Amorphous Copper-Based Nanoparticles with Clusterization-Triggered Phosphorescence for Ultrasensing 2,4,6-Trinitrotoluene

Carbonized polymer dots for discrimination of 2,4,6-trinitrotoluene and 2,4,6-trinitrophenol

It is of great significance for the discrimination of 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP) from their analogues. Here, based on the electron-deficient properties of TNT and TNP, a series of o-phenylenediamine/polyethyleneimine carbonized polymer dots (OPD/PEI CPDs) with different densities and types of amine groups (-NH2) on the surface were designed by modulating the ratio of the precursors OPD and PEI. The surface -NH2 group of OPD/PEI CPDs could form a Meisenheimer complex with TNT, triggering the Forster resonance energy transfer, while forming hydrogen bonds with hydroxyl in TNP, triggering the charge transfer and spectral overlap to produce photoinduced electron transfer accompanied with inner filter effect. When the ratio of OPD to PEI is 1:1 and the surface -NH2 content is 26.06 %, the OPD/PEI1 CPDs demonstrated a more superior sensing performance toward targets, including a low limit of detection (TNT: 324 nM and 255 µM, TNP: 21.08 nM and 318.6 nM), a rapid response (<1 s), and a rather good selectivity in the presence of 20 interferents. Moreover, the practicality of the OPD/PEI1 CPDs was further verified by an OPD/PEI1 CPDs-based paper sensor, which is capable of discriminating TNT and TNP particles and vapors as low as pg-level and ppm-level respectively.

Recognition Site Density Regulation of Schiff Base Organic Porous Polymers for Ultrasensitive and Specific Fluorescence Sensing toward Gaseous DCP

Due to the severe interference from analogues such as hydrochloric acid, it is of great significance to establish a highly reliable technique to enhance the discrimination ability toward diethyl chlorophosphate (DCP). Here, based on the electrophilicity of DCP, a series of zero-background fluorescence Schiff base materials with different densities of C═N bonds as recognition sites were designed and synthesized by modulating the chain length. It is found that the increase of the C═N bond density and the specific surface area could improve the collision efficiency with DCP, thereby improving the response speed. When the density of C═N bonds is 3.86 × 1021/cm3 and the specific surface area is 128.5 m2/g, DFDBA-POP demonstrated a more superior sensing performance toward the target analyte, including the ability to detect gaseous DCP, a rapid response (1 s), and superior selectivity even in the presence of 15 kinds of interferents including the very similar hydrochloric acid. Moreover, the practicality of DFDBA-POP was further verified by a DFDBA-POP solid-state sensor, which is capable of specifically identifying gaseous DCP. The present nonfluorescent Schiff base materials design and modulation strategy would open up a new gate for the rational design of high-performance fluorescent materials to detect and discriminate trace hazardous substances with similar structures and properties.

Electronic Effect-Tuned Cooperativity of Multiple Noncovalent Interactions for Specific Detection of ADB-Type Synthetic Cannabinoids

ADB-type synthetic cannabinoids (SCs), as a major category of new psychoactive substances, have posed global concerns due to their high abuse potential and detrimental health and social stability effects, and their rapid and accurate in situ analysis is particularly challenging when they appear in concealed forms. Here, the strategy of electronic effect tuning cooperativity of multiple noncovalent interactions was proposed for the specific detection of ADB-type SCs, a class of structurally stable yet reactive inert analytes. The optimized probe HBO-Ph, for the first time, achieved ratiometric fluorescence detection of ADB-type SCs by effectively suppressing excited-state intramolecular proton transfer and promoting intramolecular charge transfer, showcasing unparalleled detection capabilities with a low detection limit of 24.3 nM and a rapid response in 1 s. Moreover, a sensor featuring a solid-liquid separation architecture was designed to enable the rapid detection of ADB-type SCs in real-world situations, unaffected by 24 possible interfering substances. This cooperative regulation method is expected to shed light on the exploration of noncovalent interaction-based probe design strategies and provide a new approach to analyzing target molecules with limited active sites, thereby greatly promoting the present drug detection technologies.

Triggering anti-Kasha organic room temperature phosphorescence of clusteroluminescent materials

Clusterization-triggered emission (CTE) from organic materials without π-conjugated structures for room temperature phosphorescence (RTP) is fascinating with extraordinary photophysical properties and diversified applications, but rather challenging in material design owing to the limited mechanism understanding. Here, we demonstrate a facile strategy to construct CTE polymers with stimuli-responsive emission, anti-Kasha RTP and organic ultralong RTP (OURTP) by introducing ions into the hydrolyzed nonconjugated maleic anhydride and acrylamide copolymers. Thanks to the synergistic effects of hydrogen and ionic bonding with the ion-triggered electrostatic and coordinate interactions to suppress non-radiative decays and promote intersystem crossing, the amorphous copolymers show efficient photoluminescence with quantum efficiencies up to 13.5%, anti-Kasha RTP blue-shift of 29 nm, and OURTP lifetime up to 420 ms. Moreover, the temperature-dependent and water-sensitive anti-Kasha RTP and OURTP are also observed due to the formation of highly emissive CTE structure regulated by ionization. With the excellent processability and flexibility of the copolymer, lifetime-, temperature- and color-encrypted information anti-counterfeiting is designed and explored. The anti-Kasha RTP in CTE materials realized for the first time demonstrates impressive potential for multi-level encryption/anti-counterfeiting applications and more importantly, providing fundamental mechanism understanding for the rational modulation and design of CTE materials with extraordinary photophysical properties.

Dual-emission copper nanoclusters for hydrogen sulfide detection: a novel approach

Dual-emission copper nanoclusters (CuNCs) were synthesized via a novel, green and one-pot aqueous method, employing bovine serum albumin and glutathione as reducing and stabilizing agents, respectively. The CuNCs exhibited distinct fluorescence emissions at 443 nm and 612 nm under 365 nm excitation. Notably, with the increase in hydrogen sulfide concentration, the dual-emission fluorescence of CuNCs was gradually quenched, and complete quenching occurred at 280 μM. The probe demonstrated a stable response to hydrogen sulfide within the concentration range of 2.5-60.0 μM. The detection limit of hydrogen sulfide was as low as 0.32 μM, which is significantly lower than the limit set by the World Health Organization (1.5 μM). This method was successfully applied for the detection of sulfide in environmental samples, achieving remarkable recovery rates ranging from 98.2-102%. Moreover, the response mechanism and practical application potential of CuNCs as a hydrogen sulfide detection platform were investigated, offering crucial insights for the study of fluorescence properties of metal nanoclusters and the prevention and control of hydrogen sulfide pollution.

Precise counter anion modulation of the self-assembly behavior-endowed ultrasensitive and specific dual-mode visualization of nitrate

Pt(II) polypyridine complex-based probe exhibits promising performance in anion detection by the change of the absorption and emission properties based on supramolecular self-assembly. However, whether one can develop a modulation strategy of the counter anion to boost the detection sensitivity and anti-interference capability of the Pt(II) complex-based probe remains a big challenge. Here, an effective modulation strategy was proposed by precisely regulating the interaction energy through adjusting the type of the counter anions, and a series of probes have been synthesized by counter anion (X = Cl-, ClO4-, PF6-) exchange in [Pt(tpy)Cl]·X (tpy=2,2':6',2''-terpyridine), and thus the colorimetric-luminescence dual-mode detection toward nitrate was achieved. The optimal [Pt(tpy)Cl]·Cl probe shows superior nitrate detection performance including a limit of detection (LOD) (8.68 nM), rapid response (<0.5 s), an excellent selectivity and anti-interference capability even facing 14 common anions. Moreover, a polyvinyl alcohol (PVA) sponge-based sensing chip loaded with the probe enables the ultra-sensitive detection of nitrate particles with an ultralow detection limit of 7.6 pg, and it was further integrated into a detection pen for the accurate recognition of nitrate particles in real scenarios. The proposed counter-anion modulation strategy is expected to start a new frontier for the exploration of novel Pt(II) complex-based probes.

Boosting Electrochemical Reduction of Nitrate to Ammonia by Constructing Nitrate-Favored Active Cu-B Sites on SnS2

The electrochemical reduction of nitrate to ammonia is an effective method for mitigating nitrate pollution and generating ammonia. To design superior electrocatalysts, it is essential to construct a reaction site with high activity. Herein, a simple two-step method is applied to in situ reduce amorphous copper over boron-doped SnS2 nanosheets(denoted as aCu@B-SnS2-x. DFT calculations reveal the combination of amorphous copper and B-doping strategy can construct Cu-B active twins and introduce sulfur vacancies on the surface of the inert SnS2, the active twins can efficiently adsorb nitrate and forcibly separate oxygen atoms from nitrate under the assistance of the exposed Sn atom, leading to strong nitrate adsorption. Benefiting from this, aCu@B-SnS2-x exhibited an ultrahigh NH3 FE of 94.6% at -0.67 V versus RHE and the highest NH3 yield rate of 0.55 mmol h-1 mg-1 cat (9350 µg h-1 mg-1 cat) at -0.77 V versus RHE under alkaline conditions. Besides, aCu@B-SnS2-x is confirmed to remain active after various stability tests, suggesting the practicality of utilizing aCu@B-SnS2-x in industrial applications. This work highlights the feasibility of enhanced nitrate-to-ammonia conversion efficiency by combining the doping method and amorphous metal.

Eu3+-based InP/ZnS quantum dot fluorescence platform for multi-color and sensitive visualization of tetracycline

A turn-on type ratiometric fluorescence sensing system of blue quantum dot Eu-MPA-InP/ZnS was established for multi-color visualization determination of tetracycline (TC). Mercaptopropionic acid (MPA)-capped InP/ZnS quantum dots (MPA-InP/ZnS QDs) both modify the hydrophilicity of InP/ZnS QDs and serve as a scaffold for coordinating of Eu3+ ions. The blue fluorescence of Eu-MPA-InP/ZnS at 478 nm is reduced by the TC through the inner filter effect (IFE) under a single excitation wavelength of 365 nm. Rich colour gradients and a highly discriminative colour change were features of this multicolour response to TC, which allowed visual quantification of TC in a dose-dependent manner. Furthermore, by cross-linking Eu-MPA-InP/ZnS with agarose (Aga.), a mouldable Eu-MPA-InP/ZnS@Aga 96-well gel sensing device was designed to serve as a handheld sensor for on-site detection of TC. This probe expands the use of InP QDs in analytical sensing and has been effectively applied to the visual detection of tetracycline in milk and the environment.

Amination and Protonation Facilitated Novel Isoxazole Derivative for Highly Efficient Electron and Hole Separation

It is of great importance to understand the intrinsic relationship between phototautomerization and photoelectric properties for the exploration of novel organic materials. Here, in order to chemically control the protonation process, the aminated isoxazole derivative (2,2'-(isoxazolo[5,4-d]isoxazole-3,6-diyl)dibenzenaminium, DP-DA-DPIxz) with -N═ as the proton acceptor was designed to achieve the twisted intramolecular charge transfer (TICT) state which was triggered by an excited-state intramolecular proton transfer (ESIPT) process. This kind of protonation enhanced the intramolecular hydrogen bonding, conjugative effect, and steric hindrance effects, ensuring a barrierless spontaneous TICT process. Through the intramolecular proton transfer, the configuration torsion and conjugation dissociation of the DP-DA-DPIxz molecule was favored, which led to efficient charge separation and remarkable variations in light-emitting properties. We hope the present investigation will provide a new approach to design novel optoelectronic organic materials and shine light on the understanding of the charge transfer and separation process in molecular science.

Solvation effect enabled visualized discrimination of multiple metal ions

Highly efficient detection of environmental residual potentially toxic species is of concern worldwide as their presence in an excessive amount would greatly endanger the health of human beings as well as environmental sustainability. The solvation effect is a critical factor to be considered for understanding chemical reaction progress as well as the photophysical behaviors of substances and thus is promising for visualized detection of metal ions. Herein, by applying 5-amino-1,10-phenanthroline (APT) as the optical probe, a sensing strategy was proposed based on the solvation effect modulated complexation of APT towards different metal ions to achieve the visualized discrimination of four critical ions (Cu(II), Zn(II), Cd(II), and Al(III)). How the crucial intrinsic properties of the solvent (e.g., polarity, solvent free energy, and electrostatic potential) influenced the complexation and the product emission was clarified, and the detection performances were systematically evaluated with detection limits as low as the nM level and good recognition selectivity. Furthermore, a portable sensing chip was developed with potential for highly efficient analysis in complicated scenes; thus, this strategy offers a new insight into determining multiple metal ions or other critical substances upon solvation manipulation.

A Self-Accelerating Naphthalimide-Based Probe Coupled with Upconversion Nanoparticles for Ultra-Accurate Tri-Mode Visualization of Hydrogen Peroxide

The design and development of ultra-accurate probe is of great significance to chemical sensing in complex practical scenarios. Here, a self-accelerating naphthalimide-based probe with fast response and high sensitivity toward hydrogen peroxide (H2O2) is designed. By coupling with the specially selected upconversion nanoparticles (UCNPs), an ultra-accurate colorimetric-fluorescent-upconversion luminescence (UCL) tri-mode platform is constructed. Owing to the promoted reaction process, this platform demonstrates rapid response (< 1 s), an ultra-low detection limit (4.34 nM), and superb anti-interferent ability even in presence of > 21 types of oxidants, explosives, metallic salts, daily compounds, colorful or fluorescent substances. In addition, the effectiveness of this design is further verified by a sponge-based sensing chip loaded with the UCNPs/probe in recognizing trace H2O2 vapor from interferents with the three characteristic colors existing simultaneously. The proposed design of probe and tri-mode visualization detection platform is expected to open up a brand-new methodology for ultra-accurate sensing.

Design of Highly Efficient Electronic Energy Transfer in Functionalized Quantum Dots Driven Specifically by Ethylenediamine

The exploration of emerging functionalized quantum dots (QDs) through modulating the effective interaction between the sensing element and target analyte is of great significance for high-performance trace sensing. Here, the chromone-based ligand grafted QDs (QDs-Chromone) were initiated to realize the electronic energy transfer (EET) driven specifically by ethylenediamine (EDA) in the absence of spectral overlap. The fluorescent and colorimetric dual-mode responses (from red to blue and from colorless to yellow, respectively) resulting from the expanded conjugated ligands reinforced the analytical selectivity, endowing an ultrasensitive and specific response to submicromolar-liquid of EDA. In addition, a QDs-Chromone-based sensing chip was constructed to achieve the ultrasensitive recognition of EDA vapor with a naked-eye observed response at a concentration as low as 10 ppm, as well as a robust anti-interfering ability in complicated scenarios monitoring. We expect the proposed EET strategy in shaping functionalized QDs for high-performance sensing will shine light on both rational probe design methodology and deep sensing mechanism exploration.

Interfacially Confined Dynamic Reaction Resulted to Fluorescent Nanofilms Depicting High-Performance Ammonia Sensing

Sensing materials innovation plays a crucial role in the development of high-performance film-based fluorescent sensors (FFSs). In our current study, we present the innovative fabrication of four fluorescent nanofilms via interfacially confined dynamic reaction of a specially designed fluorescent building block, a new boron-coordinated compound (NI-CHO), with a chosen one, benzene-1,3,5-tricarbohydrazide (BTH). The nanofilms as prepared are robust, uniform, flexible, and thickness tunable, at least from 40 to 1500 nm. The fabricated FFSs based on Film 3, one of the four nanofilms, shows highly selective and fully reversible response to NH3 vapor with an experimental detection limit of <0.1 ppm and a response time of 0.2 s. The unprecedented high performance of the nanofilm is ascribed to the specific quenching of its fluorescence emission owing to formation of an excited-state complex between the sensing unit and the analyte molecule. Efficient mass transfer also contributes to the high performance owing to the porous adlayer structure of the nanofilm. This work provides an example to show how to develop a high-performance sensing film via controlling the film's structure, especially the thickness.

Cobalt oxyhydroxide nanosheet-modulated ratiometric fluorescence platform for the selective detection of malachite green in fish

A ratiometric fluorescence platform was developed based on the cobalt oxyhydroxide (CoOOH) nanosheet-modulated fluorescence response of blue emissive copper nanoclusters (Cu NCs) and yellow emissive o-phenylenediamine (OPD). CoOOH nanosheets showed dual function of strong absorption and oxidation ability, which can effectively quench the blue fluorescence of Cu NCs, with an excitation and emission peak maximum at 390 and 450 nm, respectively , and transfer the OPD into yellow fluorescence products, with an excitation and emission peak maximum at 390 and 560 nm, respectively. Upon introducing butyrylcholinesterase (BChE) and its substrates, CoOOH nanosheets were decomposed into Co2+, and malachite green (MG) showed strong inhibition ability to this  process. This resulted in the obvious difference on the ratio of blue and yellow fluorescence recorded on the system in the presence and absence of MG, which was utilized for the quantitative detection of MG, with a limit of detection of 0.140 μM and a coefficient of variation of 3.5%. The fluorescence ratiometric assay showed excellent detection performances in practical sample analysis.

[Au14(2-SAdm)9(Dppe)2]+: a gold nanocluster with a crystallization-induced emission enhancement phenomenon

In this work, a gold nanocluster [Au14(2-SAdm)9(Dppe)2]+ was synthesized and structurally determined by X-ray crystallography. The crystals of this cluster exhibit a 50-fold enhancement in quantum yield (5.05% for crystals) compared with its solution. Crystallographic analysis reveals that the weak intermolecular interactions (C-H⋯π, π⋯π) can inhibit the molecular vibration and thus generate the crystallization-induced emission enhancement phenomenon.