Designing Semicarbazide-Based Fluorescent Probe for Versatile Detection of Cu2+ and Formaldehyde

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A research team has designed and synthesized two fluorescent sensors, CAA and CAB, for fluorescence detection of copper ion (Cu2+) and formaldehyde.

A recent study published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy demonstrates how one fluorescent sensor, CAA, responded to Cu2+ by triggeringintramolecular charge transfer (ICT) through Cu2+-catalyzed hydrolysis (1). The study also revealed how CAA can also detect formaldehyde (FA) through photo-induced electron transfer (PET) inhibition (1).

Researchers also examined another fluorescent sensor, CAB, and it exhibited different responses. CAB had little change in photophysical properties in the presence of formaldehyde, while exhibiting a three-stage fluorescence response (fast quenching, steady increase, and slow decrease) upon the addition of Cu2+ (1).

Detecting copper ions (Cu2+) and formaldehyde is important for several key reasons. First, copper ions play essential roles in biological systems and monitoring their concentration helps understand their involvement in cellular processes and identify potential imbalances related to diseases (1). Formaldehyde is a toxic compound found in various settings. It requires accurate detection for occupational safety, environmental monitoring, and mitigating health risks (1). Reliable detection methods aid in early identification of formaldehyde exposure and facilitate advancements in analytical chemistry, environmental science, and biomedical research.

The fluorescence properties of CAA showed a fluorescence turn-on response to Cu2+, resulting from the initiation of the intramolecular charge transfer process induced by Cu2+-catalyzed hydrolysis (1). The selectivity of CAA made it a promising candidate for quantifying Cu2+ and formaldehyde, as well as for bioimaging Cu2+ in living cells (1). The fluorescence intensity exhibited a linear relationship with the analyte concentration in the range of 0.1–30 μM for Cu2+ and 1.0–50 μM for FA, with calculated detection limits (LOD) of 0.43 μM and 1.92 μM (3δ/k), respectively (1).


Developing these semicarbazide-based fluorescent probes demonstrates their potential for versatile detection of Cu2+ and formaldehyde in different detection channels (1). The distinct responses of CAA and CAB provide researchers with options for specific detection requirements, whether it is the turn-on response to Cu2+ or the ability to inhibit the photo-induced electron transfer mechanism in the presence of formaldehyde (1). These findings contribute to the advancement of sensing technologies and offer new avenues for the detection and quantification of these analytes in various fields, including environmental monitoring and biological research (1).

The published study presented a promising approach for the development of efficient fluorescent probes. It represents a progression in the study of enhanced detection methods and applications in various scientific and technological domains.


(1) He, Y.; Wang, H.; Fang, X.; Zhang, W. Zhang, J.; Qian, J. Semicarbazide-based fluorescent probe for detection of Cu2+ and formaldehyde in different channels. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2023, 299, 122818. DOI: 10.1016/j.saa.2023.122818