Hydrazine Detection during Ammonia Electro-oxidation Using an Aggregation-Induced Emission Dye

Single-Probe-Based Sensor Array for Fingerprint Recognition of Trivalent Metal Ions and Application in Water Identification

Abnormal concentration levels of trivalent metal ions (M3+) might hinder their natural biological activities in physiological processes and cause severe health hazards. Herein, a dual-chromophore probe (RhB-TPE) composed of rhodamine and tetraphenylethene (TPE) units was synthesized and explored for discriminating M3+ ions. It exhibited special aggregation and AIE properties in aqueous media. Its ensemble with anionic surfactant SDBS assemblies (RhB-TPE/SDBS) could be utilized as fluorescent sensors for selective and sensitive detection of M3+ ions such as Fe3+, Al3+, and Cr3+ by illustrating quenched TPE emission and switched-on rhodamine emission. Moreover, the use of SDBS assemblies at two concentrations could provide a single-probe-based sensor array and realize four-signal pattern recognition of different concentrations of the three M3+ ions and identify M3+ mixtures or unknown samples. The cross-reactive fluorescence variation was attributed to the M3+ influence on the FRET process from TPE to open-ring form rhodamine in the two ensemble sensors. With the coexistence of Al3+, the optimized RhB-TPE/SDBS ensemble sensor array was successfully applied to differentiate commercially available brand mineral water and purified water, as well as tap water. The present work provides a novel strategy to generate a single-probe-based sensor array and realizes fingerprint recognition of three trivalent metal ions and efficient discrimination of different types of water. The modulation FRET process of a dual chromophore in different surfactant ensembles inspires the future construction of novel and effective sensing platforms.

Discovering Facet-Dependent Formation Kinetics of Key Intermediates in Electrochemical Ammonia Oxidation by a Electrochemiluminescence Active Probe

Facile evaluation of formation kinetics of key intermediate is crucial for a comprehensive understanding of electrochemical ammonia oxidation reaction (AOR) mechanisms and the design of efficient electrocatalysts. Currently, elucidating the formation kinetics of key intermediate associated with rate-determining step is still challenging. Herein, 4-phtalamide-N-(4'-methylcoumarin) naphthalimide (CF) is developed as a molecular probe to detect N2H4 intermediate during AOR via electrochemiluminescence (ECL) and further investigated the formation kinetics of N2H4 on Pt catalysts with different crystal planes. CF probe can selectively react with N2H4 to release ECL substance luminol. Thus, N2H4 intermediate as a key intermediate can be sensitively and selectively detected by ECL during AOR. For the first time, Pt(100) facet is discovered to exhibit faster N2H4 formation kinetics than Pt(111) facet, which is further confirmed by Density functional theory calculation and the finite element simulation. The AOR mechanism under the framework of Gerischer and Mauerer is further validated by examining N2H4 formation kinetics during the dimerization process (NH2 coupling). The developed ECL active probe and the discovered facet-dependent formation kinetics of key intermediates provide a promising new tool and strategy for the understanding of electrochemical AOR mechanisms and the design of efficient electrocatalysts.

DFT Study of N-modified Co3Mo3C Electrocatalyst with Separated Active Sites for Enhanced Ammonia Oxidation

Since the facile oxidation of ammonia is one key for its utilization as a zero-carbon fuel in a direct ammonia fuel cell, developing the ammonia oxidation reaction (AOR) catalysts with cost-effective and higher activity is urgently required. However, the catalytic activity of AOR is limited by the scaling relationship of the intermediate adsorption. Based on the density functional theory, the N-modified Co3Mo3C with separated active sites of NH3 dehydrogenation and N-N coupling has been designed and investigated, which is a promising strategy to circumvent the scaling relationship, achieving improved AOR catalytic performance with a lower theoretical overpotential of 0.59 V under fast reaction kinetics condition. The calculation results show that the hollow site (Co-Mo-Mo and Co-Co-Mo) and Co site in N-modified Co3Mo3C play essential roles in NH3 dehydrogenation and N-N coupling, respectively. This work not only benefits for understanding the mechanism of AOR, but also provides a fundamental guidance for rational design of AOR catalysts.

A Reversible Mechanochromic AIEgen Based on Triphenylamine for the Selective Detection of Vitamin B2 (Riboflavin) in Aqueous Media and Histotoxicity

(E)-Ethyl 2-cyano-3-(4'-(diphenyl amino)-[1,1'-biphenyl]-4-yl) acrylate (RSJ) is a novel luminogen based on triphenylamine. It has been fully synthesized and characterized, exhibiting an incredible photophysical phenomenon known as aggregation-induced emission (AIE). This work describes a fluorescent sensor that detects vitamin B2 in mixed aqueous media with high selectivity and a low limit of detection as well as a mechanism for reversible mechanochromic luminescence. Moreover, the molecule was validated for its nontoxicity in water using a histotoxicological study. Fish subjected to two different concentrations of the "novel luminogen" that displayed photophysical phenomena during sensing of vitamin B2 (riboflavin) in mixed aqueous media did not exhibit any significant differences in the structural makeup of their liver, kidney, gills, brain, and muscle tissues when compared with the control group.

Simultaneous detection and removal of mercury (II) using multifunctional fluorescent materials

Environmental problems caused by mercury ions are increasing due to growing industrialization, poor enforcement, and inefficient pollutant treatment. Therefore, detecting and removing mercury from the ecological chain is of utmost significance. Currently, a wide range of small molecules and nanomaterials have made remarkable progress in the detection, detoxification, adsorption, and removal of mercury. In this review, we summarized the recent advances in the design and construction of multifunctional materials, detailed their sensing and removing mechanisms, and discussed with emphasis the advantages and disadvantages of different types of sensors. Finally, we elucidated the problems and challenges of current multifunctional materials and further pointed out the direction for the future development of related materials. This review is expected to provide a guideline for researchers to establish a robust strategy for the detection and removal of mercury ionsin the environment.

Histotoxicity of AIEgen Based on Triphenylamine for the Simultaneous and Discriminatory Sensing of Hg2+ and Ag+ Directly in Aqueous Media for Environmental Applications

A newly synthesized AIEgen based on triphenylamine is fully characterized and coded as BRA for the simultaneous and discriminatory selective detection of Hg2+ and Ag+ ions directly in mixed aqueous media for the identification and purification of water with a low detection limit. Moreover, we employed BRA in histotoxicity in that when compared to the control group, fish exposed to the "novel synthesized luminogen (BRA)" that demonstrated photophysical phenomena during the "sensing of mercury and silver (heavy metals) in aqueous media" did not show any major distinguishing changes in the architecture of their gills, liver, muscle, brain, kidney, and heart tissues.

Water-soluble single molecular probe for simultaneous detection of viscosity and hydrazine

Hydrazine (N₂H₄) can cause serious damage to human health, while intracellular viscosity is highly associated with many diseases and cellular dysfunctions. Herein, we report the synthesis of a dual-responsive organic molecule-based fluorescent probe with excellent water solubility being capable of detection of N₂H₄ and viscosity through dual-fluorescence channels in "turn on" manner for both. Besides sensitive detection of N₂H₄ in aqueous solution with detection limit of 0.135 μM, this probe could be used for vapor N₂H₄ detection in colorimetric and fluorescent manners. In addition, the probe demonstrated viscosity-dependent fluorescence enhancement behavior, and as high as 150-fold enhancement could be obtained at 95% glycerol aqueous solution. Cell imaging experiment revealed that the probe could be used for the discriminating of living and dead cells.

A dual-function probe with aggregation-induced emission feature for Cu2+ detection and chemodynamic therapy

Herein, a fluorescent probe (named TPACP) with aggregation-induced emission (AIE) feature was developed and utilized for the selective detection of Cu²⁺ with high sensitivity and fast-response. The resultant TPACP@Cu²⁺ complexes from coordination of TPACP with Cu²⁺ can also be potentially applied for chemodynamic and photodynamic therapy.

Corrosion protection properties of tetraphenylethylene-based inhibitors toward carbon steel in acidic medium

Four novel corrosion inhibitors (1, 2, 3 and 4) integrating different tetraphenylethylene (TPE) cations and thiocyanate (SCN^-) anions were developed. Weight-loss and electrochemical measurements were employed to assess their protective properties toward carbon steel in 0.5 M H₂SO₄, revealing them as effective corrosion inhibitors in the order of 3 > 4 > 2 > 1, with the inhibition efficiencies of 2, 3 and 4 all exceeding 97%. The inhibitory effect could be attributed to hard and soft acids and bases theory and the synergistic effect of the charged ingredients. The efficiency trend of the corrosion inhibition, as well as inhibition mechanism, was verified by multi-scaled theoretical simulations combined with grand canonical Monte Carlo and molecular dynamic methods.

A smartphone-adaptable chromogenic and fluorogenic sensor for rapid visual detection of toxic hydrazine in the environment

Hydrazine is an essential chemical in industries, but its high toxicity poses great threats to human health and environmental safety. Hence, it is of great significance to monitor the hydrazine in environment. In this work, we presented a chromogenic and fluorogenic dual-mode sensor RA for the detection of hydrazine based on nucleophilic substitution reaction. A linear relationship was obtained between the fluorescence intensity and the concentrations of N₂H₄ ranging from 0 to 35 μM (R² = 0.9936). The sensor can determine hydrazine with fast response (within 12 min), low limit of detection (0.129 μM) and high selectivity. RA was successfully used to detect N₂H₄ in real water samples with good recoveries and the results corresponded to the standard method. Furthermore, the sensor-coated portable test papers were fabricated, which can visually quantify hydrazine solutions with obvious fluorescence transformation from colorless to red. Moreover, RA-loaded papers were used to create a smartphone-adaptable RGB values analytical method for quantitative N₂H₄ detection.

Tetraphenylethene-Based Fluorescent Chemosensor with Mechanochromic and Aggregation-Induced Emission (AIE) Properties for the Selective and Sensitive Detection of Hg2+ and Ag+ Ions in Aqueous Media: Application to Environmental Analysis

It is critical to design a novel and simple bifunctional sensor for the selective and sensitive detection of ions in an aqueous media in environmental samples. As a result, in this study, tetraphenylethene hydrazinecarbothioamide (TPE-PVA), known as probe 1, was successfully synthesized and characterized as having impressive photophysical phenomena such as aggregation-induced emission (AIE) and mechanochromic properties by applying mechanical force to the solid of probe 1. The emission of the solid of probe 1 changed from turquoise blue to lemon yellow after grinding, from lemon yellow to parakeet green after annealing at 160 °C, and to arctic blue after fuming with DCM. Such characteristics could lead to a variety of applications in several fields. The probe was implemented and demonstrated remarkable selectivity and sensitivity toward mercury(II) and silver(I) ions by substantially switching off emission over other cations. Following an extensive photophysical analysis, it was discovered that detection limits (LOD) as low as 0.18344 and 0.2384 μg mL^-1 for Hg²⁺ and Ag⁺, respectively, are possible with a quantum yield (Φ) of 2.26. Probe 1 was also explored as a Hg²⁺ and Ag⁺ paper strip-based sensor and kit for practical use. The binding mechanisms of probe 1 (TPE-PVA) with Hg²⁺ and Ag⁺ were confirmed by ¹H NMR titration. These results could lead to the development of reliable onsite Hg²⁺ and Ag⁺ fluorescent probes in the future.

Schiff Base Aggregation-Induced Emission Luminogens for Sensing Applications: A Review

Fluorescence sensing can not only identify a target substrate qualitatively but also achieve the purpose of quantitative detection through the change of the fluorescence signal. It has the advantages of immense sensitivity, rapid response, and excellent selectivity. The proposed aggregation-induced emission (AIE) concept solves the problem of the fluorescence of traditional fluorescent molecules becoming weak or quenched in high concentration or aggregated state conditions. Schiff base fluorescent probes have the advantages of simple synthesis, low toxicity, and easy design. They are often used for the detection of various substances. In this review we cover late developments in Schiff base compounds with AIE characteristics working as fluorescence sensors.

Two Ratiometric Fluorescent Probes Based on the Hydroxyl Coumarin Chalcone Unit with Large Fluorescent Peak Shift for the Detection of Hydrazine in Living Cells

Hydrazine is widely used in industrial and agricultural production, but excessive hydrazine possesses a serious threat to human health and environment. Here two new ratiometric fluorescence probes, DDP and DDC, with the hydroxyl coumarin chalcone unit as the sensing site are developed, which can achieve colorimetric and ratiometric recognition for hydrazine with good sensitivity, excellent selectivity, and anti-interference. The calculated fluorescence limits of detections are 0.26 μM (DDC) and 0.14 μM (DDP). The ratiometric fluorescence response to hydrazine is realized through the adjustment of donor and receptor units in coumarin conjugate structure terminals, accompanied by fluorescence peak shift about 200 nm (DDC, 188 nm; DDP, 229 nm). Stronger electropositivity in the carbon-carbon double bond is helpful to the first phase addition reaction between the probe and hydrazine. Higher phenol activity in the hydroxyl coumarin moiety will facilitate the following dihydro-pyrazole cyclization reaction. In addition, both of these probes realized the convenient detection of hydrazine vapor. The probes were also successfully applied to detect hydrazine in actual water samples, different soils, and living cells.

Design of a ratiometric near-infrared fluorescent probe with double excitation for hydrazine detection in vitro and in vivo

Hydrazine has a wide range of industrial applications, but it is also a toxic and explosive chemical substance, which brings potential risks to human health and environmental safety. Therefore, rapid and sensitive monitoring of hydrazine is of great importance in environmental sciences and biological systems. In this work, a new near-infrared (NIR) ratiometric fluorescent probe (Ac-HY) was designed to detect hydrazine under double excitation and emission mode. Ac-HY exhibited large stokes shift (130 nm), high selectivity and sensitivity to hydrazine detection. The applications of Ac-HY probe for detecting hydrazine in vapor and imaging hydrazine in lipid droplets and zebrafish. Therefore, Ac-HY can be used to monitor the distribution of exogenous hydrazine in vitro and in vivo.

Electrochemiluminescent sensor based on an aggregation-induced emission probe for bioanalytical detection

In recent years, with the rapid development of electrochemiluminescence (ECL) sensors, more luminophores have been designed to achieve high-throughput and reliable analysis. Impressively, after the proposed fantastic concept of "aggregation-induced electrochemiluminescence (AIECL)" by Cola, the application of AIECL emitters provides more abundant choices for the further improvement of ECL sensors. In this review, we briefly report the phenomenon, principle and representative applications of aggregation-induced emission (AIE) and AIECL emitters. Moreover, it is noteworthy that the cases of AIECL sensors for bioanalytical detection are summarized in detail, from 2017 to now. Finally, inspired by the applications of AIECL emitters, relevant prospects and challenges for AIECL sensors are proposed, which is of great significance for exploring more advanced bioanalytical detection technology.

Novel Aggregation-Enhanced PEC Photosensitizer Based on Electrostatic Linkage of Ionic Liquid with Protoporphyrin IX for Ultrasensitive Detection of Molt-4 Cells

Nowadays, aggregation quenching of most organic photosensitizers in aqueous media seriously restricts analytical and biomedical applications of photoelectrochemical (PEC) sensors. In this work, an aggregation-enhanced PEC photosensitizer was prepared by electrostatically bonding protoporphyrin IX (PPIX) with an ionic liquid of 1-butyl-3-methylimidazole tetrafluoroborate ([BMIm][BF₄]), termed as PPIX-[BMIm] for clarity. The resultant PPIX-[BMIm] showed weak photocurrent in pure dimethyl sulfoxide (DMSO, good solvent), while the PEC signals displayed a 44.1-fold enhancement in a water (poor solvent)/DMSO binary solvent with a water fraction (f_w) of 90%. Such PEC-enhanced mechanism was critically studied by electrochemistry and density functional theory (DFT) calculation in some detail. Afterward, a label-free PEC cytosensor was built for ultrasensitive bioassay of acute lymphoblastic leukemia (molt-4) cells by electrodepositing Au nanoparticles (Au NPs) on the PPIX-[BMIm] aggregates and sequential assembly of protein tyrosine kinase (PTK) aptamer DNA (aptDNA). The resultant cytosensor showed a wide linear range (300 to 3 × 10⁵ cells mL^-1) with a limit of detection (LOD) as low as 63 cells mL^-1. The aggregation-enhanced PEC performance offers a valuable and practical pathway for synthesis of advanced organic photosensitizer to explore its PEC applications in early diagnosis of tumors.

Phototriggered Aggregation-Induced Emission and Direct Generation of 4D Soft Patterns

Microscopic control of macroscopic phenomena is one of the core subjects in materials science. Particularly, the spatio-temporal control of material behaviors through a non-contact way is of fundamental importance but is difficult to accomplish. Herein, a strategy to realize remote spatio-temporal control of luminescence behaviors is reported. A multi-arm salicylaldehyde benzoylhydrazone-based aggregation-induced emission luminogen (AIEgen)/metal-ion system, of which the fluorescence can be gated by the UV irradiation with time dependency, is developed. By changing the metal-ion species, the fluorescence emission and the intensity can also be tuned. The mechanism of the UV-mediated fluorescence change is investigated, and it is revealed that a phototriggered aggregation-induced emission (PTAIE) process contributes to the behaviors. The AIEgen is further covalently integrated into a polymeric network and the formed gel/metal-ion system can achieve laser-mediated mask-free writing enabled by the PTAIE process. Moreover, by further taking advantage of the time-dependent self-healing property of hydrazone-based dynamic covalent bond, transformable 4D soft patterns are generated. The findings and the strategy increase the ways to manipulate molecules on the supramolecule or aggregate level. They also show opportunities for the development of controllable smart materials and expand the scope of the materials in advanced optoelectronic applications.

Recyclable Supramolecular Assembly-Induced Emission System for Selective Detection and Efficient Removal of Mercury(II)

An efficient strategy for simultaneously detecting and removing Hg²⁺ from water is vital to address mercury pollution. Herein a supramolecular assembly G⊂H with photoluminescent properties is facilely constructed through the self-assembly of a functional pillar[5]arene bearing two N,N-dimethyldithiocarbamoyl binding sites (H) and an AIE-active tetraphenylethene derivative (G). Remarkably, the fluorescence of G⊂H can be exclusively quenched by Hg²⁺ among the 30 cations due to the formation of non-luminous ground state complex and only L-cysteine can restore fluorescence in the common 20 amino acids. Meanwhile, the probe G⊂H has a considerable thermal and pH stability, a good anti-interference property from various cations, and a satisfactory sensitivity. More importantly, G⊂H exhibits a prominent capability of Hg²⁺ removal with rapid capture rate (within 1 h) and excellent adsorption efficiency (98 %), as well as a highly efficient recyclability without losing any adsorption activity.