Turn-on Fluorescence Detection of H2O2 and TATP

Developing a novel ultraselective and ultrasensitive label-free direct spectrofluorimetric nanobiosensor for direct highly fast field detection of explosive triacetone triperoxide

BACKGROUND

Direct detection of the notorious explosive triacetone triperoxide (TATP) is very difficult because it lacks facile ionization and UV absorbance or fluorescence. Besides, the current indirect methods are time-consuming and need a pre-step for TATP cleavage to hydrogen peroxide. Moreover, they commonly show significant false-positive results in the presence of some camouflage which limits their field applications. Herein, for the first time, a novel label-free field-applicable spectrofluorimetric nanobiosensor was developed for direct TATP detection using a novel activated-protein protected gold nanocluster (ABSA-AuNCs; QY = 28.3 %) synthesized by a combined protein-assisted-ultrasonication procedure.

RESULTS

The ABSA-AuNCs revealed a fluorescence spectrum centered at 330.0 nm which was significantly quenched by TATP (binding constant = 154.06 M-1; ΔG = -12.5 kJ mol-1; E(%) = 88.5 %). This phenomenon was used as a basis for direct TATP quantification, providing a working range of 0.01-40.0 mg L-1 and a detection limit of 6.7 μg L-1 which is the lowest LOD provided for TATP detection up to now. A %RSD of 0.9 % and 1.56 % was obtained for repeatability and inter-day reproducibility, respectively. The selectivity was checked against a variety of camouflages, revealing ultra-selectivity. Several synthetic samples prepared by several camouflages and real samples (clay soil and real water media) were analyzed, revealing quantitative recoveries of TATP.

SIGNIFICANCE

During the production of the notorious explosive TATP, it can be discharged into water and soil. This novel method eliminated the false-positive results of traditional methods and is applicable for direct quantitative detection of camouflaged TATP and its residues in real soil and water samples in a highly short response time (2 min). The camouflaged TATP analysis is important for tracking the terrorist attacks in field conditions and analysis of soil and water can provide a first indication of the location of the production site.

Ratiometric luminescence detection of H2O2 in food samples using a terbium coordination polymer sensitized with 3-carboxyphenylboronic acid

A ratiometric luminescent probe was fabricated using adenosine monophosphate (AMP) as a bridging ligand and 3-carboxyphenylboronic acid (3-CPBA) as the sensitizer and functional ligand that allowed the probe to recognize hydrogen peroxide (H2O2). The probe was labeled AMP-Tb/3-CPBA. Adding H2O2 caused the nonluminescent 3-CPBA to be converted into 3-hydroxybenzoic acid, which strongly luminesces at 401 nm. This meant that adding H2O2 decreased the AMP-Tb/3-CPBA luminescence intensity at 544 nm and caused luminescence at 401 nm. The 401 and 544 nm luminescence intensity ratio (I401/I544) was strongly associated with the H2O2 concentration between 0.1 and 60.0 μM, and the detection limit was 0.23 μM. Dual emission reverse-change ratio luminescence sensing using the probe allowed environmental effects to be excluded and the assay to be very selective. We believe that the results pave the way for the development of new functionalized lanthanide coordination polymers for use in luminescence assays.

Distinguishing the responsive mechanisms of fluorescent probes to hydrogen peroxide, proteins, and DNA/RNA

The responsive mechanisms of cationic quinolinium-vinyl-N,N-dimethylaniline boronate (QVD-B) derivative probes to hydrogen peroxide (H2O2), proteins and DNA/RNA are theoretically investigated in this study. The potential energy curves of QVD-B scanned on a dihedral angle (N+-C-CC) in the first singlet (S1) state exhibit large torsional energy barriers. Additionally, the energy of the lowest unoccupied molecular orbital (LUMO) of an acceptor moiety (-3.14 eV) is lower than that of a donor moiety (-1.13 eV) in QVD-B. This demonstrates that photoinduced electron transfer (PET) quenches the fluorescence of QVD-B, as opposed to the previous report of intramolecular single-bond rotation. After reacting with H2O2, the reaction product of quinoline-vinyl-N,N-dimethylaniline (QVD) turns off the PET pathway and turns on the fluorescence at 550 nm, which is consistent with the experimental results (580 nm). Among the possible configurations of QVD-B that forms with proteins and DNA, the calculated fluorescence values of corresponding twisted QVD-B-P (638 nm) and QVD-B-D (686 nm) are consistent with the experimental results (632 and 688 nm). The frontier molecular orbital and electron-hole analysis show that the charge transfer distance follows the order of QVD (1.88 Å) < QVD-B-P (4.49 Å) < QVD-B-D (6.39 Å), which induces the fluorescence red-shifts of QVD-B-P and QVD-B-D compared to that of QVD. The multi-detection mechanism of the fluorescent probe QVD-B is attributed to PET progress and different degrees of local charge transfer after photoexcitation.

Recent advances of sensing strategies for the detection of β-glucuronidase activity

β-Glucuronidase (β-GLU), a kind of hydrolase, is widely distributed in mammalian tissues, body fluids, and microbiota. Abnormal changes of β-GLU activity are often correlated with the occurrence of diseases and deterioration of water quality. Therefore, detection of β-GLU activity is of great significance in biomedicine and environmental health such as cancer diagnosis and water monitoring. However, the conventional β-GLU activity assay suffers from the limitations of low sensitivity, poor accuracy, and complex procedure. With the development of analytical chemistry, many advances have been made in the detection of β-GLU activity in recent years. The sensors for β-GLU activity detection which have the advantages of rapid and reliable detection have been attracting increased attentions. In this paper, the principles, performances, and limitations of these β-GLU sensors, including colorimetric sensing, fluorescent sensing, electrochemical sensing for the determination of β-GLU activity, have been summarized and discussed. Moreover, the challenges and research trends of β-GLU activity assay are proposed.

Visual colorimetric detection of triacetone triperoxide based on a Fe(II)-promoted thermal decomposition process

Triacetone triperoxide (TATP) explosives, a popular choice for terrorists, have been used in many violent terrorist attacks all over the world. However, simple, rapid, and on-site detection methods of TATP are still lacking. Herein, we present a visual colorimetric method for on-site and rapid detection of TATP based on a Fe(II)-promoted thermal decomposition process of TATP. We discovered that TATP can be decomposed into H₂O₂ under heating conditions, and it reacts with Fe²⁺ to produce hydroxyl radicals (˙OH) and Fe³⁺via the Fenton reaction. The resulting ˙OH and Fe³⁺ further oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) to a yellow oxidized product (oxTMB). These reaction processes remarkably promote the chemical equilibrium shift and decrease the activation energy. Using the TATP-Fe²⁺-TMB ternary chromogenic system, the present colorimetric assay for TATP shows a dynamic range of 0.5-30 μM with a low detection limit of 0.12 μM. Additionally, common substances (e.g., inorganic salts, small organic substances, and polymers) do not interfere with TATP detection. This assay can be used for analyzing TATP in real water and camouflage samples. Furthermore, a test-paper-based method was also successfully developed for visual, rapid and on-site detection of TATP.

Free-standing, thin-film sensors for the trace detection of explosives

In a world focused on the development of cybersecurity, many densely populated areas and transportation hubs are still susceptible to terrorist attacks via improvised explosive devices (IEDs). These devices frequently employ a combination of peroxide based explosives as well as nitramines, nitrates, and nitroaromatics. Detection of these explosives can be challenging due to varying chemical composition and the extremely low vapor pressures exhibited by some explosive compounds. No electronic trace detection system currently exists that is capable of continuously monitoring both peroxide based explosives and certain nitrogen based explosives, or their precursors, in the vapor phase. Recently, we developed a thermodynamic sensor that can detect a multitude of explosives in the vapor phase at the parts-per-trillion (ppt) level. The sensors rely on the catalytic decomposition of the explosive and specific oxidation–reduction reactions between the energetic molecule and metal oxide catalyst; i.e. the heat effects associated with catalytic decomposition and redox reactions between the decomposition products and catalyst are measured. Improved sensor response and selectivity were achieved by fabricating free-standing, ultrathin film (1 µm thick) microheater sensors for this purpose. The fabrication method used here relies on the interdiffusion mechanics between a copper (Cu) adhesion layer and the palladium (Pd) microheater sensor. A detailed description of the fabrication process to produce a free-standing 1 µm thick sensor is presented.

A field-applicable colorimetric assay for notorious explosive triacetone triperoxide through nanozyme-catalyzed irreversible oxidation of 3, 3'-diaminobenzidine

A field-applicable colorimetric assay for fast detection of notorious explosive triacetone triperoxide (TATP) has been developed through the selective irreversible oxidation of 3, 3'-diaminobenzidine by hydrogen peroxide (HP) liberated during the acidic hydrolysis/degradation of TATP in the presence of MnO₂ nanozymes. The generated HP was detected by probing the absorbance of the product (indamine polymer) of the 3, 3'-diaminobenzidine (DAB) oxidation reaction at 460.0 nm. The UV-Vis measurements provided a linear range from 1.57 to 10.50 mg L^-1 TATP with a detection limit of 0.34 mg L^-1. The oxidation of DAB cannot proceed by molecular oxygen, thus it is selectively oxidized by H₂O₂; this prevents false-positive results from laundry detergents (containing O₂-releasing substances). Moreover, a naked-eye field test was developed, and a fast spot test analyzing time of 5 s was achieved. The selectivity of the assay was checked by analyzing some synthetic samples prepared with a laundry detergent as camouflage. The results of the developed assay revealed quantitative recoveries for TATP whereas the standard nanozyme-based method showed significant false-positive results. Graphical abstract.

Turn-on Fluorescent Detection of Hydrogen Peroxide and Triacetone Triperoxide via Enhancing Interfacial Interactions of a Blended System

In this work, we report the fabrication of a blend consisting of fluorescent 1 nanofibers and amberlyst-15 particles as a turn-on fluorescence sensor for trace TATP vapors. Fluorescence imaging and lifetime analysis reveal that the interface between 1 nanofibers and amberlyst-15 particles exhibits stronger photoluminescence than the unblended areas because of the formed strong hydrogen bonding between. Furthermore, the interfacial adhesion between 1 nanofibers and amberlyst-15 particles can be amplified by H₂O₂, which in turn gives rise to rapid and remarkable fluorescence enhancement. When exposed to TATP vapors, the amberlyst-15 component can rapidly decompose TATP into H₂O₂ that gives sensitive fluorescence enhancement responses of the blend. On the basis of this detection mechanism, fluorescence detection of TATP with rapid response (ca. 5 s) and high sensitivity (ca. 0.1 ppm) is achieved. Here, the resulting blend combines the pretreatment of TATP and detection responses and thereby simplifies the senor fabrication for the practical application.

Titanium dioxide nanoparticles-based colorimetric sensors for determination of hydrogen peroxide and triacetone triperoxide (TATP)

Due to its relatively simple preparation and readily available precursors, determination of triacetone triperoxide (TATP) by portable devices has become important. In this work, two different titanium dioxide nanoparticles (TiO₂NPs)-based colorimetric sensors based on complex formation on the solid surface were developed for determination of H₂O₂ and TATP. The first sensor, (3-aminopropyl)triethoxysilane (APTES) modified-TiO₂NPs-based paper sensor (APTES@TiO₂NPs), exploits peroxo-titanate binary complex formation between APTES@TiO₂NPs and H₂O₂ on chromatographic paper. The second sensor, 4-(2-pyridylazo)-resorcinol-modified-TiO₂NPs-based solid sensor (PAR@TiO₂NPs), relies on the formation of a ternary complex between Ti(IV), PAR and H₂O₂. The developed sensors were also applied to TATP determination after acidic hydrolysis of samples to H₂O₂. The limits of detection (LODs) of APTES@TiO₂NPs-based paper sensor were 3.14 × 10^-4 and 5.13 × 10^-4 mol L^-1 for H₂O₂ and TATP, respectively, whereas the LODs of PAR@TiO₂NPs solid sensor were 6.06 × 10^-7 and 3.54 × 10^-7 mol L^-1 for H₂O₂ and TATP, respectively. Possible interferences of common soil ions, passenger belongings used as camouflage materials during public transport (e.g., detergent, sweetener, acetylsalicylic acid and paracetamol-caffeine based analgesic drugs) and of other explosives were examined. The developed methods were statistically validated using t- and F- tests against the titanyl sulfate (TiOSO₄) colorimetric literature method.

Halogen Bonding Interactions for Aromatic and Nonaromatic Explosive Detection

Improved sensing strategies are needed for facile, accurate, and rapid detection of aromatic and nonaromatic explosives. Density functional theory was used to evaluate the relative binding interaction energies between halogen-containing sensor model molecules and nitro-containing explosives. Interaction energies ranged from -18 to -14 kJ/mol and highly directional halogen bonding interactions were observed with bond distances ranging between 3.0 and 3.4 Å. In all geometry optimized structures, the sigma-hole of electropositive potential on the halogen aligned with a lone pair of electrons on the nitro-moiety of the explosive. The computational results predict that the strongest interactions will occur with iodine-based sensors as, of all the halogens studied, iodine is the largest, most polarizable halogen with the smallest electronegativity. Based on these promising proof-of-concept results, synthetically accessible sensors were designed using 1,4-dihalobenzene (X = Cl, Br, and I) with and without tetra-fluoro electron withdrawing groups attached to the benzene ring. These sensing molecules were embedded onto single walled carbon nanotubes that were mechanically abraded onto interdigitated array electrodes, and these were used to measure the responses to explosive model compounds cyclohexanone and dimethyl-dinitro-benzene in nitrogen gas. Amperometric current-time curves for selectors and control molecules, including concentration correlated signal enhancement, as well as response and recovery times, indicate selector responsiveness to these model compounds, with the largest response observed for iodo-substituted sensors.

Towards the fluorogenic detection of peroxide explosives through host-guest chemistry

Two dansyl-modified β-cyclodextrin derivatives (1 and 2) have been synthesized as host-guest sensory systems for the direct fluorescent detection of the peroxide explosives diacetone diperoxide (DADP) and triacetone triperoxide (TATP) in aqueous media. The sensing is based on the displacement of the dansyl moiety from the cavity of the cyclodextrin by the peroxide guest resulting in a decrease of the intensity of the fluorescence of the dye. Both systems showed similar fluorescent responses and were more sensitive towards TATP than DADP.

Luminescence characteristics of rare-earth-doped barium hexafluorogermanate BaGeF6 nanowires: fast subnanosecond decay time and high sensitivity in H2O2 detection

Fluorides are promising host materials for optical applications. This paper reports the photoluminescent (PL) and cathodoluminescent (CL) characteristics of barium hexafluorogermanate BaGeF₆ nanowires codoped with Ce³⁺, Tb³⁺ and Sm³⁺ rare earth ions, produced by a solvothermal route. The synthesized BaGeF₆ nanowires exhibit uniform morphology and size distribution. X-ray diffraction divulges the one-dimensional growth of crystalline BaGeF₆ structure, with the absence of any impurity phases. Visible luminescence is recorded from the nanowires in green and red regions, when the nanowires are codoped with Ce³⁺/Tb³⁺, and Ce³⁺/Tb³⁺/Sm³⁺, respectively, under a UV excitation source. The PL emission from the codoped BaGeF₆ nanowires, when excited by a 254 nm source, originates from the efficient energy transfer bridges between Ce³⁺, Tb³⁺ and Sm³⁺ ions. The decay time of the visible luminescent emission from the nanowires is in the order of subnanoseconds, being one of the shortest decay time records from inorganic scintillators. The CL emission from the BaGeF₆ nanowires in the tunable visible range reveals their potential use for the detection of high-energy radiation. The PL emissions are sensitive to H₂O₂ at low concentrations, enabling their high-sensitivity detection of H₂O₂ using BaGeF₆ nanowires. A comparison with BaSiF₆ nanowires is made in terms of decay time and its sensitivity towards H₂O₂.

The decay time of BaGeF₆ nanowires codoped with rare earths is found in the order of subnanoseconds, being one of the shortest decay time records from inorganic scintillators. Their luminescence emissions are highly sensitive for H₂O₂ detection.

Carbazole- and/or triphenylamine-based D–π–D multiarylamino dyes: synthesis, characterization and photophysical properties

One-photon and two-photon fluorescence quenching by benzoyl peroxide of D–π–D multiarylamino dyes was investigated.

Enlightening surface plasmon resonance effect of metal nanoparticles for practical spectroscopic application

Pictorial depiction of applications of metal nanoparticles in different fields enlightening surface plasmon resonance effect.

Microperoxidase-11/metal–organic framework/macroporous carbon for detecting hydrogen peroxide

Schematic illustrating of the fabrication and sensing principle of the newly develpoed H₂O₂ biosensor.

Borate ester endcapped fluorescent hyperbranched conjugated polymer for trace peroxide explosive vapor detection

The hyperbranched polymer S1/ZnO nanorod array composite is very promising for a highly sensitive fluorescence device for detecting peroxide explosives.

Hierarchical supramolecules and organization using boronic acid building blocks

Current progress on hierarchical supramolecules using boronic acids has been highlighted in this feature article. The feasibility of the structure-directing ability is fully discussed from the standpoint of the generation of new smart materials.

The polar side of polyphenylene dendrimers

The site-specific functionalization of poly(phenylene) dendrimers can produce macromolecules with a range of different polarities.

Synthesis of a borylated boron–dibenzopyrromethene dye enabling the visual detection of H2O2 vapor

A boron–dibenzopyrromethene dye with a pinacolboryl group has been newly synthesized for the use as a reaction-based chemosensor. A TLC plate coated by the dye enables us to detect H₂O₂ vapor visually.

Substituent effects on oxidation-induced formation of quinone methides from arylboronic ester precursors

A series of arylboronic esters containing different aromatic substituents and various benzylic leaving groups (Br or N(+)Me3Br(-)) have been synthesized. The substituent effects on their reactivity with H2O2 and formation of quinone methide (QM) have been investigated. NMR spectroscopy and ethyl vinyl ether (EVE) trapping experiments were used to determine the reaction mechanism and QM formation, respectively. QMs were not generated during oxidative cleavage of the boronic esters but by subsequent transformation of the phenol products under physiological conditions. The oxidative deboronation is facilitated by electron-withdrawing substituents, such as aromatic F, NO2, or benzylic N(+)Me3Br(-), whereas electron-donating substituents or a better leaving group favor QM generation. Compounds containing an aromatic CH3 or OMe group, or a good leaving group (Br), efficiently generate QMs under physiological conditions. Finally, a quantitative relationship between the structure and activity has been established for the arylboronic esters by using a Hammett plot. The reactivity of the arylboronic acids/esters and the inhibition or facilitation of QM formation can now be predictably adjusted. This adjustment is important as some applications may benefit and others may be limited by QM generation.