Attogram “Meth” Detection Enabled by Selective Organic Crystal Disaggregation via Directed Crystal Level Interactions

In this contribution, completely different from traditional probes based on molecular host–guest interaction, crystal level interaction was proposed as an ultrasensitive design strategy for molecule detection. In such a strategy, crystal–guest interaction triggered rapid crystal disaggregation to gain great signal change, far more efficient than molecule scale coupling. Highly ordered pyrene methanol (PM) crystal was self-assembled with hydrogen bond chain and π–π stacking force. Its {011} surface can be destabilized by methamphetamine hydrochlorate (MA, heavily used illicit drug) selectively and efficiently. The detection limit was improved to an amazing attogram level (5.4 ag/mL, 29.1 fM), 9 orders of magnitude lower than the best reported host–guest result

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 (<b>P3</b>) of 8-pyrenyl-substituted fluorenes bridged by a 1,6-hexanyl unit as well as its counterparts 2PR-F (<b>P1</b>) and 2PR-Cz (<b>P2</b>) has been synthesized and characterized. Their chemical structures and photophysical and electrochemical properties show that the dimer <b>P3</b> 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 <b>P3</b> 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/cm² for NG. These results reveal that the multiple-pyrenyl-unit-substituted fluorene dimer <b>P3</b> is suitable for preparing a highly sensitive and efficient thin-film device for detecting nitrate esters

Schiff Base Substituent-Triggered Efficient Deboration Reaction and Its Application in Highly Sensitive Hydrogen Peroxide Vapor Detection

The organic thin-film fluorescence probe, with the advantages of not polluting the analyte and fast response, has attracted much attention in explosive detection. Different with nitro explosives, the peroxide-based explosives are hardly to be detected because of their poor ultraviolet absorption and lack of an aromatic ring. As the signature compound of peroxide-based explosives, H₂O₂ vapor detection became more and more important. Boron ester or acid is considered to be a suitable functional group for the detection of hydrogen peroxide due to its reliable reactive activity. Its only drawback lies on its slow degradation velocity. In this work, we try to introduce some functional group to make the boron ester to be easily oxidized by H₂O₂. Herein, 4-(phenyl­(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)­phenyl)­amino)­benzaldehyde (OTB) was synthesized and its imine derivatives, OTBXAs, were easily obtained just by putting OTB films in different primary amines vapors. OTBXAs show fast deboronation velocity in H₂O₂ vapor compared with OTB. The complete reaction time of (<i>E</i>)-<i>N</i>-phenyl-4-((propylimino)­methyl)-<i>N</i>-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)­phenyl)­aniline (OTBPA) was even shortened 40 times with a response time of seconds. The detection limit for H₂O₂ vapor was as low as 4.1 parts per trillion (ppt). Further study showed that it is a general approach to enhance the sensing performance of borate to hydrogen peroxide (H₂O₂) vapor by introducing an imine into an aromatic borate molecule via a solid/vapor reaction

Aggregation State Reactivity Activation of Intramolecular Charge Transfer Type Fluorescent Probe and Application in Trace Vapor Detection of Sarin Mimics

The reactivity of most Intramolecular Charge Transfer (ICT) based probes in the film state is much poorer than that in solution, due to the serious solid state aggregation of the large polarity molecules. In this contribution, an efficient method for activating the aggregation state reactivity of ICT based probes has been developed. Multiple hydrogen bonds formed by the oxime group, together with the phenol anion, could activate the aggregation state reactivity of the oxime group. By enhancing frontier orbital energy level, and constructing porous film structure, the probe becomes more compatible for highly efficient vapor phase reaction. In application, the TOP-I film can distinguish different organic phosphates with significant fluorescence change. The detection limit for diethyl chloro phosphate (DCP) is 1.2 ppb, lower than the Immediately Dangerous to Life and Health (IDLH) level of Sarin. Such a reactivity activating strategy can be extended to detect other harmful vapors by inducing suitable functional groups as the acceptor of the ICT system. Furthermore, with the increasing importance of green chemistry, the method may be beneficial for applications in solvent-free reactions

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-(<i>tert</i>-butyl)­pyridine-2-yl)-<i>N</i>,<i>N</i>-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

Simple and Efficient Chromophoric-Fluorogenic Probes for Diethylchlorophosphate Vapor

In this work, we developed two small-molecule probes for real-time and onsite detecting of diethylchlorophosphate (DCP) vapor by incorporating amine groups into Schiff base skeletons. Both probes can be easily synthesized with high yield through one-step and low-cost synthesis. They can detect DCP vapor in the chromophoric-fluorogenic dual mode, which combines both the advantages of the visualization of color sensing and the high sensitivity of the fluorescence sensing. Furthermore, its sensing is based on the “turn-on” mode which can avoid the interference arising from photobleaching or fluorescence quenching agents based on “turn-off” mode. The detection limit was quantified to be as low as 0.14 ppb