Novel 1,8-naphthalimide dye for multichannel sensing of H+ and Cu2+

New bis-photochromic compounds based on diarylimidazoles: Synthesis and multistimuli-responsive optical properties

Three new bis-photochromic molecules containing two 4,5-diarylimidazole units were synthesized and characterized. We investigated their photophysical properties and pH response characteristics in acetonitrile solutions and polymethylmethacrylate (PMMA) membranes. All compounds displayed significant pH responses for the imidazole ring in the molecular structure, which could be potentially used as pH probes. Under ultraviolet light, these compounds show photochromism and 'turn-off' fluorescence properties either in solution or in PMMA film. The mechanism of this phenomenon may be due to photoisomerization, that is the conversion of the 4,5-diarylimidazole units open-ring form to the closed-ring form. Moreover, such systems as logic gates, high density (3D) data storage systems and optical equivalents of field-effect transistors are considered necessary for optical computing.

A novel colorimetric and "turn-off" fluorescent probe based on catalyzed hydrolysis reaction for detection of Cu2+ in real water and in living cells

A novel and highly selective fluorescent 1,8-naphthalimide-based probe, 3, was designed and synthesized for rapid Cu²⁺ detection in a CH₃CN-H₂O (3:1, v/v, pH = 7.4) solution by means of a distinct hydrolysis mechanism via its Cu²⁺-promoting feature. Upon treatment with Cu²⁺, the fluorescence response of probe 3 at 550 nm abruptly decreased, which was visible to the naked eye, and this response was accompanied by a clear change of the color of the solution; the color changed from the original yellow color to colorless. This color change occurred due to the Cu²⁺-promoted hydrolysis of 3, which yielded a fluorescence-quenched product. It is inspiring that probe 3 exhibited excellent sensitivity, a short response time and strong anti-interference recognition. Compared with the allowable amount of Cu²⁺ (∼20 μM) in drinking water, the detection limit of 3 for Cu²⁺ is calculated to be 9.15 nM, which is much lower than the amount defined by standards. The probe can be successfully applied for the determination of Cu²⁺ in real aqueous samples. Furthermore, probe 3 can be used as a fluorescent sensor to detect Cu²⁺ in biological environments, demonstrating its low toxicity to organisms and good cell permeability in live cell imaging.