Bright Solid-state Fluorescence Research Articles

An ultrasensitive fluorescent breath ammonia sensor for noninvasive diagnosis of chronic kidney disease and helicobacter pylori infection

Breath ammonia detection has been a significant non-invasive approach for disease diagnosis. However, the reported methods for breath ammonia detection suffer from high cost, time-consuming, complex operation, or low selectivity. Fluorescence analysis as an alternative method has not been introduced in the detection of breath ammonia due to its insufficient sensitivity. In this work, a rationally designed strategy is proposed to improve the sensitivity of fluorescence sensors by increasing the amount of recognition site and enhancing the brightness of the solid-state fluorescence in sensor molecule. Briefly, three curcumin (CUR) derivatives BFCUR, MBFCUR and MBFCURM with D-π-A-π-D conjugated system were synthesized. Compared with the other two control molecules MBFCUR and MBFCURM, whose phenol groups at one or both ends of BFCUR were protected by a methyl group, BFCUR has two response sites, thus, two intramolecular charge transfer (ICT) interactions occurred after exposure to ammonia, suggesting the improved sensitivity. Moreover, the large steric hindrance of boron trifluoride in BFCUR can prevent the π-π stacking of molecules and endow BFCUR with bright solid-state fluorescence. BFCUR was subsequently loaded into electrospun nanofibers (ENFs) with high specific surface area, which further improved the detection sensitivity. The obtained BFCUR-loaded ENFs sensor (denoted as BFCUR-ENF) exhibited ultra-low LOD of 22 ppb for ammonia. BFCUR-ENF is successfully applied to breath ammonia detection in healthy volunteers, patients with chronic kidney disease (CKD) and Helicobacter pylori (H. pylori) infection, demonstrating its great application potentials. Taken together, the first fluorescent sensor for breath ammonia detection was successfully constructed for noninvasive diagnosis of CKD and H. pylori.

Enhanced Fluorescence and Environmental Stability of Red-Emissive Carbon Dots via Chemical Bonding with Cellulose Films.

The development of red emission carbon dots with bright solid-state fluorescence would significantly broaden their application in optoelectronic devices and sensors. Herein, a red-emissive carbon dot-based nanocomposite has been synthesized through chemical bonding with cellulose films. The red emission originating from the surface states of carbon dots was maintained in the cellulose films. Due to the stable chemical bonding, the photoluminescence intensity and emission wavelength remained unchanged for 12 months, and the quantum yield of the composite was enhanced over 4 times. It also showed outstanding stability in water or weak acid–base environments under pHs ranging from 2 to 11. Therefore, the mechanism of chemical bonding that eliminated the defects and preserved the efficient radiative process through surface states was proposed.

Novel yellow solid-state fluorescent-emitting carbon dots with high quantum yield for white light-emitting diodes

Fluorescence quenching of carbon dots (CDs) occurs in their aggregated state ascribed to direct π–π interactions or excessive resonance energy transfer (RET). Thus, CDs have been severely restricted for applications requiring phosphors that emit in the solid state, such as the fabrication of white light-emitting diodes (WLEDs). In this report, novel CDs with bright solid-state fluorescence (SSF) were synthesized by simple microwave-assisted synthesis method, using 1,4,7,10-tetraazacyclododecane (cyclen) and citric acid as precursors. Under 365 nm UV light, these CDs emit bright yellow SSF, indicating they successfully overcome the aggregation-induced fluorescence quenching (ACQ) effect. When the excitation wavelength (λex) is fixed at 450 nm, the emission peak of the CDs is centered at 546 nm with the Commission Internationale de l’Eclairage chromaticity (CIE) coordinates of (0.43, 0.55), which means that they can be combined with a blue-emitting chip in order to fabricate WLEDs. More importantly, the absolute quantum yield (QY) of these CDs powder reached 48% at λex of 450 nm, which was much higher than many previously reported SSF-emitting CDs and indicating their high light conversion ability in solid-state. Thanks to the excellent optical property of these CDs powder, they were successfully used in the preparation of high-performance WLEDs. This study not only enriches SSF-emitting CD-based nanomaterials with good prospects for application, but also provides valuable reference for subsequent research on the synthesis of solid-state fluorescent CDs.