Date Published: November 12, 2018
Publisher: John Wiley and Sons Inc.
Author(s): Salah M. Tawfik, Mirkomil Sharipov, Sarvar Kakhkhorov, Mohamed R. Elmasry, Yong‐Ill Lee.
Novel multiple emitting amphiphilic conjugated polythiophene‐coated CdTe quantum dots for picogram level determination of the 2,4,6‐trinitrophenol (TNP) explosive are developed. Four biocompatible sensors, cationic polythiophene nanohybrids (CPTQDs), nonionic polythiophene nanohybrids (NPTQDs), anionic polythiophene nanohybrids (APTQDs), and thiophene copolymer nanohybrids (TCPQDs), are designed using an in situ polymerization method, which shows highly enhanced fluorescence intensity and quantum yield (up to 78%). All sensors are investigated for nitroexplosive detection to provide a remarkable fluorescence quenching for TNP and the quenching efficiency reached 96% in the case of TCPQDs. The fluorescence of the sensors are quenched by TNP through inner filter effect, electrostatic, π−π, and hydrogen bonding interactions. Under optimal conditions, the detection limits of CPTQDs, NPTQDs, APTQDs, and TCPQDs are 2.56, 7.23, 4.12, and 0.56 × 10−9m, respectively, within 60 s. More importantly, portable, cost effective, and simple to use paper strips and chitosan film are successfully applied to visually detect as little as 2.29 pg of TNP. The possibility of utilizing a smartphone with a color‐scanning APP in the determination of TNP is also established. Moreover, the practical application of the developed sensors for TNP detection in tap and river water samples is described with satisfactory recoveries of 98.02−107.50%.
The determination of trace amounts of chemical explosives is a key challenge toward efforts to secure public places and monitor drinking and waste water. It was reported that the explosive power of 2,4,6‐trinitrophenol (TNP) is similar to a highly explosive compound TNT.1 Apart from its explosive nature, TNP is considered as a main toxic pollutant, which harshly affects soil and ground water and poses a significant health hazard because of its high solubility in water.2 Short‐term exposure to TNP causes eye and skin irritation, whereas long‐term exposure may cause damage to the kidneys and respiratory organs.3 Therefore, the development of rapid, sensitive, selective, and on‐site sensory systems for the detection of traces of TNP is of considerable current attention for both national security and environmental protection.
In conclusion, highly sensitive and selective sensors based on novel nanohybrids, CPTQDs, NPTQDs, APTQDs, and TCPQDs for explosive‐TNP detection were developed. The fluorescence of sensors was selectively quenched by the addition of TNP due to the IFE and molecular interaction mechanisms. The LOD for TNP was determined to be 0.56 × 10−9m using TCPQDs sensor, which is exceptionally low. We also applied these sensors in tap and river water samples and showed remarkable sensitivity with acceptable recovery results. Furthermore, a facile paper sensor for TNP detection was developed successfully using filter paper coated with TCPQDs, thereby enabling us to detect TNP by naked eyes. More interestingly, this paper sensor was coupled with a smartphone to make it suitable for on‐site application. We also designed TCPQD‐doped chitosan film to visualize the quantitative detection of TNP. The developed method proposes reliable and accurate detection of TNP, which is foreseen to open new avenues for the development of facile sensing strategies to prevent environmental contamination and terrorist threats.
All materials, instrumentation, and methods are provided as the Supporting Information.
The authors declare no conflict of interest.