Abstract
As an important sort of dithiocarbamate bactericide, thiram has been widely used for fruits, vegetables and mature crops to control various fungal diseases; however, the thiram residues in the environment pose a serious threat to human health. In this work, silver nanoparticles (AgNPs) were grown in-situ on cotton swab (CS) surfaces, based on the mussel-inspired polydopamine (PDA) molecule and designed as highly sensitive surface-enhanced Raman scattering (SERS) swabs for the conformal rapid detection of bactericide residues. With this strategy, the obtained CS@PDA@AgNPs swabs demonstrated highly sensitive and reproducible Raman signals toward Nile blue A (NBA) probe molecules, and the detection limit was as low as 1.0 × 10−10 M. More critically, these CS@PDA@AgNPs swabs could be served as flexible SERS substrates for the conformal rapid detection of thiram bactericides from various fruit surfaces through a simple swabbing approach. The results showed that the detection limit of thiram residues from pear, grape and peach surfaces was approximately down to the level of 0.12 ng/cm2, 0.24 ng/cm2 and 0.15 ng/cm2 respectively, demonstrating a high sensitivity and excellent reliability toward dithiocarbamate bactericides. Not only could these SERS swabs significantly promote the collection efficiency of thiram residues from irregular shaped matrices, but they could also greatly enhance the analytical sensitivity and reliability, and would have great potential for the on-site detection of residual bactericides in the environment and in bioscience fields.
Highlights
Thiram, an important member of dithiocarbamate bactericides, has been widely used in agriculture fields to protect fruit, vegetable, ornamental plants and crops from various fungal diseases [1,2,3]
We present a convenient and rational strategy for the in-situ growth of abundant AgNPs onto cotton swab surfaces based on the mussel-inspired surface chemistry, and we explore them as flexible surface-enhanced Raman scattering (SERS) swabs for the detection of trace thiram residues
As a three-dimensional flexible material, cotton swabs have large specific surfaces and a superior permeability, and these characters enable them to be an appropriate candidate for the fabrication of flexible SERS substrates [34]
Summary
An important member of dithiocarbamate bactericides, has been widely used in agriculture fields to protect fruit, vegetable, ornamental plants and crops from various fungal diseases [1,2,3]. Compared to the above mentioned analytical methods, SERS would be an excellent technique for the label-free and sensitive detection of thiram, and it would be expected to be one of the best candidates for on-site bactericide detection in real applications [12,20] Despite these exciting advantages, most current SERS substrates are based on various metal nanostructures immobilized on a series of rigid supporting substrates, such as glass sheets, silicon wafers and porous alumina [21]. PDA could serve as a versatile molecule platform for synthesizing various metal nanostructures on the desirable scaffold, and for providing a promising opportunity to fabricate flexible SERS substrates for the on-site analysis of thiram bactericide residues from the real-world surface. The scalable and reproducible approach would have great potential for environmental monitoring and the ultrasensitive detection of trace harmful chemicals in the agriculture, environment and bioscience fields
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