Instant Visual Detection of Trinitrotoluene Particulates on Various Surfaces by Ratiometric Fluorescence of Dual-Emission Quantum Dots Hybrid

Abstract

To detect trace trinitrotoluene (TNT) explosives deposited on various surfaces instantly and on-site still remains a challenge for homeland security needs against terrorism. This work demonstrates a new concept and its utility for visual detection of TNT particulates on various package materials. The concept takes advantages of the superior fluorescent properties of quantum dots (QDs) for visual signal output via ratiometric fluorescence, the feasibility of surface grafting of QDs for chemical recognition of TNT, and the ease of operation of the fingerprint lifting technique. Two differently sized CdTe QDs emitting red and green fluorescences, respectively, have been hybridized by embedding the red-emitting one in silica nanoparticles and covalently linking the green-emitting one to the silica surface, respectively, to form a dual-emissive fluorescent hybrid nanoparticle. The fluorescence of red QDs in the silica nanoparticles stays constant, whereas the green QDs functionalized with polyamine can selectively bind TNT by the formation of Meisenheimer complex, leading to the green fluorescence quenching due to resonance energy transfer. The variations of the two fluorescence intensity ratios display continuous color changes from yellow-green to red upon exposure to different amounts of TNT. By immobilization of the probes on a piece of filter paper, a fingerprint lifting technique has been innovated to visualize trace TNT particulates on various surfaces by the appearance of a different color against a yellow-green background under a UV lamp. This method shows high selectivity and sensitivity with a detection limit as low as 5 ng/mm(2) on a manila envelope and the attribute of being seen with the naked eye.

Dummy Molecularly Imprinted Polymers-Capped CdTe Quantum Dots for the Fluorescent Sensing of 2,4,6-Trinitrotoluene

“…In comparison with the other work on MIP@QDs for use in detection applications, [25][26][27][28]41,42 the developed DMIP@QDs showed excellent selectivity but low sensitivity. This problem of low sensitivity commonly exists for MIP@QDs-based systems.…”

A positively charged silver nanowire membrane for rapid on-site swabbing extraction and detection of trace inorganic explosives using a portable Raman spectrometer

“…requires analytical methods with high speed and sensitivity [2,3]. Numerous analytical methods, such as laser photoacoustic spectroscopy [4], fluorescence [5][6][7], surface-enhanced Raman spectroscopy (SERS) [8,9], nano-electrical devices [10], mass spectrometry, ion mobility spectroscopy, and X-ray imaging [11] have been used or proposed as suitable methods for the detection and quantification of nitro-explosives, such as 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) and 2,4,6-trinitrophenol (TNP) et al Capillary electrophoresis (CE) [12], ion chromatography (IC) [13], electrospray ionization mass spectrometry (ESI-MS) [14], and electrospray ionization ion mobility spectrometry (ESI-IMS) [15] have been employed to detect characteristic ions of inorganic explosives, such as ClO 4 − , ClO 3 − , or NO 3 − [16,17], which are known for their high stability and non-volatility. Recently, the capability of thermal desorption ion mobility spectrometry (TD-IMS) for the on-site sensitive detection of typical nitro-explosives such as TNT and RDX has been demonstrated.…”

A fluorescence ratiometric sensor for hypochlorite based on a novel dual-fluorophore response approach

“…Such a large enhancement is desirable for precise detection. Although some ratiometric sensors with two fluorophores for other analytes have been previously reported [39][40][41], however, in these sensors, only one fluorophore responded to analyte, the second fluorophore was insensitive to the analyte. The ratio changes in these sensors were usually less than 10-fold.…”