Self-reduction of gold@platinum bimetallic nanoparticles on Ti₃C₂T_<i>x</i> MXene nanoribbons coupled with hydrogel and smartphone technology for colorimetric detection of silver ions

In recent years, numerous colorimetric methods have been developed for the detection of silver ions (Ag⁺), yet there remains a need for a simple, sensitive, real-time and quantitative sensing platform. Herein, Ti₃C₂T_<i>x</i> MXene nanoribbons (Ti₃C₂T_<i>x</i>NRs) were utilized as the carrier material, and gold@platinum (Au@Pt) bimetallic nanoparticles were decorated onto the Ti₃C₂T_<i>x</i>NR surface, for the first time, <i>via</i> a facile self-reduction method. The resulting Au@Pt-Ti₃C₂T_<i>x</i>NR nanohybrid exhibited excellent catalytic activity, facilitating the oxidation of 3,3',5,5'-tetramethylbenzidine, a colorless substrate, to generate a blue product (oxTMB), displaying prominent peroxidase-like activity. In the presence of Ag⁺, a remarkable inhibiting effect was observed on the catalytic activity of the Au@Pt-Ti₃C₂T_<i>x</i>NR nanohybrids, effectively halting the generation of oxTMB. Based on this, the as-obtained Au@Pt-Ti₃C₂T_<i>x</i>NR nanozyme was then utilized to develop a novel colorimetric sensing platform for Ag⁺ detection, with a low detection limit of 1.57 nM and a wide linear detection range from 5.0 nM to 9.0 μM. In addition, by combining the unique advantages of hydrogel materials and smartphone technology, a simple, real-time and quantitative platform for Ag⁺ monitoring was constructed, highlighting its potential for practical applications in Ag⁺ detection.