White Light Research Articles

Robust structure, spectral adjustability of single-component silicate oxyapatite Sr2La8(SiO4)6O2: Ce/Tb/Sm toward phosphor-converted wLEDs application

The lack of photons in electromagnetic spectrum region of 400–450 nm, termed cyan gap among other photoluminescence (PL) coverage issues, confines the full-visible- spectrum white light's overall capability for color rendering in part of previously studied single-component phosphors. Herein, we have mechanistically investigated that a Ce3+ incorporated silicate oxyapatite Sr2La8(SiO4)6O2 (SLS) phosphor, via a facile sol-combustion synthesis under low temperature, shows efficient cyan PL with broad full width at half maxima (fwhm, ∼90 nm) and high quantum yield (QY, ∼46.3 %) as a result of tendentious dual-site occupations and parity-allowed 4f1 ↔ 5d transitions of Ce3+, based on a combination of steady/transient-state spectroscopy and theoretical calculations. According to the principle of color superposition, the color-tunable PL, including the white emission with low coordinated color temperature (CCT) and high color rendering index (CRI), is realized by further codoping the characteristic green/red line emissions from Tb3+ and Sm3+ ions in the SLS: Ce. The low PL QY (∼32.7 %) from the monodoped Tb or Sm, due to its forbidden 4f-4f transitions, is cleverly alleviated via cascade-connected energy transfer (ET) from Ce → Tb → Sm. The direct ET from Ce → Sm is hardly occurred because of the metal-mental charge transfer (MMCT) effect. Finally, a prototype pc-wLED assembled via a remote ‘capping’ packaging strategy and using only the stably composition-optimized white-emitting SLS: Ce/Tb/Sm demonstrates attractive performance of the designed device (CCT 4243 K, CRI (Ra) 87, CIE (0.365, 0.381), and LE 76 lm⋅W−1 under 120 mA) and the phosphor is promising for high-quality of light.

Some properties of habituation of siphon withdrawal in the slimy clam (Ruditapes decussatus)

A first approximation to the study of learning processes in bivalves is presented. A habituation procedure was developed using the slimy clam Ruditapes decussatus. The percentage of siphon withdrawal when they were exposed to a white light was measured. In Experiment 1, a habituation-discrimination procedure was used to study the stimulus intensity effect (350-lm vs 806 lm). Clams exposed to 350-lm showed a faster habituation than those exposed to 806-lm. Experiment 2 studied the effect of stimulus and intertrial interval (ITI) duration using a 2×2 design. Trials lasted 20 or 180 seconds, and the ITI lasted 5 or 10 minutes. A combined effect of these two parameters was obtained. Habituation was faster in clams exposed to 180-sec trials with a 5-min ITI. Finally, in Experiment 3 clams were trained with five blocks of five trials with a 5-min ITI. Groups differed on trial duration (20 or 180 s). The results showed a general spontaneous recovery effect that was more pronounced for the 180 s group. Also, it was found in this experimental condition a reduced response 24 hours after finishing training (long-term habituation). Altogether, this series of experiments constitutes a first systematic demonstration of habituation in bivalves.

Photoluminescence Properties of Novel BaLiZn3(BO3)3:RE (RE = Sm3+, Tb3+, Dy3+, and Pb2+) Blue, Green, Orange-Red Emitting Phosphors for White Light Emitting Diodes

Photoluminescence Properties of Novel BaLiZn3(BO3)3:RE (RE = Sm3+, Tb3+, Dy3+, and Pb2+) Blue, Green, Orange-Red Emitting Phosphors for White Light Emitting Diodes

Integrated transcriptomic and miRNA-seq analysis of Pak-choi provides insight into the molecular mechanisms involved in the preservation of postharvest quality by white LED light irradiation

Low-intensity white light-emitting diode (LED) irradiation effectively delays postharvest senescence in pak-choi at 20 °C and 90 % relative humidity. In this study, RNA-seq and miRNA-seq analyses were conducted on samples collected at 0 d (initial sample) and 5 d (CK and LED-treated samples) to evaluate the regulatory effects of white LED irradiation on miRNA. The resulting data revealed a total of 23 differentially expressed miRNAs (DEmiRNAs) in the CK/LED group on 5 d of storage. LED irradiation induced the expression of AP2 family genes and the biosynthesis of aliphatic glucosinolates by modulating the level of bra-miR172 family miRNAs. LED irradiation also stimulated the expression of genes associated with the photosynthetic pathway in pak-choi and regulated biosynthesis of ascorbic acid and resistance-associated transcription factors by modulating the level of novel miRNAs. Furthermore, LED irradiation suppressed cellulase and polygalacturonase activity, and maintained the pectin content. These findings demonstrate the ability of white LED light irradiation to significantly delay the postharvest senescence process in pak-choi by modulating miRNA expression.

A Plasmonic Nanoledge Array Sensor for Selective Detection of Cardiovascular Disease Biomarkers in Human Whole Blood.

Optical sensors face challenges when detecting ultralow amounts of analytes in whole blood, including signal quenching due to optical absorption and false positives due to nonspecific binding. This study introduces gold nanoscale array features termed nanoledges (NLs), which interact with incident white light to produce a transmitted surface plasmon resonance (tSPR) signal. This extraordinary optical transmission (EOT) spectrum occurs in the near-infrared (NIR) region, thereby minimizing signal quenching caused by visible-light absorption from blood proteins and pigments. To develop a sensitive, selective, and label-free optical biosensor for detecting various levels of cardiac troponin I (cTnI) in very small volumes of whole blood samples, DNA aptamers are tethered to the NL surface, specifically binding to the cTnI biomarker. This biological binding activity alters the refractive index at the NL surface, causing a peak shift in the EOT spectrum and enabling quantification of cTnI levels. The NL array chip demonstrated high sensitivity for cTnI detection in buffer, human serum (HS), and human whole blood (HB), with detection limits of 0.079, 0.084, and 0.097 ng/mL, respectively. Control measurements using blank target mediums and those containing up to 125 ng/mL of other proteins, such as myoglobin, creatine kinase, and heparin, showed minimal interference and high specificity. The NL plasmonic array's performance in biosensing underscores its promise for clinical analysis and its potential development as a point-of-care platform for early cardiovascular disease (CVD) diagnostics.

Mitochondria-Targeting AIEgens as Pyroptosis Inducers for Boosting Type-I Photodynamic Therapy of Tongue Squamous Cell Carcinoma.

The development of a photosensitizer (PS) that induces pyroptosis could be a star for photodynamic therapy (PDT), particularly with type-I PSs that produce reactive oxygen species (ROS) in a hypoxic tumor microenvironment. Since pyroptosis is a recently characterized cell death pathway, it holds promise for advancing PDT in oncology, with PSs playing a critical role. Herein, we develop a PS named Th-M with aggregation-induced emission (AIE) characteristics for type-I PDT against tongue squamous cell carcinoma (TSCC). Th-M stands out for its exceptional mitochondrial-targeting ability, which triggers mitochondrial dysfunction and leads to Caspase-3 and Gasdermin E (GSDME) cleavage under white light irradiation, inducing pyroptosis in TSCC cells. Our studies verify the effectiveness of Th-M in destroying cancer cells in vitro and suppressing tumor growth in vivo while also demonstrating a favorable biosafety profile. This work pioneers the application of Th-M as a mitochondria-targeted, type-I PS that leverages the mechanism of pyroptosis, offering a potent approach for the treatment of TSSC with promising implications for future PDT of cancers.

Wettability Behaviour of Metal Surfaces after Sequential Nanosecond and Picosecond Laser Texturing.

This study examines the wettability behaviour of 304 stainless steel (304SS) and Ti-6Al-4V (Ti64) surfaces after sequential nanosecond (ns) and picosecond (ps) laser texturing; in particular, how the multi-scale surface structures created influence the lifecycle of surface hydrophobicity. The effect of different post-process treatments is also examined. Surfaces were analysed using Scanning Electron Microscopy (SEM), a white light interferometer optical profiler, and Energy Dispersive X-ray (EDX) spectroscopy. Wettability was assessed through sessile drop contact angle (CA) measurements, conducted at regular intervals over periods of up to 12 months, while EDX scans monitored elemental chemical changes. The results show that sequential (ns + ps) laser processing produced multi-scale surface texture with laser-induced periodic surface structures (LIPSS). Compared to the ns laser case, the (ns + ps) laser processed surfaces transitioned more rapidly to a hydrophobic state and maintained this property for much longer, especially when the single post-process treatment was ultrasonic cleaning. Some interesting features in CA development over these extended timescales are revealed. For 304SS, hydrophobicity was reached in 1-2 days, with the CA then remaining in the range of 120 to 140° for up to 180 days; whereas the ns laser-processed surfaces took longer to reach hydrophobicity and only maintained the condition for up to 30 days. Similar results were found for the case of Ti64. The findings show that such multi-scale structured metal surfaces can offer relatively stable hydrophobic properties, the lifetime of which can be extended significantly through the appropriate selection of laser process parameters and post-process treatment. The addition of LIPSS appears to help extend the longevity of the hydrophobic property. In seeking to identify other factors influencing wettability, from our EDX results, we observed a significant and steady rate of increase in the carbon content at the surface over the study period.

Optical characteristics, Judd-Ofelt analysis of enhanced luminescence by flux in thermally stable, novel Eu3+- doped BaZr(PO4)2 phosphor for indoor lighting applications

A series of novel single phased Eu3+ doped BaZr(PO4)2 phosphor were synthesized employing simple solid-state reaction route and studied the influence of different chlorides as fluxes (NH4Cl, KCl, LiCl and NaCl) on structural and photoluminescence properties. The structural characterization reveals pure phase formation of the as prepared phosphors with monoclinic crystal structure. The photoluminescence (PL) spectra recorded under 392 nm excitation depicts intense emission at 612 nm. Further, the concentration of Eu3+ ion was well tuned by carefully studying the PL spectra and the optimised amount of Eu3+ ion in BaZr(PO4)2 is found to be 3.0 mol%. The luminescence properties of phosphor with added aforementioned fluxes were also studied in detail. NH4Cl was found to be the best among all the fluxes taken and the photoluminescence intensity of phosphor gets enhanced by 1.43 times of without flux. The Judd-Ofelt theory was employed for determination of spectral parameters from photoluminescent emission spectra. The temperature dependent photoluminescent studies establishes stability of phosphor emission at operating temperatures. The CIE coordinates were evaluated that confirms the pure red emission under n-UV excitation. All the studies indicate the potential of the said phosphor in phosphor converted white light emitting diodes as red emitter and indoor lighting.

Isolation, purification, characterization and stability analysis of melanin pigment from Mesona chinensis

In this study, the isolation and purification of melanin pigment from Mesona chinensis (MCM) were conducted, and the structural characterization and stability evaluation of MCM were performed. The results indicate that MCM is consistent with the spectral features of catechins and polyphenols, identified the stretching vibrations of functional groups such as OH, CH, CO, and CO. It is inferred that the structure of MCM is consistent with that of theophylline and it is mainly composed of phenolic acids, terpenoids, and organic acids. Stability evaluations indicate that MCM exhibits stability under white light, ultraviolet (UV) light, neutral, and alkaline environments, and it shows low sensitivity to reducing agents.

Colour tunability of Dy3+ & Sm3+ activated yttrium aluminium gallium nanocrystals for display applications

A set of powder samples of Y3AlGa4O12 doped with Dy3+ and Sm3+ with different concentration of Sm3+ ion were prepared via sol-gel synthesis. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive (EDS), Fourier transform infrared (FTIR) and photoluminescence spectral studies were carried out. All the diffraction peaks matched the cubic lattice Y3AlGa4O12, as given by the XRD. The SEM images revealed aggregated spherical particles ranging from 50 to 130 nm. The EDS analysis confirmed the presence of the initial chemicals in the synthesized samples. FTIR spectrum was used to examine the vibrational modes in the sample. Under a 366 nm excitation wavelength, the emission spectrum showed the peaks at 492 nm (blue), 580 nm (yellow), 673 nm (red), and 760 nm (near-infrared) corresponding to the characteristic transitions 4F9/2 → 6H15/2,13/2,11/2,9/2 of the Dy3+ ion, respectively. In comparison, the peaks at 568 nm, 614 nm, 664 nm, and 711 nm corresponded to the characteristic transitions 4G5/2 → 6H5/2,7/2,9/2,11/2 of the Sm3+ ion. Under near ultraviolet light excitation, the superposition of these blue, yellow and red colours produced excellent white light emission. The intensities of these transitions varied with the concentration of Sm3+ ion and the excitation wavelength. The emission spectrum of Dy3+ overlapped with the excitation spectrum of Sm3+, indicated possible energy transfer from Dy3+ to Sm3+. According to Inokuti-Hirayama's theory of energy transfer, the mechanism of energy transfer was understood to be quadrupole-quadrupole interaction. The CIE chromaticity co-ordinates and correlated colour temperature values showed that these samples were suitable for light-emitting diode applications.

Mixed former effect in barium borophosphate glasses on the red (Eu3+)-blue (Eu2+) emission for LEDs

The synergistic mixing of P2O5 and B2O3 glass formers at a constant concentration of BaO as a glass modifier plays a vital role in generating a single-phase phosphor doped with Eu2O3 for white light-emitting diodes (WLEDs). Herein, a glass system of nominal composition xP2O5∙(50-x)B2O3∙49.5BaO∙0.5Eu2O3 (0 ≤ x ≤ 50 mol%) was prepared using a melt-quenching technique under normal atmospheric conditions. While the XRD patterns demonstrated the amorphous nature, the SEM micrographs proved the formation of cluster structures. Structural characterization using ATR-FTIR spectroscopy revealed the presence of main vibrational structural units associated with borate and phosphate glass formers, including BO3, BO4−, P=O, PO2−, and PO32−. The IR spectra at x = 0 and 50 mol% exhibit characteristic metaborate and metaphosphate absorption peaks, respectively. In contrast, the mixing of both B2O3 and P2O5 at equal concentrations (x = 25 mol%) has resulted in the absence of absorption peaks assigned to the BO3 and P=O units, thus indicating the mixed structural effect. This is assigned to the formation of B-O-P bonds, with the BO4−, PO2−, and PO32− as the main structural units. These structural changes affect the reduction process of Eu3+ to Eu2+, as demonstrated by the corresponding photoluminescence spectra and observed by the cathodoluminescence micrographs. Photoluminescence studies showed tunable emission from red (Eu3+) to white light (Eu2+ and Eu3+) under UV excitation, with the P2O5 content rising from 0 to 50 mol% due to the growing Eu2+ population formed by the reduction of Eu3+. The optical basicity was observed to decrease with the P2O5 content, favouring the reduction process. The demonstrated tunable single-host white phosphor makes this an attractive system for energy-efficient WLED applications.

Effect of laser energy on the fretting wear resistance of femtosecond laser shock peened Ti6Al4V

Femtosecond laser shock peening (FsLSP) is performed on engineering alloys to improve their wear resistance in dry and oil-lubricated sliding conditions. In this study, the influence of FsLSP on the fretting wear behavior of Ti6Al4V alloy is studied. For this purpose, FsLSP treatment, with laser energies of 50, 100, 150, and 200 μJ, is performed on a Ti6Al4V sample which mainly consists of α-phase. Topographical investigations using white light interferometry reveal that with increase in the laser energy, the coverage area of laser-induced periodic surface structures (LIPSSs) decreases, and the extent of surface pitting damage increases, leading to higher surface roughness. While surface hardness also initially increases with increasing laser energy, it remains invariant when the energy is increased beyond 150 μJ. Sub-surface microstructural investigations and kernel average misorientation maps obtained from electron backscatter diffraction reveal that FsLSP treatment leads to the formation of severely deformed and mildly deformed layers along the depth of the alloy surface. Surface hardening due to FsLSP is attributed to the activation of prismatic <a>, basal <a> slip systems, and 101¯2, 112¯3 tensile twins in the severely deformed zone along with grain refinement, which is an outcome of dynamic recrystallization. Fretting wear tests indicate that the coefficient of friction (CoF) of FsLSP treated alloys is consistently lesser than that of its as-received counterpart, whose CoF is 0.38. In contrast, the wear resistance, quantified by the wear rate, wear volume and wear depth, is highest in the sample treated with laser energy of 100 μJ but lower for the as-received as well as 150 and 200 μJ laser treated samples. These results are explained on the basis of the differences in the contact area, formation of surface hardening layer and the size and integrity of asperities on the surface, which in turn influences the dominant fretting wear mechanism.

Charge separation in a copper(I) donor-chromophore-acceptor assembly for both photoanode and photocathode sensitization.

A copper(I) donor-chromophore-acceptor triad bearing 1,8-napthalenemonoimide as the electron acceptor and triphenylamine as the electron donor was synthesized. Photophysical and electrochemical characterization suggest stepwise photoinduced charge separation upon excitation of the copper(I)-based metal-to-ligand charge transfer (MLCT) transition. Analyses of femtosecond transient absorption data of the triad show that intersystem crossing from the 1MLCT to the 3MLCT state is followed by two electron-transfer steps with time constants of 20 ps and 722 ps yielding a presumed final charge-separated state with a radical cation on the donor and radical anion on the acceptor that has an 18 ns lifetime in acetonitrile. Finally, this triad was anchored onto n-type (ZnO) and p-type (NiO) semiconductor surfaces to construct a photoanode and photocathode respectively. Successful photocurrent generation from both electrodes upon white light illumination confirms the potential utilization of such systems in dye-sensitized photoelectrochemical cells.

Fluorescence Carbon Dots from Blood-Berries for Sensing Cr6+ Ions in Water and Application in White Light Emitting Diode.

Conventional techniques for identifying heavy metal ions in water are laborious and time-consuming. Therefore, it is necessary to create innovative sensing technologies that can detect with greater sensitivity and speed. Although there have been reports of optical-based assays utilising fluorescent nanomaterials, these assays usually rely on variations in signal strength. However, this approach has significant drawbacks when it comes to environmental monitoring. Fluorescence carbon dots (CDs) have been prepared by facile synthesis from Blood berries. A homemade heavy metal optical detector is constructed to accurately identify heavy metal ions, exclusively Cr6+ ions in a water medium. Their optical emission signature varies based on the specific chromium ions in solution, and the emission intensity also changes depending on its concentration. The quenching behaviour is attributed to the interaction between the metallic cations and the fluorescent surface states of the carbon dots. Another application is the encapsulation of CDs in PVDF polymer to form a flexible film and use it as a phosphor for LED conversion.

Investigation on luminescent characteristics of Tb3+/Dy3+co-doped boro-phosphate glass for cool white LED and radiation shielding applications

The Tb3+/Dy3+ co-doped Boro-Phosphate Glass (BPANZDyTb) was produced (40 B2O3 + 39P2O5 + 5 Al2O3 + 5 NaF + 10 ZnO + 0.5 Tb2O3 + 0.5 Dy2O3) using melt-quenching technique. X-ray diffraction measurements, Raman, and Fourier Transform Infrared were used to evaluate the structural behavior of the prepared glass. Powder-XRD spectra, in the 10–90° range showed that the prepared glass was amorphous. FTIR analysis reveals that the network contains a variety of structural groups, including B-O-B, BO4, BO, P-O, PO2, P-O-B, and PO4 units. The UV–visible diffuse reflectance spectroscopy was used to record and study the optical linear properties of Tb3+/Dy3+ co-doped Boro-Phosphate Glass (BPANZDyTb). The photoluminescence excitation peak was obtained at 348 nm. The emission peaks were located at 484 nm (4F9/2 → 6H15/2 → blue), 576 nm (4F9/2 → 6H13/2 → yellow), and 662 nm (4F9/2 → 6H11/2 → red). Tb3+ ions are located at 412 nm (5D3 → 7F5), 441 nm (5D3 → 7F4), 546 nm (5D4 → 7F5), and 625 nm (5D4 → 7F3). The result of CIE 1931 chromaticity coordinates indicate that the prepared glass is suitable material for cold white light emitting diode applications due to its color coordinates x = 0.3106 and y = 0.3240 and correlated color temperature (CCT) values about 6768 K. The gamma-ray parameters such as half-value layer (HVL), mass attenuation coefficient (μ/ρ), mean free path (MFP), and effective atomic number (Zeff) of the BPANZDyTb glass were studied using Phy-X software. The results of the gamma-ray parameter show that the Dy3+ ions and Tb3+ ions co-doped BoroPhosphate glass is an appropriate material for radiation shielding applications.

Wormlike Micellar Glycerol Solutions Formed from a Double-Tailed Surfactant with Two Quaternary Ammonium Head Groups.

Herein, a quaternary ammonium surfactant with dual heads and tails, N1,N1,N1,N3,N3-pentamethyl-N3-(3-(2-tetradecylhexadecanamido)propyl)propane-1,3-diaminium dibromide, abbreviated as Di-C14-N2, was synthesized. For the first time, clear observation of aggregate structures formed by surfactants in pure glycerol systems was achieved using cryogenic transmission electron microscopy (cryo-TEM). The system's rheological properties were analyzed using both steady-state shear and oscillatory rheological measurements. The lubricating efficiency of the Di-C14-N2 glycerol solution was assessed for its tribological properties using a tribological wear tester, white light interferometer, and scanning electron microscope. In glycerol, Di-C14-N2 formed long wormlike micelles, which resulted in a glycerol solution with the zero-shear viscosity of 1013 Pa·s at 90 mM, which is the most viscous glycerol system up to now. The system displayed distinct rheological properties from the aqueous system, as evidenced by two intersections in the loss and storage moduli. The formed wormlike micelles in glycerol lead to a significant alteration in the viscoelasticity of the system, thus endowing the Di-C14-N2 glycerol solution with potential as an eco-friendly lubricant. The friction coefficient of the system was found to be 23% lower and the wear rate was 83% lower than that of pure glycerol after the addition of Di-C14-N2. This demonstrates that the addition of Di-C14-N2 greatly improves the frictional properties of pure glycerol. This study offers the possibility of directly observing the aggregate structures formed by surfactants in pure glycerol systems. It contributes to the exploration of the self-assembly behavior of surfactants in nonaqueous polar media, thereby aiding in a deeper understanding of the correlation between molecular structure, mesoscale structure, and macroscopic properties.

Maltese Coastline Never Sleeps: The Effects of Artificial Light at Night (ALAN) on the Local Infralittoral Assemblages—A Case Study

Aside from the most notorious threats, the Mediterranean Sea faces novel and poorly explored impacts from artificial light at night (ALAN), which influences natural light–dark cycles and affects marine ecosystems. This study investigates the impact of ALAN on coastal infralittoral assemblages in Malta, where such effects remain unexplored. Using Baited Remote Underwater Videos (BRUVs), we examined the influence of different light intensities on species assemblages and behaviour at two sites: a light-polluted harbour and a darker reef area. Our findings reveal significant differences in fish community composition between light treatments and habitats. Among the 23,955 individuals recorded across multiple taxa, Boops boops accounted for 80% of observations. From our results, light intensity had a more substantial impact on community structure than habitat type, with species-specific responses to light. Predatory species such as Trachurus trachurus displayed increased activity under high-intensity white light, while Apogon imberbis and Serranus scriba were more abundant under red light, irrespective of habitat. These results underscore the role of ALAN in altering marine community dynamics and emphasise the need for sustainable management strategies to mitigate its impact on the biodiversity of the Mediterranean. This study provides initial empirical evidence of ALAN’s effects in Maltese waters, contributing to broader efforts to understand and manage light pollution in marine ecosystems.

White‐Light‐Emitting Ln‐MOF as Luminescent Probe for Selective Detection of Nitroaromatic Compounds

AbstractMetal‐organic frameworks (MOFs) as an efficient and convenient sensing material for environmental pollutants have attracted widespread attention in recent years. Here in, we synthesized a series of lanthanide co‐doping MOFs, EuxTb1‐x‐MOFs (x=0, 0.005, 0.00667, 0.01, 0.02 and 1) under solvothermal conditions. The luminescence colors can be adjusted by changing metal molar mass ratios and altering excitation wavelength. Fortunately, a near white‐light‐emitting material Eu0.01Tb0.99‐MOF was obtained under the excitation at 350 nm, whose CIE coordinates of (0.3444, 0.3409) are very close to standard white light coordinates (0.3333, 0.3333). We further studied the fluorescence sensing performances of Eu‐MOF, Tb‐MOF and Eu0.01Tb0.99‐MOF towards NACs. The results indicate that all MOFs can selectively detect 4‐nitroaniline, 4‐nitrophenol and 2‐nitrophenol with good sensitivity and recyclability.

White Light Emission from Zn(II) and DMSO-Induced Copper Nanocluster Assembly.

An assembly of metal nanoclusters driven by appropriate surface ligands and solvent environment may engender entirely new photoluminescence (PL). Herein, we first synthesize histidine (His) stabilized copper nanoparticles (CuNPs) and, subsequently, copper nanoclusters (CuNCs) from it using 3-mercaptopropionic acid (MPA) as an etchant. The CuNCs originally emit bluish-green (λem=470 nm) PL with a low quantum yield (QY∼1.8 %). However, it transformed into a dual-emissive nanocluster assembly (Zn-CuNCs) in the presence of Zn(II) salt, having a distinct blue emission band (λem=420 nm) and a red emission band (λem=615 nm) with eight times QY (∼9.1 %) enhancement. The temperature-dependent emission spectra of Zn-CuNCs depicted that the blue emission band persists for all the temperature ranges (0-80 °C) while the red emission band vanishes at high temperatures (70-80 °C). Thus, the blue emission may originate from the locally excited state (LES) emission of the nanoclusters, while the red emission originates from through-space interaction (TSI) and Cu(I)…Cu(I) interaction within the assembly. Adding dimethyl sulfoxide (DMSO) further modifies the emission intensities; the red band was amplified four times, while the blue band was diminished by 2.5 times. The transmission electron microscopy (TEM) images unveiled that the Zn-CuNCs are a large assembly of tiny nanoclusters, which become more compact in DMSO. The blue emission possesses steady-state fluorescence anisotropy, while the red emission shows no anisotropy. Further, near-perfect white light emission(WLE) was rendered with CIE coordinates of (0.33, 0.32) by combining the dual emission of the Zn-CuNCs with the original green emission of the CuNCs.

Research on CdSe/ZnS Quantum Dots-Doped Polymer Fibers and Their Gain Characteristics.

Polymer fibers are considered ideal transmission media for all-optical networks, but their high intrinsic loss significantly limits their practical use. Quantum dot-doped polymer fiber amplifiers are emerging as a promising solution to this issue and are becoming a significant focus of research in both academia and industry. Based on the properties of CdSe/ZnS quantum dots and PMMA material, this study experimentally explores three fabrication methods for CdSe/ZnS quantum dots-doped PMMA fibers: hollow fiber filling, melt-drawing, and melt extrusion. The advantages and disadvantages of each method and key issues in fiber fabrication are analyzed. Utilizing the CdSe/ZnS quantum dots-doped PMMA fibers that were fabricated, we theoretically analyzed the key factors affecting gain performance, including fiber length, quantum dots doping concentration, and signal light intensity. Under the conditions of 1.5 W power and 445 nm laser pumping, a maximum on-off gain of 16.2 dB was experimentally achieved at 635 nm. Additionally, using a white light LED as the signal source, a broadband on-off gain with a bandwidth exceeding 70 nm and a maximum gain of 12.4 dB was observed in the 580-650 nm range. This research will contribute to the development of quantum dots-doped fiber devices and broadband optical communication technology, providing more efficient solutions for future optical communication networks.