Sensitive and Selective Determination of Benzidine by Synthesized tragacanth-poly (Acrylic acid-co-acrylamide-GQD) Hydrogel Nanocomposite as a Highly Stable Fluorescent Probe

Benzidine is known as a toxic and highly carcinogenic substance, so its determination is an essential issue. Until now, no effective and stable fluorescent probe based on hydrogel nanocomposite has been reported for the determination of this substance. In this work, for the first time, the synthesis and use of tragacanth-poly (acrylic acid-co-acrylamide-GQD) hydrogel nanocomposite (H-GQD) as a novel, high-stable, and selective fluorescence hydrogel nanocomposite for the identification of benzidine is reported. To achieve the maximum responsiveness of this hydrogel nanocomposite to determine benzidine, various parameters such as pH, ionic strength, hydrogel nanocomposite concentration, sensitivity, and selectivity were investigated. The results of the investigations showed that the synthesized H-GQD has excellent stability, selectivity, and linearity range of 0.3 - 12 ppm with a limit of detection of 0.098 ppm. The results of the investigation of real water samples showed that the H-GQD has excellent recovery in the range of 93.3 - 106.6%. Finally, we believe that this H-GQD as a new and highly stable fluorescent probe can be a starting point for its application in various fields and industries to identify benzidine in water samples.

Flexible surface-enhanced Raman scatting substrates: recent advances in their principles, design strategies, diversified material selections and applications

Surface-enhanced Raman scattering (SERS) is widely used as a powerful analytical technology in cutting-edge areas such as food safety, biology, chemistry, and medical diagnosis, providing ultra-fast, ultra-sensitive, nondestructive characterization and achieving ultra-high detection sensitivity even down to the single-molecule level. Development of Raman spectroscopy is strongly dependent on high-performance SERS substrates, which have long evolved from the early days of rough metal electrodes to periodic nanopatterned arrays building on solid supporting substrates. For rigid SERS substrates, however, their applications are restricted by sophisticated pretreatments for detecting solid samples with non-planar surfaces. It is therefore essential to reassert the principles in constructing flexible SERS substrates. Herein, we comprehensively review the state-of-the-art in understanding, preparing and using flexible SERS. The basic mechanisms behind the flexible SERS are briefly outlined, typical design strategies are highlighted and diversified selection of materials in preparing flexible SERS substrates are reviewed. Then the recent achievements of various interdisciplinary applications based on flexible SERS substrates are summarized. Finally, the challenges and perspectives for future evolution of flexible SERS and their applications are demonstrated. We propose new research directions focused on stimulating the real potential of SERS as an advanced analytical technique for commercialization.

Light-Activated Hydroxyapatite Photocatalysts: New Environmentally-Friendly Materials to Mitigate Pollutants

This review focuses on a reasoned search for articles to treat contaminated water using hydroxyapatite (HAp)-based compounds. In addition, the fundamentals of heterogeneous photocatalysis were considered, combined with parameters that affect the pollutants’ degradation using hydroxyapatite-based photocatalyst design and strategies of this photocatalyst, and the challenges of and perspectives on the development of these materials. Many critical applications have been analyzed to degrade dyes, drugs, and pesticides using HAp-based photocatalysts. This systematic review highlights the recent state-of-the-art advances that enable new paths and good-quality preparations of HAp-derived photocatalysts for photocatalysis.

Carbon dots-decorated hydroxyapatite nanowires–lanthanide metal–organic framework composites as fluorescent sensors for the detection of dopamine

A ratiometric composite fluorescent probe (HAPNWs-CDs-Tb/MOF) with hydroxyapatite carrier and the fluorescence ratio of carbon dots and lanthanide metal organic framework as the response signal was prepared for the detection of dopamine.

Quantitative detection of crystal violet using a surface-enhanced Raman scattering based on a flower-like HAp/Ag nanocomposite

Herein, we proposed a simple one-pot sol-thermal strategy to prepare a highly sensitive and reproducible SERS substrate. The silver-doped hydroxyapatite nanocomposite (HAp/Ag) could suppress the oxidation of silver nanoparticles, which endow the SERS substrate with good stability and reproducibility. Due to the strong interaction between the HAp/Ag substrate and the analytes, a stronger Raman signal generated during the process of SERS detection. In particular, the HAp/Ag substrate enabled the determination of rhodamine 6G (R6G) and crystal violet (CV), and the limits of detection (LOD) were low at 10^-6 M and 10^-5 M, respectively. In addition, the HAp/Ag substrate could be used for the quantitative analysis of CV in wastewater with a good linear relationship between 10^-2 and 10^-5 M. In this context, the HAp/Ag substrate combines the superior properties of both Ag NPs and HAp particles, providing a potential method for monitoring the environment and building a convenient SERS platform to detect pollutants in wastewater.

Probing blood plasma samples for the detection of diabetes using SERS aided by PCA and LDA multivariate data analyses

Fabrication of a SERS-active substrate using Langmuir–Blodgett and self-assembly techniques for the detection of diabetes from blood plasma samples.