ABSTRACT
In this study, surface-enhanced Raman scattering substrates were investigated by the electrodeposition method to detect low concentrations of pesticides via the electrodeposition method with different agents from silver and gold precursors on APTES-modified ITO glass. A dual-potential method supplied three electrodes and was performed with a nucleation potential of 0.7 V for 2 s and a growth potential of -0.2 V for 500 s. The Ag film produced by the electrodeposition approach has great surface uniformity and good SERS signal amplification for the thiram insecticide at low concentrations. Interestingly, the ITO/APTES/Ag substrate extensively increased the sensitivity than the other investigated ones, thanks to the adequate assistance of amino groups of APTES in the denser and hierarchical deposition of Ag NPs. These observations were additionally elucidated via finite-difference time-domain (FDTD) calculation. For thiram, the detection was set at 10-8 M with an enhancement factor of up to 3.6 × 107 times. Comparing the SERS spectra of thiram at concentrations of 10-3, 10-4, and 10-5 M with a relative standard deviation (RSD) of less than 7.0% demonstrates excellent reproducibility of the ITO/APTES/Ag substrate. In addition, the special selectivity of the ITO/APTES/Ag substrate for thiram demonstrates that these nanostructures can identify pesticides with extreme sensitivity.
ABSTRACT
Deep eutectic solvents (DESs) have recently emerged as an alternative solvent for nanoparticle synthesis. There have been numerous advancements in the fabrication of silver nanoparticles (Ag NPs), but the potential of DESs in Ag NP synthesis was neither considered nor studied carefully. In this study, we present a novel strategy to fabricate Ag NPs in a DES (Ag NPs-DES). The DES composed of á´ -glucose, urea, and glycerol does not contain any anions to precipitate with Ag+ cations. Our Ag NPs-DES sample is used in a surface-enhanced Raman scattering (SERS) sensor. The two analytes for SERS quantitation are nitrofurantoin (NFT) and sulfadiazine (SDZ) whose residues can be traced down to 10-8 M. The highest enhancement factors (EFs) are competitive at 6.29 × 107 and 1.69 × 107 for NFT and SDZ, respectively. Besides, the linearity coefficients are extremely close to 1 in the range of 10-8 to 10-3 M of concentration, and the SERS substrate shows remarkable uniformity along with great selectivity. This powerful SERS performance indicates that DESs have tremendous potential in the synthesis of nanomaterials for biosensor substrate construction.
ABSTRACT
Cyanides, which are extremely toxic chemicals that are rapidly absorbed into the human body and interact with cytochrome oxidase, strongly inhibit cellular respiration to body death with convulsions. Cyanide ions that exist in many forms in nature such as those found in apricot kernels, cassava roots, and bamboo shoots as cyanogenic glycosides are inevitably used in various industries, including gold and silver mining as well as in dyes and plastic industries. In this study, for the sake of developing ultrahigh-sensitive sensors for cyanide monitoring in a simple manner, we chemically synthesize Aucore-Agshell hybrid nanomaterials of different core/shell thicknesses for colorimetric sensors and fiber optical sensors. Their sensing principle relies on the formation of the Ag/Au cyanocomplex upon cyanide injection. The generated metal cyanocomplex induced changes in refractive indices, causing changes in properties of localized surface plasmon resonance (LSPR), i.e., optical absorbance change for the colorimetric sensors. For fiber optical sensors, the hybrid metal nanoparticles were immobilized on the fiber core surface and the metal cyanocomplex formation induced changes in the fiber cladding refractive index, enabling quantitative cyanide detection with ultrahigh sensitivity. The LSPR-based colorimetric sensor provided the lowest detectable cyanide concentration of 5 × 10-6 M, whereas the value for the fiber-based sensor was 8 × 10-11 M.
ABSTRACT
This article presents a review of many types of SERS sensors for food safety and environmental pollution monitoring based on detecting rhodamine. It introduces the basic concepts of substrates, enhancement factors, and mechanisms, devices' sensors integrated with the microstructure. Here, we review the state-of-the-art research in the field of rhodamine monitoring and highlight the applications of SERS sensors. The trends in the development of substrates for different applications have been mentioned with the aim of providing an overview of the development of different SERS substrates. Thus, an efficient approach for rhodamine detection has a good perspective for application in environmental monitoring.
