CdS QDs/N-methylpolypyrrole hybrids as fluorescent probe for ultrasensitive and selective detection of picric acid

An overview of polymer surface coated synthetic quantum dots as therapeutics and sensors applications

Quantum dots (QDs) are a class of remarkable materials that have garnered significant attention since their initial discovery. It is noteworthy to mention that it took approximately a decade for these materials to be successfully implemented in practical applications. While QDs have demonstrated notable optical properties, it is important to note that these attributes alone have not rendered them a feasible substitute for traditional organic dyes. Furthermore, it is worth noting that the substance under investigation exhibited inherent toxicity and instability in its initial state, primarily due to the presence of a heavy metal core. In the initial stages of research, it was observed that the integration of nanocomposites had a positive impact on the properties of QDs. The discovery of these nanocomposites was motivated by the remarkable properties exhibited by biocomposites found in nature. Recent discoveries have shed light on the potential utilization of QDs as a viable strategy for drug delivery, offering a promising avenue to enhance the efficacy of current pharmaceuticals and pave the way for the creation of innovative therapeutic approaches. The primary objective of this review was to elucidate the distinctive characteristics that render QDs highly suitable for utilization as nanocarriers. In this study, we will delve into the multifaceted applications of QDs as sensing nanoprobes and their utilization in diverse drug delivery systems. The focus of our investigation was directed toward the utilization of QD/polymer composites in sensing applications, with particular emphasis on their potential as chemical sensors, biosensors, and physical sensors.

A series of phenanthroline-imine compounds: Computational, OLED properties and fluorimetric sensing of nitroaromatic compounds

In this study, Schiff base compounds (1-5) were synthesized by the reaction of 5-amino-1,10-phenanthroline with various aldehydes. The molecular structures of the synthesized compounds were characterized by FT-IR, ¹H/¹³C NMR and mass spectroscopic methods. Single crystals of 1 were obtained and their molecular structures in crystalline form were determined by single crystal X-ray diffraction study. The sensor properties of the synthesized compounds against nitroaromatic compounds [nitrobenzene (NB), 4-nitrophenol (NP), 2,4-dintrophenol (DNP) and 1,3,5-trinitrophenol (TNP)] were investigated by fluorescence spectroscopy. Compound 3 have highest sensitivity for the sensing of 1,3,5-trinitrophenol (TNP) (Ksv: 4.63 × 10⁴ M^-1) with LOD of 4.01 µM while compound 5 showed the highest sensitivity for 2,4-dinitrophenol (DNP) (Ksv: 5.71 × 10⁴ M^-1) with LOD of 4.75 µM. In addition, the structural parameters (bond angles/lengths), contour diagrams of HOMO/LUMO molecular orbitals, molecular electrostatic potential (MEP) maps, non-linear optical (NLO) and OLED properties were investigated by computational studies. According to the HOMO and LUMO energies, the NLO property of the molecule (5) is higher than both other molecules and the reference substance urea.

Dielectric barrier discharge-accelerated one-pot synthesis of sulfur quantum dots for fluorescent sensing of lead ions and L-cysteine

Here, we report a novel method for the one-pot facile synthesis of sulfur quantum dots (SQDs) based on a dielectric barrier discharge (DBD)-accelerated H₂O₂ etching strategy within merely 20 min. The formation mechanism of SQDs was investigated, with which an "ON-OFF-ON" fluorescence sensor was developed for the detection of Pb²⁺ ions and L-cysteine.

Dual-emission ratiometric fluorescence probe based on copper nanoclusters for the detection of rutin and picric acid

In this paper, polyvinylpyrrolidone-templated copper nanoclusters (PVP-CuNCs) were synthesised using a hydrothermal method. Through the electrostatic interaction between PVP-CuNCs and rhodamine 6G, a dual-emission ratiometric fluorescent probe was constructed, and two well-separated emission peaks appeared at 420 nm and 570 nm. The selective detection of rutin and picric acid was achieved by fitting the relationship between the ratiometric fluorescence intensity (F₄₂₀/F₅₇₀) and the concentration of the target detection substance. The limits of detection of rutin and picric acid were 0.84 μM and 0.27 μM, respectively. The synthesised material has high stability and successfully allows the determination of rutin content in drugs and picric acid content in water samples with satisfactory recoveries.

Accurately selected 1,3,4-thiadiazole and coumarin unit to construct fluorescent probes that effectively detect 2,4,6-trinitrophenol

Two remarkablely fluorimetric probes were developed to rapidly detect 2,4,6-trinitrophenol (TNP). With the help of density functional theory (DFT) calculations, we confirmed that using 1,3,4-thiadiazole skeleton as recognition group and coumarin unit as fluorophore would show excellent application prospects in terms of TNP detection. The probes LK-1 and LK-2 displayed green and orange emission with fluorescence quenching yield as high as 83.7% and 75.1% in solution. Further evaluation demonstrated that they display outstanding selectivity and sensitivity for rapid and visual detection of TNP. Both fluorescent color and fluorescence emission spectrum had significant changes and these phenomena could easily observe via naked-eye and analytical instrument. The detection limits of them were 97 nM and 71 nM. What's more, application in real water samples and solid phase paper tests illustrated the practical significance of detection of TNP.

A selective fluorescent probe based on citrate doped polypyrrole for dual determination of VO2+/Fe3+ in biological samples

A novel water-soluble PPy–Cit polymer is synthesized as a selective fluorescent sensor for dual determination of VO2+ and Fe3+ ions sequentially by the time discrimination method in blood serum and dietary supplement vanadyl sulfate tablet samples.

Preparation of carbon quantum dots/polyaniline nanocomposite: Towards highly sensitive detection of picric acid

Carbon quantum dots/polyaniline (CQDs/PANI) nanocomposite was successfully prepared by in-situ polymerization of aniline. CQDs were synthesized hydrothermally from gelatin with a diameter size of 4.2 nm and a 17% quantum yield. FTIR, UV-vis absorption, fluorescence spectrophotometer, XRD, TEM, XPS and lifetime decay were used to characterize the obtained nanocomposite. The formation of PANI revealed a high quenching effect on CQDs where the TEM images showed that the formed CQDs were greatly embedded in PANI matrix. In this study, CQDs/PANI nanocomposite was used for the detection of picric acid (PA) in the range 0.37-1.42 μM with a low detection limit (LOD) of 0.056 μM. The prepared sensor showed good enhancement and sensitivity towards PA in comparison to pristine CQDs and other nanostructured materials. The mechanism of PA detection has been studied where it was observed that PA is electrostatically interacted to the nanocomposite through - OH group of PA and the protonated PANI salt formed in CQDs/PANI nanocomposite by fluorescence resonance energy transfer applications. The proposed CQDs/PANI sensor was then utilized in real water samples and successfully determined the different amounts of PA spiked into tap water.

N-alkylation briefly constructs tunable multifunctional sensor materials: Multianalyte detection and reversible adsorption

A series of N-alkyl-substituted polybenzimidazoles (SPBIs), synthesized by simple condensation and N-alkylation, act as functional materials with tunable microstructures and sensing performance. For their controllable morphologies, the formation of nano-/microspheres is observed at the n(RBr)/n(PBI) feed ratio of 5:1. Products with different degrees of alkylation can recognize metal ions and nitroaromatic compounds (NACs). For example, SPBI-c, obtained at the feed ratio of 1:1, can selectively detect Cu2+, Fe3+, and NACs. By contrast, SPBI-a, obtained at the feed ratio of 0.1:1, can exclusively detect Cu2+ with high sensitivity. Their sensing mechanisms have been studied by FT-IR spectroscopy, SEM, XPS, and DFT calculations. Interestingly, the SPBIs can adsorb Cu2+ in solution and show good recyclability. These results demonstrate that polymeric materials with both sensing and adsorption applications can be realized by regulating the alkylation extent of the main chain, thus providing a new approach for the facile synthesis of multifunctional materials.

Recent Developments in the Field of Explosive Trace Detection

Explosive trace detection (ETD) technologies play a vital role in maintaining national security. ETD remains an active research area with many analytical techniques in operational use. This review details the latest advances in animal olfactory, ion mobility spectrometry (IMS), and Raman and colorimetric detection methods. Developments in optical, biological, electrochemical, mass, and thermal sensors are also covered in addition to the use of nanomaterials technology. Commercially available systems are presented as examples of current detection capabilities and as benchmarks for improvement. Attention is also drawn to recent collaborative projects involving government, academia, and industry to highlight the emergence of multimodal screening approaches and applications. The objective of the review is to provide a comprehensive overview of ETD by highlighting challenges in ETD and providing an understanding of the principles, advantages, and limitations of each technology and relating this to current systems.

A novel SERS selective detection sensor for trace trinitrotoluene based on meisenheimer complex of monoethanolamine molecule

Trinitrotoluene (TNT) is a primary component in chemical explosives, making them a common focus in public safety detection. However, it is very difficult to achieve selective and sensitive detection of the TNT molecule in practical application. In the present study, a simple surface enhanced Raman scattering (SERS) sensing based on monoethanolamine (MEA) - modified gold nanoparticles (Au NPs) was expanded for high selectivity and sensitive detecting of TNT in an envelope, luggage, lake water, and clothing through a quickly sampling and detection process. The monoethanolamine molecule based on Meisenheimer complex lights up ultra-high Raman scattering of a nonresonant molecule on the superficial coat of gold nanoparticles. Using this detection sensor, a molecular bridge can be established to selectively detect trinitrotoluene with a detection limit of 21.47 pM. We were able to rapidly identification trinitrotoluene molecule with a powerful selective over the familiar interfering substances nitrophenol, picric acid, 2,4-dinitrophenol, and 2,4-dinitrotoluene. The outcome in this work supply an efficient solution to the test of trinitrotoluene and to establishing a SERS sensor analytical strategy. The studies have demonstrated that the MEA-Au NPs based SERS sensing can be potentially used in field detection the trace amount of chemical explosives for public security.

A stilbazolium dye-based chromogenic and red-fluorescent probe for recognition of 2,4,6-trinitrophenol in water

Probe DMAS-DP in water shows highly selective decrease in absorbance (475 nm) and fluorescence intensity (615 nm) with 2,4,6-trinitrophenol and colour change from red to yellow (visible light) and red fluorescent to black (365 nm light).