A pH switchable hydrophilic fluorescent BODIPY sodium disulfonate for Fe3+ multicolor detection: Experimental and DFT studies.

BODIPY-based chemosensors are widely used owing to merits like good selectivity, high fluorescence quantum yield, and excellent optical stability. As such, a pH-switchable hydrophilic fluorescent probe, BODIPY-PY-(SO3Na)2, was developed for detection of Fe3+ ion in aqueous solutions. BODIPY-PY-(SO3Na)2 revealed strong fluorescence intensity and was responsive to pH value in the range of 6.59-1.96. Additionally, BODIPY-PY-(SO3Na)2 showed good selectivity and sensitivity towards Fe3+. A good linear relationship for Fe3+ detection was obtained from 0.0 µM to 50.0 µM with low detecting limit of 6.34 nM at pH 6.59 and 2.36 nM at pH 4.32, respectively. The response to pH and detection of Fe3+ induced obvious multicolor changes. BODIPY-PY-(SO3Na)2 can also be utilized to quantitatively detect Fe3+ in real water sample. Different mechanisms of Fe3+ detection at investigated pH values were unraveled through relativistic density functional theory (DFT) calculations in BODIPY-PY-(SO3Na)2 and experiments of coexisting cations, anions and molecules. These results enabled us to gain a deeper understanding of the interactions between BODIPY-PY-(SO3Na)2 and Fe3+ and provide valuable fundamental information for design of efficient multicolor chemosensors for Fe3+ as well.

A colorimetric indicator-displacement assay based on stable Cu2+ selective carbon dots for fluorescence turn-on detection of pyrophosphate anions in urine.

Determination of PPi levels in urine represents a measurable factor for diagnostic, treatment, and monitoring of urolithiasis. Owing to the quenching ability of Cu2+ on fluorescent carbon dots (CDs) and strong binding affinity between Cu2+ and PPi, we develop a new off-on assay for PPi detection using newly BPHA CDs (BPHA: N,N-bis(pyridin-2-ylmethyl)hexan-1-amine). The fluorescence intensity of BPHA CDs was significantly quenched by Cu2+ ("off") through forming BPHA CDs/Cu2+ complexes and the fluorescence intensity of BPHA CDs /Cu2+ system was completely resumed by PPi ("on") owing to the release of free Cu2+. The fluorescence turn-off/on approach showed a highly selective response to PPi over the large family of other anions. The detection limits were 0.094 µM for Cu2+ and 0.025 µM for PPi, respectively. A wide linear range for PPi was up to 4400 µM. The indicator displacement assay (IDAs) using pyrocatechol violet (PV) as a colorimetric indicator was carried out to detect PPi with the naked eyes. The "off-on" fluorescent sensor based on BPHA CDs shows many merits, including convenient operation, cost-saving, high sensitivity, selectivity, stability and wide detecting range, which is applied to PPi detection in human urine sample.