Uranyl ion (UO 2 2+) pollution is a serious environmental problem, and developing novel adsorption materials is essential for UO 2 2+ monitoring and removal. Although some progress is achieved, it is still a challenging task to develop an adsorption material with indicating signal for real-time evaluation of the adsorption degree and the UO 2 2+ concentration. Herein, this paper describes a smart photonic crystal hydrogel (PCH) material, which not only can be used for real-time monitoring function but also can be utilized for UO 2 2+ removal based on the chelation of UO 2 2+ with ligand groups in PCH material. The working principle is based on the binding of a uranyl ion to multiple ligand groups, which results in the shrinkage of PCH material and triggers a blue-shift of diffraction wavelength. Consequently, the adsorption degree and the UO 2 2+ concentration can be sensitively evaluated by measuring the diffraction shift or observing the color change with naked eye. With this PCH material, the lowest detectable concentration for UO 2 2+ is 10 × 10 −9 m, and the maximum adsorption capacity at 298 K is 169.67 mmol kg −1 . In addition, this material also holds good selectivity and regeneration feature, and shows desirable performance for UO 2 2+ analysis in real water samples.

A novel aptasensor platform has been developed for quantitative detection of adenosine triphosphate (ATP) based on a ratiometric surface-enhanced Raman scattering (SERS) strategy. The thiolated 3'-Rox-labeled complementary DNA (cDNA) is first immobilized on the gold nanoparticle (AuNP) surface and then hybridizes with the 3'-Cy5-labeled ATP-binding aptamer probe (Cy5-aptamer) to form a rigid double-stranded DNA (dsDNA), in which the Cy5 and Rox Raman labels are used to produce the ratiometric Raman signals. In the presence of ATP, the Cy5-aptamer is triggered the switching of aptamer to form the aptamer-ATP complex, leading to the dissociation of dsDNA, and the cDNA is then formed a hairpin structure. As a result, the Rox labels are close to the AuNP surface while the Cy5 labels are away from. Therefore, the intensity of SERS signal from Rox labels increases while that from Cy5 labels decreases. The results show that the ratio between the Raman intensities of Rox labels and Cy5 labels is well linear with the ATP concentrations in the range from 0.1 to 100 nM, and the limit of detection reaches 20 pM, which is much lower than that of other methods for ATP detection and is also lower than that of SERS aptasensor for ATP detection. The proposed strategy provides a new reliable platform for the construction of SERS biosensing methods and has great potential to be a general method for other aptamer systems.

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The stimuli-responsive DNA hydrogel has attracted wide attention in the fields of chemical and biological sensing. However, it is still a challenge to integrate characteristics with low-cost, high mechanical strength, and signal self-expression into a DNA hydrogel simultaneously. Herein, a stimuli-responsive 2D photonic crystal double network DNA hydrogel (2D PhC DN-DNA hydrogel) sensing platform is developed via combining the signal self-expression of 2D PhC array with the selective recognition of polyacrylamide (PAM)/DNA DN hydrogel. The change of DNA configuration induced by specific target triggers the change of 2D PhC DN-DNA hydrogel volume, leading to a shift of the Debye diffraction ring diameter. In order to verify the feasibility of this strategy, the 2D PhC DN-DNA hydrogel with C-rich sequences is chosen as a proof-of-concept. The results indicate that the hydrogel has good detection performance for pH and Ag+/Cys. And the Debye diffraction ring diameter of the hydrogel is correlated with the concentration of the Ag+/Cys in the range of 0.5–20 μM. Compared with previously pure DNA hydrogel sensing platform, the 2D PhC DN-DNA hydrogel features low-cost preparation process and label-free determination. Meanwhile, only a laser pointer and a ruler are needed for the determination of targets, which shows that the hydrogel has application prospect in the development of portable response equipment.