Solvothermal aldol condensation of primary alcohols for the controlled formation of carbonized polymer dots with tunable optical properties and selective sensing

Abstract

Fluorescent carbonized polymer dots (CPDs) were produced in a single solvothermal step by oxidizing primary alcohols (C₃–C₁₀ rather than C₁–C₂) with H₂O₂ in the presence of catalytic H₂SO₄ at 200 °C. Spectroscopic and control experiments show that H₂O₂ first oxidizes the alcohol to the corresponding aldehyde, which undergoes acid-catalyzed aldol condensation/dehydration to build sp² conjugated polymer frameworks that nucleate and grow into ∼100 nm nanoparticles. The emissive CPDs disperse readily in solution, maintain stable excitation dependent photoluminescence from pH 1 to 14, and can be tuned in terms of yield and absorbance/emission intensity by varying the oxidant/acid ratio or alcohol chain length. Functionally, CPDs exhibit pronounced, selective fluorescence quenching by Fe³⁺ and p-nitrophenol, with respective detection limits of 83 nM and 21 nM, affording selective detection with high sensitivity for them. These attributes transform low toxicity alcohol feedstocks into robust nanoprobes for environmental monitoring and pollutant analysis, underscoring the sustainability and versatility of this aldehydation–aldol–carbonization strategy.