Highly Exfoliated Boron Nitride Nanosheets via Carboxyl Nanocellulose for Thermally Conductive Nanocomposite Films

The continuous development of electronic devices toward high-power and integrated directions has led to an increasing demand for renewable polymer composite materials with high thermal conductivity and electrical insulation to solve the problem of overheating in electronic devices. Cellulose is inherently insulating, with insufficient thermal conductivity. Although boron nitride nanosheets (BNNSs) have excellent thermal conductivity, hexagonal boron nitride (h-BN) ligands in their raw state are prone to aggregation, which limits their performance. In this work, h-BN was first ball-milled and amino-modified, and then, carboxylated nanofibrillated cellulose (COOH-CNF) was used to disperse the BNNSs. With the help of amide bonding, the BNNSs were uniformly dispersed in the nanocellulose (CNF) matrix; this reduced the aggregation and the presence of voids between the BNNSs and promoted the construction of effective thermal channels. The resulting composite slurry was stably dispersed and could be filtered to form a film; the best overall performance was achieved for a BNNS loading of 30% with a thermal conductivity (TC) of 9.00 W·m–1·K–1 (pure CNF 1.88 W·m–1·K–1). In addition, the volume resistivity reached 9.38 × 1013 Ω·cm (pure CNF of 2.53 × 1013 Ω·cm) and the electrical strength reached 22.67 kV·mm (17.04 kV·mm for CNF). Our results showed that the BNNS-CNF composite film had high TC and excellent insulating properties; therefore, its application in the thermal management of electronic devices has broad application prospects

Highly Selective Fluorescent Probe Based on Hydroxylation of Phenylboronic Acid Pinacol Ester for Detection of Tyrosinase in Cells

The detection of tyrosinase, a biomarker for melanoma, is of great significance. Herein, a fluorescent tyrosinase probe, with resorufin as the fluorophore and <i>m</i>-tolylboronic acid pinacol ester as the receptor, is proposed. The response relies on the tyrosinase-catalyzed hydroxylation of phenylboronic acid pinacol ester at an adjacent position followed by 1,6-rearrangement elimination to release resorufin. This probe well quantifies tyrosinase in the range from 1 to 100 U mL^–1 with a detection limit of 0.5 U mL^–1. Importantly, the probe exhibits high selectivity for tyrosinase over other biological substances including reactive oxygen species. In addition, it is successfully applied to the imaging of tyrosinase in cells. This probe provides a novel platform for selective detection of tyrosinase in biosystems

Discrimination of Cell Death Types with an Activatable Fluorescent Probe through Visualizing the Lysosome Morphology

Cell death plays a vital role in body development, maintenance of tissue function, and homeostasis. Accurate evaluation of cell death types is of great importance for pharmacological and pathological research. However, there is a lack of efficient fluorescent probes to discriminate various cell states. Here, we design and synthesize a novel activatable fluorescent probe PNE-Lyso to detect intracellular pH and hexosaminidases with two kinds of fluorescence signals. PNE-Lyso could distinguish dead cells from healthy cells based on a dual-color mode by targeting the lysosome and evaluating lysosomal hexosaminidase activity. Significantly, PNE-Lyso could also discriminate apoptotic and necrotic cells through visualizing lysosome morphology that is adjusted by the integrity of the lysosome membrane. Moreover, probe PNE-Lyso was successfully applied to investigate the drug-induced cell death process. To the best of our knowledge, this work is the first time cell death types have been distinguished based on a single fluorescent probe

Near-Infrared and Naked-Eye Fluorescence Probe for Direct and Highly Selective Detection of Cysteine and Its Application in Living Cells

The near-infrared (NIR) fluorescence sensor for rapid, selective, and sensitive detection of cystenine (Cys) is of great importance in both biological and environmental sciences. Herein, we report a specific probe with turn-on fluorescence property, visible color change with naked-eye, and large wavelength shift on UV spectra for highly selective detection of Cys over homocysteine (Hcy) and glutathione (GSH) in both HEPES buffer (10 mM, pH 7.4) and diluted human serum. The probe based on the conjugate addition–cyclization reaction has a low limit of detection to Cys (0.16 μM as NIR fluorescence sensor and 0.13 μM as UV sensor). Kinetic study indicated that the probe has a very rapid response to Cys, owing to the much higher pseudo-first-order reaction constant with Cys (299 M^–1 s^–1) than with Hcy (1.29 M^–1 s^–1) or GSH (0.53 M^–1 s^–1). Upon addition of Cys to a solution of the probe, the color changed from purple to cyan, with the maximum wavelength shifting from 582 to 674 nm in the UV spectrum and a fluorescence emission at 697 nm appearing. It has been successfully applied for determination of Cys in diluted serum and bioimaging of Cys in living cells with low cell toxicity

Delivery of nanosecond laser pulses by multimode anti-resonant hollow core fiber at 1 um wavelength

In this paper we explore the application of low-loss multimode anti-resonant hollow-core fiber (MM-AR-HCF) in the delivery of nanosecond laser pulses at 1 um wavelength. MM-AR-HCF of large core offers a rich content of low-loss higher-order modes which plays a key role in the efficient coupling and transmission of high-power laser of degraded beam quality. In the experiment, laser pulses of an average pulse energy of 21.8 mJ with 14.6 ns pulse width (corresponding a peak power of 1.49 MW) are transmitted through MM-AR-HCF of 9.8 m length without damaging. Up to 94 % coupling efficiency is achieved where the incident laser beam suffers a degraded beam quality with and of 2.18 and 1.99 respectively. Laser-induced damage threshold (LIDT) of MM-AR-HCF measures 22.6 mJ for 94 % coupling efficiency, which is 7 times higher than that for multimode silica optical fiber with a core diameter of 200 um