Thermal contact-induced patterning of multicolor carbonized polymer dots for chemical sensing and anti-counterfeiting applications

Fluorescent patterns of carbonized polymer dots (CPDs), an emerging subclass of carbon-based quantum dots, possess multifunctional properties attractive for solid-state applications, such as anti-counterfeiting labels and chemical sensing devices. However, the time-consuming and multistep procedures from colloidal synthesis to patterning hinder their broader utilization, highlighting the need for a direct and versatile fabrication technology. Herein, we report a thermal contact-induced patterning strategy for the ultra-rapid simultaneous in situ synthesis and patterning of multicolor CPDs on solid substrates within 60 s. Heat is delivered through direct contact between a heated metal stamp and precursor-substrate composites, triggering localized thermal reactions that convert various organic precursors into photoluminescent carbon-based nanomaterials. Mechanistic studies reveal that the high thermal conductivity of metal stamps enhances interfacial heat transfer, thereby efficiently inducing CPD generation at contact regions. This method enables the fabrication of not only multicolor CPDs but also silicon-carbon dots from diverse precursors on various solid supports, including cellulose paper and glass fiber substrates. With broad compatibility, this strategy allows for the flexible patterning of CPDs with robustness suitable for security encoding. Building on this straightforward route, paper-based analytical devices featuring tailored fluorescence intensity- and distance-based optical readouts are further demonstrated for diverse sensing applications, including metal ion detection, pH sensing, and buffer capacity analysis. By bridging synthesis and patterning into a single step, this universal and scalable fabrication strategy opens new avenues for rapid advances in security and chemical sensing technologies.