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Hydrogen sulfide (H 2 S), as a hazardous gas, is often found around dump areas. Long term exposure can cause harm to health, it is highly necessary to develop some simple and sensitive methods for on-site H 2 S detection. Herein, a convenient photothermal assay has been designed for the quantitation of H 2 S using a handheld thermometer as readout. Au@Ag nanocubes (Au@Ag NCs), a core-shell nanocomposite with strong light absorption at ∼450 nm, was chosen as a novel photothermal agent in this study. Under the laser irradiation at 450 nm, the Au@Ag NCs show a strong photothermal effect, and a significant temperature enhancement can be measured by the thermometer easily. The presence of H 2 S can lead to the deposition of sulfur onto Au@Ag NCs, altering the localized surface plasmon resonance absorption, size, surface composition, and morphology of Au@Ag NCs and hence leading to the reduction of photothermal effect. The change of the temperature has a linear relationship with the H 2 S concentration in the range of 0.5–80.0 μM with a detection limit of 0.35 μM. By combining with simple sample purification procedures, the developed method has been applied to detect H 2 S in garbage odor gas with satisfactory results. Image 1 • A simple and sensitive photothermal assay is developed for quantitative detection of H 2 S. • The photothermal conversion properties of Au@Ag nanocube can be changed by the addition of H 2 S. • The molecular detection can be translated into a simple temperature test. • This method can be applied to detect H 2 S around dumps with a simple sample pretreatment. [ABSTRACT FROM AUTHOR]

To meet the increasing need for point-of-care testing (POCT), simple and portable readout strategies would be highly desirable. Thermometer with high accuracy and straightforward readout is an ideal tool for the development of new POCT methods. The exploration of new thermometer-based detection methods is of great significance. In this study, a simple biosensor for glucose based on the photothermal effect of gold nanorods using a simple thermometer as readout has been developed. In the presence of glucose oxidase, glucose can react with the dissolved oxygen to produce H 2 O 2. With the help of Fe2+, H 2 O 2 can etch gold nanorods (AuNRs) to different aspect ratios. The decrease of the aspect ratio of AuNRs leads to the blue-shift of the localized surface plasmon resonance peak, resulting in a decrease of photothermal effect in the near-infrared regions and the temperature of the system decreased. The change of the temperature has a linear relationship with the logarithm of glucose concentration in the range of 1.0–10.0 mM with a detection limit of 0.8 mM. The proposed method possesses a bias offset of −0.03 mM for glucose detection compared to the hospital method. Since many enzymatic reactions can produce H 2 O 2 , the principle can be modified to detect different targets by simply change of the enzyme used. A photothermal biosensor for glucose based on the different photothermal effect of different aspect ratio of gold nanorods has been developed. [Display omitted] • Etching of gold nanorods effectively decrease their photothermal effect. • Molecular detection was translated into a simple temperature test. • This mechanism can be adjusted to detect other targets by changing the enzyme. [ABSTRACT FROM AUTHOR]