Superhydrophobic Silica Aerogels Encapsulated Fluorescent Perovskite Quantum Dots for Reversible Sensing of SO₂ in a 3D-Printed Gas Cell

Recently emerging perovskite quantum dots (PQDs) with several excellent optical properties, such as quantum efficiency, narrow band emission, and tunable emission wavelength, have promising applications in solar cells and light emitting diodes. However, relatively rare applications of PQDs can be found in the field of sensing, mainly due to the very easy degradation of PQDs upon exposure to water or ambient humidity. In this work, for the first time CH3NH3PbBr3 PQDs were encapsulated into superhydrophobic silica aerogels (AGs) to protect PQDs from being degraded by water. The synthesized PQDs@AGs not only maintain the strong fluorescence emission activity of PQDs but also show excellent stability in the presence of water. Additionally, PQDs@AGs have abundant pores making them very suitable for gas sensing. For improving sensing performances, 3D-printing technology is introduced into gas cell design and fabrication for the first time. Finally, a novel, sensitive, selective, and reversible fluorescence sensor for SO2 gas based on the PQDs@AGs functional material and the 3D-printed gas cell has been developed

Alcohol-Stable Perovskite Nanocrystals and Their In Situ Capsulation with Polystyrene

In recent years, lead halide perovskite nanocrystals (PNCs) have presented potential scalable applications in all fields due to their outstanding properties. However, most commonly used PNCs capped with oleic acid (OA) and oleylamine (OAm) suffer from bad stability in polar solutions and thus require various surface protections with organic or inorganic materials. Encapsulation with highly hydrophobic polystyrene (PS) is one of the most efficient ways to protect PNCs; however, the presently used swelling–shrinking strategy faces several challenges, such as weak interaction between PS chains and the surface ligands in nonpolar media causing a low encapsulation efficiency, and serious aggregation of PS particles during the shrinkage process leading to very different particle sizes. Herein, alcohol-stable polyacrylic acid-capped CsPbBr3 PNCs (i.e., PAA-PNCs) are first synthesized and then in situ encapsulated with PS shells by polymerizing styrene monomer on the PNC surfaces in a polar organic solvent (e.g., ethanol). The in situ PS-encapsulated PAA-PNCs (i.e., PAA-PNCs@iPS) exhibit outstanding monodispersity, remarkable water, heat, and UV stability, high fluorescence activity, and color purity. The unique synthesis strategy and good performances of PAA-PNCs@iPS will boost the applications of PNCs in LEDs, biological imaging, and chemosensing

Anodic, Cathodic, and Annihilation Electrochemiluminescence Emissions from Hydrophilic Conjugated Polymer Dots in Aqueous Medium

Hydrophilic poly­[2-methoxy-5-(2-ethyl­hexyloxy)-1,4-phenylene­vinylene] (MEH-PPV) conjugated polymer dots (CP-dots) capped by Triton X-100 were synthesized. For the first time, the electrochemiluminescence (ECL) emission of CP-dots was investigated in aqueous solution. At the glassy carbon/water interface, the CP-dots have excellent and multichannel ECL properties, such as having annihilation ECL activity in the absence of coreactants, and give bright anodic and cathodic ECL emission (590 nm) in the presence of tri-<i>n</i>-propylamine (TPrA) and peroxydisulfate (S₂O₈^2–), respectively. The versatile ECL properties of the hydrophilic CP-dots combined with their low cytotoxicity, good biocompatibility, and easy bioconjugation may suggest promising applications of this new type of ECL nanomaterial in novel biosensing and bioimaging, and new types of light-emitting devices

Installing Logic Gates in Permeability Controllable Polyelectrolyte-Carbon Nitride Films for Detecting Proteases and Nucleases

Proteases and nucleases are enzymes heavily involved in many important biological processes, such as cancer initiation, progression, and metastasis; hence, they are indicative of potential diagnostic biomarkers. Here, we demonstrate a new label free and sensitive electrochemiluminescent (ECL) sensing strategy for protease and nuclease assays that utilize target-triggered desorption of programmable polyelectrolyte films assembled on graphite-like carbon nitride (g-C₃N₄) film to regulate the diffusion flux of a coreactant. Furthermore, we have built Boolean logic gates OR and AND into the polyelectrolyte films, capable of simultaneously sensing proteases and nucleases in a complicated system by breaking it into simple functions. The developed intelligent permeability controlled enzyme sensor may prove valuable in future medical diagnostics

Fast, Sensitive, and Selective Ion-Triggered Disassembly and Release Based on Tris(bipyridine)ruthenium(II)-Functionalized Metal–Organic Frameworks

Metal–organic frameworks (MOFs) are microporous materials assembled from metal ions and organic linkers. Recently, many studies have been focused on the syntheses of MOFs with permanent porosity for various applications. However, no attention has been paid to controllable disassembly of MOFs and related applications. In this work, for the first time we synthesized novel tris­(bipyridine)­ruthenium­(II)-functionalized MOFs (i.e., RuMOFs) that could be ion-responsively disassembled and release massive guest materials loaded in the frameworks. The synthesized RuMOFs exhibited much stability in aqueous solutions containing H⁺, and many metal ions, but could be selectively and sensitively disassembled by Hg²⁺ ions, resulting in the release of large quantities of Ru­(bpy)₃²⁺. The target-responsive release mechanism was investigated and discussed in detail. On the basis of the ion-responsive disassembly and release, an ultrasensitive electrochemiluminescence sensing method for Hg²⁺ has been developed with a very low limit of detection (5.3 × 10^–13 M). It was envisioned that the RuMOFs and similar target-responsive functional MOF materials would have promising applications in ultrasensitive and highly selective chemical sensing and even in accurately controllable drug delivering and releasing

Electrochemiluminescence of Water-Soluble Carbon Nanocrystals Released Electrochemically from Graphite

Electrochemiluminescence of Water-Soluble Carbon Nanocrystals Released Electrochemically from Graphit

Encapsulation of Strongly Fluorescent Carbon Quantum Dots in Metal–Organic Frameworks for Enhancing Chemical Sensing

Novel highly fluorescent (FL) metal–organic frameworks (MOFs) have been synthesized by encapsulating branched poly-(ethylenimine)-capped carbon quantum dots (BPEI-CQDs) with a high FL quantum yield into the zeolitic imidazolate framework materials (ZIF-8). The as-synthesized FL-functionalized MOFs not only maintain an excellent FL activity and sensing selectivity derived from BPEI-CQDs but also can strongly and selectively accumulate target analytes due to the adsorption property of MOFs. The selective accumulation effect of MOFs can greatly amplify the sensing signal and specificity of the nanosized FL probe. The obtained BPEI-CQDs/ZIF-8 composites have been used to develop an ultrasensitive and highly selective sensor for Cu²⁺ ion, with a wide response range (2–1000 nM) and a very low detection limit (80 pM), and have been successfully applied in the detection of Cu²⁺ ions in environmental water samples. It is envisioned that various MOFs incorporated with FL nanostructures with high FL quantum yields and excellent selectivity would be designed and synthesized in similar ways and could be applied in sensing target analytes

Electrochemiluminescence Imaging-Based High-Throughput Screening Platform for Electrocatalysts Used in Fuel Cells

High throughput screening is very important for accelerating the discovery of fuel cell catalysts. In this paper, a novel electrochemiluminescence (ECL, a technology changing electric current into light) imaging-based screening platform for electrocatalysts used in fuel cells has been developed. The ECL imaging-based screening platform consists of bipolar electrode array-bridged electrochemical (EC)/ECL twin cells, by which electrocatalytic reduction currents of O2 can be imaged directly by ECL. The ECL imaging-based screening platform is simple in instrumentation, can image the “current–voltage” dependence directly, reversibly, and sensitively, and may enable the activities of electrocatalysts to be evaluated in a high-throughput way. The developed ECL imaging-based screening platform is envisioned to have promising applications in high throughput combinatorial screening of electrocatalysts for fuel cells

Carbon Dioxide Gas Sensor Based on Ionic Liquid-Induced Electrochemiluminescence

Electrochemiluminescence of the luminol–O2 system in an electrolyte-free N,N-dimethylformamide (DMF)–dipropylamine (DPA) cosolution is induced by the formation of a carbamate ionic liquid (IL) from the reaction between CO2 and DPA, on the basis of which a facile ECL sensor for measuring atmospheric CO2 has been developed. This ECL sensing method shows several advantages in the detection of CO2, such as high safety, high selectivity, wide linear response range, and good sensitivity. The gas sensor was found to have a linear response range from 100 ppm to 100 v/v% and a detection limit of 80 ppm (at signal-to-noise ratio of 3). This is the first reported IL-induced ECL sensor for a gas, thus the principle of this type of sensor and the IL-induced ECL mechanism have been demonstrated in detail