NIR Photoluminescence Research Articles

Discovering the potential of biomaterial-based mesoporous and magneto-luminescent nanohybrid (Nd-doped Hydroxyapatite/Fe3O4) for cancer theragnosis

Multimodality nanoplatforms play a crucial role in advancing medical interventions by integrating multiple functionalities into a single system. However, issues like intricate production processes and biocompatibility persist. Herein, a facile synthesis of a biomaterial-based mesoporous nanocarrier, HAp:Nd+SPIONs@mSiO2 is reported. The nanohybrid with ∼100 nm average size, comprised of Nd-doped hydroxyapatite (HAp:Nd) nanophosphor, Fe3O4 superparamagnetic iron oxide nanoparticles (SPIONs), and mesoporous silica, exhibiting magneto-luminescent properties. The nanohybrid showed NIR to NIR photoluminescence properties important for deep tissue imaging. The mesoporous nanohybrid was loaded with Indocyanine green (ICG), a photosensitizer and photothermal dye, as a model drug (∼6 μg/mg of nanoparticles) with a high absorption stability retaining >75 % drug until 24 h incubation in pH 6 and 7.4, respectively. Nanoparticles demonstrated dual functionality by generating heat through magnetic and photonic stimulation, as well as producing reactive oxygen species (ROS) upon excitation with 808 nm light. In vitro assays on aggressive triple-negative breast cancer cells (MDA-MB-231) showed the high biocompatibility of nanohybrid with and without ICG, while a significant toxicity was seen after irradiation of NIR light due to ROS production. Noticeably, the nanohybrids also exhibit the ability to monitor temperature changes via Nd3+ associated NIR luminescence. The nanoplatform integrates clinically relevant components like hydroxyapatite, SPIONs, mesoporous silica and ICG, highlighting its potential for translational applications. The developed nanohybrids, with combined NIR-mediated photothermal and photodynamic effects, magnetic photothermal capabilities, and NIR/MR imaging, offer promise in addressing cancer heterogeneity and improving conventional treatments with reduced side effects.

Enhancing the inherent NIR photoluminescence in SrLaLiTeO6 through Cr3+-Yb3+ co-substitution for high performance pc-LEDs.

Until now, double perovskite tellurates have not been reported to exhibit inherent NIR photoluminescence. Therefore, the current study's revelation of inherent NIR luminescence in SrLaLiTeO6 double perovskite centered at 970 nm under 340 nm excitation is particularly intriguing. This phenomenon is attributed to the photoluminescence of Te4+ ions. This study also examines the NIR luminescence of Cr3+-Yb3+ co-doped SrLaLiTeO6. The host and SrLaLiTeO6:3%Cr3+, y%Yb3+ (y = 1, 2, 4, 6, 8, 10 mol%) were synthesized using the solid-state ceramic route. The successful incorporation of Cr3+ and Yb3+ ions into the host lattice was confirmed through XRD, Raman, and diffuse reflectance spectral analyses. Under 270 nm excitation, the photoluminescence (PL) of SrLaLiTeO6:Cr3+ exhibits a blueshift of the PL band to 965 nm due to the 4T2(4F) → 4A2g(4F) emission component of Cr3+ ions. The excited-state lifetime of SrLaLiTeO6:0.5%Cr3+ was measured at 36 μs, but this decreased to 26 μs as the Cr3+ concentration reached 10 mol%, primarily due to the enhancement of non-radiative energy transfer between Cr3+ ions. Incorporating Yb3+ into the system results in additional spectral lines with an enhanced intensity in the range of 970 nm to 1125 nm when excited at 270 nm. These emission lines correspond to the 2F5/2 → 2F7/2 transitions of Yb3+ ions, indicating an efficient energy transfer from Cr3+ to Yb3+. Furthermore, the study also reveals that Yb3+ emission is observed even without Cr3+ ions in SrLaLiTeO6 under 340 nm excitation, suggesting the possibility of energy transfer from the host to Yb3+ ions. The thermal stability and crystal field parameters of the synthesized phosphors are also explained in detail. To explore the potential of these phosphors in practical applications, phosphor-converted NIR LEDs were fabricated using SrLaLiTeO6, SrLaLiTeO6:3% Cr3+, and SrLaLiTeO6:3% Cr3+, 1%Yb3+.

Judd-Ofelt analysis and NIR spectroscopy properties of Nd3+-doped Na2O/NaF-Al2O3-Y2O3-P2O5 glass and transparent glass-ceramics containing NaYP2O7 crystals

In the present work, the Nd3+-doped Na2O/NaF-Al2O3-Y2O3-P2O5 glass and transparent glass-ceramics were fabricated by conventional melting-quenching and subsequent heat treatment. The glass structure was studied by XRD, DSC, and FTIR spectrum, the fluorophosphate glass exhibits a more compact cross-link network. The UV–Vis–NIR absorption spectra, Judd-Ofelt theory, and photoluminescence spectra were used to explore the absorption and NIR spectroscopic features of the Nd3+-doped phosphate and fluorophosphate glasses. Under the excitation of 582 nm, the intense NIR emission in the Nd3+-doped glasses originating from the internal transition 4F3/2 → 4IJ/2 (J = 13, 11 and 9) was observed, and the transition 4F3/2 → 4I11/2 (1053 nm) is the most dominate. The transparent glass-ceramics (GC) was fabricated via heat treating on the precursor glass (PG) at Tg+100 °C, and the precipitation of NaYP2O7 crystals in GC was confirmed by XRD and SEM. With the benefit of the existence of the NaYP2O7 crystals, the Nd3+-doped GC exhibits higher NIR emission intensity, higher quantum efficiency (72.85% and 84.11%), larger σ(λp) values of 4.24×10-20 cm2 and 4.86×10-20 cm2, larger σ × Δλeff values of 10.22×10-26 cm3 and 11.67×10-26 cm3 than that of PG. These results indicate that the Nd3+-doped phosphate and fluorophosphate glasses and glass-ceramics may be used as a gain medium for 1053 nm laser emission.

Increased NIR photoluminescence of Egyptian blue via matrix effect optimization

The exceptionally high NIR photoluminescence of the ancient pigment Egyptian blue is due to its very stable phase cuprorivaite (CaCuSi4O10). This compound has recently attracted significant attention, leading to numerous applications for sensors, luminescent solar concentrators, energy-saving, and biomedicine. Here we report an innovative manufacturing process for producing high-grade cuprorivaite, characterized by fine crystal grains and a significantly increased NIR photoluminescence emission. The unprecedented ultra-high NIR emission (quantum yield ΦEM ≈ 30 %) is almost three times higher than the best one reported so far. This is an important turning point for the extension of applications of cuprorivaite to new sectors and can greatly boost its exploitation. The new high-efficiency cuprorivaite is obtained by solid-state synthesis, using silica nanoparticles as a starting material and avoiding fluxing agents. No doping with rare-earths or other elements has been employed, making synthesis straightforward and sustainable. The material obtained has been fully characterized in terms of crystalline, morphological, and optical properties and compared to cuprorivaite obtained through traditional melt-flux synthesis. The main difference observed is that the tiny crystals obtained through the new synthesis method are practically devoid of the glassy phase, rich in copper and impurities, that is instead largely present in Egyptian Blue pigment synthesized with traditional melt-flux synthesis. We speculate that this glassy phase is responsible for the partial suppression of the intrinsic photoluminescence of cuprorivaite, demonstrating how limiting the glassy phase can increase the external quantum efficiency of Egyptian blue.

Visible to NIR-II Photoluminescence of Atomically Precise Gold Nanoclusters.

Atomically precise gold nanoclusters (NCs) have emerged as a new class of precision materials and attracted wide interest in recent years. One of the unique properties of such nanoclusters pertains to their photoluminescence (PL), for it can widely span visible to near-infrared-I and -II wavelengths (NIR-I/II), and even beyond 1700 nm by manipulating the size, structure, and composition. The current research efforts focus on the structure-PL correlation and the development of strategies for raising the PL quantum yields, which is nontrivial when moving from the visible to the near-infrared wavelengths, especially in the NIR-II regions. This review summarizes the recent progress in the field, including i) the types of PL observed in gold NCs such as fluorescence, phosphorescence, and thermally activated delayed fluorescence, as well as dual emission; ii) some effective strategies that are devised to improve the PL quantum yield (QY) of gold NCs, such as heterometal doping, surface rigidification, and core phonon engineering, with double-digit QYs for the NIR PL on the horizons; and iii) the applications of luminescent gold NCs in bioimaging, photosensitization, and optoelectronics. Finally, the remaining challenges and opportunities for future research are highlighted.

Evaluating the Phosphorescence duration of Zn2P2O7 glass–ceramic activated by Dy3+/Pr3+ for LED applications

The present study focuses on investigating the phosphorescence efficiency of binary zinc–phosphate glasses co-doped with dysprosium and/or praseodymium oxides together with their corresponding glass ceramics. The studied glass series was prepared directly by the conventional melting and quenching method. Differential thermal analysis (DTA) indicated an exothermic peak at 550 °C that was applied to yield glass-ceramic samples. The major monoclinic phase of Zn2P2O7 was detected by X-ray diffraction (XRD). FTIR and SEM–EDAX were applied to identify the structural morphology of the prepared samples. The optical efficiency was characterized through UV–Visible–NIR absorption spectra and photoluminescence analysis. Both light emissions and their corresponding lifetimes were enhanced significantly in glass–ceramic. These samples display high CRI, low color temperature, and CIE values comparable to those expected for pure white-light and warm yellow emitting diodes.

Solution-processed Er3+-Doped GeS2 chalcogenide glass films with NIR photoluminescence towards functional flexibility and integration.

Rare-earth doped chalcogenide films are major components in flexible and integrated photonic and optoelectronic devices for modern communication systems, metrology, and optical sensing. However, it is still challenging to develop a high concentration of rare-earth doping chalcogenide film with a smooth surface to realize efficient photoluminescence (PL). Here, we demonstrate that Er3+-doped GeS2 films are prepared by spin-coating based on a two-step dissolution process. Such a two-step process provides the high solubility of Er3+ in GeS2 films and exhibits efficient emission at ∼1.5 µm crossing the telecommunication C-band. The highest PL emission intensity is obtained in GeS2 films doped with 1.4 mol% of Er3+, and this PL in GeS2 films is reported for the first time. We propose adjustments of annealing parameters for improving the PL characteristics in such materials. Through the control precision of the heating rate and annealing temperature, the smooth surface of GeS2 films enables efficient photo-luminescence. This two-step dissolution-based strategy would pave a new path to design luminescent chalcogenide films for application in flexible and integrated optoelectronics and photonics.

Understanding Oligonucleotide Hybridization and the Role of Anchoring on the Single-Walled Carbon Nanotube Corona Phase for Viral Sensing Applications

Semiconducting single-walled carbon nanotubes (SWCNTs) with tailored corona phases (CPs), or surface adsorbed molecules, have emerged as a promising interface for sensing applications. The adsorption of an analyte can be specifically transduced as a modulation of their band gap near-infrared (nIR) photoluminescence (PL). One such CP ideal for this purpose is single-stranded DNA (ssDNA), where subsequent sequence dependent hybridization can result in PL emission wavelength shifts. Due to ssDNA adsorption to the SWCNT surface, the resultant non-canonical hybridization and its effect on SWCNT photophysical properties are not well understood. In this work, we study 20- and 21-mer DNA and RNA hybridization on the complementary ssDNA-SWCNT CP in the context of nucleic acid sensing for SARS-CoV-2 sequences as model analytes. We found that the van’t Hoff transition enthalpy of hybridization on SWCNT CP was -11.9 kJ mol-1, much lower than that of hybridization in solution (-707 kJ mol-1). We used SWCNT solvatochromism to calculate the solvent exposed surface area to indicate successful hybridization. We found that having a 30-mer anchor region in addition to the complementary region significantly improved PL response sensitivity and selectivity, with (GT)15 anchor preferred for RNA targets. Coincubation of ssDNA-SWCNT with analyte at 37°C resulted in faster hybridization kinetics without sacrificing specificity. Other methods aimed to improve CP rearrangement kinetics such as bath sonication and surfactant additions were ineffective. We also determined that target sequence choice is important as secondary structure formation in target is negatively correlated with hybridization. Best performing CPs showed detection limits of 11 nM and 13 nM for DNA and RNA targets respectively. Finally, we simulated sensing conditions using saliva environment, showing sensor compatibility in biofluids. In total, this work elucidates key design features and processing to enable sequence specific hybridization on ssDNA-SWCNT CP.

“Structural and NIR photoluminescence studies from Nd3+-doped yttrium niobate: A potential material for photonics”

In the present work, an original sol-gel methodology is explored for the synthesis of Nd3+-doped yttrium niobate materials. The main goal was to assess the effect of the dopant concentration on the structural and luminescent properties, specifically in the near-infrared region, aiming for a future biophotonics application. X-ray diffraction and Raman spectroscopy analyses revealed the crystallization of the cubic Y3NbO7 and monoclinic YNbO4 phases, with preferential stabilization of the cubic Y3NbO7, a fluorite-like structure, irrespective of the dopant concentration. All samples presented an intense NIR emission in the second biological window (1000–1500 nm) under excitation at 808 nm (NIR–I excitation), with a prevalence for the 1064 nm emission, indicating the potential application in the biophotonics field. Up to 5 mol% Nd3+ content did not modify the spectral profiles, and the lifetime decay for the 4F3/2 emission level showed that the quenching concentration was 1.78 mol% Nd3+. Higher Nd3+ content revealed broader emission bands, attributed to higher occupation of Y3NbO7 symmetry sites. Emission at NIR-IIa biological window, at 1336 nm, attributed to the 4F3/2 → 4I13/2 was detected indicating the distribution of Nd3+ ions in a low phonon energy environment. The as-reported materials reveal potential application as solid-state lasers and bioimaging probes at NIR-IIa biological window.

Near-Infrared-Luminescent Gold Nanoclusters Stabilized by End-Grafted Biocompatible Polymer Chains for Bioimaging

Gold nanoclusters (AuNCs) are an emerging class of nanomaterials for bioimaging, featuring high photostability, size-dependent luminescence, large Stokes shifts, long photoluminescence lifetimes, and good biocompatibility. However, when stabilized by small ligands, AuNCs exhibit a limited colloidal stability. Here, we report the synthesis of original “hairy” AuNCs with a diameter under 2 nm and NIR photoluminescence (for both one-photon and two-photon excitation), stabilized by biocompatible end-grafted poly(N-acryloyl morpholine) (PNAM) chains prepared by RAFT polymerization. The AuNCs synthesis was carried out directly in water in the presence of thiol-terminated PNAM-SH chains. Compared with AuNCs stabilized by small ligands, our PNAM-AuNCs exhibit much better colloidal stability (unchanged for more than two months), a 2-fold increase in photoluminescence lifetimes, and significantly enhanced quantum yields. Moreover, their properties could be successfully tuned using PNAM chains with molecular weights ranging from 3000 to 11 000 g·mol–1. These PNAM-AuNCs offer an excellent platform for the development of bioimaging probes without organic dyes.

Detailed optical analysis of Dy3+ and Pr3+ co-doped alumino-borate glasses for visible lighting applications

A new glass series with nominal molar composition of 60B2O3 + 30NaF + 10Al2O3 co-doped with Dy3+ and Pr3+, synthesized by melt quench was reported. The influence of Rare Earth (RE) ratio variation on prepared glasses was investigated by using Fourier Transform Infra-Red spectroscopy, UV–Vis–NIR absorption spectroscopy, Photoluminescence, Decay curves and Density measurements. Their X-Ray Diffraction and FTIR spectra revealed the glassy nature and confirmed that AlO6, AlO4, BO3 and BO4 units are the main structural units of that matrix. A non-linear variation following the same trend for tetragonal borate units (N4), Band gap, non-linear optical properties, Density, Molar Volume etc. was observed. Different optical parameters were obtained by UV–Vis–NIR spectroscopy. The Bonding parameter obtained from Nephelauxetic study indicated ionic nature of Dy3+ and covalent nature of Pr3+ ions. Photoluminescence excitation and emission spectra were recorded under variety of excitation wavelengths and corresponding color parameters were calculated using 1931 CIE standards. A detailed yellow to blue ratio analysis was reported as a function of RE ion concentration and excitation wavelengths. Composition DPNAB(x = 0.7) displayed the best performance with CIE coordinates (0.33, 0.37). Existence of Energy transfer from Dy3+ and Pr3+ was evidenced by the spectral overlap diagram and lifetime values obtained from fitting of Decay curves. From the obtained results, prepared glasses can be suggested for solid-state lighting devices like WLEDs and display devices.

Understanding Oligonucleotide Hybridization and the Role of Anchoring on the Single-Walled Carbon Nanotube Corona Phase for Viral Sensing Applications

Semiconducting single-walled carbon nanotubes (SWCNTs) with tailored corona phases (CPs), or surface-adsorbed molecules, have emerged as a promising interface for sensing applications. The adsorption of an analyte can be specifically transduced as a modulation of their band-gap near-infrared (nIR) photoluminescence (PL). One such CP ideal for this purpose is single-stranded DNA (ssDNA), where subsequent sequence-dependent hybridization can result in PL emission wavelength shifts. Due to ssDNA adsorption to the SWCNT surface, the resultant noncanonical hybridization and its effect on SWCNT photophysical properties are not well understood. In this work, we study 20- and 21-mer DNA and RNA hybridization on the complementary ssDNA-SWCNT CP in the context of nucleic acid sensing for SARS-CoV-2 sequences as model analytes. We found that the van’t Hoff transition enthalpy of hybridization on SWCNT CP was −11.9 kJ mol–1, much lower than that of hybridization in solution (−707 kJ mol–1). We used SWCNT solvatochromism to calculate the solvent-exposed surface area to indicate successful hybridization. We found that having a 30-mer anchor region in addition to the complementary region significantly improved PL response sensitivity and selectivity, with a (GT)15 anchor preferred for RNA targets. Coincubation of ssDNA-SWCNTs with an analyte at 37 °C resulted in faster hybridization kinetics without sacrificing specificity. Other methods aimed to improve CP rearrangement kinetics such as bath sonication and surfactant additions were ineffective. We also determined that the target sequence choice is important as secondary structure formation in the target is negatively correlated with hybridization. Best-performing CPs showed detection limits of 11 and 13 nM for DNA and RNA targets, respectively. Finally, we simulated sensing conditions using the saliva environment, showing sensor compatibility in biofluids. In total, this work elucidates key design features and processing to enable sequence-specific hybridization on ssDNA-SWCNT CPs.

Heterostructured BiOCl–LaOCl S-scheme composites with improved visible-light photocatalytic activity on Rhodamine B dye

In this work, we report the synthesis of heterostructured BiOCl–LaOCl composites by using KCl as a source of chlorine and varying contents of LaOCl as raw materials in the presence of ethylene glycol at a temperature of 100 °C by using the solvothermal method. The prepared composites were characterized by X-ray diffraction, UV–Visible NIR spectroscopy, photoluminescence spectroscopy, SEM, TEM, EDX mapping, BET, and XPS analysis. TEM analysis revealed that the LaOCl particles were deposited on the surface of the BiOCl microspheres. The photo-efficiency of the BiOCl–LaOCl composite as photocatalyst was assessed by decomposing the Rhodamine B dye in an aqueous solution under irradiation from sunlight. The composite was found to have a higher rate of degradation of the dye solution than those of pure BiOCl and LaOCl semiconductors. The BiOCl–LaOCl‐1 composite exhibited the maximum catalytic activity of all the synthesized materials. The ability of the composite to degrade the dye was studied by using UV–Vis spectroscopy. The apparent rate of reaction of BiOCl–LaOCl‐1 was 0.1209 min−1, four and six times higher than those of BiOCl–LaOCl-2 and BiOCl, respectively. The results of the scavenger test revealed that the superoxide and hole radicals were mainly responsible for photodegradation. The high BET surface area of the composite also indicated enhanced photocatalytic activity.

Titanium Nanoparticles Modified NIR Emission of Neodymium Doped Magnesium Zinc-Sulfophosphate Glass: Effect of Heat Treatment on Surface Plasmon Resonance Bands

New type plasmonic sensitizer, titanium nanoparticles (Ti NPs) shown potential in enhancing photoluminescence of rare-earth ions (REIs) as doped into magnesium zinc-sulfophosphate (MZS) glass for optical to optic application. Here, neodymium ions (Nd3+)-doped MZS glass with Ti NPs inclusion gone heat treatment (HT) at 450°C for 6 and 12 hours in order to tune the NPs size and tailor their plasmonic strength. The sample was characterized using X-ray diffractometer (XRD), high-resolution transmission electron microscope (HRTEM), and photoluminescence (PL) spectrometer. Heat treatment (HT) grows Ti NPs with a mean size ≈ 16 nm. The SPR bands are probed around 585and 739 nm. The SPR band intensities change with HT duration. The NIR PL bands were perceived around 878 nm, 1050 nm and 1322 nm corresponding to 4F3/2→4I9/2, 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions, accordingly. The PL transition 4F3/2→4I9/2 (878 nm) and 4F3/2→4I13/2 (1322 nm) is enhanced about 1.44 and 1.52 times respectively, after 12 hours HT. The results show that HT enhances PL through SPR amplification. These findings may be useful in developing solid-state lasers and optical materials.

Altering coupled mode of surface plasmon resonance mediated by silver and gold nanoparticles through heat treatment: Judd ofelt, racah and NIR-luminescence of neodymium doped magnesium–zinc-sulfophosphate glass

Manipulating surface plasmon resonance (SPR) of silver (Ag) and gold (Au) nanoparticles (NPs) in amorphous material may open new possibilities in optic and photonic fields. Driven by this fact, heat treatments (HT) were used to tune the excitation mode of SPR. The Nd3+ doped magnesium-zinc-sulfophosphate glasses embedded with Ag and Au NPs were heat-treated at 450 °C for 6 and 12 h and characterized using X-ray diffractometer (XRD), high-resolution transmission electron microscope (HRTEM), UV–Vis–NIR absorption and photoluminescence (PL) spectrometer. The mean size of NPs was slightly reduced (4.68 nm→ 4.35 nm) after 12 h of HT due to the elastic ripening process, causes by internal pressure within NPs. Unusual multiple SPR bands were evidence around 419, 481, 613, 676, 776, 848 and 939 nm after the glass (AgAu6h) is heat-treated for 6 h. Thirteen absorption bands are recorded within 326–875 nm, corresponding to the Nd3+ ion transitions. The NIR PL bands of Nd3+ ion were detected around 878 nm, 1050 nm, and 1322 nm corresponding to 4F3/2 → 4I9/2, 4F3/2 → 4I11/2, and 4F3/2 → 4I13/2 transitions, respectively. Overall, sample coded AgAu12 h disclosed the highest bandwidth gain of 0.09, 1.14, and 3.06 ( × 10−22 cm3) assigned to transition 4F3/2 → 4I9/2, 4F3/2 → 4I11/2, and 4F3/2 → 4I13/2, respectively, with a quantum efficiency of 21.06% (for transition 4F3/2 → 4I11/2). The HT can modify the intensity of PL through different NPs assemblies (single, dimer, trimer) and bonding modes (e.g: longitudinal dipolar or quadrupolar coupling mode). The unique optical feature discovered may be useful in customizing solid-state laser materials.

Judd-Ofelt analysis, visible to NIR photoluminescence emission under 450 nm and 976 nm excitations and energy transfer of barium fluorotellurite glasses doping with Ho3+, Yb3+, Ho3+:Yb3+

Judd-Ofelt analysis, visible to NIR photoluminescence emission under 450 nm and 976 nm excitations and energy transfer of barium fluorotellurite glasses doping with Ho3+, Yb3+, Ho3+:Yb3+

Enhancement and broadening of near infrared photoluminescence in Ag2X (X= S, Se) quantum dots via Cd doping for mini light-emitting diodes towads non-invasive bioimaging

Exploring excellent near infrared-II (NIR-II) emitting materials is desirable for the advancement of high quality bioimaging, in virtue of the lower scattering, deep penetration and high sensitive of biological components in the second optical transmission window. Colloidal Ag2X (X = S, Se) nanocrystals exhibit tunable NIR photoluminescence in the second NIR region. However, the lack of highly efficient broadband NIR emitting Ag2X (X = S, Se) nanocrystals limits their spectroscopy applications. Herein, cadmium (Cd) doped Ag2X (X = S, Se) nanocrystals were prepared through a facile hydrothermal method at room temperature. The NIR luminescence was efficiently enhanced through controllable doping a little amount of Cd ions into the Ag2X (X = S, Se) quantum dots (QDs). Simultaneously, the great broadening of NIR emission was achieved in the Cd doped Ag2Se QDs, and the maximum full width at half maximum could reach up to 530 nm. Following the general principles of photoluminescence light-emitting diode (LED) devices, the fabricated NIR mini LEDs) light sources based on Cd doped Ag2Se QDs exhibited broadband NIR electroluminescence and superior optoelectronic stability, and were successfully employed for clear vessel imaging. The works proves the feasibility of NIR mini LEDs in non-invasive bioimaging, and paves way for the miniaturized broadband NIR light sources.

Optically Switchable NIR Photoluminescence of PbS Semiconducting Nanocrystals using Diarylethene Photoswitches.

Precisely modulated photoluminescence (PL) with external control is highly demanded in material and biological sciences. However, it is challenging to switch the PL on and off in the NIR region with a high modulation contrast. Here, we demonstrate that reversible on and off switching of the PL in the NIR region can be achieved in a bicomponent system comprised of PbS semiconducting nanocrystals (NCs) and diarylethene (DAE) photoswitches. Photoisomerization of DAE to the ring-closed form upon UV light irradiation causes substantial quenching of the NIR PL of PbS NCs due to efficient triplet energy transfer. The NIR PL fully recovers to an on state upon reversing the photoisomerization of DAE to the ring-open form with green light irradiation. Importantly, fully reversible switching occurs without obvious fatigue, and the high PL on/off ratio (>100) outperforms all previously reported assemblies of NCs and photoswitches.

NIR photoluminescence of ZnGa2O4:Cr nanoparticles synthesized by hydrothermal process

NIR photoluminescence of ZnGa2O4:Cr nanoparticles synthesized by hydrothermal process

Facile fabrication of binary BiOCl-Cu2CoSnS4 and ternary BiOCl-Cu2CoSnS4-TiO2 heterojunction nano photocatalyst for efficient sunlight-driven removal of direct blue 71 in an aqueous medium

We report a novel BiOCl-Cu2CoSnS4-TiO2 ternary heterojunction nanocomposite fabricated via a simple chemical precipitation method by anchoring Cu2CoSnS4 and TiO2 on the surface of spherical BiOCl particles using ethylene glycol as a solvent at an ambient temperature (100 °C, 4 h). The as-synthesized BiOCl-Cu2CoSnS4-TiO2 nanocomposite was examined by transmission electron microscopy, UV–visible NIR spectroscopy, X-ray diffraction (XRD), time-resolved fluorescence (TRF), photoluminescence spectroscopy (PL), and N2 adsorption-desorption tests. XRD spectra of BiOCl-Cu2CoSnS4-TiO2 heterojunction show the diffraction peaks corresponding to tetragonal Cu2CoSnS4 nanoparticles and the tetragonal phase of BiOCl. The peaks of TiO2 are not viewed in the XRD pattern of BiOCl-Cu2CoSnS4-TiO2 nanocomposite which may be due to the presence of a low concentration of TiO2 in the composite. PL and time-resolved fluorescence confirm the separation of electron-hole pairs which could aggressively participate in the direct blue 71 dye degradation. The BiOCl-Cu2CoSnS4-TiO2-1 heterojunction degraded 91.48% direct blue 71 under natural sunlight which is higher than the bare BiOCl, Cu2CoSnS4 nanoparticles and TiO2 nanoparticles, and binary BiOCl-Cu2CoSnS4 composite. The electron-hole pair’s separation leads to higher photoactivity driven by the heterojunction interface between BiOCl, Cu2CoSnS4 nanoparticles, and TiO2 nanoparticles. The photogenerated h+, O2•−, and •OH radicals were responsible for the degradation of direct blue 71 over BiOCl-Cu2CoSnS4-TiO2 heterojunction as confirmed by the radical capture experiment.