Rare Earth Hydroxide as a Precursor for Controlled Fabrication of Uniform ß-NaYF4 Nanoparticles: A Novel, Low Cost, and Facile Method.

In recent years, rare earth doped upconversion nanocrystals have been widely used in different fields owing to their unique merits. Although rare earth chlorides and trifluoroacetates are commonly used precursors for the synthesis of nanocrystals, they have certain disadvantages. For example, rare earth chlorides are expensive and rare earth trifluoroacetates produce toxic gases during the reaction. To overcome these drawbacks, we use the less expensive rare earth hydroxide as a precursor to synthesize ß-NaYF4 nanoparticles with multiform shapes and sizes. Small-sized nanocrystals (15 nm) can be obtained by precisely controlling the synthesis conditions. Compared with the previous methods, the current method is more facile and has lower cost. In addition, the defects of the nanocrystal surface are reduced through constructing core⁻shell structures, resulting in enhanced upconversion luminescence intensity.

Assessment of spectroscopic parameters of solvated Eu(dmh)3 phen organometallic complex in various basic and acidic solvents.

We report on the comprehension of novel europium activated hybrid organic Eu(dmh)3 phen (Eu: europium, dmh: 2,6-dimethyl-3,5-heptanedione, phen: 1,10 phenanthroline) organo-metallic complexes, synthesized at different pH values by the solution technique. Photo physical properties of these complexes in various basic and acidic solvents were probed by UV-vis optical absorption and photoluminescence (PL) spectra. Minute differences in optical absorption peaks with variable optical densities were encountered with the variation in solvent from basic (chloroform, toluene, tetrahydrofuran) to acidic (acetic acid) media, revealing bathochromic shift in the absorption peaks. The PL spectra of the complex in various acidic and basic organic solvents revealed the position of the emission peak at 613 nm irrespective of the changes in solvents whereas the excitation spectrum almost matched with that of the UV-vis absorption data. The optical density was found to be maximum for the complex with pH 7.0 whereas it gradually decreased when pH was lowered to 6.0 or raised to 8.0 at an interval of 0.5, demonstrating its pH sensitive nature. Several spectroscopic parameters related to probability of transition such as absorbance A(λ), Napierian absorption coefficient α(λ), molecular absorption cross-section σ(λ), radiative lifetime (τ0 ) and oscillator strength (f) were calculated from UV-vis spectra. The relative intensity ratio (R-ratio), calculated from the emission spectra was found to be almost the same in all the organic solvents. The optical energy gap, calculated for the designed complexes were found to be well in accordance with the ideal acceptance value of energy gap of the emissive materials used for fabrication of red organic light-emitting diode (OLED). The relation between Stoke's shift and solvent polarity function was established by Lippert-Mataga plot. This remarkable independence of the electronic absorption spectra of Eu complexes on the nature of the solvent with unique emission wavelength furnishes its potential to serve as a red light emitter for solution processed OLEDs, display panels and solid-state lighting.

PHASE DEPENDENT OPTICALLY STIMULATED LUMINESCENCE IN CU-DOPED Sr4Si3O8Cl4.

Phase dependent optically stimulated luminescence (OSL) is studied in Cu-doped Sr4Si3O8Cl4. The Study shows that samples in which amount of contributing strontium metasilicate phase in Cu-doped Sr4Si3O8Cl4 is less, show intense OSL while those samples in which strontium metasilicate phase is more show weak OSL. The observed Cu luminescence is also found to be phase dependent. Sample in which Sr4Si3O8Cl4 phase is dominant, the observed Cu luminescence is around 350 nm whereas an additional longer wavelength band around 450 nm is observed when the strontium metasilicate phase is present in significant amount. The relatively phase pure, Cu-doped Sr4Si3O8Cl4 shows good OSL properties. The sensitivity of such material is 3.89 times more compared to commercial Al2O3:C (Landauer Inc.). High sensitivity, good linearity and reusability, along with low fading make this material as good OSL phosphor and may find applications in OSL based radiation dosimetry.

A low-cost smartphone-based platform for highly sensitive point-of-care testing with persistent luminescent phosphors.

Through their computational power and connectivity, smartphones are poised to rapidly expand telemedicine and transform healthcare by enabling better personal health monitoring and rapid diagnostics. Recently, a variety of platforms have been developed to enable smartphone-based point-of-care testing using imaging-based readout with the smartphone camera as the detector. Fluorescent reporters have been shown to improve the sensitivity of assays over colorimetric labels, but fluorescence readout necessitates incorporating optical hardware into the detection system, adding to the cost and complexity of the device. Here we present a simple, low-cost smartphone-based detection platform for highly sensitive luminescence imaging readout of point-of-care tests run with persistent luminescent phosphors as reporters. The extremely bright and long-lived emission of persistent phosphors allows sensitive analyte detection with a smartphone by a facile time-gated imaging strategy. Phosphors are first briefly excited with the phone's camera flash, followed by switching off the flash, and subsequent imaging of phosphor luminescence with the camera. Using this approach, we demonstrate detection of human chorionic gonadotropin using a lateral flow assay and the smartphone platform with strontium aluminate nanoparticles as reporters, giving a detection limit of ≈45 pg mL-1 (1.2 pM) in buffer. Time-gated imaging on a smartphone can be readily adapted for sensitive and potentially quantitative testing using other point-of-care formats, and is workable with a variety of persistent luminescent materials.

Simple and rapid chemiluminescence aptasensor for Hg2+ in contaminated samples: A new signal amplification mechanism.

Detection of ultralow concentration of heavy metal ion Hg2+ is important for human health protection and environment monitoring because of the gradual accumulation in environmental and biological fields. Herein, we report a convenient chemiluminescence (CL) biosensing platform for ultrasensitive Hg2+ detection by signal amplification mechanism from positively charged gold nanoparticles ((+)AuNPs). It is based on (+)AuNPs charge effect and aptamer conformation change induced by target to stimulate the generation of CL in the presence of H2O2 and luminol without high salt medium. Notably particularly, the typical problem of the high salt medium from (-) AuNPs system, like influencing aptamers' bind with target and hindering CL reaction can be effectively addressed through the direct introduction of (+)AuNPs. Therefore, the proposed biosensing exhibits a high sensitivity toward target Hg2+ with a detection limit of 16 pM, which is far below the limit (10nM) defined by the U.S. Environmental Protection Agency in drinkable water, and is about 10-fold lower than the previously reported aptamer-based assays for Hg2+. This sensing platform provides a simple, rapid, and cost-effective approach for label-free sensitive detection of Hg2+. Moreover, it is universal for the detection of other targets. Undoubtedly, such a direct utilizing of (+)AuNPs' charge effect will provide a new signal amplification way for label-free aptamer-based CL analysis.

In vivo biodistribution and toxicity assessment of triplet-triplet annihilation-based upconversion nanocapsules.

Triplet-triplet annihilation (TTA)-based upconversion nanocapsules (UCNCs) have great potential in biological and medical applications. However, there are numerous unresolved issues with respect to the safety of these novel nanomaterials. In this work, for the first time, we studied the in vivo biodistribution of UCNCs which were synthesized by co-loading platinum (II)-tetraphenyl-tetrabenzoporphyrin (PtTPBP) and boron dipyrromethene derivative (BDP) into bovine serum albumin (BSA)-stabilized soybean oil droplets, and systematically assessed the potential toxicity of UCNCs both in vitro and in vivo. The results showed that UCNCs had no significant influence on the proliferation or the migration of HeLa cells even when the dosage was increased to 12 mg/mL. The biodistribution results demonstrated that UCNCs mainly accumulated in the mononuclear phagocyte system (MPS) including the liver and spleen after intravenous injection of the nanocapsules. When mice were intravenously injected with 1200 mg/kg of the UCNCs over a period of 60 days, no noticeable toxicity was observed under these treatment conditions as shown by body weight results, histological analyses, hematological analyses and blood biochemical examinations. This research inspires further studies on UCNCs for biomedical applications.

Assessment of terbium (III) as a luminescent probe for the detection of tuberculosis biomarkers.

A detection method for nicotinic acid, a specific metabolite marker of Mycobacterium tuberculosis present in cultures and patients' breath, is studied in complex solutions containing other metabolites and in biological media such as urine, saliva and breath condensate. The method is based on the analysis of the luminescence increase of Tb(3+) complexes in the presence of nicotinic acid due to the energy transfer from the excited ligand to the lanthanide ion. It is shown that other potential markers found in M. tuberculosis culture supernatant, such as methyl phenylacetate, p-methyl anisate, methyl nicotinate and 2-methoxy biphenyl, can interfere with nicotinic acid via a competitive absorption of the excitation photons. A new strategy to circumvent these interferences is proposed with an upstream trapping of volatile markers preceding the detection of nicotinic acid in the liquid phase via the luminescence of Tb(3+) complexes. The cost of the method is evaluated and compared with the Xpert MTB/RIF test endorsed by the World Health Organization.

Highly efficient förster resonance energy transfer in a fast, serum-compatible immunoassay.

Highly efficient FRET leads to important enhancements for homogeneous immunoassays. By using the novel phosphorescent dye EuLH and BHQ-10 as a donor-acceptor pair, the FRET efficiency increases to >99.5 %, leading to significantly improved signal-to-background ratio, precision and linear range. The phosphorescence detection enabled full compatibility to serum samples for this fast-responding immunoassay.

Rapid consecutive three-component coupling-Fiesselmann synthesis of luminescent 2,4-disubstituted thiophenes and oligothiophenes.

(Hetero)aroyl chlorides, alkynes, and ethyl 2-mercapto acetate can be reacted in a consecutive three-component synthesis to give 2,4-disubstituted thiophene 5-carboxylates in good to excellent yields. In the sense of a pseudo-five-component reaction highly blue luminescent symmetrical terthiophenes and a quinquethiophene can be synthesized in excellent yield.

Noninjection facile synthesis of Gram-scale highly luminescent CdSe multipod nanocrystals.

Nearly all reported approaches for synthesis of high quality CdSe nanocrystals (NCs) involved two steps of preparation of Cd or Se stock solution in advance and then mixing the two reactants via hot-injection in high temperature. In this manuscript, Gram-scale CdSe multipod NCs were facilely synthesized in a noninjection route with the use of CdO and Se powder directly as reactants in paraffin reaction medium containing small amount of oleic acid and trioctylphosphine. The influence of various experimental variables, including reaction temperature, nature and amount of surfactants, Cd-to-Se ratio, and the nature of reactants, on the morphology of the obtained CdSe NCs have been systematically investigated. After deposition of ZnS shell around the CdSe multipod NCs, the PL QY of the obtained CdSe/ZnS can be up to 85%. The reported noninjection preparation approach can satisfy the requirement of industrial production bearing the advantage of low-cost, reproducible, and scalable. Furthermore, this facile noninjection strategy provides a versatile route to large-scale preparation of other semiconductor NCs with multipod or other morphologies.

Development of bioluminescent enzyme immunoassay for s-equol using firefly luciferase and its application to the assessment of equol-producer status.

In this study, we developed a specific bioluminescent enzyme immunoassay (BLEIA) for S-equol, employing firefly luciferase as a labeling enzyme, as an alternative to HPLC methods. Satisfactory correlation (r=0.992) was shown when this S-equol BLEIA was compared with HPLC. The cross-reactivity with R-equol as its diastereoisomer is <5%, and that with daidzein, which is the substrate of equol, is 0.02%. Frequencies of Japanese equol producers determined using two distinct approaches were compared: a threshold value for urinary S-equol concentration of 232 ng/ml gave frequencies of 32% of men and 19% of women. These values correspond to the results for log(10)-transformed urinary S-equol to daidzein ratio threshold of -1.75, namely, 34% of men and 19% of women. When the changes in concentration of urinary equol and daidzein were measured after ingestion of isoflavone, the maximum concentration (C(max)) of urinary equol appeared after 9.6 h of isoflavone consumption; this C(max) was 2 h later than that for daidzein. The S-equol BLEIA documented in this study is expected to be an important tool for the assessment of equol producer status and demonstration of the bioavailability of isoflavone.

Development of an aequorin luminescence calcium assay for high-throughput screening using a plate reader, the LumiLux.

A luminescence assay using a new plate reader, the LumiLux (PerkinElmer, Waltham, MA), has been validated for high-throughput screening (HTS). In this study, we compared the aequorin luminescence-based calcium mobilization assay to the fluorescence-based calcium assay. A cell line stably co-expressing apo-aequorin, a chimeric G-protein, and a G-protein-coupled dopamine receptor was used to screen a collection of 8,106 compounds using the Hamamatsu Photonics (Bridgewater, NJ) FDSS6000 and LumiLux as the plate readers. The assay parameters evaluated included hit rate correlation, signal-to-noise ratio, and overall assay performance calculated by Z and standard deviation. The average Z values and hit rates were comparable between assay platforms;however, the standard deviation for the agonist aequorin assay was significantly smaller. There was also a significant decrease in the number of false-positives with the aequorin assay. These results suggest that the aequorin assay in combination with the new plate reader, LumiLux, provides a simple, cost-effective, robust, and sensitive assay for HTS