A novel TiO2-modified THPP-BCP composite optical waveguide sensor for the determination of ethylenediamine at ppb level.

Composite thin films OWG sensors show higher sensitivity than single film-based OWG sensors, making them particularly useful in the detection of trace gases. In this work, we developed a new tetra hydroxyphenyl porphyrin (THPP)-bromocresol purple (BCP)/TiO2 gel composite film-based OWG (THPP-BCP/TiO2-OWG) sensor for identifying ethylenediamine (EDA) gas. The fabricated sensor was characterized using ultraviolet and infrared spectroscopy and atomic force microscopy. The test result shows that the response of the THPP-BCP/TiO2-OWG composite film sensor to analytes was 3-4 times higher than that of the single film THPP-OWG sensor. The THPP-BCP/TiO2-OWG sensor exhibited excellent selectivity and remarkable response to EDA gas at a concentration of < 1 ppb at room temperature, with fast response (1 s) and recovery (3 s) times. The high refractive index TiO2 film contributes to OWG's sensitivity, while the THPP and BCP's sensitivity to bases further increased the sensor's response to EDA gas. The combination of THPP-BCP thin film and TiO2 gel film provides a powerful platform for OWG sensors that are highly sensitive, specific, and stable in the detection of trace gases.

NIR persistent luminescence nanoparticles based turn-on aptasensor for autofluorescence-free determination of 17ß-estradiol in milk.

Consistent exposure to 17ß-estradiol through drinking water and food can cause health problems. Although many simple and sensitive fluorescence sensors of 17ß-estradiol have been reported, most of them are based on fluorescence quenching test mode working in visible light range, which are inferior in anti-interference ability and quantitative range. Here, we developed a near-infrared (NIR) phosphorescence aptasensor for the detection of 17ß-estradiol that has no background fluorescence. The aptasensor was based on Foster resonance energy transfer (FRET) between aptamer conjugated NIR persistent luminescence nanoparticles (PLNPs-Apt) and MoS2 nanosheets. The 17ß-estradiol was quantified by the recovery of PLNPs' phosphorescence. This assay can detect 17ß-estradiol in 0.5 mL samples with the LOD of 0.29 ng mL-1 and in concentrations of more than three orders of magnitude (from 0.5 ng mL-1 to 1.2 µg mL-1). This aptasensor exhibited selectivity for 17ß-estradiol and was applicable in complex milk samples.

Conjugation of a photosensitizer to near infrared light renewable persistent luminescence nanoparticles for photodynamic therapy.

We report 808 nm NIR light renewable NIR persistent luminescence sensitized photodynamic therapy (PDT). Persistent luminescence provides an internal light source to generate singlet oxygen for PDT. This work paves the way for the next generation of PDT without any need for continuous external light irradiation.

Optical waveguide sensor of volatile organic compounds based on PTA thin film.

In this study, a sensitive optical waveguide (OWG) sensor for the detection and identification of volatile organic compounds (VOCs) was reported. The sensing membrane is constructed by immobilization of peroxopolytungsten acid (PTA) thin film over a single-mode potassium ion (K(+)) exchanged glass OWG by spin-coating method. A laser beam was coupled into and out of the glass optical waveguide using prism couplers, and dry air functioned as a carrier gas. The sensor was tested for various volatile organic compounds (VOCs), and it showed higher response to the chlorobenzene gas compared to other VOCs. Therefore, we used the OWG sensor to detect chlorobenzene gas as a typical example of VOCs. The sensor exhibits a linear response to chlorobenzene gas in the range of 0.4-1000 ppm with rapid response and good reversibility. The constructed sensor is easy to fabricate and it has some unique qualities which can be characterized as inexpensive, sensitive, and reusable.