A pH-applicative fluorescent probe with long measuring range for monitoring hydrazine in water samples and Arabidopsis thaliana

A single excitation dual emission semi-salamo type multi-functional probe for sensitive pH and Cu2+ detection

pH and Cu2+ ion concentration changes are linked to disorders like Alzheimer's and cancer. Rapid detection of pH and Cu2+ ions is critical for public health and environmental concerns. The semi-salamo-type probe (E)-2-hydroxy-1-naphthaldehyde O-(2-(aminooxy)ethyl) oxime (NSS) demonstrated substantial dual-functional performance, sensing pH change and Cu2+ ions. A single excitation and double emission characteristic on the probe NSS made it distinctive. Probe NSS exhibits pH-dependent excited state intramolecular proton transfer (ESIPT), and its optical properties vary based on the pH environment. Probe NSS detects pH changes from 2 to 11 by changing the "off-on-off" of the excited state intra-molecular proton transfer (ESIPT) mechanism, exhibiting rapid, reversible, and selective responses. In addition, the luminescent salamo-like naphthalene-based probe NSS can coordinate with Cu2+ ions, achieving great selectivity and sensitivity to identify Cu2+ ions with a detection limit of 0.84 ppb (13.2 nM) Probe NSS can detect Cu2+ ions in actual water samples such as tap water and yellow river water. The test strip loaded with probe NSS enabled quick and accurate detection of Cu2+ ions in water samples. Consequently, the versatile salamo-type probe NSS lays the foundation for developing high sensitivity and fast-response dual-mode pH meters as well as Cu2+ sensing.

Quinoline-derived electron-donating/withdrawing fluorophores for hydrazine detection and applications in environment and bioimaging

Substitution can be employed to competently tune the photophysical properties of chemosensors. The effect of substituents on the absorption and emission properties of quinoline probes was investigated. Therefore, salicylaldehyde (S), N-diethylamino-salicylaldehyde (D), and nitro-salicylaldehyde (W)-based quinoline Schiff base derivatives were investigated with hydrazine and studied for their photophysical properties. The nucleophilic substitution reaction was used as a sensing mechanism between the probes and hydrazine and investigated with 1H NMR, HR-MS characterizations, and DFT calculations. The sensitivity of QW-R is greater than that of QS-R and QD-R because of the stronger intramolecular charge transfer (ICT) in QW-R. The calculated LOD values are 28 nM for QS-R, 30 nM for QD-R, and 9 nM for QW-R. The probes were employed to monitor gaseous hydrazine using a smartphone and analyze solution forms of hydrazine in soil, water, and food samples, and living cells. Moreover, the in situ hydrazine release was monitored with bioimaging by administering an isoniazid drug. Significantly, the electronic effect of substituents over fluorescence showing, ranging from electron-donating to electron-withdrawing was investigated. We anticipate that this approach may be a promising strategy for the rational design of fluorescent sensors.

Advances in Optical Probes for the Detection of Hydrazine in Environmental and Biological Systems

Hydrazine, as a crucial raw material in the fine chemical industry, plays an indispensable role in fuel, catalyst, pesticide and drug synthesis. Due to its good water solubility and high toxicity, hydrazine can cause irreparable damage to water and soil in the environment, and it can also be released by taking certain drugs, which brings potential risks to human health. Therefore, it is vital to develop a method that can specifically detect hydrazine in the environment and in vivo. As an effective analysis and detection tool, fluorescence probe has attracted extensive attention in recent years. In this review, we summarized and classified hydrazine fluorescence probes based on various reaction mechanisms, and discussed their structures and applications in the past ten years. At least, we briefly outline the challenges and prospects in this field.