Citric acid coated K2GdF7:Ce/Tb nanocrystals for broad and reversible photoluminescence pH sensing

Abstract

An pH-sensitive citric acid coated Ce/Tb:KGd 2 F 7 nanocrystals with a broad detection range from 3 to 10 is established. Under the 254 nm excitation, the Tb 3+ emission intensity originated from Ce 3+ → Gd 3+ →Tb 3+ decreases gradually with the increase of pH, while its intensity almost keeps unchanged in pH 3 to 6 and increases in pH 6 to 10 under the 311 nm excitation, which activates the ratiometric pH sensing with high sensitivity. An pH-sensitive citric acid coated Ce/Tb:KGd 2 F 7 NCs with a broad detection range from 3 to 10 is established. Under 254 nm excitation, the Tb 3+ emission intensity decreases gradually with the increase of pH, while its intensity almost keeps unchanged below 6 and increased in pH 6 to 10 under 311 nm excitation. • Citric acid coated Ce/Tb:KGd 2 F 7 NCs were prepared via a one-pot hydrothermal strategy. • Under the 254 nm excitation, the PL intensity decreases gradually with the increase of pH. • The intensity almost kept unchanged in pH 3 to 6 and increased in pH 6 to 10 under the 311 nm excitation. • A ratiometric pH sensing route with high sensitivity was obtained.