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(a) SERS spectra of 10⁻⁶ M and 10⁻⁵ M of MB/CV mixtures on MoO3@MIPs. Inset: SERS spectra of CV (10⁻⁵ M) on MoO3@MIPs and MoO3@NIPs; (b) intensity ratio of the peak at 1400 cm⁻¹ and 1588 cm⁻¹ on 10 measured sites and the calculated RSD; (c) SERS spectra of mixtures composed of 10⁻⁵ M CV and lower level of MB (10⁻⁶ to 5 × 10⁻⁶ M); (d) relationship between normalized I1588/I1400 and CCV/MB. For every detected sample, SERS spectra were obtained from ten different spots. To exclude the interference from surficial molecules, the MoO3@MIP substrates immersed from the mixture of CV and MB were washed with acetonitrile and methanol–acetic acid (4 : 1, v/v) solution
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A sensitive and selective SERS sensor with easy and excellent recyclability is highly demanded because of its great potential application in complex detection environments. Here, using methylene blue (MB) as a model target, a semiconductor-based SERS substrate composed of a MoO3 nanorod core and a uniform molecule-imprinting polymethacrylic acid sh...
Citations
... Additional peaks appear in the fingerprint area between 1000-500 cm -1 for all the asprepared catalysts, indicating the presence of metal oxide in ZSM-5. The characteristic bands of MoO3 show absorbance bands around 999-995, 900-877, 561-554 cm -1 [30]. Furthermore, the additional characteristic peaks for Co3O4 show around 667, 626, and 580 cm -1 [31,32]. ...
The conversion of lignocellulose biomass to value-added chemicals is challenging. In this paper, the conversion process of diphenyl ether (DPE) as a model lignin compound to phenol and vanillin compounds involved a bifunctional catalyst in reaching the simultaneous one-pot reaction in mild conditions with a high yield product. The catalysts used in this conversion are hierarchical ZSM-5 zeolites and their cobalt oxide and molybdenum oxide impregnated derivate. The ZSM-5 zeolites were synthesized using alternative precursors from natural resources, i.e., Indonesian natural zeolite and kaolin. The physicochemical properties of the catalysts were determined with various characterization methods, such as: X-ray Diffraction (XRD), Fourier Transform Infra Red (FT-IR), Scanning Electron Microscope - Energy Dispersive X-ray (SEM-EDX), X-ray Fluorescence (XRF), Surface Area Analyzer (SAA), and NH3-Temperature Programmed Desorption (NH3-TPD). The catalytic activity on conversion of DPE substrates showed that the MoOx/HZSM-5 produced the highest %yield for phenol and vanillin products; 31.96% at 250 °C and 7.63% at 200 °C, respectively. The correlation study between the physicochemical properties and the catalytic activity shows that the dominance of weak acid (>40%) and mesoporosity contribution (pore size of ~ 9 nm) play roles in giving the best catalytic activity at low temperatures. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
... However, to the best of our knowledge, very few are reported for selective and recyclable SERS substrates based on semiconductor NMs because of inadequate separation capability and non-selective performance. 12,14 Broadly, molecule-imprinting polymers (MIPs) with SERSactive substrates have significantly improved SERS selectivity besides the sensitivity for noble metal NMs. 7−11 Similar MIP strategies have been applied for selective SERS detection based on semiconductor NMs (e.g., MoO 3 12,13 and MoS 2 14 ) to improve selectivity and recyclability. ...
... In addition to the sensitivity, selectivity, and stability, the reusability of SERS substrates is also a pressing issue for practical applications, which is generally rare for noble metal NM-as well as semiconductor NM-based SERS substrates. 9,10,12,13 Herein, the assynthesized MoO 2 /N-doped-carbon nanocomposite has been tested for three successive reusable cycles for SERS detection. During the recycling process, photocatalysis of the MoO 2 core has been verified to be helpful in the degradation of MB (1 × 10 −4 M). ...
... The XRD analysis was further carried out to verify the stability of the reused MoO 2 / N-doped-carbon substrate during cyclic testing by xenon irradiation (after the third cycle) as well as acidic ethanol washing (after the fifth cycle), as represented in Figure S10 (see Supporting Information). The formation of MoO 3 (JCPDS 050508) was observed under ultraviolet light emitted from xenon irradiation (300 W, λ = 100−1800 nm) after the third cycle, which may be the primary reason for the ∼ 4−13% decrease in the SERS intensity during each process of selfcleaning by photocatalytic elimination ( Figure S10 This further allowed a selective photocatalytic elimination of adsorbed MB in a specific "elect-and-eliminate" approach, 12 and the recycling experiments were further carried out. Figure 10b shows that no pronounced MB peaks were detected from the first-run used MoO 2 /N-doped-carbon nanocomposite after 30 min of irradiation, implying the total elimination of adsorbed MB from a mixed ternary MB/MO/RhB solution. ...
... where I SERS refers to the SERS signal from the number of probe molecules (N SERS ) and I Bulk represents the Raman signal caused by number of probe molecules (N Bulk ). 21,[36][37][38]41 The number of molecules in the reference (N Bulk ) was estimated using the focal volume of the laser spot incident on the analyte and the density of the material. Similarly, the number of molecules in the sample (N SERS ) was estimated by considering the total number of analyte molecules spread on the substrate, assuming a complete homogeneous adsorption of the analyte as well as homogeneous distribution across the SERS samples and the fraction of area falling within the laser spot. ...
... where I SERS refers to the SERS signal from the number of probe molecules (N SERS ) and I Bulk represents the Raman signal caused by number of probe molecules (N Bulk ). 21,[36][37][38]41 The number of molecules in the reference (N Bulk ) was estimated using the focal volume of the laser spot incident on the analyte and the density of the material. Similarly, the number of molecules in the sample (N SERS ) was estimated by considering the total number of analyte molecules spread on the substrate, assuming a complete homogeneous adsorption of the analyte as well as homogeneous distribution across the SERS samples and the fraction of area falling within the laser spot. ...
The enhancement of the Surface-enhanced Raman Scattering (SERS) property of the plasmonic metal oxide semiconductor nanostructures, by controlling their phase, shape, size and oxygen vacancies to detect trace amount of organics is of significant interest. In this study, a simple surfactant free hydrothermal strategy was proposed to fabricate crystalline h-MoO3-x and α-MoO3-x nanomaterials with tunable plasmonic properties. Herein, the crystal phase, morphology and oxygen vacancy of MoO3-x nanostructures were precisely controlled under suitable synthetic conditions. The plasmonic properties of the as-synthesized h-MoO3-x and α-MoO3-x micro/nanostructures were controlled by adjusting the residual volume in the autoclaving chamber. In addition, the plasmonic MoO3-x exhibited SERS activity with detection limit as low as 1.0 × 10⁻⁹ M and the maximum enhancement factor (EF) up to 6.99× 10⁵ for h-MoO3-x, while for α-MoO3-x, the detection limit was 1.0 × 10⁻⁷ M with corresponding EF up to 8.51 × 10³; comparable with plasmonic noble metal nanomaterials without a “hot spot”.
... Beyond this limit, the intensities of peaks tend to be significantly weakened as the analytes get farther away from the plasmonic core [26]. One major advantage of the core-shell structures is the formation of over-irregular structures, especially for those involving bulk MIPs, whereas MIP layers on core-shell structures are evenly coated on the surface of the plasmonic nanostructures, making it easier to extract the template molecules [29,30]. Unlike in the irregular MIPs, the templates are deeply embedded into the crosslinked bulk material that makes it hard to remove. ...
... With the involvement of a polymer layer, MIPs often exhibit drawbacks such as unnecessary background signals and noise. Moreover, a study by Wang and others demonstrated that with the increasing thickness of the polymer shell, the contact between the analyte and plasmonic material which is necessary to produce the SERS effect, is retarded, decreasing the charge transfer effect, negatively affecting the resulting SERS signals [29]. Therefore, in designing a MIP-based system for SERS application, it is important to find an optimal condition to maintain the effect of SERS that generates through a physical means of SERS mechanism even with possible interferences brought by the layer of MIPs. ...
The detection of specific pesticides on food products is essential as these substances pose health risks due to their toxicity. The use of surface-enhanced Raman spectroscopy (SERS) takes advantage of the straightforward technique to obtain fingerprint spectra of target analytes. In this study, SERS-active substrates are made using Au nanoparticles (NPs) coated with a layer of polymer and followed by imprinting with a pesticide–Cypermethrin, as a molecularly imprinted polymer (MIP). Cypermethrin was eventually removed and formed as template cavities, then denoted as Au NP/MIP, to capture the analogous molecules. The captured molecules situated in-between the areas of high electromagnetic field formed by plasmonic Au NPs result in an effect of SERS. The formation of Au NP/MIP was, respectively, studied through morphological analysis using transmission electron microscopy (TEM) and compositional analysis using X-ray photoelectron spectroscopy (XPS). Two relatively similar pesticides, Cypermethrin and Permethrin, were used as analytes. The results showed that Au NP/MIP was competent to detect both similar molecules despite the imprint being made only by Cypermethrin. Nevertheless, Au NP/MIP has a limited number of imprinted cavities that result in sensing only low concentrations of a pesticide solution. Au NP/MIP is thus a specific design for detecting analogous molecules similar to its template structure.
... These "holes" render the MIP-SERS sensors with "memory" function, which can selectively capture target molecules to the metal surface for SERS generation under the excitation of the incident light. 37 It is well-known that noble metal particles determine the enhancement factor. Generally, nanoparticles (NPs) with tips or sharp edges, such as nanorods, 20 nanowool balls, 38 nanostars, 39,40 nanoflowers, 21 and nanosheets, 41 have better Raman enhancement ability and are popular in SERS substrate fabrication. ...
Molecularly imprinted polymers (MIPs) receive extensive interests, 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, non-destructive property, high sensitivity and rapidity. Accordingly, MIPs based SERS (MIP-SERS) sensors have attracted significant research interest for versatile applications especially in the field of chemo and bio analysis, 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. Firstly, the basic structure of the MIP-SERS sensors is briefly outlined. Secondly, novel imprinting strategies are highlighted mainly including multi-functional monomer imprinting, dummy template imprinting, living/controlled radical polymerization and stimuli-responsive imprinting. Thirdly, typical application of MIP-SERS sensors in chemo/bio analysis 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.
... Under adequate UV light irradiation, templates were completely removed and the sensor was regenerated to be used up to 5 consecutive cycles. On the other hand, Wang et al. [106] developed a sensor based on MoO3, also active in SERS, covered with a MIP for the selective detection of methylene blue. In this case the material was treated with acid to generate hydroxyl groups on the surface and then functionalized with MPS to further grow the polymer on the surface. ...
... The greatest variability is usually found in the way the polymer is obtained and the transduction mechanism used (Table 5) [108]. On the other hand, Wang et al. [106] developed a sensor based on MoO 3 , also active in SERS, covered with a MIP for the selective detection of methylene blue. In this case the material was treated with acid to generate hydroxyl groups on the surface and then functionalized with MPS to further grow the polymer on the surface. ...
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.
