Aggregation-induced Enhancement Effect Research Articles

Facile synthesis of fluorescent carboxymethyl cellulose polymer dots and multi-purpose applications in pH and glucose sensing

Herein, fluorescent carboxymethyl cellulose polymer dots (B-PDs) were synthesized by a straightforward route under mild conditions using ethylenediamine-modified carboxymethyl cellulose (CMC-NH2) and phenylboronic acid as precursors. The B-PDs exhibit a uniform nanoscale size distribution, good water solubility, photostability and excellent fluorescence emission with a high fluorescence quantum yield of 21.6 %. The B-PDs display a reversible fluorescence response with blue emission in acidic solution and green emission in alkaline solution. Moreover, the B-PDs can be designed as an excellent fluorescent sensor for glucose detection. After the addition of glucose, the FL intensity at λex = 388 nm can be enhanced due to the assembly of glucose on the B-PDs based on the reversible reaction between boronic acid and cis-diols through the aggregation-induced enhancement effect (AIE). Two good linear relationships can be obtained between (F-F0)/F0 and the glucose amount ranging from 0 ∼ 0.005 M (R2 = 0.9971) and 0.01 ∼ 1.2 M (R2 = 0.9984), and the detection limit (LOD) was calculated to be 52 μM (3σ/slope). Meanwhile, the proposed probe was successfully utilized to analyze glucose in human urine samples (recovery: 97.9–104.1 %, RSD: 2.64–4.23 %) by the standard addition method, indicating good feasibility as a practical platform for sensing.

Novel nitrogen-doped carbon dots for “turn-on” sensing of ATP based on aggregation induced emission enhancement effect

In this work, a nitrogen-doped carbon dots (CDs) was successfully synthesized by hydrothermal synthesis of polyethylenimine (PEI) and citric acid. The as-prepared CDs suffered from aggregation-caused quenching (ACQ) with a high concentration, but after adding adenosine triphosphate (ATP), the CDs aggregated. The generation of aggregates caused the rotation of the surface groups on CDs and reduced the non-radiation decay. The QY of CDs in water was 9.25 %, and increased to 16.60 % and 63.38% in the addition of 100 and 1000 μM ATP. And then, the enhancement of the radiation rate led to the aggregation induced enhancement effect (AIEE). Moreover, we also found that the proportion of precursors for CDs synthesis was a key factor in the occurrence of AIEE. Therefore, such CDs would be excellent candidates as fluorescent probes for the label-free detection of ATP. Our proposed method exhibited simple and easy preparation of nanoprobe, quick response (3 min), wide range of linear rage (1–2000 μM) and eco-friendly. In addition, the method performed successfully as a “turn-on” sensor for detection of ATP in the tablet with a recovery of 100.1~106.9% and RSD below 3.5%.

Microwave-assisted synthesis of carbon dots for "turn-on" fluorometric determination of Hg(II) via aggregation-induced emission.

A fluorescent probe is presented for sensitive determination of Hg(II). It is based on aggregation induced enhancement effect (AIEE) of carbon dots co-doped with nitrogen and sulfur (N,S-CDs). The N,S-CDs were prepared by a one-pot microwave-assisted method using glycerol as the reaction solvent, and cystine as the source for C, N and S. The resulting CDs are well soluble in water and have a turn-on fluorescence response to Hg(II). The incubation time and ratio of raw materials were optimized. Fluorescence, best measured at excitation/emission wavelengths of 325/385 nm, increases linearly in the 1-75 μM Hg(II) concentration range, and the detection limit is 0.5 μM. The method performed successfully when detecting Hg(II) in spiked tap and lake waters, with recoveries between 92 and 106%. Graphical abstract Schematic presentation of the aggregation induced enhancement of the fluorescence of carbon dots co-doped with nitrogen and sulfur after addition of Hg(II).