Luminescent Particles Research Articles

Luminescent material based on the [Eu(TTA)3(H2O)2] complex incorporated into modified silica particles for biological applications

Amino-functionalized luminescent silica particles were investigated for use in immunoassays. The particles were prepared by the Stöber method where the [Eu(TTA)3(H2O)2] complex (TTA: 3-thenoyltrifluoroacetonate) was incorporated into silica particles during the hydrolysis and condensation of TEOS: tetraethylorthosilicate. Then, the amino groups were introduced in the particle surface using APTS: 3-aminopropyltriethoxisilane. The resulting particles were characterized by scanning electron microscopy (SEM), X ray diffraction (XRD) and photoluminescence spectroscopy. In order to demonstrate the viability of the use of luminescent particles as optical markers, an enzyme–substrate reaction was performed using HRP: horseradish peroxidase. It was possible to verify the binding of HRP-oxidized LDL (low density lipoprotein) and anti-oxLDL antibody-luminescent silica particles through the evaluation of the presence of HRP. The bioassay data open a broad field for the development of protein-tagged luminescent particles for use in biomedical sciences.

Protein Quantification Using Resonance Energy Transfer between Donor Nanoparticles and Acceptor Quantum Dots

A homogeneous time-resolved luminescence resonance energy transfer (TR-LRET) assay has been developed to quantify proteins. The competitive assay is based on resonance energy transfer (RET) between two luminescent nanosized particles. Polystyrene nanoparticles loaded with Eu(3+) chelates (EuNPs) act as donors, while protein-coated quantum dots (QDs), either CdSe/ZnS emitting at 655 nm (QD655-strep) or CdSeTe/ZnS with emission wavelength at 705 nm (QD705-strep), are acceptors. In the absence of analyte protein, in our case bovine serum albumin (BSA), the protein-coated QDs bind nonspecifically to the EuNPs, leading to RET. In the presence of analyte proteins, the binding of the QDs to the EuNPs is prevented and the RET signal decreases. RET from the EuNPs to the QDs was confirmed and characterized with steady-state and time-resolved luminescence spectroscopy. In accordance with the Förster theory, the approximate average donor-acceptor distance is around 15 nm at RET efficiencies, equal to 15% for QD655 and 13% for QD705 acceptor, respectively. The limits of detection are below 10 ng of BSA with less than a 10% average coefficient of variation. The assay sensitivity is improved, when compared to the most sensitive commercial methods. The presented mix-and-measure method has potential to be implemented into routine protein quantification in biological laboratories.

Introduction to the special issue ‘Tracer Applications in Sediment Research’

Introduction to the special issue ‘Tracer Applications in Sediment Research’

One-step synthesis of polymer core-shell particles with a carboxylated ruthenium complex: a potential tool for biomedical applications.

Luminescent core-shell particles are structures widely applied to biomedical purposes with the potential of combining multiple features within one single particle. The development of particles that are easily synthesised and tunable for each application, combining biocompatibility, easy bioconjugation and a high detection signal as a label, is highly desired. In this work, we describe a one-step synthesis of poly[styrene-co-(2-hydroxyethyl methacrylate)], PSHEMA, core-shell particles containing [Ru(4,4'-dicarboxilate-2,2'-bpy)3] luminescent complexes. These particles show monodispersity, biocompatibility, easy functionalization and dye incorporation to focus on bioapplications, such as cell-tracking and diagnostics. The monomers assemble during the polymerization and produce core-shell structures with hydrophilic-hydrophobic character. This allows the concentration of hydrophilic ruthenium complexes onto the shell and incorporation of hydrophobic molecules (e.g. diphenylanthracene) due to the hydrophobic character of styrene. The incorporation of the Ru complex resulted in higher photostability compared to the free dye. Furthermore, carboxylic groups on the particle surface originated from carboxylated ligands of Ru complexes were used to immobilize biomolecules. The particles were successfully used as a diagnostic label for dengue fever (DF) infection. Using the complexes in the immunospot assay the test provided a detection limit (DL) of 187 ng mL-1 for the viral non-structural glycoprotein NS1. The particles showed a considerable decrease in the DL and allowed the diagnosis of the infection 24 hours earlier compared to common available assays based on gold nanoparticles. In addition, the particles were tested with an adherent grown fibroblast cell line and showed potential biocompatibility.

Modification of polyester fibers for protection of securities

An effective method for protecting securities from counterfeiting is to incorporate into the paper mass chemical fibers containing specific additives distributed in a predetermined manner throughout the fiber length. Results from modifying polyester fibers with luminescent dyes using a crazing mechanism were presented. SEM and AFM were used to show craze generation steps, their transformation into fibrils, and redistribution of modifiers incorporated into the crazes in the fiber surface layer. A procedure for concentrating luminescent dyes and colloidal nickel particles on localized fiber parts with alternation of untreated parts and those containing the specific additives was described. The magnetic susceptibility of fiber parts containing ferromagnetic nickel was confirmed experimentally by measurements of the fiber magnetic moment using a high-field magnetic measurement system. Polyester fibers with parts of luminescent color separation alternating along the length were produced. It was concluded that the technology for modifying chemical fibers using a crazing mechanism enabled the controlled incorporation of specific additives in localized fiber parts. This satisfied optimally criteria for protecting paper filled with such fibers from counterfeiting.

Effect of Sr2+ doping on the luminescence properties of YVO4:Eu3+,Sr2+ particles prepared by a solvothermal method

Well-dispersed Eu3+ and Sr2+ co-doped YVO4 luminescent particles (YVO4:Eu3+,Sr2+) on the submicron scale were prepared by a facile solvothermal method at low temperature. The effect of Sr2+ doping on the luminescence of YVO4:Eu3+,Sr2+ particles was investigated by fixing the Eu3+ doping concentration at 7 mol%. It was found that the luminescence intensity of the as-prepared YVO4:Eu3+,Sr2+ particles increased with the Sr2+ doping concentration x to reach a two-fold enhancement when x = 5 %, and then decreased for higher x. We also investigated the effect of thermal annealing on the luminescence properties of the YVO4:Eu3+ and YVO4:Eu3+,Sr2+ particles. A remarkable enhancement in their luminescence properties was observed after annealing at 900 °C in air for 30 min. It was showed that the annealed YVO4:Eu3+,Sr2+ particles exhibited a two-fold stronger emission than the annealed YVO4:Eu3+. This work indicates that Sr2+ doping is beneficial to the luminescence enhancement for both the as-prepared and annealed YVO4:Eu3+,Sr2+ particles.

Zirconia nanocrystals as submicron level biological label

Inorganic nanocrystals are of increasing interest for their usage in biology and pharmacology research. Our interest was to justify ZrO2 nanocrystal usage as submicron level biological label in baker's yeast Saccharomyces cerevisia culture. For the first time (to our knowledge) images with sub micro up-conversion luminescent particles in biologic media were made. A set of undoped as well as Er and Yb doped ZrO2 samples at different concentrations were prepared by sol-gel method. The up-conversion luminescence for free standing and for nanocrystals with baker's yeast cells was studied and the differences in up-conversion luminescence spectra were analyzed. In vivo toxic effects of ZrO2 nanocrystals were tested by co-cultivation with baker's yeast.

An effect of laser pre-annealing on the enhancement of light emission of Si nanocrystal thin film

A multilayered thin film of SiO/Si has been irradiated by CO2 laser in a dot by dot scanning mode, followed by furnace thermal annealing at 1100°C to form Si nanocrystals (Si-NCs) via a phase separation process. Such a laser pre-annealing treatment could enhance the intensities of photoluminescence and electroluminescence of Si-NC by a factor of ∼3 for both. Characterization measurements show that the enhancements are due to the production of extra nucleation sites for Si-NCs, which suppresses the formation of large sized and poorly luminescent Si particles and increases the density of highly luminescent Si-NC.

Rapid Detection of Hendra Virus Using Magnetic Particles and Quantum Dots

A proof-of-concept for the development of a fast and portable Hendra virus biosensor is presented. Hendra virus, a deadly emerging pathogen in Australia, can be co-localized, concentrated and revealed using simultaneously magnetic and luminescent functional particles. This method should be applicable for the early detection of any other virus by targeting the specific virus with the corresponding antibody.

Search for ultraviolet luminescence of soil particles at the Phoenix landing site, Mars

The Optical Microscope (OM) on the Phoenix Mars lander (operated from May through October 2008) was used to search for visible-wavelength luminescence of soil particles excited by ultraviolet (UV) illumination (λ=360–390nm). No luminescent particles were found, with the possible exception of a few potentially luminescent features comprising about 0.02% of the total soil volume. The luminescence quantum efficiency of bulk soil as well as individual soil particles at the Phoenix site is constrained to less than 0.04%. A similar UV experiment will be performed by the Mars Hand Lens Imager (MAHLI) on the upcoming Mars Science Laboratory (MSL) mission. We compare OM and MAHLI UV experiments to each other and suggest a strategy to search for UV-excited luminescence with MAHLI.

Synthesis and characterization of nano silicon and titanium nitride powders using atmospheric microwave plasma technique

We have demonstrated a simple, scalable and inexpensive method based on microwave plasma for synthesizing 5 to 10 g/h of nanomaterials. Luminescent nano silicon particles were synthesized by homogenous nucleation of silicon vapour produced by the radial injection of silicon tetrachloride vapour and nano titanium nitride was synthesized by using liquid titanium tetrachloride as the precursor. The synthesized nano silicon and titanium nitride powders were characterized by XRD, XPS, TEM, SEM and BET. The characterization techniques indicated that the synthesized powders were indeed crystalline nanomaterials. A simple, scalable and inexpensive method based on microwave plasma was developed for synthesizing 5 to 10 g/h of silicon and titanium nitride nanopowders. Silicon was synthesized by homogenous nucleation of silicon vapour while titanium nitride was synthesized by using liquid titanium tetrachloride as the precursor.

Gd2O2S:Eu3+ and Gd2O2S:Eu3+/Gd2O2S hollow microspheres: Solvothermal preparation and luminescence properties

Highly monodisperse and homogeneous Gd2O2S:Eu3+ and Gd2O2S:Eu3+/Gd2O2S hollow microspheres were synthesized successfully by the template method and recoating process. XRD, FESEM, TEM, TG–DTA, FT-IR, UV–vis DRS, and PL were used to characterize the obtained phosphors. The results show that the Gd2O2S:Eu3+ and Gd2O2S:Eu3+/Gd2O2S hollow microspheres are of pure hexagonal phase of Gd2O2S, with diameters of around 260 and 300nm, respectively. Meanwhile, the DRS result of Gd2O2S:Eu3+/Gd2O2S hollow microspheres exhibits that the absorption edge apparently shifts to blue in comparison with that of the Gd2O2S:Eu3+ hollow microspheres. Upon 325nm excitation, the phosphors exhibit red emission corresponding to the 5D0→7F2 transition of the Eu3+ ions, and Gd2O2S:Eu3+/Gd2O2S hollow spheres show a higher luminous intensity than Gd2O2S:Eu3+. The enhancement mechanism was investigated in detail, indicating that the recoating process on luminescent particles may greatly improve the luminous intensity.

Nanocomposites: Highly Luminescent Metal–Organic Frameworks Through Quantum Dot Doping (Small 1/2012)

The cover image features the synergic combination of ultraporous crystals with functional nanoparticles for the fabrication of smart devices. With a one-pot approach, quantum dots are embedded in the framework crystal without affecting the properties of the luminescent particles. The final framework composite represents a new class of ultraporous luminescent materials that has been tested as a molecular sieve sensor. For more information, please read the Full Paper “Highly Luminescent Metal-Organic Frameworks Through Quantum Dot Doping” by D. Buso, P. Falcaro, and co-workers, beginning on page 80.

Modified Stöber synthesis of highly luminescent dye-doped silica nanoparticles

Dye-doped silica nanoparticles (NPs) have been demonstrated to be sensitive labeling markers for biosensing and bioimaging. Their flexible conjugation, excellent photostability and ultrasensitivity make them a powerful tool in biological analysis. Although there have been many reports on the basic research and application of these NPs, they are far from reaching their full potential. Silica NPs can be obtained through two principal approaches: the Stober synthesis and the microemulsion method. The Stober synthesis has the advantage of being easily scaled up for commercial applications and the possibility to effortlessly transfer the NPs into aqueous solutions (typical of bioanalysis). However, further investigation on the impact of the synthesis parameters on the particles size and on the doping process are needed in order to obtain highly luminescent particles. In this study a modified Stober synthesis is proposed and a systematic study of the different reagents is reported, which provides a better picture on the influence of ethanol, ammonia, water, silica precursors, and dye concentration on the final morpho-optical properties. As a result, samples of luminescent silica NPs from 10 to 300 nm have been synthesized and optimized to be highly promising labels for biological applications.

Synthesis and upconversion luminescence properties of monodisperse Y 2O 3:Yb, Ho spherical particles

Monodispersed spherical Y 2O 3:Yb, Ho upconversion luminescence (UCL) particles with sizes of 40–200 nm are prepared using a homogeneous precipitation method. It is found that aging time, varying between 90 and 10 min, has a profound influence on the precursor size, which systematically decreases from 230 nm to 50 nm. The precursor shows poor stability when aging time is 10 min, and the stability of precursor can be improved by increasing the urea concentration. The UCL spectra of Y 2O 3:Yb, Ho with different particle sizes are investigated. The results indicate that the integrated emission intensity ratio of green to red ( R green/red) exhibits a gradual decrease from 2.7 to 0.45 when the particle size decreases from 200 nm to 40 nm, and the possible reasons are evaluated.

External quantum efficiency analysis of Si solar cells with II-VI nanocrystal luminescent down-shifting layers

Abstract Luminescent down-shifting (LDS) as a purely optical approach increases a solar cell's ultra-violet to blue response by shifting short-wavelength light to longer-wavelengths where the external quantum efficiency (EQE) of solar cells is higher. We propose a simple, universally applicable, optical model to analyze EQE spectra of solar modules with LDS layers using only two parameters. The model is successfully tested on ethylene-vinyl acetate encapsulated Si solar cells with CdSe/ZnS nanocrystals as luminescent particles. For a beneficial effect in the investigated system, LDS efficiencies (the fraction of photons transmitted into the cell compared to photons absorbed by the LDS layer) of more than 0.8 are needed with a maximum possible short-circuit current increase of + 3.4%.

Fluorescent metal–organic framework for selective sensing of nitroaromatic explosives

Highly luminescent micrometre-sized fine particles of a Zn(II) metal-organic framework (MOF) of a new π-electron rich tricarboxylate dispersed in ethanol is demonstrated as a selective sensory material for the detection of nitroaromatic explosives via a fluorescence quenching mechanism.

Metal-enhanced photoluminescence from carbon nanodots

In the last couple of years, carbon dots have emerged as a new novel luminescent particle for applications in fluorescence and microscopy in some ways analogous to quantum dots and silicon nanocrystals/particles. As with any fluorescent label or tag, absolute fluorescence intensity, brightness, and particle photostability are a primary concern. In this communication we subsequently show that similar to classical fluorophores, carbon dots located in the near-field, near to Plasmon supporting materials, show enhanced intensities and improved photostabilities.

Luminescent magnetic particles: structures, syntheses, multimodal imaging, and analytical applications

Luminescent magnetic particles (LuMaPs) are attractive tools for life science applications such as multimodal imaging, analyte monitoring, nanotherapeutics, and combinations thereof. LuMaPs consist of at least one magnetic and one luminescent component which often are incorporated in a (polymeric) matrix. Alarge variety of materials do exist for the components that make up LuMaPs. However, a smart selection and combination is required for achieving useful tools. While the magnetic component mainly influences the response to a magnetic field, the luminophore can act as label, sensor, or therapeutic agent. The matrix fulfills tasks such as stabilizing the luminophore and magnet, carrying useful functional groups on its surface, or hosting smart drug delivery systems. Surface modifications with targeting ligands can further improve the applicability of LuMaPs, for example in biomedicine. This review provides an overview on LuMaPs with respect to the materials used and to its structures. Routes toward LuMaPs are outlined, and potential applications are discussed.

Drug delivery: Magnetic Luminescent Porous Silicon Microparticles for Localized Delivery of Molecular Drug Payloads (Small 22/2010)

AbstractMagnetic manipulation, fluorescent tracking, and localized delivery of a drug payload to cancer cells in vitro is demonstrated, using nanostructured porous silicon microparticles as a carrier. The multifunctional microparticles are prepared by electrochemical porosification of a silicon wafer in a hydrofluoric acid‐containing electrolyte, followed by removal and fracture of the porous layer into particles using ultrasound. The intrinsically luminescent particles are loaded with superparamagnetic iron oxide nanoparticles and the anti‐cancer drug doxorubicin. The drug‐containing particles are delivered to human cervical cancer (HeLa) cells in vitro, under the guidance of a magnetic field. The high concentration of particles in the proximity of the magnetic field results in a high concentration of drug being released in that region of the Petri dish, and localized cell death is confirmed by cellular viability assay (Calcein AM).