Black phosphorus quantum dots are useful oxidase mimics for colorimetric determination of biothiols

Single-holed cobalt - nitrogen - carbon hollow structure with oxidase-mimicking activity for the chemiluminescence determination of β - galactosidase activity

A single-holed cobalt - nitrogen - carbon (Co - N - C) hollow structure nanozyme has been fabricated by in situ growth of zeolitic imidazolate framework (ZIF - 67) on the polystyrene (PS) sphere and following treatment by high-temperature carbonization. The Co - N - C nanostructure mimics the activity of oxidase and can activate O2 into reactive oxygen species (ROS), giving a remarkable enhancement on the chemiluminescence (CL) signal of luminol - O2 reaction. The Co - N - C oxidase mimic has further been exploited in the biosensing field by the determination of the activity of β - galactosidase (β - gal). The CL method for β - gal activity has a linear range of 0.5 mU·L-1 to 5.0 U·L-1, a detection limit of 0.167 mU·L-1, and the precision of 3.1% (5.0 U·L-1, n = 11). This method has been employed to assess inhibitor screening of β - gal and determine activity of β - gal in spiked human serum samples.

Phosphorene quantum dots: synthesis, properties and catalytic applications

Phosphorene quantum dots (PQDs) belong to a new class of zero-dimensional functional nanostructures with unique physicochemical and surface properties in comparison with few-layer phosphorene and other 2D analogues. Tunable band gap as a function of number of layers, ease of passivation and high carrier mobility of PQDs have attracted considerable attention in catalysis research due to which spectacular progress has been made in PQD research over the last few years. PQDs are now considered as promising catalytic materials for electrocatalytic water splitting and nitrogen reduction, lithium-sulfur batteries, solar light-driven energy devices and biocatalysis, either in pristine form or as an active component for constructing heterostructures with other 2D materials. In the light of these recent advances, it is worthwhile to review and consolidate PQD research in catalytic applications to understand the challenges ahead and suggest possible solutions. In this review, we systematically summarize various synthetic strategies including ultrasonic and electrochemical exfoliation, solvothermal treatment, blender breaking, milling, crushing and pulsed laser irradiation. Furthermore, the physiochemical properties of PQDs are discussed based on both experimental and theoretical perspectives. The potential applications of PQDs in catalysis with special emphasis on photocatalysis (solar light-driven energy devices) and electrocatalysis (oxygen evolution reactions and hydrogen evolution reactions) -are critically discussed along with the present status, challenges and future perspectives.

Light-accelerating oxidase-mimicking activity of black phosphorus quantum dots for colorimetric detection of acetylcholinesterase activity and inhibitor screening

A feasible and sensitive colorimetric platform was established for the assay of acetylcholinesterase (AChE) activity and evaluation of its inhibitor screening, based upon the light-accelerating oxidase-mimicking activity of black phosphorus quantum dots (BP QDs). The BP QDs were synthesized through a thermal exfoliation method and characterized using various techniques. The BP QDs exhibit oxidase-mimicking catalytic activity on dissolved oxygen-mediating oxidation of 3,3',5,5'-tetramethylbenzidine, a typical substrate of oxidase. This results in a transformation of 3,3',5,5'-tetramethylbenzidine into its blue oxidized product, which has a visible absorption peak at 652 nm. The exposure of 365 nm light irradiation significantly accelerates the oxidase-mimicking activity of the BP QDs and speeds up the reaction efficiency. AChE can specifically catalyze the decomposition of its substrate acetylthiocholine chloride to thiocholine. Thiocholine has reducing capacity and can thus reduce the oxidase-mimicking activity of the BP QDs. As a result, the oxidation of 3,3',5,5'-tetramethylbenzidine is hindered and the blue solution becomes paler. This gives a linear response for AChE ranging from 0.5 to 10.0 mU mL-1 and a detection limit of 0.17 mU mL-1. The assay was successfully applied to evaluate inhibitor screening with neostigmine as the model.

A novel luminol chemiluminescence system induced by black phosphorus quantum dots for cobalt (II) detection

Black phosphorus quantum dots (BP QDs) were prepared through a solvothermal exfoliation method in alkaline N-methyl-2-pyrrolidinone. The BP QDs induce distinct chemiluminescence (CL) of alkaline luminol directly. A possible reaction mechanism is proposed by the study of CL spectrum, ultraviolet-visible absorption spectra, electron paramagnetic resonance spectra as well as radical scavenging experiments. The presence of BP QDs significantly increases generation of active oxygen species, which oxidize luminol and lead to intense CL emission at 425 nm. The reaction of luminol with BP QDs are specifically catalyzed by cobalt (II) ion, this presents a sensitive CL method for cobalt (II) ion. A linear response range extends from 2.5 to 2000.0 pmol/L cobalt (II) ion and a detection limit of 0.7 pmol/L (3s_b) is acquired. The method displays a good precision approved by a relative standard deviation of 1.9% at 100.0 pmol/L cobalt (II) ion solution (n = 11). A preliminary application of the method was conducted by successful determination of cobalt amount in silica gel and rain water samples.