High SERS performance of functionalized carbon dots in the detection of dye contaminants

INTRODUCTION

The long-term overuse of malachite green (MG) has potential carcinogenic, teratogenic, and mutagenic effects. The functional nanocomposite is novel and challenging to construct and implement through surface enhanced Raman scattering (SERS) strategy to reveal the contributions in application.

OBJECTIVES

The novel Ag-CDs (carbon dots)-PBA (phenyl boric acid) nanocomposite was constructed by a facile route to detect toxic MG molecule with high SERS sensitivity and good uniformity.

METHODS

The enhanced substrate used for the detection of MG has been successfully constructed using PBA modulated Ag-CDs on a structured surface with rich binding sites.

RESULTS

The fabricated Ag-CDs-PBA substrate can be used to analyze various probe molecules exhibiting high sensitivity, good signal reproducibility, and excellent stability. The mechanism between components has been proved by calculations originating from the plasmonic Ag and active electronic transmission among the bridging CDs and PBA via the close spatial π-π effect. In addition, the accelerated separation of electron-hole pairs was triggered to further improve the SERS activity of the hybrid via a bidirectional charge transfer (CT) process. Significantly, the Ag-CDs-PBA system shows distinctive selectivity, in which PBA can hinder the interference of other species without specific hydroxyl groups.

CONCLUSION

Based on this deeper insight on plasmon-mediated mechanism, the SERS substrate was successfully practiced for quantitative determination in real water and fish samples. The strategy developed promises to be a new sensor technology and has great potential for environmental and food safety applications.

A porous silicon composite with irregular silver nano-dendritic particles: a rapid optical sensor for trace detection of malachite green in freshwater fish

This study focused on creating a SERS composite particle specifically designed for detecting malachite green. We synthesized silver nano-dendritic structures on p-type porous silicon using an external electric field, separating them from the silicon wafer. Ultrasonic crushing yielded irregular silver nanodendrite-modified porous silicon composite particles. Upon being tested in an aqueous solution of malachite green, these composite particles demonstrated significant surface-enhanced Raman scattering effects. Our findings highlight the exceptional performance of the SERS substrate composed of porous silicon and irregular silver nano-dendritic particles. It exhibited high sensitivity, specificity, consistent signal strength, and reliability in detecting trace amounts of malachite green in water. Under ideal conditions, the substrate could detect malachite green at concentrations as low as 10-8 M. Moreover, its swift response to trace amounts of malachite green in fish underscores its potential as an effective Raman detector.

A highly sensitive surface-enhanced Raman scattering sensor with MIL-100(Fe)/Au composites for detection of malachite green in fish pond water

Concerns about food safety have been arisen due to the improper use of chemicals in aquaculture. Malachite green (MG) has attracted attention because of its illegal usage and its potential negative impacts on the environment and public health. Surface-enhanced Raman scattering (SERS) platforms coupled with different SERS substrates have been employed for rapid analysis of MG residues in food. However, the most commonly used SERS substrates were non-reusable and showed limited detection sensitivity. In this study, a novel SERS substrate with a good recyclability and a high sensitivity was prepared by electrostatically assembling together a metal-organic framework material called materials of institute lavoisie-100(Fe) (MIL-100(Fe)) and Au NPs. The lowest detectable concentration of MG was 10^-13 M based on the optimal substrate. The SERS sensor was applied for the detection of the trace MG in fish pond water, which was accomplished with the correlation coefficients R² = 0.991-0.996 in a concentration range of 10^-6-10^-13 M. Moreover, MIL-100(Fe)/Au was recycled at least five times, realizing a "detection to degradation", showing great potential for food contamination monitoring due to its distinguished performance.

Surface Modification of Bi2O3 Nanoparticles with Biotinylated β-Cyclodextrin as a Biocompatible Therapeutic Agent for Anticancer and Antimicrobial Applications

Bismuth oxide nanoparticles with appropriate surface chemistry exhibit many interesting properties that can be utilized in a variety of applications. This paper describes a new route to the surface modification of bismuth oxide nanoparticles (Bi₂O₃ NPs) using functionalized beta-Cyclodextrin (β-CD) as a biocompatible system. The synthesis of Bi₂O₃ NP was done using PVA (poly vinyl alcohol) as the reductant and the Steglich esterification procedure for the functionalization of β-CD with biotin. Ultimately, the Bi₂O₃ NPs are modified using this functionalized β-CD system. The particle size of the synthesized Bi₂O₃ NPs is found to be in the range of 12-16 nm. The modified biocompatible systems were characterized using different characterization techniques such as Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and Differential Scanning Calorimetric analysis (DSC). Additionally, the antibacterial and anticancerous effects of the surface-modified Bi₂O₃ NP system were also investigated.

Dual-reverse-signal ratiometric fluorescence method for malachite green detection based on multi-mechanism synergistic effect

The proposition of ratiometric detection mode has demonstrated great superiority in improving analysis accuracy by forming self-calibration. Herein, the novel dual-reverse-signal ratiometric fluorescence detection for malachite green (MG) was first achieved based on synergistic effect of fluorescence resonance energy transfer (FRET) and inner filter effect (IFE). The ratiometric fluorescence probe (B-RCDs) was self-assembled via electrostatic attraction between blue-emission carbon dots (BCDs) and red-emission carbon dots (RCDs), followed with FRET effect from BCDs to RCDs and exhibited dual-emission at 450 nm and 627 nm. In the presence of MG, the IFE effect between MG and RCDs quenched the fluorescence at 627 nm and restored the fluorescence at 450 nm, sending out two reverse signals along with an obvious color change from pink to purple (302 nm UV lamp). This ratiometric method not only simplified the preparation process, but also improved the detection sensitivity, showing a low limit of detection (LOD) of 41.8 nM, which exhibited superiority than that of single-signal RCDs (157.3 nM). This method held a rapid response of 10 min and represented satisfactory recoveries (99.14%-109.08%) in real water samples, revealing it was a promising candidate in the fast, sensitive and practical detection of MG. Moreover, the design of synergistic effect supplied a new perspective for the development of ratiometric sensing in the future.

Size controlled silver nanoparticles on β-cyclodextrin/graphitic carbon nitride: an excellent nanohybrid material for SERS and catalytic applications

A nanohybrid (NH), having high dispersion of silver nanoparticles (AgNPs) on β-cyclodextrin (β-CD)/graphitic carbon nitride (g-CN), designated as AgNPs/β-CD/g-CN-NH, was synthesized and characterized. It was exploited for a couple of environmental remediation applications like SERS sensing and catalytic reduction of specific organic pollutants in water. It showed excellent SERS activity as a Raman probe for the detection of malachite green (MG). Its enhancement factor (EF) and detection limit for MG were equal to 7.26 × 10⁶ and 1 × 10^-9 M, respectively. The relative standard deviation (RSD) was equal to 3.8% which indicates high homogeneity of AgNP dispersion and signal reproducibility of the SERS substrate. The NH displayed high catalytic activity for the reduction of eosin yellow (EY) in the presence of NaBH₄ with the rate constant (k) of 0.1142 min^-1. A comparison of the present NH with other reported materials reveals better SERS and catalytic activities of the former than those of the latter. The SERS activity of the NH was also examined for sensing of other triphenylamine dyes like methyl violet (MV), and it was successful. The same NH also exhibited high catalytic activity towards the reduction of Congo red (CR). The results of both studies clarify that the NH is an excellent SERS substrate and efficient catalyst for the detection of organic environmental pollutants having structures similar to MG and their degradation. This is due to the distribution of the controlled size of AgNPs on g-CN promoted by β-CD. Therefore, we focus our attention on future environmental applications of the nanohybrid as a very cheap SERS substrate and a very active catalyst.

Cyclodextrin-assisted surface-enhanced Raman spectroscopy: a critical review

Numerous approaches have been proposed to overcome the intrinsically low selectivity of surface-enhanced Raman spectroscopy (SERS), and the modification of SERS substrates with diverse recognition molecules is one of such approaches. In contrast to the use of antibodies, aptamers, and molecularly imprinted polymers, application of cyclodextrins (CDs) is still developing with less than 100 papers since 1993. Therefore, the main goal of this review is the critical analysis of all available papers on the use of CDs in SERS analysis, including physicochemical studies of CD complexation and the effect of CD presence on the Raman enhancement. The results of the review reveal that there is controversial information about CD efficiency and further experimental investigations have to be done in order to estimate the real potential of CDs in SERS-based analysis.

Facile synthesis of Au nanoparticle-coated Fe3O4 magnetic composite nanospheres and their application in SERS detection of malachite green

A facile method for synthesizing Au nanoparticle-coated Fe₃O₄ magnetic composite nanospheres (Fe₃O₄@Au MCS) via seed-mediated growth and iterative reduction is reported. The nanospheres were then successfully used to detect malachite green (MG) residues in water bodies via surface-enhanced Raman scattering (SERS) technique. Fe₃O₄@Au MCS has excellent optical properties and superparamagnetism; it can be dispersed into the solution to fully adsorb target molecules and then collected with a magnet to increase the molecular density and the number of SERS hot spots. Magnetic enrichment was superior to conventional detection method. The limit of detection for MG was 10^-7 M and the enhancement factor was 1.1 × 10⁵. The logarithm of the SERS intensity of the characteristic peak at 1618 cm^-1 exhibited a linear relationship with the logarithm of the MG concentration over the range of 10^-3- 10^-7 M, with a correlation coefficient of 0.966. The Fe₃O₄@Au MCS had good uniformity of SERS signals, with a 18.59% relative standard deviation for the SERS intensity. MG detection in aquaculture water conformed with the established quantitative regulations. The SERS spectrum calculated with density function theory for MG adsorbed on Fe₃O₄@Au MCS was very close to the experimental spectrum, which verified enhancement by the substrate. Overall, Fe₃O₄@Au MCS enabled ultrasensitive, quantitative SERS detection of MG.

A Europium-based MOF Fluorescent Probe for Efficiently Detecting Malachite Green and Uric Acid

Lanthanide (such as Tb and Eu) metal-organic frameworks (MOFs) have been widely used in fluorescent probes because of their multiple coordination modes and brilliant fluorescence characteristic. Many lanthanide MOFs were applied in detecting metal ions, inorganic anions, and small molecules. However, it's rarely reported that Ln-MOF was devoted to detecting malachite green (MG) and uric acid (UA). We prepared a europium-based metal-organic framework (Eu-TDA) (TDA = 2,5-thiophenedicarboxylic acid group). Luminescence studies demonstrated that Eu-TDA can rapidly detect MG and UA with excellent selectivity and sensitivity, where individual quenching efficiency K_sv (MG: 5.8 × 10⁵ M^-1; UA: 4.15 × 10⁴ M^-1) and detection limit (MG: 0.0221 μM; UA: 0.689 μM) were regarded as the excellent MOF sensors for detecting MG and UA. The quenching of Eu-TDA's fluorescence emission by MG and UA was likely due to the spectral overlap, energy transfer, and competition. Among 11 metal cations and 14 anions, Eu-TDA can quickly and effectively recognize MG and UA with highly selective and sensitive properties. Our method possesses potential application in detecting UA in human blood and MG in the fishpond.

Rapid and sensitive detection of trace malachite green and its metabolite in aquatic products using molecularly imprinted polymer-coated wooden-tip electrospray ionization mass spectrometry

In this study, a molecularly imprinted polymer-coated wooden-tip (MIPCWT) electrospray ionization mass spectrometry (ESI-MS) method was developed for rapid and sensitive detection of trace malachite green (MG) and its metabolite in aquatic products.