A Naked‐eye Colorimetric pH and Temperature Sensor Based on Gold Nanoparticle‐Loaded Stimuli‐Sensitive Dendrimers

Abstract Gold nanoparticles (AuNPs) show unique size‐ and shape‐dependent photosensitive properties resulting from localized surface plasmon resonance, which can be exploited in colorimetric sensors. Polyamidoamine (PAMAM) dendrimers are suitable nanotemplates of AuNPs and nanoplatforms of some stimuli‐responsive materials. In this study, AuNP was loaded in phenylalanine (Phe)‐modified PAMAM dendrimers with dual pH‐ and temperature‐sensitive properties to produce a naked‐eye colorimetric sensor with responsivity to both pH and temperature. The ultraviolet‐visible (UV‐Vis) spectra of AuNP‐loaded PAMAM‐Phe‐Suc were changed by heating at pH 4 and 5, but unchanged at pH above 5.5. The UV‐Vis spectra of AuNP‐loaded PAMAM‐Phe and PAMAM‐Suc were only slightly changed by heating at pH above 5.5 and at pH 4 and 5, respectively. In solution, AuNP‐loaded PAMAM‐Phe‐Suc changed color (from brown to gray) under high temperature (≥50 °C) and acidic (pH≤5) conditions, suggesting its functionality as a naked‐eye colorimetric dual pH and temperature sensor.