Due to the significant healthcare burden associated with foodborne illness, developing platforms suitable for the on-site detection of food pathogens is of critical importance to public health. Low-cost, equipment-free approaches are desired to allow for point-of-use contamination monitoring along the food supply chain. Here, we demonstrate the compatibility of an Escherichia coli responsive colorimetric DNAzyme-crosslinked hydrogel sensor with a wide range of food products. Sensor functionality involves an E. coli detecting DNAzyme-substrate complex that cleaves the hydrogel crosslinking in the presence of the target bacteria, resulting in a release of gold nanoparticles that is visible to the naked eye. Naked-eye detection of E. coli at concentrations of 105 CFU mL-1 has been shown in milk as well as samples extracted from produce, leafy greens, and ready-to-eat foods such as rotisserie chickens. The functionality, simplicity, and versatility of this sensing platform may improve the feasibility of frequent pathogen monitoring in the food production pipeline, with the potential to mitigate future outbreaks of foodborne illness.

Herein, a colorimetric and smartphone dual-channel sensor has been constructed for the sensitive detection of acetone based on a chemically driven redox-cycling reactive system. In the redox-cycling system, o-phenylenediamine (OPD) acted as the colorimetric substrate. Initially, colorless OPD was oxidized by Cu2+ ions to generate Cu+ ions and light yellow 2,3-diaminophenazine (DAP). The Fenton-like reaction between hydrogen peroxide (H2O2) and generated Cu+ ions initiated the production of Cu2+ ions and hydroxyl radicals (·OH). The resulting ·OH and reproduced Cu2+ ions could further catalyze other OPD molecules, leading to the formation of more light yellow DAP molecules, with a distinct ultraviolet absorption peak appearing at 440nm. And this process continued until all OPD was completely consumed in the cycling reaction system. Interestingly, acetone was introduced into the redox-cycling system, leading to a colorless solution and a reduction of absorbance intensity at 440nm. Based on this phenomenon, a colorimetric sensor with excellent sensitivity and selectivity has been designed for the visual detection of acetone. The sensor exhibited a linear correlation with acetone concentrations within the range of 2μM to 5mM, achieving a detection limit of 0.5μM. Notably, RGB color space analysis was performed for the quantitative detection of acetone with the assistance of a smartphone. The results were in good agreement with the data obtained via UV-visible absorption spectroscopy. Furthermore, the strategy realized therapid detection of acetone in real tap water, river water, and lake water samples.

Silver nanoparticles and Cu (II) as a colorimetric sensor for detection of cefazolin in food and biological samples.

Dual-function Ag2O/Zn-hemin MOF composites for radioactive iodide: performance and mechanism studies for removal and efficient visual detection.

Colorimetric wood-based CO2 sensor with dendrite structures via synergistic delignification-quaternization for monitoring fresh-cut mango freshness

Colorimetric and Fluorometric Sensors for Oxalate: A Comprehensive Review of Chromogenic Materials and Mechanisms

AuNP-based colorimetric and fluorometric sensors for detection of pathogenic bacteria: A review (2015–2025)

ZnO nanoparticle-based colorimetric and optical sensor for detection of trivalent chromium: A practical approach for environmental monitoring

Reactive colorimetric and turn-on fluorometric sensors for Al3+ and Fe3+: Structure dependent selective sensing of Al3+ ions

Symmetric azobenzene-substituted diketopyrrolopyrroles dyes as acid-base switchable molecular-probe for colorimetric paper-based sensors

Microplasma synthesis of magnetic carbon hybrids as new colorimetric sensor probes for detecting and quantifying of phenolic compounds.

In recent years, a significant focus has been directed toward fluorogenic chemosensors for the optical detection of heavy metal ions due to their detrimental effects on both the environment and human health. Methods combining fluorometry and colorimetry have been widely utilized for sensing heavy metal ions because they are straightforward, lucrative, easy to use, and enable rapid on-site analysis. As a result, numerous research groups have dedicated extensive efforts to developing versatile fluorometric and colorimetric sensors for heavy metals. The development of innovative, highly selective, and sensitive chromogenic fluorosensors, along with their detection capabilities, remains a captivating area within supramolecular chemistry. This review outlines key aspects of the detection process, including spectroscopic changes, selectivity, sensitivity, visible colour shifts, and potential in vivo recognition of heavy metal ions. It also emphasizes recent progress over the past decade in the fluorometric and colorimetric detection of heavy metal cations, such as Hg²⁷, Cd²⁷, As3+/As5+, and Pb2+, using chromogenic and fluorogenic chemical receptors.

Programmable printing of a colorimetric sensor array mimicking human olfactory system for real-time detection of meat freshness

PVP functionalized NH2-Ti-MOF fluorescence and colorimetric sensor for catechol.

Dual-signal fluorescence and colorimetric sensor based on N,P co-doped carbon dots for selective detection of doxycycline.

Ultra-low-cost paper-based colorimetric sensor for selective naked-eye detection of cobalt(II) ions

Bacteria identification using colorimetric sensor array for volatile organic compounds (VOC) in wound models

Iron single-atom nanozyme with dual enzyme-like activities for detection of environmental pollutants and colorimetric sensing array to identification of phenolic species.

Ultrasensitive bacterial detection using colorimetric detector of DNA nanosheets with enzyme activity.

Rapid on-site detection of chromium contamination in foods using a naked-eye DMSA-AuNPs colorimetric sensor