Yixun Gao

Concise and Efficient Fluorescent Probe via an Intromolecular Charge Transfer for the Chemical Warfare Agent Mimic Diethylchlorophosphate Vapor Detection

Sarin, used as chemical warfare agents (CWAs) for terrorist attacks, can induce a number of virulent effects. Therefore, countermeasures which could realize robust and convenient detection of sarin are in exigent need. A concise charge-transfer colorimetric and fluorescent probe (4-(6-(tert-butyl)pyridine-2-yl)-N,N-diphenylaniline, TBPY-TPA) that could be capable of real-time and on-site monitoring of DCP vapor was reported in this contribution. Upon contact with DCP, the emission band red-shifted from 410 to 522 nm upon exposure to DCP vapor. And the quenching rate of TBPY-TPA reached up to 98% within 25 s. Chemical substances such as acetic acid (HAc), dimethyl methylphosphonate (DMMP), pinacolyl methylphosphonate (PAMP), and triethyl phosphate (TEP) do not interfere with the detection. A detection limit for DCP down to 2.6 ppb level is remarkably achieved which is below the Immediately Dangerous to Life or Health concentration. NMR data suggested that a transformation of the pyridine group into pyridinium salt via a cascade reaction is responsible for the sensing process which induced the dramatic fluorescent red shift. All of these data suggest TBPY-TPA is a promising fluorescent sensor for a rapid, simple, and low-cost method for DCP detection, which could be easy to prepare as a portable chemosensor kit for its practical application in real-time and on-site monitoring.

A BODIPY dye as a reactive chromophoric/fluorogenic probe for selective and quick detection of vapors of secondary amines

A new reaction based fluorescence turn-off strategy for detection of secondary amines was developed. The probe shows fast response and high selectivity to secondary amines in solution/film at sub-ppm levels through chromogenic and fluorescent dual-mode signal changes.

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

The vapor of peroxide explosives (PEs) is difficult to detect using fluorescent probes because PEs are not typical quenching agents, not having nitro groups or aromatic units that can easily interact with electron-rich probes. Three borate ester endcapped pyrenyl–fluorene copolymers were reported for the detection of PEs, including a hyperbranched polymer (S1) and two linear polymers with borate esters on fluorenyl (S2) or pyrenyl (S3) units. It was found that the hyperbranched polymer S1 has greater steric hindrance, more external borate ester groups, higher HOMO level and higher fluorescence quantum yield, which give it higher sensitivity to H2O2 vapor than S2 and S3. To further amplify the sensing performance toward H2O2 vapor, a polymer/ZnO nanorod array composite was used, exploiting the catalytic ability and high area to volume ratio of the ZnO nanorod array. The fluorescence of the S1 film is quenched by ∼60% and ∼30% under saturated vapor of H2O2 and TATP, respectively, for 300 s at room temperature, and the detection limit for H2O2 is estimated to be 1.6 ppb. These results reveal that the S1/ZnO nanorod array composite is very promising for the preparation of a highly sensitive fluorescence device for detecting the vapor of peroxide explosives.

Femtogram level detection of nitrate ester explosives via an 8-pyrenyl-substituted fluorene dimer bridged by a 1,6-hexanyl unit.

Compared with nitroaromatic explosives detection, nitrate esters are far from wide attention possibly because of their shortage of aromatic ring and difficulty in being detected. Three fluorescent chemical probes for trace nitrate ester detection: an intramolecular dimer (P3) of 8-pyrenyl-substituted fluorenes bridged by a 1,6-hexanyl unit as well as its counterparts 2PR-F (P1) and 2PR-Cz (P2) has been synthesized and characterized. Their chemical structures and photophysical and electrochemical properties show that the dimer P3 film has a higher molar extinction coefficient, larger steric hindrance, higher area-to-volume ratio, and matching energy level with nitrate ester explosives, which contributes to higher sensitivity and moderate selectivity for sensing of nitrate ester explosives such as nitroglycerin (NG). The fluorescence of the P3 film is rapidly about 90% quenched upon exposure to a saturated vapor of NG for 50 s and almost 100% quenched for 300 s at room temperature due to photoinduced electron transfer between the probe and analyte. In addition, a very sensitive, rapid, simple, and low-cost surface-sensing method by disposable filter-paper-based test strips is demonstrated. The contact-mode approach exhibits a detection limit as low as 0.5 fg/cm(2) for NG. These results reveal that the multiple-pyrenyl-unit-substituted fluorene dimer P3 is suitable for preparing a highly sensitive and efficient thin-film device for detecting nitrate esters.

Highly efficient nitrate ester explosive vapor probe based on multiple triphenylaminopyrenyl-substituted POSS

Compared with nitroaromatic explosive detection, nitrate ester explosive detection has not received considerable attention possibly due to the absence of an aromatic ring and their difficulty in being detected. An eight triphenylamino-pyrenyl substituted POSS (P8PT) was designed as a sensory material. POSS was chosen as the skeleton due to its nano structure, multiple reactive sites, structural similarity with nitrate esters and high thermal stability, which will contribute to large surface area induced high sensitivity, tunable sensory units number, stronger interaction force with nitrate esters and high stability. For comparison, triphenylamino-pyrene (Py-TPA) (without POSS), one and three Py-TPA substituted POSS were also synthesized and characterized. Their chemical structures, photophysical and electrochemical properties show that P8PT has a 3-D symmetrical spatial conformation, higher molar extinction coefficient, higher area-to-volume ratio, multiple exciton transfer path, and matched energy level with nitrate ester explosives, which will all contribute to highly efficient sensing performance and efficient selectivity for the detection of nitrate ester explosives such as nitroglycerin (NG). The fluorescence of the P8PT film is 63% quenched upon exposure to a saturated vapor of NG for 50 s and 92% quenched for 300 s at room temperature due to photoinduced electron transfer between the probe and NG. These results reveal that P8PT is suitable for preparing a highly sensitive and efficient thin-film device for detecting nitrate esters.

Highly efficient single fluorescent probe for multiple amine vapours via reaction between amine and aldehyde/dioxaborolane

A fluorescent probe with multiple reactive groups which can detect vapours of different primary amines and secondary amines simultaneously with fast response in seconds and high sensitivity at ppt–ppm levels was realized.

Dual functional and multiple substituted fluorescent star-shaped POSS for a 1 + 1 > 2 explosive vapour detection

A dual functional and multiple substituted fluorescent star-shaped POSS has been designed and synthesized. There is effective FRET between the different functional arms. Compared with a single functional probe, the dual functional POSS showed a much better sensing performance to explosive NG and a comparable performance to TNT vapor.

Fluorescent diphenylfluorene-pyrenyl copolymer with dibenzothiophene-S,S-dioxide and adamantane units for explosive vapor detection

A fluorescent diphenylfluorene-pyrenyl copolymer with dibenzothiophene-S,S-dioxide (SO) and adamantane units has been successfully synthesized via a Suzuki–Miyaura cross-coupling reaction. After studying the sensing properties of a series of diphenylfluorene-pyrenyl materials towards TNT vapor, it was found that the dibenzothiophene-S,S-dioxide (SO) units introduced into the diphenylfluorene-pyrenyl copolymers can simultaneously enhance the photostability and sensing performance of the fluorescent sensing materials. This simple strategy can be used as a promising approach for the development of fluorescent conjugated sensing materials.