Photoluminescence Emission Research Articles

Effect of Concentration of TiO2 Nanoparticles on Thiadiazole Derivative and Their Molecular Docking Study.

In the present work, we report the synthesis of TiO2 nanoparticles by hydrothermal method using titanium isopropoxide. The synthesized TiO2 nanoparticles were investigated by Powder X-ray diffraction, FE-SEM with EDX, Photoluminescence, UV-Visible absorption and Fluorescence emission spectroscopy. Fluorescence intensity and absorption values of 4-[5-(2,5-Dimethyl-pyrrol-1-yl)-[1,3,4]thiadiazol-2-ylsulfanylmethyl]-6-methoxy-chromen-2-one (DTYMC) molecule decreases with adding the concentration of TiO2 nanoparticles. Stern-Volmer equation for steady state method is found to be linear and its co-relation coefficient is found to be r = 0.88, which indicates the presence of dynamic quenching. Binding orientations of the DTYMC ligand with targeted proteins are Thymidylate synthase (TS) - PDB ID: 1JU6, The type II topoisomerases (TOP2α) - PDB ID: 4FM9 and Human thymidine phosphorylase (hTP) - PDB ID: 2WK6. The obtained result suggests that, the DTYMC molecule exhibits inhibitory activity against the overexpression of TS receptor which causes non-small cell lung cancer (NSCLC). Antimicrobial study of TiO2 NPs has been determined.

Tunable Single‐Phase White Light Emission from Complex Perovskite Sr3CaNb2O9: Dy3+/Eu3+ Phosphors

AbstractSr3CaNb2O9:Dy3+/Eu3+ phosphors with a complex perovskite structure are prepared using a high‐temperature solid‐ state reaction technique. These phosphors are doped either singly or in combination with Dy3+/Eu3+ ions, resulting in efficient energy transfer from Dy3+ to Eu3+ and thus tunable‐color emission. Under 353 nm excitation, the Sr3CaNb2O9:Dy3+ phosphor emits blue (492 nm), yellow (583 nm), and red (682 nm) light, with the optimal doping concentration of Dy3+ of 0.04%. When excited by 394 nm (7F0 → 5L6), the Sr3CaNb2O9:Eu3+ phosphor exhibits two most intense emissions centered at 593 nm (5D0 → 7F1) and 614 nm (5D0 → 7F2). The decrease in luminescence intensity with increasing doping concentration of Dy3+ and Eu3+ is due to the cross‐relaxation associated with electric dipole–dipole interaction. Photoluminescence emission measurements under excitations of 353 and 365 nm indicate that the Sr3CaNb2O9:0.04Dy3+/0.05Eu3+ phosphor shows excellent thermal stability, even at a temperature of 150 °C, where the luminescence intensity preserves 79% of its initial value at room temperature. The electroluminescence performance of the Sr3CaNb2O9:0.04Dy3+/0.05Eu3+ phosphor is tested with 365 nm LED chips for potential use in white LEDs. The results confirm that Sr3CaNb2O9:0.04Dy3+/0.05Eu3+ phosphor has great potential for use in high‐power white LED applications as a single matrix.

Combinatorial composition-gradient and -aligned CsPb(Br1−xIx)3 films by IR-laser MBE

We investigated the combinatorial synthesis and characterization of a halide perovskite CsPb(Br1−xIx)3 composition-gradient film deposited on a SrTiO3(001) substrate using infrared laser molecular beam epitaxy. In halide perovskite materials, the diffusion speed of the halogen ions is high, making it difficult to form a continuous composition-gradient film. This is because halogen ions diffuse across the entire film surface, making it impossible to specify the anion composition that changes at each position. In this study, a contact-shadow mask process was introduced to suppress the interdiffusion of halogen ions. Consequently, a CsPb(Br1−xIx)3 composition-gradient and -aligned film in which the chemical composition of CsPbBr3 and CsPbI3 changed digitally was formed and systematically characterized for the optical bandgap and photoluminescence emission wavelength with respect to the chemical composition of the halogen ion. This deposition process is expected to be promising for exploring halide perovskite materials with complex chemical compositions, such as triple-cation halide perovskites.

Room temperature polarization-resolved Raman and photoluminescence in uniaxially strained layered MoS2

Transition metal dichalcogenides (TMDCs) are one of the material systems of choice toward achieving room temperature quantum coherence. Externally applied strain is used as a more common control mechanism to tune electro-optical properties in TMDCs like molybdenum disulfide (MoS2). However, room temperature electron–phonon interactions in the presence of strain in transition metal dichalcogenides are still not fully explored. In this work, we employ uniaxial strain dependent Raman and photoluminescence (PL) studies on monolayer and bilayer MoS2 to explore electron–phonon physics. Helicity-resolved Raman in MoS2 obeys robust selection rules. Our studies reveal clear modification in these helicity-based selection rules in the presence of moderate uniaxial strain (ϵ = 0.4%–1.2%). The selection rules are restored upon clear symmetry breaking of the in-plane vibrational mode (ϵ > 1.2%). We assign these changes to the onset of Fröhlich interaction in this moderate strain regime. The changes in Raman scattering are accompanied by changes in valley selective relaxation observed through non-resonant photoluminescence (PL). The moderate strain regime also exhibits the onset of PL polarization for indirect excitonic emission under non-resonant excitation. Our experimental observations point toward electron–phonon coupling mechanisms affecting both valley-selective electron relaxation during PL emission as well as polarization-selective Raman scattering of two-dimensional semiconductors at room temperature.

Water-Induced Turn-on of Lanthanide Photoluminescence Emission and Application in Colorimetric Sensing of Trace Water

Water-Induced Turn-on of Lanthanide Photoluminescence Emission and Application in Colorimetric Sensing of Trace Water

A novel photoluminescence theory and design rule based on solution entropy for rare earth ion doped alkaline metal silicates

This paper introduces an innovative theory for customizing photoluminescence (PL) emission wavelengths in rare earth ion (Eu2+) doped alkaline earth metals (Ca, Mg) silicates, rooted in the entropy of fusion and configurational entropy of congruent and incongruent silicates, respectively, aiming to reveal dynamic deformation of the tetrahedral SiO4 ligand within these materials. Using FactSage, we computationally calculate the fusion entropy of congruent silicates in the CaO-MgO-SiO2 system. Synthesized ternary silicates confirm our theory by highlighting correlations between lower/higher fusion entropy (for congruent) and configurational entropy (for incongruent) silicates, leading to red/blue shifts in PL emission wavelengths. In binary silicate systems, we observe an inverse correlation between PL emission wavelengths and fusion entropy of congruent silicates or pseudo-congruent silicates like MgSiO3, whose solid-liquid decomposition temperature is close to its melting point. Furthermore, the non-ideal liquid phase entropy of incongruent silicates positioned between congruent CaMgSi2O6 (Pyroxene) and congruent Ca2MgSi2O7 (Akermanite) in the MgO-CaO-SiO2 ternary phase diagram comprehensively explains diverse PL emission wavelengths. Beyond its scholarly impact, this work expands perspectives in lighting and photonic research, opening an exciting frontier in entropy-lighting research and enabling predictions of host chemical composition and tunable PL emission wavelengths, particularly relevant to LED technologies.

Unravelling the interaction of ethyl cinnamate in 2-hydroxypropyl and methyl-β-cyclodextrin by spectroscopic and theoretical evaluation for enhanced antibacterial activities

Essential oil components are the most common agents used to inhibit pathogens. Ethyl cinnamate (ECIN) is a hydrophobic essential oil component with well-known antibacterial properties but is poorly soluble in water, which limits its applications. In this study, inclusion complexes (ICs) were prepared by encapsulating ECIN in β-cyclodextrin (βCD), 2-hydroxypropyl-βCD, or methyl-βCD using an ultrasonication method to enhance water solubility and thermal and antibacterial properties. UV–Vis absorption and fluorescence spectral results indicated strong non-covalent interactions between ECIN and βCD derivatives in aqueous solution, and double reciprocal profiles revealed a guest:host stoichiometry of 1:1. Fourier-transform infrared and proton nuclear magnetic resonance spectroscopy investigations revealed that the phenyl ring of ECIN is located deeply in the CD nanocavities. X-ray diffraction, ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence, and field emission scanning electron microscopy were performed to obtain crystalline, optical, and morphological information on solid ECIN-CDs. Thermogravimetric/differential thermal studies confirmed the improved stability of ECIN in solid CD-ICs by detecting an increase in the degradation temperature of ECIN from 50–140 °C to 310–410 °C. Further, the geometrical and frontier molecular orbital structures of the ECIN-CDs were theoretically evaluated using parametric method-3. Finally, antibacterial assays conducted against the foodborne pathogens Staphylococcus aureus and Escherichia coli revealed that encapsulated ECIN had a greater inhibitory effect, which suggested the devised nanocarriers promote the solubilization of essential oil components in aqueous solutions.

Multiple stimuli-responsive double perovskite structured Ca2MgWO6: x % Eu3+ (x = 1–11 mol) red-emitting luminescent systems to combat counterfeiting

The rapid escalation of counterfeiting activities in recent years has posed significant challenges across diverse fields, such as pharmaceuticals, currency, luxury goods, and electronics. In response, inorganic phosphors have emerged as promising tools to combat counterfeiting due to their inherent durability and stability. The present work focuses on the synthesis of Ca2MgWO6:x % Eu3+ (x = 1–11 mol) luminescent systems via a gel-combustion route. The structural analysis of the synthesized luminescent systems confirmed a monoclinic crystal phase with a P21/n space group. The morphological study of the luminescent system revealed a network-like structure comprising interconnected particles. Photoluminescence emission spectra show a prominent red emission peak at 616 nm, corresponding to the 5D0→7F2 4f–4f electronic transition of Eu3+ ions in the host matrix. The emitted red light demonstrates a color purity and quantum efficiency of 93.1 % and 77.41 %, respectively. The anti-counterfeiting security patterns were developed using the Ca2MgWO6:x % Eu3+ (x = 9 mol) luminescent system showcase virtually invisible under normal light. However, developed patterns exhibit vivid red luminescence when exposed to multiple stimuli UV light at 365 and 395 nm, which envisages the versatility of the systems for enhancing product authentication and protecting against fraudulent activities across multiple industries. The aforementioned results demonstrated the efficacy of Ca2MgWO6: Eu3+ luminescent systems for integration into advanced security measures.

Dy doped calcium silicates synthesized using agro-food wastes and conventional chemicals as resources: a comparative study

Based on an earlier study, a mimic composition 38SiO2-60CaO-0.5Dy2O3-0.2Na2O-1MgO-0.1Al2O3-0.1TiO2-0.1Fe2O3 (wt.%) are synthesized by solid-state reaction method. The structural, morphological, and optical properties of the synthesized sample presented in this study are compared with the corresponding properties of a similar sample derived from rice husk ash and eggshell powder as resources. The conventional chemicals derived sample are multi-phasic, containing β−Ca2SiO4, γ−Ca2SiO4, Ca3Si2O7, and CaFeO3 phases, and the CaO/SiO2 ratio was believed to be affecting the room temperature stabilization of the β phase. Field emission scanning electron microscopy images showed that twinned particles, cracks, and edge dislocations were present in the synthesized sample. The presence of precipitates in the micrographs indicated that Dy ions were segregated on the surface of the sample. The optical bandgap of the samples was 3.7 eV, as calculated by diffuse reflectance spectroscopy. The photoluminescence emission spectrum contained characteristic emission peaks of the Dy3+ ions. Apart from these, additional peaks were observed due to the titanium ions present in the sample. Understanding the properties of calcium silicates containing multiple dopant ions is important to develop a white light-emitting diode. The properties of the mineral-derived sample are compared to those of the agro-food waste-derived similar sample.

Red-emitting phosphors NaLiXF6:Mn4+ (X = Ti, Si) for white LEDs with high color rendering index and low correlated color temperature

White light-emitting diodes (WLEDs) are widely used in various lighting applications due to their high brightness and energy efficiency. However, commercial WLEDs, which typically combine YAG:Ce3+ phosphors with blue light-emitting diode chips, often lack red components, resulting in a high correlated color temperature (CCT) and a low color rendering index (CRI). To address this issue, two novel Mn4+-doped red-emitting phosphors, NaLiTiF6 and NaLiSiF6, were synthesized using an ion exchange method. Both phosphors exhibit strong red light with a pronounced zero-phonon line (ZPL) emission under blue light excitation. Optimal photoluminescence emission intensities were observed at Mn4+ concentrations of 6% for NaLiTiF6 and 9% for NaLiSiF6. When the temperature increased from 303 K to 413 K, both phosphors demonstrated outstanding brightness and chromatic stability. Integrated into phosphor-converted light-emitting diodes (pc-LEDs), the device incorporating NaLiTiF6:6%Mn4+ achieved a CRI of 95.1 and a CCT of 3172 K, while the device with NaLiSiF6:9%Mn4+ showed a CRI of 87.9 and a CCT of 3784 K. In addition, the luminous efficacy, CRI, and CCT of both prototype pc-LEDs maintained minimal variation with increasing driving current. These results indicate the stability and suitability of the synthesized phosphors for enhancing the performance of warm WLEDs applications.

Large-Area Bright Emission of Plasmon-Coupled Dark Excitons at Room Temperature.

Brightening dark excitons in transition metal dichalcogenide monolayers (MLs) can provide large-area ultrathin devices for applications in quantum information science and optoelectronics. For practical applications of dark excitons, a robust and bright emission over a wide area at room temperature is desirable; however, no reliable approach has been demonstrated thus far. In this study, an efficient approach is presented for brightening dark excitons at room temperature over a large area of a WSe2 ML via coupling between plasmons and dark excitons. When a WSe2 ML is placed on gold micropillars (Au MPs), dark excitons are efficiently coupled to strongly localized surface plasmons at the edges of the Au MPs, along with a strong photoluminescence (PL) emission. Room-temperature dark exciton emission is confirmed via energy-, angle-, and time-resolved spectroscopy experiments, as well as confocal PL mapping. This study provides a generalizable method for the practical application of dark exciton.

Efficient one-pot strategy for fluorescent conjugated polymers derived from 8-amino-1-naphthalene-3,6-disulfonic acid: Synthesis, thermal and optical properties

Schiff base polymers, also known as poly(imines) or poly(azomethine)s, constitute a subset of conjugated polymers. The Schiff base compound was synthesized via the condensation reaction between 8-amino-1-naphthalene-3,6-disulfonic acid and 4-hydroxybenzaldehyde. Subsequently, both 8-amino-1-naphthalene-3,6-disulfonic acid and its Schiff base derivative were polymerized into a poly(naphthol) (PANAPDSA) and Schiff base polymer (PANAPDSASB) under alkaline condition using H2O2 (35 % aqueous solution) as oxidant via oxidative polycondensation (OP). The chemical structures of the synthesized compounds were approved using NMR, FT-IR, UV–Vis, element and LC-MS/MS spectroscopic techniques. The synthesized polymers exhibited lower optical and electrochemical band gaps compared to their respective monomers, suggesting their potential utility as semiconductor materials. The poly(naphthol) derivative exhibited high fluorescent emission intensity of 1000 a.u. when excited at 300 nm with a photoluminescence (PL) emission quantum yield of 13.6 % at 392 nm of emission wavelength in N,N-dimethylformamide (DMF) solution. Weight average molecular weight (Mw) values of PANAPDSA and PANAPDSASB ranged from 9500 Da to 11200 Da, with PDI values between 1.12 and 1.13. The synthesis of conjugated polymers could hold significant importance in technological advancements.

Large-Scale Synthesis of Carbon Dots Driven by Schiff Base Reaction at Room Temperature

Photoluminescent carbon dots (CDs) have received increasing attention because of their admirable photophysical performances. The current strategies for synthesizing CDs typically require high energy consumption levels, and the ability to synthesize CDs at ambient temperature would be highly desirable. Herein, we design an energy-efficient approach to synthesize CDs through a Schiff base crosslinking between 2,5-dihydroxy-1,4-benzoquinone and tetraethylenepentamine at room temperature. The obtained CDs possess maximum photoluminescence (PL) emissions of 492 nm. Moreover, the proposed CDs possess good stability and a concentration-dependent PL and their maximum emissions can redshift from 492 to 621 nm as the CDs concentration increases. Because of their good luminescent properties, the CDs can be employed as optical probes for doxorubicin detection using the inner filter effect. This study develops a powerful approach for the large-scale synthesis of CDs with a superior performance.

Structural and angle-resolved optical and vibrational properties of chiral trivial insulator InSeI

Chiral materials, known for their unique structural and quantum properties, have garnered significant interest, with InSeI emerging as a promising chiral topologically trivial insulator. In this study, we introduce a scalable Bridgman crystal growth technique to synthesize large, environmentally stable single crystals of InSeI, achieving centimeter-sized chiral crystals with superior quality. Notably, this work marks the first report of photoluminescence (PL) emission from exfoliated InSeI chiral chains, alongside a detailed exploration of their polarization-dependent optical and phononic properties. Our Bridgman-grown crystals exhibit excellent structural integrity, enhanced exfoliation characteristics, and increased resistance to light-induced degradation compared to those produced by traditional solid-state methods. A microscopy analysis confirms the distinct chiral structure of InSeI, and the first in situ nanometer spatial resolution electron energy loss spectroscopy measurements establish a bandgap of 2.08 eV, consistent with the cryogenic PL emission peak. Angle-resolved Raman spectroscopy, combined with calculated vibrational properties, identifies five distinct frequency regions in the Raman modes, predominantly associated with In-, In-I, In-Se-I, and Se-atomic motions, with significant intensity variations under different polarization orientations. This study not only offers a practical method for synthesizing high-quality InSeI but also provides the first comprehensive experimental insights into its unique optical and vibrational properties, significantly advancing the understanding of chiral material systems.

Fabrication of BiVO4/Ag2CrO4 heterojunction composites modified with graphene oxide for enhanced photoelectrochemical and photocatalytic performance.

A novel GO/BiVO4/Ag2CrO4 heterojunction photocatalyst was prepared by depositing Ag2CrO4 on the highly active (040) facet of BiVO4, followed by incorporating graphene oxide (GO) through an in situ precipitation method. This synergistic modification of BiVO4 by Ag2CrO4 and GO results in excellent photocatalytic performance, with a degradation efficiency of 94.6% coupled with a maximum rate constant of 0.223 min-1, which is 2.40, 2.19 and 0.66 times higher than that of BiVO4, Ag2CrO4, and BiVO4/Ag2CrO4, respectively, for the degradation of ciprofloxacin (CIP) under visible light irradiation. The degradation efficiency of ciprofloxacin was evaluated using total organic carbon (TOC) analysis. Under investigated conditions, the GO/BiVO4/Ag2CrO4 photocatalyst achieved a TOC reduction of 63.4%. The enhanced photocatalytic performance is attributed to the beneficial role of GO in facilitating electron transport for photo-charge carrier migration, leading to strong interfacial coupling between BiVO4 and Ag2CrO4, which in turn promotes efficient charge separation and transfer. The physicochemical properties of the fabricated heterojunction photocatalysts were characterized using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) coupled with energy-dispersive X-ray (EDX) analysis, Brunauer-Emmett-Teller (BET) analysis, Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), and photoluminescence (PL) emission spectroscopy, while the photoelectrochemical properties of the fabricated photocatalyst were investigated through electrochemical impedance spectroscopy (EIS), Mott-Schottky plots, and photocurrent response analysis. The scavenging experiment was conducted to confirm the role of H+ and ·O2 - in the photocatalytic degradation of ciprofloxacin, which aids in proposing probable degradation mechanism for ciprofloxacin under visible light irradiation. Hence, this study offers an effective strategy for fabricating heterojunction photocatalysts aimed at enhancing the photodegradation of pollutants in wastewater.

Crystallographic Profiling, Core-Shell Electronic Configurations, and Investigations of Frequency-Dependent Dielectric Characteristics of Sb2O3-V2O5 Micro Ceramics

A series of V2-xSb2xO5-δ (Sb-V-O) ceramic powder samples with molar concentrations ranging from 0.05 to 0.08 were synthesized using a solid-state reaction method. Crystallographic analysis conducted through Rietveld refinement indicates that at a molar fraction of x=0.05, the orthorhombic V₂O₅ phase is observed. Conversely, at molar concentrations of x=0.06, 0.07, and 0.08, the orthorhombic phase of V2O5 and the tetragonal phase of SbVO4 are present simultaneously. X-ray photoelectron spectroscopy (XPS) was employed to ascertain the elemental oxidation states, revealing the presence of V5+, V4+, Sb3+ ions, and Sb0 metal atoms, along with O1s photoelectron peaks. The photoluminescence (PL) emission spectrum suggests transitions from a shallow donor level to the valance band. The room temperature AC conductivity and dielectric property results reveal a systematic decrease in the dielectric constant. The AC conductivity experimental data was accurately modeled using the Almond-West formalism, yielding high R2 values (0.9968–0.9986) and low chi-square errors (1.157×10⁻11–9.42×10⁻12) obtaining hopping frequency values for each composition (x = 0.05–0.08). AC conductivity (σac) decreased from 5.08×10⁻⁴ S/m to 2.40×10⁻⁴ S/m at 10 MHz, while DC conductivity (σdc) dropped from 7.22×10⁻⁵ S/m to 1.55×10⁻⁵ S/m. This reduction in conductivity is attributed to structural changes from Sb³⁺ substitution, which disrupts polaronic conduction by reducing the number of available O2⁻ ions and promoting SbVO₄ phase formation, hindering charge transport. The Sb₂O₃-V₂O₅ ceramics exhibit promising potential for energy storage applications, particularly in capacitors requiring high dielectric constants at low frequencies. At lower frequencies, grain boundaries inhibit conduction, enhancing dielectric constant values; at elevated frequencies, grain conduction predominates, lowering dielectric constant in accordance with Koop’s phenomenological theory, favoring applications in multi-layer ceramic capacitors. A notably higher dielectric loss factor (εr'') at low frequencies (10 Hz–1 kHz) indicates lossy behavior, beneficial for microwave absorption, while its stabilization above 10 kHz suggests minimal energy dissipation, ideal for high-frequency electronic and dielectric devices.

Coordinated Anions Tune Z-Type Ligand Displacement from Colloidal CdSe and InP Nanocrystal Surfaces.

Neutral metal salts coordinate to the surfaces of colloidal semiconductor nanocrystals (NCs) by acting as Lewis acid acceptors for the NC surface anions. This ligand coordination has been associated with increased emission due to the passivation of surface hole traps. Here, variation of the anionic ligands of metal salts is used to study anion effects on metal complex Lewis acidity and surface coordination at CdSe and InP NCs. To resolve dynamic ligand exchange processes, the tetracarbonylcobaltate anion, [Co(CO)4]-, is used as a monoanionic ligand for which IR spectroscopy can readily identify displacement of neutral M[Co(CO)4]x species (M = Cd or In; x = 2 or 3, respectively) upon addition of neutral donor ligands. Notably, although Cd[Co(CO)4]2 is more Lewis acidic than cadmium oleate, the former is more readily displaced from the NC surfaces. Lewis acidity and X-type anion exchange are, therefore, factors to be considered when performing postsynthetic addition of metal salts for NC photoluminescence emission enhancement.

Synthesis of white light emanating mixed lanthanide complexes with organic ligand for laser and optoelectronic applications

A series of mixing of complexes [EuxTb1-x.L3] was synthesized using the solvent-assisted grinding method. The chemical composition of complexes is determined by elemental analysis. Energy dispersive X-ray analysis (EDAX) was applied to ascertain the purity of complexes. The morphology and nature of the synthesized complex were investigated using scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The photoluminescent excitation (PL) and photoluminescent emission (PLE) spectra were examined as a function of the concentration of Eu3+ and Tb3+ ions to predict the tuning of color in both state solution and solid. Thermogravimetric data analysis reveals that these complexes have good thermal stability, supporting their application in producing organic light-emitting diodes. The radiative rate (Arad), quantum efficiency (φ), and JO intensity parameters (Ωλ) were calculated. Studying these complexes' Urbach energy, optical band gap, and refractive index suggests their potential application in semiconductor and solar cell devices. The Commission International de I'Eclairage 1931 (CIE) coordinates (x,y) can be obtained from the emission spectra of complexes, indicating that color can be adjusted to nearly white light (x = 0.3201,y = 0.3319) by changing the Tb3+ and Eu3+ ion concentrations.

Exclusive Generation of Single-Atom Sulfur for Ultrahigh Quality Monolayer MoS2 Growth.

Preparation of high-quality two-dimensional (2D) transition metal dichalcogenides (TMDCs) is the precondition for realizing their applications. However, the synthesized 2D TMDCs (e.g., MoS2) crystals suffer from low quality due to the massive defects formed during the growth. Here, we report single-atom sulfur (S1) as a highly reactive sulfur species to grow ultrahigh-quality monolayer MoS2. Derived from battery waste, sulfurized polyacrylonitrile (SPAN) is found to be exclusive and efficient in releasing S1. The monolayer MoS2 prepared by SPAN exhibits an ultralow defect density of ∼7 × 1012 cm-2 and the narrowest photoluminescence (PL) emission peak with full-width at half-maximum of ∼47.11 meV at room temperature. Moreover, the statistical resonance Raman and low-temperature PL results further verify the significantly lower defect density and higher optical quality of SPAN-grown MoS2 than those of the conventional S-powder-grown samples. This work provides an effective approach for preparing ultrahigh-quality 2D single crystals, facilitating their industrial applications.

Width-dependent continuous growth of atomically thin quantum nanoribbons from nanoalloy seeds in chalcogen vapor

Nanoribbons (NRs) of atomic layer transition metal dichalcogenides (TMDs) can boost the rapidly emerging field of quantum materials owing to their width-dependent phases and electronic properties. However, the controllable downscaling of width by direct growth and the underlying mechanism remain elusive. Here, we demonstrate the vapor-liquid-solid growth of single crystal of single layer NRs of a series of TMDs (MeX2: Me = Mo, W; X = S, Se) under chalcogen vapor atmosphere, seeded by pre-deposited and respective transition metal-alloyed nanoparticles that also control the NR width. We find linear dependence of growth rate on supersaturation, known as a criterion for continues growth mechanism, which decreases with decreasing of NR width driven by the Gibbs-Thomson effect. The NRs show width-dependent photoluminescence and strain-induced quantum emission signatures with up to ≈ 90% purity of single photons. We propose the path and underlying mechanism for width-controllable growth of TMD NRs for applications in quantum optoelectronics.