Simple One-step Solid-state Synthesis of Highly Crystalline N Doped Carbon Dots As Selective Turn Off-sensor for Picric Acid and Metanil Yellow

Tellurium Containing Long Lived Emissive Fluorophore for Selective and Visual Detection of Picric Acid through Photo-Induced Electron Transfer

A novel tellurium (Te) containing fluorophore, 1 and its nickel (2) and copper (3) containing metal organic complex (MOC) have been synthesized to exploit their structural and optical properties and to deploy these molecules as fluorescent probes for the selective and sensitive detection of picric acid (PA) over other commonly available nitro-explosives. Furthermore, density functional theory (DFT) and single crystal X-ray diffraction (SCXRD) techniques revealed the inclusion of "soft" Tellurium (Te) and "hard" Nitrogen (N), Oxygen (O) atoms in the molecular frameworks. Owing to the presence of electron rich "N" and "O" atoms along with "Te" in the molecular framework, 1 could efficiently and selectively sense PA with more than 80 % fluorescence quenching efficiency in organic medium and having detection limit of 4.60 μM. The selective detection of PA compared to other nitro-explosives follows a multi-mechanism based "turn-off" sensing which includes photo-induced electron transfer (PET), electrostatic (π-π stacking and π-anion/cation) interaction, intermolecular hydrogen bonding and inner filter effect (IFE). The test strip study also establishes the sensitivity of 1 for detection of PA.

Nitrogen and Sulfur Co-doped Carbon Dots as a Turn-Off Fluorescence Probe for the Detection of Cerium and Iron

Carbon dots has becoming one of the most promising fluorescence sensors to determine the trace level of heavy metals in environments because of their advantages in optical properties, response time, and convenient operation procedures. Herein, a novel nitrogen and sulfur co-doped carbon dots (NS-CDs) were prepared though microwave assisted approach using DL-malic acid and allyl thiourea for the first time. Due to the existence of nitrogen and sulfur, the as-prepared NS-CDs exhibited bright blue fluorescence at 430 nm upon 330 nm excitation, with a fluorescence quantum yield of 19.8%. The sensitivity study of NS-CDs against metal ions and organic molecules has approved that the fluorescence could be further quenched by Ce⁴⁺ and Fe³⁺ ions, with the same linear detection ranges varying from 10 to 90 µM. The limits of detection (LOD) were determined as low as 0.75 µM and 0.67 µM for Ce⁴⁺ and Fe³⁺ ions, respectively. The possible quenching mechanism is explained by inner filter effect and static quenching mechanism for Ce⁴⁺ ions, while the quenching effect caused by Fe³⁺ ions is attributed to the inner filter effect, static and dynamic quenching mechanisms. Additionally, the developed sensor was used for the detection of Ce⁴⁺ and Fe³⁺ ions in tap water with satisfactory recoveries. Finally, the designed NS-CDs sensor possesses good biocompatibility against MA104 cells, suggesting the sensor can be potentially applied to detect Ce⁴⁺ and Fe³⁺ ions in environment and biological systems.