Photoluminescence Research Articles

Zeolite-decorated black TiOx quantum dots for photocatalytic degradation of organic cationic dyes under LED light irradiation

Defect engineering is a promising strategy to reduce the band gap of semiconductors, enhancing their photocatalytic activity under visible light by introducing intra-bandgap energy states. Among the materials studied, oxygen-deficient black TiOx stands out due to its potential in photocatalytic reduction and hydrogen evolution. However, the valence band edge maximum (VBM) of TiOx is not thermodynamically favorable for the direct oxidation of water to hydroxyl radicals (H2O/•OH). Although the formation of extensive oxygen vacancies is necessary to extend the light absorption of black TiOx to longer wavelengths, a high density of oxygen vacancies (Ov) significantly shortens the diffusion length of charge carriers within the TiOx, leading to increased recombination of electrons and holes (e-/h+), thereby suppressing photocatalytic activity. To overcome these limitations, confining TiOx particles to the quantum dot (QD) size range and constructing heterojunctions with a secondary phase can substantially improve charge carrier separation and photocatalytic performance. In addition to engineering the electronic structure of composite photocatalysts, the preaccumulation of pollutants and their subsequent degradation is an effective strategy. This method decreases the distance between the adsorbed pollutant and the active sites for reactive oxygen species (ROSs) generation, enhancing the efficiency of the photocatalytic degradation process. In this study, we confined TiOx particles to the quantum dot size range by constructing a heterojunction with H-Beta zeolite, which contains defect-induced energy states within its wide band gap. This type of zeolite is particularly effective in adsorbing cationic azo dyes, facilitating pre-accumulation and degradation. The synthesized catalysts were extensively characterized using HRTEM to determine the average size of the TiOx particles and photoluminescence (PL) analysis to investigate charge carrier separation. Our results demonstrated that while TiOx alone showed negligible degradation efficiency, and no •OH were detected, the QD TiOx/Z4 composite achieved complete oxidation of CV by •OH, as confirmed by TOC analysis. The photocatalytic degradation mechanism was proposed based on these experimental findings. These insights could be of significant interest to researchers exploring defective semiconductors for photocatalytic oxidation of organic pollutants in the liquid phase under visible light (LED) irradiation.

Optical characterization of GaN:Eu microcrystals grown by the ammonothermal method

Eu-doped gallium nitride (GaN:Eu) microcrystals with a wurtzite crystal structure were synthesized using the ammonothermal method. The Eu concentration of GaN:Eu microcrystals estimated by glow discharge mass spectrometry (GDMS) was 5.8 × 1020 atoms/cm3. The morphology of GaN:Eu microcrystals was characterized by scanning electron microscopy (SEM). The exposed crystal faces of GaN:Eu microcrystals were identified as {10−10}, {10−11}, (000−1), and (0001), respectively. The photoluminescence excitation (PLE), photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra of GaN:Eu microcrystals revealed two luminescent sites of Eu3+ ions, designated as Eu0 and Eu1. The Eu0 was excited in the range of 300 nm to 420 nm, resulting in the observation of four characteristic luminescence peaks at 599 nm (5D0-7F1), 620 nm (5D0-7F2), 632 nm (5D1-7F4), and 663 nm (5D0-7F3). The Eu1 was associated with O2- ions and emitted light at specific excitation wavelengths. The main luminescence peak of the Eu1 was located at 614 nm, accompanied with characteristic peaks at 578 nm, 591 nm, and 698 nm. In view of the distinct luminescence properties of the Eu0 and the Eu1, the energy transfer processes of two luminescence sites were proposed.

Achieving efficient self-trapped excitons emission by suppressing defect level in Sb3+ doped metal halide

The field of metal halide engineering has made considerable progress, yet additional studies are needed to completely grasp the intriguing principles that govern their luminescence. In this work, we report a novel zero-dimensional (0D) organic-inorganic metal halide hybrid (OIMH) (C3H12N2)2InCl7 (C3H12N2 = 1,3-propane diamine cation) and reveal its interesting luminescent properties through experimental research and theoretical calculations. The photoluminescence (PL) of (C3H12N2)2InCl7 is a synergistic combination of intrinsic self-trapped exciton (STE) emission and defect-bound exciton (DBE) emission. Doping with Sb3+ induces several changes in (C3H12N2)2InCl7, including defect passivation, a reduction in the band gap, and structural shrinkage. These modifications result in a transition of PL centers to external STE emission, with the photoluminescence quantum yield (PLQY) increasing from 4.44 % to 68.70 %. Our work proposes, for the first time, the synergistic emission of STE and DBE and reveals the effect of metal ion doping, providing new insights into the mechanisms of materials exhibiting multifunctional exciton emission.

Single ZnO Nanowire for Electrical and Optical NO2 Gas Sensing: Origin of Reversible and Irreversible Gas Effects Investigated by Photoluminescence Spectroscopy.

In this work, the gas sensing properties of a single ZnO nanowire (NW) are investigated, simultaneously in terms of photoluminescence (PL) and photocurrent (PC) response to NO2 gas, with the purpose of giving new insights on the gas sensing mechanism of a single 1D ZnO nanostructure. A single ZnO NW sensing device was fabricated, characterized, and compared with a sample made of bundles of ZnO NWs. UV near-band-edge PL emission spectroscopy was carried out at room temperature and by lowering the temperature down to 77 K, which allows detection of resolved PL peaks related to different excitonic transition regions. Surface effects were observed in PL maps, considering different nano and microstructures. Electrical and optical measurements were acquired at the same time during the NO2 gas exposure, allowing for the comparison of PL and PC response times and signal recovery. During NO2 gas desorption, irreversible behavior in the surface-related and donor-acceptor pair (DAP) regions is interpreted as the effect of an initial transient when electronic transfer from the gas molecules to the bulk occurs through the ZnO NW surface which acts as a channel. To the best of our knowledge, this is the first work which investigates the simultaneous PL optical and PC electrical response signals of a single ZnO NW to gas exposure.

Understanding the Size‐Dependent Photostability and Photoluminescence Intermittency of Blue‐Emitting Core/Graded Alloy/Shell “giant”‐Quantum Dots

AbstractRecently, giant quantum dots (g‐QDs) with a core/interface graded alloy shell/shell structure have shown promise in reducing photoluminescence (PL) intermittency and improving photostability. However, this approach has been mainly demonstrated with red and green emitting g‐QDs but the blue‐emitting graded alloy QDs has remained less explored. To tackle this challenge, a composition gradient method is employed to create three blue‐emitting CdZnS/CdxZn1–xS/ZnS core/interface graded alloy shell/shell (C/A/S) quantum dots (QDs) with different diameters. The sample with the largest diameter (gQD‐3) exhibits superior optical characteristics, with a photoluminescence quantum yield (PLQY) of approximately 62% and around 80% ON/radiative events at the single‐particle level. Conversely, the smallest diameter (gQD‐1) sample shows lower PLQY and only 30% radiative events with longer OFF/nonradiative events. Probability distribution analysis of PL trajectories, fitted with a truncated power law, reveals a significantly higher carrier de‐trapping rate in gQD‐3 compared to gQD‐1, attributed to its proximity to band edge trap states. Additionally, the largest diameter sample retains remarkable optical performance during 48 h of continuous UV irradiation in colloidal suspension and single‐particle levels. These findings show optimized core/shell structures, gradual alloy interfaces, and outer shell coatings can stabilize blue‐emitting quantum dots, advancing next‐gen optoelectronics.

Evaluation of Band Structure of Single Crystalline Si-Rich SiSn thin Film

We evaluated the bandgap energy and optical properties of single-crystalline silicon-tin (Si1-x Sn x ) thin films utilizing Photoluminescence (PL), spectroscopic ellipsometry (SE), and X-ray photoelectron spectroscopy (XPS). The PL and SE results showed that the indirect and direct bandgap energy decrease with increasing Sn fraction. Furthermore, the change in the direct bandgap energy is larger than the indirect bandgap energy. This shows that Si1-x Sn x approaches the direct transition type. Then, the Sn fraction from the indirect-to-direct bandgap is estimated to be 47.2%. In addition, XPS results showed that the difference in valence band maximum between Si1-x Sn x and pure Si increased depending on Sn fraction. This is responsible for the decrease in the indirect and direct bandgap energy.

Optically Active, Paper-Based Scaffolds for 3D Cardiac Pacing.

In this work, we report the design and fabrication of a light-addressable, paper-based nanocomposite scaffold for optical pacing and read-out of in vitro grown cardiac tissue. The scaffold consists of paper cellulose microfibers functionalized with gold nanorods (GNRs) and semiconductor quantum dots (QDs), embedded in a cell-permissive collagen matrix. The GNRs enable cardiomyocyte activity modulation through local temperature gradients induced by modulated near-infrared (NIR) laser illumination, with the local temperature changes reported by temperature-dependent QD photoluminescence (PL). The micrometer-sized paper fibers promote the tubular organization of HL-1 cardiac muscle cells, while the NIR plasmonic stimulation modulates reversibly their activity. Given the nanoscale spatial resolution and facile fabrication, paper-based nanocomposite scaffolds with NIR modulation offer excellent alternatives to electrode-based or optogenetic methods for cell activity modulation, at the single cell level, and are compatible with 3D tissue constructs. Such paper-based optical platforms can provide new possibilities for the development of in vitro drug screening assays and heart disease modeling.

Optical Properties of Multilayered Staggered SiGe Nanodots Depending on Si Spacer Growth Temperature

The optical properties of the multilayered staggered SiGe nanodots (NDs) embedded in the Si spacers fabricated at varying Si growth temperatures are clarified in conjunction with the effect of strain by Photoluminescence (PL) and Raman spectroscopy. We found that compressive strain is induced in the SiGe NDs, with higher growth temperatures of the Si spacer resulting in stronger compressive strain. PL spectra indicate that the higher growth temperature leads to a wider bandgap. This transition energy behavior is caused by not only the strain in the SiGe NDs but also the Ge segregation. Furthermore, luminescence from the SiGe NDs was observed along with luminescence originated at the Si/SiGe interface in the SiGe NDs with a small dot size. This phenomenon was caused by the small energy difference of the conduction-band minima between the SiGe NDs and the tensile-strained Si spacers and the small volume of the tensile-strained Si spacers.

Innovative In Situ Passivation Strategy for High-Efficiency Sb2(S,Se)3 Solar Cells.

An effective defect passivation strategy is crucial for enhancing the performance of antimony selenosulfide (Sb2(S,Se)3) solar cells, as it significantly influences charge transport and extraction efficiency. Herein, a convenient and novel in situ passivation (ISP) technique is successfully introduced to enhance the performance of Sb2(S,Se)3 solar cells, achieving a champion efficiency of 10.81%, which is among the highest recorded for Sb2(S,Se)3 solar cells to date. The first principles calculations and the experimental data reveal that incorporating sodium selenosulfate in the ISP strategy effectively functions as an in situ selenization, effectively passivating deep-level cation antisite SbSe defect within the Sb2(S,Se)3 films and significantly suppressing non-radiative recombination in the devices. Space-charge-limited current (SCLC), photoluminescence (PL), and transient absorption spectroscopy (TAS) measurements verify the high quality of the passivated films, showing fewer traps and defects. Moreover, the ISP strategy improved the overall quality of the Sb2(S,Se)3 films, and fine-tuned the energy levels, thereby facilitating enhanced carrier transport. This study thus provides a straightforward and effective method for passivating deep-level defects in Sb2(S,Se)3 solar cells.

Crystal Structure, Optical, Photoluminescence, Raman, and Magnetic properties for Sm-doped Cr-Mg-Bi Ferrites using sensor

The current work,A series of rare earth Sm3+ ion substituted Cr-Mg-Bi ferrites Cr0.7Mg0.2Bi0.1SmxFe2-xO4 (x = 0.00, 0.02, 0.04, and 0.06) have beensynthesized by thesol-gel auto-combustion method. The XRD, FESEM, HRTEM,UV-Vis, FTIR, Raman spectroscopy, Photo Luminesce and Magnetic Properties analysis have been used to investigate structural, morphological, optical, Raman spectroscopy, Photo Luminesce and Magnetic Properties. Every sample contains a single-phase spinel structure, as confirmed by XRD.The substitution of Sm3+ ions is found to increase the lattice parameter from 8.258–8.248Å.A monotone diffraction peak (311) is visible near small angles of degrees (35.33 to 35.13). The Debye-Scherrer equation, the nanoparticles' crystallite size ranges from 35.357–54.778 nm.FE-SEMs reveal a spherical grain that groups and has a porous form, with particles 38.13 to 53.28 nmin size.HR-TEM micrographs illustrate spherical morphology and their average particle size decreases from 55.32 to 65.42 nm. The selected area electron diffraction (SAED) pattern confirms the crystal planes which were revealed from XRD calculations.The spinel structure was confirmed by FTIR spectroscopy, which found 414 cm-1 and 516 cm-1 vibrational band at the octahedral and tetrahedral sites.As the concentration of Sm3+ rises, the direct and indirect band gap energy values determined from UV-Vis show an increase and decrease.The generated NPs' semiconducting nature is confirmed by the strong correlation between the g-value and particle size change.Photoluminescence (PL) investigation shows that all processed samples have four bands.(i) peak centered at 412 nm, which is near-band edge emission and corresponds to the ultraviolet (UV) band,(ii) The violet band has a high-intensity peak at 434 nm,(iii) The blue band is related to a low-intensity, sharp peak located at 466 nm, and (iv) A broad peak at 502 nm with a very low intensity distinguishes the green band.The Raman spectroscopy investigation revealed that the CMBSF nanoparticles had a mixed spinel structure. The magnetic investigation shows that when the Sm content of ferrites increases, saturation magnetization drops from 39.86 to 33.16 emu/g.The sample's coercivity (Hc) increases from 16.06 to 21.90 KOe with Sm substitution.

Chiral cadmium-amine complexes for stimulating non-linear optical activity and photoluminescence in solids based on aurophilic stacks.

The design of high-performance optical materials can be realized using coordination polymers (CPs) often supported by non-covalent interactions, such as metallophilicity. The challenge is to control two or more optical effects, e.g., non-linear optics (NLO) and photoluminescence (PL). We present a new strategy for the combination of the NLO effect of second-harmonic generation (SHG) and the visible PL achieved by linking dicyanidoaurate(i) ions, which form luminescent metallophilic stacks, with cadmium(ii) complexes bearing chiral amine ligands, used to break the crystal's symmetry. We report a family of NLO- and PL-active materials based on heterometallic Cd(ii)-Au(i) coordination systems incorporating enantiopure propane-1,2-diamine (pda) ligands (1-S, 1-R), their racemate (2), and enantiopure trans-cyclopentane-1,2-diamine (cpda) ligands (3-S, 3-R). Due to acentric space groups, they exhibit the SHG signal, tunable within the range of 11-24% of the KDP reference, which was correlated with the dipole moments of Cd(ii) units. They show efficient blue PL whose energy and quantum yield, the latter ranging from 0.40 to 0.83, are controlled by Cd(ii) complexes affecting the Au-Au distances and vibrational modes. We prove that chiral Cd(ii)-amine complexes play the role of molecular agents for the stimulation of both the NLO and PL of the materials based on aurophilic stacks.

Low temperature recombination luminescence of Mg3Y2Ge3O12:Tb3+

A study was conducted to examine the recombination processes in persistent phosphor Mg3Y2Ge3O12:Tb3+ garnet at low temperatures. Photoluminescence (PL), recombination luminescence (RL), electron paramagnetic resonance (EPR), and EPR detected by PL or RL were measured.In samples with low Tb3+ concentration, a broad PL and RL band around 400–450 nm and characteristic Tb3+ lines were observed. However, in samples with high Tb3+ concentration, only Tb3+ lines were present. Both the broad-band and the line components exhibit long-lasting tunneling luminescence with hyperbolic decay. After 263 nm UV irradiation signals of intrinsic electron (F-type) and hole (V-type) trapping centres were observed in the EPR spectra. Such signals were also observed in RL-detected EPR spectra, indicating that the broad RL band at low Tb3+ concentrations originates from tunneling recombination between these intrinsic traps. At high Tb3+ concentrations, the RL-EPR spectrum was not observed, suggesting that intrinsic electron and Tb-related hole trapping centres probably participate in the tunneling recombination.

Exploring the potential of epoxy nanocomposites infused with Alq3 for UV sensing applications

This research explores the morphological, molecular, and photoluminescent properties of epoxy-based nanocomposite sheets containing Alq3, as well as their response to UV irradiation. By analyzing the surface morphology via SEM, it is observed that the pristine epoxy sheets exhibit uniformity, while the nanocomposites display dispersed nanoparticles, influenced by the concentrations of dopants. Raman spectroscopy reveals changes in molecular structures and vibrational modes, with broadened peaks indicating potential interactions between the additives and epoxy matrix. The photoluminescence (PL) emission spectra show enhancements in intensity and shifts in peak wavelengths toward the green emission region, significantly influenced by the dopants. UV irradiation causes changes in both Raman and PL signals, with varying effects on different nanocomposite configurations. Linear regression analysis demonstrates strong correlations between signal changes and irradiation time, particularly pronounced in epoxy/Alq3 nanocomposite sheets, with marginal errors from Raman and PL signal-induced changes of 5% and 2%, respectively. Additionally, stability and reproducibility assessments reveal consistent signal trends over prolonged UV exposure and high reproducibility with minimal error of less than 5%. Overall, these epoxy nanocomposite sheets display promising results for UV sensing applications due to their sensitivity, linearity, stability, and reproducibility.

Design and synthesis of dicyanoethylene derivatives functionalized with carbazole possessing the properties of obvious aggregation-induced emission and reversible high-contrast mechanofluorochromism

This study devotes to the design, preparation, and examination of two novel D-A structured molecules, designated as CCEDBF and BCCEDBF, which are derived from carbazole unit, dicyanoethylene segment, and dibenzofuran unit. The distinctive D-A molecular architectures and highly twisted spatial configurations of these compounds facilitate pronounced intramolecular charge transfer (ICT) while also imparting robust solid-state luminescence, exhibiting emission efficiencies of 0.518 and 0.739, respectively, and notable aggregation-induced emission (AIE) with AIE factors of 43 and 30. Significantly, both CCEDBF and BCCEDBF demonstrate reversible mechanofluorochromic (MFC) behavior characterized by high fluorescence contrast. Mechanical grinding of the initial powders results in a shift in their emission colors, transitioning from green and yellow-green to yellow and orange-red, respectively, alongside a corresponding shift in emission peaks from 525 nm to 536 nm–558 nm and 597 nm. Powder X-ray diffraction (PXRD) examination of the initially synthesized, mechanically processed, and vaporized samples reveals that the observed fluorescence color change is due to a structural transformation between ordered crystalline and disordered amorphous configurations induced by the application of the external force. The red shift in photoluminescence (PL) spectra post-grinding is attributed to a reduced band gap, driven by factors such as extended π-conjugation length, enhanced planar intramolecular charge transfer (PICT) effect, strengthened π-π interactions and exciton coupling, as well as the increase in the orbitals overlap between neighboring molecular. Moreover, the presence or absence of tert-butyl substituents attaching to the 3- and 6-positions of the carbazole units significantly impacts the photophysical properties of these materials.

Investigation of structural, optical, and electrical characterization of nanostructured Bi30Sb10Se60-based photodetector applications

This study thoroughly investigates the optical absorption properties of Bi30Sb10Se60 thin films, focusing on their applicability in photo-sensing technologies. By employing a range of spectrophotometric techniques, including transmission and reflection analyses, the research identifies a direct energy gap of 1.68 eV, along with dispersion and oscillator energies of 14.36 eV and 3.42 eV, respectively. These parameters reveal the material's interaction capabilities with light. The study highlights the heterojunction's pronounced photosensitivity, especially at lower reverse biases, indicating its promise for photo-sensing applications. Photoluminescence (PL) spectra show broad defect emission bands with peaks at 475 nm, 487 nm, 510 nm, and 525 nm, which provide insights into recombination processes. Additionally, Energy Dispersive Spectroscopy (EDS) confirms the films' near-stoichiometric composition, while Thermal Gravimetric Analysis (TGA) demonstrates the high thermal stability of the films. The findings include high responsivity and detectivity of the photodetector, though the linear dynamic range (LDR) and signal-to-noise ratio (SNR) are comparatively lower. Overall, the research advances the understanding of Bi30Sb10Se60 thin films, paving the way for their use in optimized photoresponsive devices within optoelectronic technologies.

Coexistence of the Band Filling Effect and Trap-State Filling in the Size-Dependent Photoluminescence Blue Shift of MAPbBr3 Nanoparticles.

The size-dependent photoluminescence (PL) blue shift in organometal halide perovskite nanoparticles has traditionally been attributed to quantum confinement effects (QCEs), irrespective of nanoparticle size. However, this interpretation lacks rigor for nanoparticles with diameters exceeding the exciton Bohr radius (rB). To address this, we investigated the PL of MAPbBr3 nanoparticles (MNPs) with diameters ranging from ~2 to 20 nm. By applying the Brus equation and Burstein-Moss theory to fit the PL and absorption blue shifts, we found that for MNPs larger than rB, the blue shift is not predominantly governed by QCEs but aligns closely with the band filling effect. This was further corroborated by a pronounced excitation-density-dependent PL blue shift (Burstein-Moss shift) at high photoexcitation densities. Additionally, trap-state filling was also found to be not a negligible origin of the PL blue shift, especially for the smaller MNPs. The time-resolved PL spectra (TRPL) and excitation-density-dependent TRPL are collected to support the coexistence of both filling effects by the high initial carrier density (~1017-1018 cm-3) and the recombination dynamics of localized excitons and free carriers in the excited state. These findings underscore the combined role of the band filling and trap-state filling effects in the size-dependent PL blue shift for solution-prepared MNPs with diameters larger than rB, offering new insights into the intrinsic PL blue shift in organometal halide perovskite nanoparticles.

High temperature photoluminescence dependence and energy migration of Tb3+-Incorporated K3Y(BO2)6 phosphors

This study investigates the structural and photoluminescence (PL) characteristics of Tb3+-incorporated K3Y(BO2)6 (KYBO) phosphors synthesized via a microwave-assisted sol-gel technique. X-ray diffraction (XRD) and Rietveld refinement confirmed the formation of a pure hexagonal phase, with lattice expansion due to Tb³⁺ doping. PL studies revealed strong green emissions centered at 541 nm, attributed to the ⁵D₄ → ⁷F₅ transitions of Tb³⁺ ions, with the highest intensity observed at 5 wt% Tb³⁺. A decrease in emission was observed at higher concentrations due to concentration quenching. Temperature-dependent PL measurements revealed reverse thermal quenching enhancing PL intensity. Chromaticity analysis based on CIE 1931 coordinates showed stable green emission across all concentrations, with a maximum color purity of 89.74% observed for the KYBO:3 wt% Tb³⁺ sample. The results, along with reverse thermal quenching behavior observed between 470K and 550K, suggest that these phosphors exhibit excellent potential for lighting and display technologies.

Photoluminescence decay of mobile carriers influenced by imperfect quenching at particle surfaces with subdiffusive spread.

We recently presented a quantitative model to explain the particle-size dependence of photoluminescence (PL) quantum yields and revealed that exciton quenching is not diffusion controlled, but limited by surface reactions. However, the exciton decay kinetics has not been analyzed yet using our theoretical model. Here, we study kinetic aspects of the model and show that it should be extended to take into account subdiffusion rather than normal diffusion to maintain consistency with the observed complex decay kinetics; we also show that the PL decay kinetics is nonexponential even when the PL quenching is limited by surface reactions under subdiffusion. Our theoretical analysis of the PL quantum yield and the PL decay kinetics provides a comprehensive picture of mobile charge carriers, immobile polarons, and self-trapped excitons.

Micellar mediated preparation of cadmium sulfide (CdS) nanoparticles: Influence of cleavable spacer based cationic gemini surfactant

Cleavable spacer (s = diamido) based cationic gemini surfactant (with different alkyl tail lengths (m) abbreviated as g1; m = 12, g2; m = 14 or g3; m = 16), in aqueous micellar solution, was used to control the size and morphology of cadmium sulfide (CdS) nanoparticles (NPs), via modified chemical precipitation technique. The purity and stability of all CdS NPs were characterized by EDAX, FT-IR, TGA and zeta potential (ζ). By varying the geminis, significant size reduction (2–6 nm), enhanced capping capacity, and higher energy band gap (∼4.1 eV) have been found in CdS-g1 compared to other NPs, by using Dynamic Light Scattering (DLS), TEM, XRD and UV–visible spectroscopy. Photoluminescence (PL) spectra revealed an emission at 525 and 630 nm, showing the effect of geminis m concerning surface states of NP. Additionally, antioxidant and antimicrobial (on Gram-negative (E. coli and P. aeruginosa) and Gram-positive (S. aureus and B. subtilis) strains) activities of CdS NPs were examined by DPPH radical scavenging and agar plating-spot disc inoculation method, respectively. The results recommended a significant antioxidant activity in CdS-g1 with 45.6 %, while, selective antimicrobial activity was obtained on E. coli and S. aureus in all NP systems.

Symmetry-Broken Electronic State of CsPbBr3 Cubic Perovskite Nanocrystals.

The development of densely packed, self-assembled perovskite nanocrystals (PeNCs) with a favorable transition dipole moment (TDM) orientation is crucial for their application in solution-processable electronic devices. In this study, we fabricated anisotropic CsPbBr3 PeNCs with a symmetry-broken electronic state on quartz substrates modified by 3-aminopropyltrimethoxysilane (APS). Densely packed and self-assembled monolayers of cubic PeNCs were formed on the substrates by using a dip coating technique. The angle-dependent absorption and photoluminescence (PL) spectra confirmed that the PeNC monolayer on the APS-treated substrate exhibited anisotropic electronic states in the in-plane and out-of-plane directions of the substrate. In contrast, when the quartz substrate was modified with the long alkyl silane coupling agent, octadecyltrimethoxysilane, the absorption and PL spectra exhibited no angular dependence, indicating the absence of anisotropy. Experimental and simulated results confirmed the presence of vertical TDMs in the densely packed PeNCs on the APS-treated substrate, which could be attributed to the effect of the amino groups of the APS on the facet of the cubic PeNCs facing the quartz substrate. Hence, surface chemical modifications of the substrate can aid in the precise control of the symmetry of the electronic states and TDM orientation in cubic PeNCs. These findings can promote the development of densely packed, high-coverage PeNC films with a controllable TDM orientation for applications in electronic devices such as solar cells, sensors, and light-emitting diodes.