Photoluminescent Materials Research Articles

Highly Luminescent Inorganic-Organic Hybrids with Molecularly Dispersed Perylene.

A highly photoluminescent material was obtained by the incorporation of perylene into an inorganic-organic hybrid film. Octosilicate, a layered alkali silicate, was modified with a cationic surfactant, dioleyldimethylammonium ion, to accommodate perylene molecularly and uniformly. The perylene-doped dioleyldimethylammonium octosilicate films were fabricated by simply casting the toluene solution of perylene with dispersed dioleyldimethylammonium octosilicate on substrates. Near-unity photoluminescence quantum efficiency was achieved for hybrids containing a high concentration of perylene.

Multifunctional nanolayered renewable carbon for electromagnetic interference and energy devices

Controlled carbonization of biomass leads to nanolayered graphitic structures with characteristic crystalline sp2 hybridization, conductive properties up to 600 S/m, and electromagnetic interference shielding effectiveness of 47.7 dB at 12 GHz. We investigate functional properties of nanolayered renewable carbon, including conductive and photoluminescent features, leading to a new understanding of structure–property correlation and their graphitic multilayered nanostructures. Some unique and novel behaviors, such as negative dielectric factors, hold promise in the areas of cofactor sensors and electromagnetic interference shielding due to their correlation with the absorption of microwave radiation. An electromagnetic interference device demonstrates an application of these nanographitic carbon materials. These conductive and photoluminescent carbon materials hold significant promise in applications such as power electronics, batteries, and sensors, where they may replace conventional metal and graphene.

The Role of Polyhedral Oligomeric Silsesquioxanes in Optical Applications

The popularity of polyhedral oligomeric silsesquioxanes (POSS) for use in hybrid organic–inorganic materials and devices has grown in the past two decades due to desirable properties such as good thermal stability and biocompatibility, as well as their potential to be functionalized for a wide range of applications, from polymer composites to optoelectronics. Herein, the role of POSS for photonic applications, including sensing, bioimaging, and optoelectronic devices, is summarized. Functionalized POSS building blocks commonly incorporated with luminescent materials are identified, and areas of potential growth within the field are discussed. The addition of POSS to light‐emitting materials is widely shown to prevent aggregation in organic lumophores and inorganic nanocrystals, leading to reduced photoluminescence quenching. The POSS unit is also capable of acting as a passivating agent for nanocrystals and thin films, improving the emission quantum yields of photoluminescent materials and devices. POSS therefore offers the potential to enhance both the functional and photonic properties of cutting‐edge hybrid technologies.

Investigating the thermographical effect on optical properties of Eu doped Y2O3:TiO2 nanocomposite synthesized via sol-gel method

Recent developments in nanocomposites have attracted the interest of researchers in synthesizing nanocomposite-based photoluminescent materials. Lanthanides have been studied extensively as photoluminescent materials especially the Europium, owing to their simple energy level diagram, long luminescence lifetime, high emission quantum yield, and narrow emission bands in the visible region. The major limitation of using Europium for its practical application as a luminescent material is its low absorption coefficient that prevents the direct excitation of the Eu3+ ions. To improve the absorption, Europium has been doped with Y2O3 due to its similar energy level scheme i.e., 5D2 and 5L6. In our work, we have prepared Europium doped Y2O3:TiO2 nanocomposite and investigated its structural, morphological, and optical properties using characterization tools such as X-ray Diffraction (XRD), Scanning electron microscopy (SEM), High resolution transmission electron spectroscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Energy dispersive X-ray spectroscopy (EDS), Elemental mapping, UV–vis-IR, and Photoluminescence (PL) spectroscopy. The material showed good optical properties and its application as a thermographic phosphor is studied via coating a NUV-LED and observing the change in intensity with varying temperature under UV irradiation. The material can be used as a thermographic phosphor and even for the LED fabrication.

Unexpected organic hydrate luminogens in the solid state

Developing organic photoluminescent materials with high emission efficiencies in the solid state under a water atmosphere is important for practical applications. Herein, we report the formation of both intra- and intermolecular hydrogen bonds in three tautomerizable Schiff-base molecules which comprise active hydrogen atoms that act as proton donors and acceptors, simultaneously hindering emission properties. The intercalation of water molecules into their crystal lattices leads to structural rearrangement and organic hydrate luminogen formation in the crystalline phase, triggering significantly enhanced fluorescence emission. By suppressing hydrogen atom shuttling between two nitrogen atoms in the benzimidazole ring, water molecules act as hydrogen bond donors to alter the electronic transition of the molecular keto form from nπ* to lower-energy ππ* in the excited state, leading to enhancing emission from the keto form. Furthermore, the keto-state emission can be enhanced using deuterium oxide (D2O) owing to isotope effects, providing a new opportunity for detecting and quantifying D2O.

Facile synthesis of chitosan membrane containing Eu3+ complex with intense emission in the red region

The research on development of materials with higher efficient photoluminescent properties, is the aim of several researchers around the world. Photoluminescent materials containing Rare Earths (RE3+) can be applied in various technological sectors, mainly in light emitting devices. In this sense, this work reports on obtaining of polymeric membranes based on chitosan and gelatin containing [Eu (TTA)3(H2O)2] on the surface. The materials presented high intensity of photoluminescence emission with narrow bands attributed to the intraconfigurational 4f transitions of Eu3+. To keep the material in the desiccator containing silica gel, showed the loss of water molecule, in which contributed significantly with the intensity of emission. The lifetime values showed values between 0.42 and 0.55 ms, higher than many values reported in literature. The surface morphology of the materials showed a homogeneous profile free of cracks. The materials presented interesting photoluminescent properties that make them candidates for possible application in lighting or imaging devices.

Eu3+-doped SiO2–Y2O3 containing Sr2+ for application as fingerprinting detector

The use of photoluminescent materials in forensic science is essential for the development of systems that improve the final quality of images, so the results provided by security institutions can be more accurate. Thus, the utilization of trivalent Rare Earth ions (RE 3+ ) doped materials, in this case the Eu 3+ ion, is interesting, since it has a lifetime on the ms scale and an intense emission with a monochromatic character in the red region. Furthermore, materials with red emission with applications in the forensic area are rare and financially expensive. Because of that, luminescent materials based on SiO 2 –Y 2 O 3 :Eu 3+ , Sr 2+ represent an alternative more accessible to current photonic materials for application in the field of forensic investigation. Intense photoluminescence in the visible red region of the material obtained in this work was observed, both in the isolated material and impregnated in the digital printing present on the surface of a glass slide. The isolated material presented a lifetime between 1.65 and 1.78 ms, with results of structural microdeformation and network parameters that did not significantly influence the properties of the system, showing its robustness before and after its application on the fingerprint. Even coated on fingerprints, the materials showed intense emission and monochrome character in the red region assigned to the thin emission band positioned around 612 nm. The projections of the sublevels of the 7 F 1 crystal field level calculus performed by the method of equivalent nearest neighbors (MENN) do not show significant changes for this system. In summary, this work shows characteristics that are of paramount importance to obtain images with a higher resolution of latent fingerprints for possible forensic applications with higher robustness during applications. • Intense emission in the red region. • Very well recognition of fingerprint with high quality. • Easy way to prepare material for forensic application. • Good adherence of material on the fingerprint.

Novel Fluorene-based compounds: Investigation on the synthesis, function and fluorescence mechanism

Fluorene-based compounds are known for their unique role in photoluminescence and electroluminescent materials. Based on this idea, a series of fluorene-based fluorescent compounds were designed and synthesized by the Suzuki coupling reaction. The luminescence effect was evaluated by comparing fluorescence intensity and fluorescence quantum yield of the control compounds. The research indicated that the novel fluorene-based compounds 2,7-di(quinol-4-yl)-9,9-dimethylfluorene(F4) and 2,7-di(indole-5-yl)-9,9-dimethyl fluorene (F5) have better fluorescence characteristics. They are used as sensors for the recognition of nitro compounds and metal ions. In addition F4 has good selectivity and sensitivity to TNP(160600 M−1, 2.63 μM) and Fe3+ (121140 M−1, 1.68 μM). Finally, fluorescence quenching mechanism of F4 with TNP was studied by theoretical calculation.

The influence of deposition time on the photoluminescent properties of SiOxCy thin films obtained by Cat-CVD from monomethyl silane precursor

In recent years, silicon-related photoluminescent materials have attracted great attention due to their optical properties. This work aims to study the deposited silicon oxycarbide (SiOxCy) thin films by using the Organic Catalytic Chemical Vapor Deposition (O-Cat CVD) technique. Monomethyl Silane gas [MMS; (CH3-SiH3)] was used as an organometallic silicon precursor, and tantalum (Ta) filament was used as a catalyst. The influence of deposition time on the photoluminescent properties, resulting from the Si/C ratio in thin layers, was assessed. The nature of shifted silicon-oxygen stretching bonds from their stoichiometry value was discussed by Fourier Transform Infrared (FTIR) analysis. The chemical composition of the SiOxCy matrix was confirmed by X-ray Photoelectron Spectroscopy (XPS) analysis. Wide and intense photoluminescence (PL) emissions were observed for as-deposited films at substrate temperatures as low as 200 °C and the origin of emissions was explained by different defect mechanisms. Moreover, the shift of PL spectra from the red to the blue band was also explained. This investigation provides further understanding of the SiOxCy thin film properties to improve its optical properties and produce it more safely.

Highly sensitive and selective detection of Alprenolol using upconversion nanoparticles functionalized with amphiphilic conjugated polythiophene

Upconversion nanoparticles (UCNPs) are exclusive photoluminescent (PL) materials with the ability to convert low-energy excitation into high-energy emission via multiphoton absorption processes. In this research, a novel amphiphilic conjugated polythiophene was prepared to act as a functionalizing agent for NaLuF4:Yb3+/Er3+ UCNPs. The UCNPs, which were coated with amphiphilic polythiophene, were characterized by using FTIR, TGA, SEM, TEM, UV, and PL. This material was used as an optical sensor to detect Alprenolol, which is widely used for the treatment of high blood pressure. The developed sensor displays good analytical performance including a low limit of detection (LOD = 0.22 nM) and good linearity in the range of 0.5 nM to 75 μM. Furthermore, this sensor was applied successfully to determine the level of Alprenolol in human urine and serum samples with good recoveries of 97–104%.

Solid state-synthesized lanthanum orthovanadate (LaVO4) Co-doped with Eu as efficient photoluminescent material

The compositional and structural properties of nanocrystalline lanthanum orthovanadate (LaVO4), obtained through solid-state synthesis and co-doped with Eu3+ were investigated. Lanthanum and vanadium oxides were used as only starting reagents to synthesize LaVO4-Eu3+ nanocrystalline powders using a high-energy ball-milling (HEBM) process followed by air heating in temperatures between 600 and 1200 °C. The La2O3 powder, which served as the precursor for the HEBM synthesis, had a residual europium impurity which was found to be the effective Eu3+ ions source in the production of Eu:LaVO4. The powders were characterized using X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron (XPS), Fourier-transform infrared (FTIR) absorption spectroscopy, emission spectroscopy (PL - photoluminescence and excitation spectra, UV–Vis DRS method), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The mean size of crystallites of LaVO4 were in the range of 53 nm–84 nm for annealing temperatures in the range of 600 °C–1200 °C, respectively. Due to a very low content of Eu3+ ions (less than 0.1 wt %) in the synthesized powders, the luminescence behavior of lanthanum orthovanadate with the monoclinic structure could be observed. The correlation between the structural, morphological and photoluminescent properties of LaVO4 was examined for the first time in this work.

Recent Progress on Photoluminescent Zeolite-based Composite Materials

Recent Progress on Photoluminescent Zeolite-based Composite Materials

Origin of intense blue-green emission in SrTiO3 thin films with implanted nitrogen ions: An investigation by synchrotron-based experimental techniques

The present study utilizes synchrotron-based x-ray diffraction (XRD), photoluminescence (PL), and x-ray absorption near edge structure (XANES) spectroscopic techniques to comprehend the evolution of optical intense blue-green emission in 100 keV nitrogen (N) ion implanted $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ (STO) thin films deposited by RF magnetron sputtering technique. The XRD pattern shows a shift in reflections at lower N ion fluences and the amorphization of the films at higher fluences. A disordered phase induced by implantation in the STO films leads to an intense blue-green emission due to oxygen (O) vacancies and N ($2p$) bound states. A schematic diagram of energy levels has been proposed to explain the origin of PL emission. The XANES spectra at Ti $K$ edge reflect a change in the valency of Ti ions and the local atomic structure of ordered and disordered phases of STO with an increase in N ion fluence. The splitting of peak assigned to ${e}_{g}$ orbitals, and discrepancy in ratio ${d}_{{z}^{2}}/{d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ observed in the Ti $L$- and O $K$-edge spectra, confirm a distortion in $\mathrm{Ti}{\mathrm{O}}_{6}$ octahedral structure and modifications in O $2p$-Ti $3d$ hybridization states. The synchrotron-based techniques reveal that N ion implanted STO can be a good photoluminescent material exhibiting a variety of emissions through bound states of O vacancies and implanted N ions.

Supramolecular Engineering of Efficient Artificial Light-Harvesting Systems from Cyanovinylene Chromophores and Pillar[5]arene-Based Polymer Hosts.

Enhanced emission and adjustable wavelength for single luminogen systems are highly desirable in the scope of photoluminescent materials. Herein, a supramolecular strategy has been proposed for supramolecular assembly-induced enhanced emission and valid emission manipulation by fabricating an amphiphilic copolymer host material with pillar[5]arene units as the side chains, whereby cyanovinylene-based (CV) derivatives are anchored to the polymer hosts via host-guest interactions. The guest-bearing copolymers can further form luminescent supramolecular polymer nanoparticles (SPNs). Remarkably, the as-prepared SPNs exhibit dramatic emission enhancement and tunable fluorescence wavelength, ascribing to the synergetic effects involving the restriction of intramolecular motions and the prevented excimer formation for CV moieties, as endowed by host-guest interactions and the entanglement of the polymer chains. Furthermore, the SPNs can be established as efficient artificial light-harvesting systems via the inclusion of Nile red into the particles for broadened emission spectra. As a proof-of-concept study, the use of pillar[5]arene-containing polymer hosts largely facilitates the emission enhancement and wavelength adjustment for the inherent luminogens, setting the basis for the supramolecular design of highly tunable luminescent systems.

Melt and solution processable novel photoluminescent polymer blends for multifaceted advanced applications

To overcome the limitation of traditional photoluminescent materials, a cost-effective photoluminescence polymer was synthesized by a simple and one-step technique using benzyl alcohol as the starting material and aqueous sulfuric acid as the catalyst. The synthesized photoluminescent polymer showed photoluminescence properties independent of the excitation wavelength together with high thermal stability and excellent mechanical properties. The synthesized photoluminescent polymer was incorporated into different polymers viz. thermoplastic as well as thermoset polymers by melt and solution processes, respectively, to achieve photoluminescent polymer blends. The thermal, mechanical, and photoluminescent properties of the fabricated blends were improved or remained almost the same with the photoluminescence polymer contents, strongly proving that the photoluminescent polymer was well dispersed in the polymeric matrix. The potential applications of the photoluminescence polymer blends were investigated for 3D printing and a fluorescent ink. The study paves a way for the development of photoluminescent materials for various applications.

Integrating photoluminescent nanomaterials with photonic nanostructures

Photoluminescence is a light-matter interaction phenomenon of utmost interest for research and technological innovation. Luminescent materials posses several characteristics, such as the quantum yield, Stokes shift, bandwidth, energy transfer coefficients and lifetime of excited states, among others. These factors, though dependent on intrinsic properties of each material, are not immutable; they are highly sensitive to the optical constraints imposed by its surroundings. In particular, nearby surfaces can modify the local electromagnetic field and the density of optical states, strongly affecting the luminescent emission spectrum, intensity and directionality. Different strategies have been developed to control the emission of molecular or nano-sized photoluminescent materials, making use of recent progress in the field of plasmonics, photonic crystals and optical microcavities. The purpose of this article is to summarize the fundamental underlying physical concepts leading to modified photoluminescent properties, as well as to review the latest experimental advances aiming for the synergistic combination of luminescent nano-sources and either photonic or plasmonic nanostructures. Special attention to hybrid structures, such as those combining plasmonics and photonic crystals, will also be addressed.

Synthesis of Multi-Functional Carbon Quantum Dots for Targeted Antitumor Therapy.

Carbon dots are nano-sized photoluminescence materials which have good biocompatibility and low cytotoxicity, while the previously synthesized carbon dots lack tumor targeting capability and therapy function so that it cannot achieve the purpose of diagnosis and treatment. Herein, a new kind of multi-functional carbon dots (GFCDs) is promising to be applied in tumor cells imaging and clinical targeted therapy. Gallic acid (GA) was used as the carbon resource and antitumor active molecule, folic acid (FA) was used as the nitrogen resource and tumor targeting molecule, and citric acid monohydrate (CA) was used as the auxiliary carbon source. Multi-functional GACDs were synthesized by a simple one-step microwave-assisted procedure and analyzed with UV - vis spectrophotometer, fourier transform infrared spectrometer, transmission electron microscopy and X-ray photoelectron spectrometer. Results show that the diameter of GFCDs is about 3nm. And GFCDs are pale-yellow under natural light which turn blue under 360nm UV lamp. Besides ester bond is the connecting mode between functional molecules. In addition, the results of in vitro cell imaging experiments and in vivo antitumor experiments demonstrate the targeting imaging and antitumor abilities towards Hela cells. The synthesis route and properties of GFCDs.

Photoluminescent Composite Materials by Embedding Carbon Dots in Zeolites

Photoluminescent Composite Materials by Embedding Carbon Dots in Zeolites

Lyotropic liquid crystalline phases of anisotropic nanoparticles of organic-inorganic metal halide perovskites: photoluminescence from self-assembled ordered microstructures of semiconductors.

A simple method (which could be completed within 60 minutes at 298 K) was developed to transform layered organic-inorganic metal halide perovskites into colloidal lyotropic liquid crystalline dispersions with microscopic structural orderliness as well as semiconducting properties and photoluminescence. Experimentally, hexagonal-shaped mesogenic nanoplatelets of two-dimensional lead iodide perovskites (R-NH3)2PbI4 were synthesized by antisolvent-induced rapid microcrystallization and stabilized by surfactants, and self-assembled into discotic-nematic phases with optical anisotropy and greenish-blue fluorescence. Combining the stimuli-responsive, light-interactive, and reconfigurable ordered structures of liquid crystals with the adjustable semiconductivity of hybrid perovskites, these photoluminescent soft anisotropic materials may be used for polarized light emission or detection.

Direct molecular confinement in layered double hydroxides: from fundamental to advanced photo-luminescent hybrid materials

We report here new approaches for the direct intercalation of layered double hydroxides (LDHs) from carbonate-LDHs by using various organic acids as proton sources for de-carbonation.