A high performance and highly-controllable core-shell imprinted sensor based on the surface-enhanced Raman scattering for detection of R6G in water

A new PdMOF-loaded molecularly imprinted polyaniline nanocatalytic probe for ultratrace oxytetracycline with SERS technique

In this paper, a new Pd metal organic framework (PdMOF) surface molecularly imprinted polyaniline nanocatalytic probe (PdMOF@MIP) with dual functions of recognition and catalysis was synthesized. It is found that the PdMOF@MIP nanoprobe can not only identify OTC but also catalyze the new nanoreaction of NaH2PO2-HAuCl4 to generate gold nanoparticles (AuNPs), and the generated AuNPs could be traced by surface-enhanced Raman scattering (SERS). When OTC specifically binds to PdMOF@MIP to generate PdMOF@MIP-OTC conjugate, its catalytic effect is weakened and the analytical signal is reduced linaerly. Accordingly, a new, highly sensitive, selective and simple SERS/RRS/Abs trimode detection platform for OTC was constructed. The linear range of SERS was 0.0625 ng/mL ∼ 1.75 ng/mL and the limit of detection was 0.015 ng/mL. This new nanocatalytic probe detection strategy can also be used for the selective detection of other antibiotics such as tetracycline and doxycycline, respectively. In addition, the nanocatalytic mechanism has been investigated.

Preparation of surface molecular imprinting fluorescent sensor based on magnetic porous silica for sensitive and selective determination of catechol

A magnetic fluorescent molecularly imprinted sensor was successfully prepared and implemented to determine catechol (CT). Fe3O4 nanoparticles were synthesized by the solvothermal technique and mesoporous Fe3O4@SiO2@mSiO2 imprinted carriers were prepared by coating nonporous and mesoporous SiO2 shells on the surface of the Fe3O4 subsequently. The magnetic surface molecularly imprinted fluorescent sensor was created after the magnetic mesoporous carriers were modified with γ-methacryloxyl propyl trimethoxy silane to introduce double bonds on the surface of the carries and the polymerization was carried out in the presence of CT and fluorescent monomers. The magnetic mesoporous carriers were modified with γ-methacryloxyl propyl trimethoxy silane and double bonds were introduced on the surface of the carriers. After CT binding with the molecularly imprinted polymers (MIPs), the fluorescent intensity of the molecularly imprinted polymers (Ex = 400 nm, Em = 523 nm) increased significantly. The fluorescent intensity ratio (F/F0) of the sensor demonstrated a favorable linear correlation with the concentration of CT between 5 and 50 μM with a detection limit of 0.025 μM. Furthermore, the sensor was successfully applied to determine CT in actual samples with recoveries of 96.4-105% and relative standard deviations were lower than 3.5%. The results indicated that the research of our present work provided an efficient approach for swiftly and accurately determining organic pollutant in water.

Preparation of SiO2@Ag@molecular imprinted polymers hybrid for sensitive and selective detection of amoxicillin using surface-enhanced Raman scattering

In this work, we fabricated a 300 nm-sized silver-coated silica (SiO₂@Ag) SERS substrate. Based on SiO₂@Ag, we designed SiO₂@Ag@molecular imprinted polymers (SiO₂@Ag@MIPs) to realize selectively detection of amoxicillin by coating a molecular imprinted layer averagely thinner than 10 nm on SiO₂@Ag. The as-prepared SERS-active substrate demonstrates excellent enhancement for amoxicillin as well as the enhancement factors were 1.63 × 10⁶ of SiO₂@Ag@MIPs and 2.97 × 10⁵ of SiO₂@Ag, respectively. The SiO₂@Ag@MIPs core-shell hybrids as SERS substrates and the minimum detectable concentration of amoxicillin was as low as 2.7 × 10^-9 M, and the detection limit of SiO₂@Ag was 2.7 × 10^-7 M. The linear relationship between intensities of characteristic peaks and concentrations of amoxicillin was established. Both SiO₂@Ag and SiO₂@Ag@MIPs substrates were highly sensitive and could achieve qualitative and semi-quantitative analysis of amoxicillin in aqueous media with good linear correlations. Based on the above, SiO₂@Ag@MIPs will be conducive to detecting actual samples and expanding the practical application.

Molecularly imprinted 3D SERS sensor with inorganic frameworks for specific and recyclable SERS sensing application

Poor selectivity and reusability of Au/Ag nanostructures are the main challenges for surface-enhanced Raman spectroscopy (SERS) in real sample detection. Herein, a novel specific and reusable three-dimensional (3D) SERS sensor with dual functions of selective trapping and photocatalytic degradation was designed. Firstly, Au-Ag bimetallic nanoparticles decorated silicon nanowires array (SiNWs-AuAg) were prepared as 3D SERS substrate. Then, silicon-based inorganic-framework molecularly imprinted TiO₂ (TiO₂@SiMIP) was synthesized and immobilized on SiNWs-AuAg by using rhodamine 6G (R6G) as template molecule. Owing to the excellent SERS performance of SiNWs-AuAg and the specific affinity of TiO₂@SiMIP to template molecule, the prepared SERS sensor enables sensitive and selective detection of R6G in food samples with a limit of detection (LOD) of 0.27 nM. In addition, due to the photocatalysis of TiO₂ and the stability of silicon-based inorganic framework, the residual templates in TiO₂@SiMIP can be completely removed by UV irradiation, and the imprinted cavity of regenerated sensors still maintained good selectivity after regeneration by UV irradiation.

Zr-based metal organic framework nanoparticles coated with a molecularly imprinted polymer for trace diazinon surface enhanced Raman scattering analysis

In this study, a new surface imprinted polymer of type MOFs-MIPs was synthesized with diazinon as template and Zr-based metal organic framework (UiO-67) as matrix for trace diazinon surface enhanced...

Sensitive, Reusable, Surface-Enhanced Raman Scattering Sensors Constructed with a 3D Graphene/Si Hybrid

Surface-enhanced Raman scattering (SERS) substrates based on graphene and its derivatives have recently attracted attention among those interested in the detection of trace molecules; however, these substrates generally show poor uniformity, an unsatisfactory enhancement factor, and require a complex fabrication process. Herein, we design and fabricate three-dimensional (3D) graphene/silicon (3D-Gr/Si) heterojunction SERS substrates to detect various types of molecules. Notably, the detection limit of 3D-Gr/Si can reach 10^-10 M for rhodamine 6G (R6G) and rhodamine B (RB), 10^-7 M for crystal violet (CRV), copper(II) phthalocyanine (CuPc), and methylene blue (MB), 10^-8 M for dopamine (DA), 10^-6 M for bovine serum albumin (BSA), and 10^-5 M for melamine (Mel), which is superior to most reported graphene-based SERS substrates. Besides, the proposed 3D-Gr/Si heterojunction SERS substrates can achieve a high uniformity with relative standard deviations (RSDs) of less than 5%. Moreover, the 3D-Gr/Si SERS substrates are reusable after washing with ethyl alcohol to remove the adsorbed molecules. These excellent SERS performances are attributed to the novel 3D structure and abundantly exposed atomically thin edges, which facilitate charge transfer between 3D-Gr and probe molecules. We believe that the 3D-Gr/Si heterojunction SERS substrates offer potential for practical applications in biochemical molecule detection and provide insight into the design of high-performance SERS substrates.

An overview on molecular imprinted polymers combined with surface-enhanced Raman spectroscopy chemical sensors toward analytical applications

Surface-enhanced Raman spectroscopy (SERS) is a powerful and high-speed detection technology. It provides information on molecular fingerprint recognition with ultrahigh sensitive detection. However, it shows poor anti-interference capacity against complex matrices. Molecularly imprinted polymers (MIPs) can achieve specific recognition of targets from complex matrices. Through introducing the MIP separation system, the MIP-SERS chemical sensor can effectively overcome the limitation of complex matrix interference, and further improve the stability of sensors for detection. Herein, the materials and structures of integrated MIP-SERS sensors are systematically reviewed, and its application as a sensor for chemical detection of hazardous substances in environmental and food samples has been addressed as well. To broaden the prospects of application, we have discussed the current challenges and future perspectives that would accelerate the development of versatile MIP-SERS chemical sensors.

Molecular-Imprinting-Based Surface-Enhanced Raman Scattering Sensors

Molecularly imprinted polymers (MIPs) receive extensive interest, owing to their structure predictability, recognition specificity, and application universality as well as robustness, simplicity, and inexpensiveness. Surface-enhanced Raman scattering (SERS) is regarded as an ideal optical detection candidate for its unique features of fingerprint recognition, nondestructive property, high sensitivity, and rapidity. Accordingly, MIP based SERS (MIP-SERS) sensors have attracted significant research interest for versatile applications especially in the field of chemo- and bioanalysis, showing excellent identification and detection performances. Herein, we comprehensively review the recent advances in MIP-SERS sensors construction and applications, including sensing principles and signal enhancement mechanisms, focusing on novel construction strategies and representative applications. First, the basic structure of the MIP-SERS sensors is briefly outlined. Second, novel imprinting strategies are highlighted, mainly including multifunctional monomer imprinting, dummy template imprinting, living/controlled radical polymerization, and stimuli-responsive imprinting. Third, typical application of MIP-SERS sensors in chemo/bioanalysis is summarized from both small and macromolecular aspects. Lastly, the challenges and perspectives of the MIP-SERS sensors are proposed, orienting sensitivity improvement and application expanding.

Preparation and luminescence properties of core–shell structure composites SiO2@ANA-Si–Eu and SiO2@ANA-Si–Eu–L and core–shell–shell structure composites SiO2@ANA-Si–Eu@SiO2 and SiO2@ANA-Si–Eu–L@SiO2

Preparation and properties of core–shell and core–shell–shell structure composites with good luminescence properties.

High-sensitive imprinted membranes based on surface-enhanced Raman scattering for selective detection of antibiotics in water

Poly(vinylidene fluoride) (PVDF) is known as one of the widely used membrane separation materials with excellent physical and chemical properties. In this work, we combine surface-enhanced Raman scattering (SERS) detection technology, membrane separation technology and molecular imprinting technology (MIT) to improve sensitivity and selectivity for selective detection of the enrofloxacin hydrochloride in water. In this investigation, PVDF membranes were used as the support materials and different experiment parameters were investigated to obtain the best property. Meanwhile, the Ag nanoparticles (Ag NPs) modified by 3-methacryloxypropyltrimethoxysilane (KH-570) were used as the SERS substrates and they were uniformly dispersed on the surface of the membrane. Finally, Ag-based SERS imprinted membranes (ASIMs) with specific recognition property were successfully prepared with enrofloxacin hydrochloride as the template molecule, acrylamide (AM) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as the cross-linker agent and 2,2'-azobis(2-methylpropionitrile) (AIBN) as the initiator by a facile and versatile precipitation polymerization strategy. Under the optimal condition, it was presented good linear relationship (R² = 0.994) between the Raman signal (at 1390.8 cm^-1) and the concentration (10^-3 mol·L^-1-10^-7 mol·L^-1) of the templates, and the limit of detection was determined as 10^-7 mol·L^-1. The morphology and characters were investigated and the results proved that the SERS imprinted membranes could be used into the selective detection of antibiotics and it provided a novel approach of antibiotics detection.

Rapid and sensitive detection of enrofloxacin hydrochloride based on surface enhanced Raman scattering-active flexible membrane assemblies of Ag nanoparticles

The abuse of antibiotics resulted in the pollution of river is more and more serious and it was necessary to exploit a sensitive detection method to improve the traditional analysis measurement. In this test, it is reported an Ag-based SERS sensing membrane synthesized by the technique of SERS detection and membrane separation. SERS analysis technique presented sensitive detection property, which could be applied into trace analysis. Membrane separation could effectively enrich the analytes to improve the sensitivity. The SERS membrane was synthesized by filtrating Ag nanoparticles (NPs) on the surface and investigating the amount of PVP and Ag NPs to the sensitivity. Meanwhile, the addition of Ag NPs effectively improved the hydrophilia to promote the detection effectivity in the water. By the investigations of optical analysis, the SERS membrane presented high sensitivity in the detection of antibiotics. Under the optimal condition, the SERS intensity presented good linear relationship with the concentration of antibiotics between 1.0 nmol L^-1 and 200 nmol L^-1. This method provided a sensitive detection approach and broadened the investigation field of antibiotics detection.

Molecularly Imprinted Polymer-Based Hybrid Materials for the Development of Optical Sensors

We report on the development of new optical sensors using molecularly imprinted polymers (MIPs) combined with different materials and explore the novel strategies followed in order to overcome some of the limitations found during the last decade in terms of performance. This review pretends to offer a general overview, mainly focused on the last 3 years, on how the new fabrication procedures enable the synthesis of hybrid materials enhancing not only the recognition ability of the polymer but the optical signal. Introduction describes MIPs as biomimetic recognition elements, their properties and applications, emphasizing on each step of the fabrication/recognition procedure. The state of the art is presented and the change in the publication trend between electrochemical and optical sensor devices is thoroughly discussed according to the new fabrication and micro/nano-structuring techniques paving the way for a new generation of MIP-based optical sensors. We want to offer the reader a different perspective based on the materials science in contrast to other overviews. Different substrates for anchoring MIPs are considered and distributed in different sections according to the dimensionality and the nature of the composite, highlighting the synergetic effect obtained as a result of merging both materials to achieve the final goal.

Multi-hydrogen bond assisted SERS detection of adenine based on multifunctional graphene oxide/poly (diallyldimethyl ammonium chloride)/Ag nanocomposites

Nanocomposites of graphene oxide/poly (diallyldimethyl ammonium chloride)/Ag nanoparticles (GO/PDDA/Ag NPs) were constructed via a self-assembly process as a surface-enhanced Raman scattering (SERS) substrate, in which functional macromolecules PDDA were utilized to load GO and support Ag NPs. Fundamental SERS performance of this SERS substrate was evaluated using rhodamine 6G (R6G), which displayed excellent enhancement effect, transferable nature and high stability of the synthesized GO/PDDA/Ag NPs substrate. Furthermore, the synthesized SERS substrate was employed in the sensitive detection of adenine with a linear range of 0.05-1000 μM and low detection limit of 1 nM. Other than the large surface area of GO, multiple-hydrogen bond interactions between adenine and the modified PDDA were another important factor in capturing adenine molecules and enhancing SERS signal. The hydrogen bond interaction was calculated using quantum mechanical calculations. Moreover, determination of adenine in aqueous solutions was achieved with good anti-interference ability against other nucleic bases with similar structures, such as guanine, cytosine and thymine. Therefore, GO/PDDA/Ag can be anticipated to be a potential substrate for label-free, fast and sensitive SERS detection of adenine in the field of bioanalysis.

Selectivity/Specificity Improvement Strategies in Surface-Enhanced Raman Spectroscopy Analysis

Surface-enhanced Raman spectroscopy (SERS) is a powerful technique for the discrimination, identification, and potential quantification of certain compounds/organisms. However, its real application is challenging due to the multiple interference from the complicated detection matrix. Therefore, selective/specific detection is crucial for the real application of SERS technique. We summarize in this review five selective/specific detection techniques (chemical reaction, antibody, aptamer, molecularly imprinted polymers and microfluidics), which can be applied for the rapid and reliable selective/specific detection when coupled with SERS technique.

A high-performance SERS-imprinted sensor doped with silver particles of different surface morphologies for selective detection of pyrethroids in rivers

Ag-MIPs were prepared through a multistep procedure, in which MPS and LC were selected as the template molecules. These materials could selectively rebind the templates and could be detected using Raman spectroscopy.