Ru(phen)(dppz)(L)](PF6)2, where L is (2-pyrazinyl)(2-pyridyl)(methyl)amine (H-L) with different substituents (-OMe for 2, -H for 3), phen is 1,10-phenanthroline, and dppz is dipyridophenazine, respectively. Compared with the previously reported ratiometric probe 1 with a di(pyrid-2-yl)(methyl)amine ligand, complex 2 can be employed for not only ratiometric emissive detection of Aβ aggregation but also ratiometric imaging detection of Aβ fibrils. In ratiometric emissive detection, as the incubation time of the Aβ sample (Aβ40 and Aβ42) was prolonged, a new phosphorescence emission band appeared with gradual enhancement of the emission intensity, while the fluorescence emission was basically unchanged, which could be treated as an intrinsic internal reference signal. In comparison, a larger ratiometric photoluminescence enhancement (I640/I440) was observed for Aβ40 aggregation with respect to Aβ42. In ratiometric imaging detection, the imaging signals obtained from the phosphorescence emission are much brighter than the fluorescence emission in both Aβ40 and Aβ42 fibrils. As indicated by molecular docking results, stronger interactions were found between complex 2 with Aβ40 fibrils, which included π/π, π/C-H, and π/H interactions between bidentate ligands dppz and phen with amino acid residues. Moreover, computational calculations were carried out to assist the interpretation of these experimental findings.

A ‘Turn-on’ fluorogenic probe for selective and specific detection of Hg(II) ions

Mercury (Hg2+) and its associated compounds have drawn serious concern from the scientific communities for their extreme toxicity to human beings. The present article introduced a chromone-benzoxazole embracing an effective fluorogenic probe, (E)-3-(((4-(benzo[d]oxazol-2-yl) phenyl) imino) methyl)-2-methoxy-2H-chromen-4-ol (BPMC) for selective and specific detection of Hg2+ ions having detection and quantification limit in the µM range. A significant photoluminescence enhancement has been observed from BPMC solution (water-DMSO mixture, 50 % v/v) displaying low to highly intense blue-violet photoluminescence under a 365 nm UV lamp due to the inhibition of intramolecular charge transfer (ICT) and excited state intramolecular proton transfer (ESIPT) processes involved in BPMC. Furthermore, to achieve on-site detection of Hg2+ ions and investigate the practical utility of our developed probe, we have fabricated a BPMC-stained paper-strips-based test kit and demonstrated its practical effectiveness for on-spot detection. The details of the detection mechanism have been revealed through 1H NMR, FT-IR, and high-resolution mass spectrometric analysis. The present report evokes a broader perspective for tailoring ICT and ESIPT-based chromo-fluorogenic probes to accelerate their real-world application and environmental monitoring.

Efficient Redirection of Trapped Broad-Band Fluorescence from Substrates into Free Space Using c-Si Metasurfaces.

Fluorescent dye films on transparent substrates are essential for OLEDs, flexible displays, X-ray detection, and wireless optical communications. However, their efficiency is often hampered by fluorescence trapping due to total internal reflection (TIR) and waveguiding. This study tackles this longstanding challenge by reconceptualizing the integration of dye films with nanoantenna metasurfaces. Traditional methods involve directly spin-coating films onto c-Si metasurfaces on quartz substrates, resulting in edge luminescence and weak inner signals. We present a straightforward, adjustable approach by integrating dye films on the opposite side of quartz substrates, reaching a 2.5-fold photoluminescence enhancement and improving the uniformity of the emission compared to the conventional methods. These gains stem from redirecting a significant portion of leaked fluorescence light trapped inside the substrate into free space, surpassing TIR conditions through in-plane diffraction orders of the metasurfaces across the full RGB spectrum. Our findings facilitate the design of more efficient luminescent devices.