Melamine is one of the most frequently detected adulterants in dairy products.The current study proposes a surface-enhanced Raman spectroscopy(SERS)-based analytical tool for fast and reliable screening of melamine in...Melamine is one of the most frequently detected adulterants in dairy products.The current study proposes a surface-enhanced Raman spectroscopy(SERS)-based analytical tool for fast and reliable screening of melamine in bovine milk.A hand-held Raman spectrometer was used in conjunction with a substrate composed of silver nanoparticles(AgNPs)that was 2D printed onto glass fiber(GF)filter paper.Under optimized conditions,a sensitive and fingerprint-like signal at 674 cm^(-1) was obtained.The AgNPs/GF substrate exhibited high sensitivity to melamine in milk down to 1.9498×10^(-5)mg/mL,which is well below the USA and EU safety limits(2.5×10^(-3)mg/mL).Remarkably,the proposed technology was also highly reproducible,showing spot-to-spot and block-to-block variations below 3.3%and 4.9%at 674 cm^(-1) in Raman intensity,respectively.The characteristic peak intensity and concentration of melamine showed an acceptable linear relationship(R^(2)=0.9909)within the range of 0.0001-1 mg/mL.Overall,the method established in this study can provide an efficient and effective method for the quantitative target screening and detection of melamine in dairy products.展开更多
The proposed work aims to develop a sensitive surface-enhanced Raman spectroscopy(SERS)nano-biosensor.The inverted nano pyramid array on silicon substrate fabricated using electron beam lithography(EBL)was utilised as...The proposed work aims to develop a sensitive surface-enhanced Raman spectroscopy(SERS)nano-biosensor.The inverted nano pyramid array on silicon substrate fabricated using electron beam lithography(EBL)was utilised as a master template and the mold was later replicated via nanoimprinting process to prepare gold-coated polymer nanopyramid three-dimensional(3D)SERS substrate.The fast and versatile replication process using nanoimprinting lithography(NIL)can produce polymer nanopyramids in a low-cost and reproducible fashion.Also,the proposed fabrication protocol can be easily upscale for large scale fabrication.The intense electric field confinement at nanotips and four edges of gold-coated polymer nanopyramid enhanced the Raman signal of probe molecules,i.e.,Rhodamine 6G with a limit of detection down to 3.277×10−9 M was achieved.This work also underlines the efficiency of gold-coated polymer nanopyramid arrays in the spectral detection of hemoglobin proteins at low concentrations.The Raman signal enhancement mechanism was further studied through the electromagnetic simulation using COMSOL Multiphysics.In addition,bending test experiments were performed to understand the effect of flexibility on SERS signal response.The fabricated gold-coated polymer nanopyramids arrays could pave the way for the development of low-cost SERS platforms for the detection of hazardous biological and chemical compounds at ultra-low concentrations in practical applications.展开更多
Sensitivity is crucially important for surface-enhanced Raman spectroscopy(SERS)application to detect trace-level polycyclic aromatic hydrocarbons(PAHs)in the seawater.In this study,a high sensitivity three-dimensiona...Sensitivity is crucially important for surface-enhanced Raman spectroscopy(SERS)application to detect trace-level polycyclic aromatic hydrocarbons(PAHs)in the seawater.In this study,a high sensitivity three-dimensional(3-D)SERS substrate composed with syringe filter,glycidyl methacrylate-ethylene dimethacrylate(GMA-EDMA)porous material and optimal parameters(57 nm,pH 13)gold nanoparticles(Au NPs)was developed for the detection of PAHs in water.The enhancement effect and repeatability of this 3-D substrate were also explored.The Raman intensity of pyrene using 3-D SERS substrate is about 8 times higher than that of substrate only using p H 13 gold colloid solution and about 12 times higher than that of substrate using natural Au NPs and GMA-EDMA porous material,which means both the pH 13 AuN Ps and the GMA-EDMA porous material are important factors for the sensitivity of this 3-D SERS substrate.Good repeatability of this optimal 3-D substrate was obtained.The relative standard deviation(RSD)is less than 8.66% on the same substrate and less than 3.69% on other different substrates.Four kinds of PAHs,i.e.,phenanthrene,pyrene,benzo(a)pyrene,benzo(k)fluoranthene and their mixture,were detected at the different concentrations.Their limits of detection(LODs)are 8.3×10^-10(phenanthrene),2.1×10^-10(pyrene),3.8×10^-10(benzo(a)pyrene)and 1.7×10^-10 mol L^-1(benzo(k)fluoranthene),respectively.In addition,these four PAHs were also detected by fluorescence spectroscopy to evaluate the sensitivity of SERS technology using this optimal 3-D SERS substrate.The results showed that the sensitivity of SERS based on the 3-D SERS substrate even using the portable Raman system was closed to that of fluorescence spectroscopy.Therefore,the SERS technology using this optimal 3-D substrate is expected to be an in-situ method for the detection of environmental PAHs.展开更多
In this study,a convenient method of preparing the substrate is proposed with one-pot synthesis of silver colloid under body heat,and the SERS detection uses the fresh substrate to avoid the drawback of substrates’sh...In this study,a convenient method of preparing the substrate is proposed with one-pot synthesis of silver colloid under body heat,and the SERS detection uses the fresh substrate to avoid the drawback of substrates’short life of use.The synthesis of silver colloid is carried out in a 10 mL vial by using ascorbic acid as a reductant and trisodium citrate as a stabilizer.The vial is grasped with the palm of the experimenter for several minutes without shaking.The proposed method is simple,rapid,green energy and cost-effective.By adjusting the concentration of trisodium citrate,not only the particle size can be controlled from about 110 nm to 50 nm but also the homogeneity of nanoparticles can be improved.As a SERS substrate,the silver colloid has high batch reproducibility and showed good SERS activity.The relative standard deviation between different manufacturers is 5.51%when the substrate of silver colloid is used for the detection of rhodamine 6 G.Using the substrate,the lowest detection concentrations of rhodamine 6 G,crystal violet,enrofloxacin,melamine and leucomalachite green are 1.0×10-8,6.1×10-8,1.4×10-6,7.1×10-5 and 5.1×10-8 mol/L,respectively.Results demonstrate that the developed method has the advantage of convenience and high efficiency in the field preparation of reliable SERS substrate.展开更多
Plasmonic surface of flexible multilayered nanofibers possesses special superiority for the surface-enhanced Raman scattering(SERS)sensing of molecules and microbial cells.However,the fabrication of flexible plasmonic...Plasmonic surface of flexible multilayered nanofibers possesses special superiority for the surface-enhanced Raman scattering(SERS)sensing of molecules and microbial cells.However,the fabrication of flexible plasmonic nanofibers with high sensitivity and reproducibility is difficult.Herein,we report a smart strategy for fabricating flexible plasmonic fibers,in which compact and homogeneous gold nanoparticles(Au NPs)are in-situ grown on the high-curvature surface of multilayered fibers of electrospun polyvinylidene fluoride(PVDF).Firstly,the surface of PVDF fibers is changed electrically,and Au seeds are deposited on the surface of PVDF fibers using electrostatic driving force.Secondly,a stable AuI_(4)−complex is formed employing coordination between I−and AuCl4−ions,which could decrease the reduction potential of AuCl4−and restrain the self-nucleation,and then the reduction reaction of AuI4−is initiated by introducing PVDF@Au seeds to pull down the barrier of potential energy.Finally,in-situ growth of AuNPs is generated on the high-curvature surface of PVDF nanofibers,and large-scale hotspots are generated by adjacent AuNPs coupling in the three-dimensional(3D)space of multilayered fibers.Membrane of PVDF@Au nanofibers also realizes the sensitive detection of thiram molecules(low limit of detection of 0.1 nM)and good reproducibility(relative standard deviation of 10.6%).Meanwhile,due to the multilayered construction of PVDF@Au nanofibers,a valid SERS signal on 3D surface of bacteria could be generated.3D distribution of hotspots on multilayered PVDF@Au nanofibers gives a clear advantage for SERS sensing of organic molecules and microbial cells.展开更多
基金supported by National Natural Science Foundation of China(21804058)Shanxi Scholarship Council of China(2021-068)+1 种基金Shanxi Agricultural University High-Level Talent Project(2021XG013)Shanxi Postdoc Reward(SXBYKY2022001).
文摘Melamine is one of the most frequently detected adulterants in dairy products.The current study proposes a surface-enhanced Raman spectroscopy(SERS)-based analytical tool for fast and reliable screening of melamine in bovine milk.A hand-held Raman spectrometer was used in conjunction with a substrate composed of silver nanoparticles(AgNPs)that was 2D printed onto glass fiber(GF)filter paper.Under optimized conditions,a sensitive and fingerprint-like signal at 674 cm^(-1) was obtained.The AgNPs/GF substrate exhibited high sensitivity to melamine in milk down to 1.9498×10^(-5)mg/mL,which is well below the USA and EU safety limits(2.5×10^(-3)mg/mL).Remarkably,the proposed technology was also highly reproducible,showing spot-to-spot and block-to-block variations below 3.3%and 4.9%at 674 cm^(-1) in Raman intensity,respectively.The characteristic peak intensity and concentration of melamine showed an acceptable linear relationship(R^(2)=0.9909)within the range of 0.0001-1 mg/mL.Overall,the method established in this study can provide an efficient and effective method for the quantitative target screening and detection of melamine in dairy products.
基金The authors would like to acknowledge the state-of-the-art nanofabrication and characterisation facilities by the Indian Nanoelectronics Users Program(INUP)of IIT Bombay.The authors also acknowledge the Science and Engineering Research Board(SERB-DST),India(EEQ/2017/000370),for providing financial support for this research.
文摘The proposed work aims to develop a sensitive surface-enhanced Raman spectroscopy(SERS)nano-biosensor.The inverted nano pyramid array on silicon substrate fabricated using electron beam lithography(EBL)was utilised as a master template and the mold was later replicated via nanoimprinting process to prepare gold-coated polymer nanopyramid three-dimensional(3D)SERS substrate.The fast and versatile replication process using nanoimprinting lithography(NIL)can produce polymer nanopyramids in a low-cost and reproducible fashion.Also,the proposed fabrication protocol can be easily upscale for large scale fabrication.The intense electric field confinement at nanotips and four edges of gold-coated polymer nanopyramid enhanced the Raman signal of probe molecules,i.e.,Rhodamine 6G with a limit of detection down to 3.277×10−9 M was achieved.This work also underlines the efficiency of gold-coated polymer nanopyramid arrays in the spectral detection of hemoglobin proteins at low concentrations.The Raman signal enhancement mechanism was further studied through the electromagnetic simulation using COMSOL Multiphysics.In addition,bending test experiments were performed to understand the effect of flexibility on SERS signal response.The fabricated gold-coated polymer nanopyramids arrays could pave the way for the development of low-cost SERS platforms for the detection of hazardous biological and chemical compounds at ultra-low concentrations in practical applications.
基金supported by the National Natural Science Foundation of China (No. 41476081)the Major Research and Development Project in Shandong Province (Nos. 2016GSF115020, 2019GHY112027)the Shandong Provincial Natural Science Foundation (No. ZR2015DM007)
文摘Sensitivity is crucially important for surface-enhanced Raman spectroscopy(SERS)application to detect trace-level polycyclic aromatic hydrocarbons(PAHs)in the seawater.In this study,a high sensitivity three-dimensional(3-D)SERS substrate composed with syringe filter,glycidyl methacrylate-ethylene dimethacrylate(GMA-EDMA)porous material and optimal parameters(57 nm,pH 13)gold nanoparticles(Au NPs)was developed for the detection of PAHs in water.The enhancement effect and repeatability of this 3-D substrate were also explored.The Raman intensity of pyrene using 3-D SERS substrate is about 8 times higher than that of substrate only using p H 13 gold colloid solution and about 12 times higher than that of substrate using natural Au NPs and GMA-EDMA porous material,which means both the pH 13 AuN Ps and the GMA-EDMA porous material are important factors for the sensitivity of this 3-D SERS substrate.Good repeatability of this optimal 3-D substrate was obtained.The relative standard deviation(RSD)is less than 8.66% on the same substrate and less than 3.69% on other different substrates.Four kinds of PAHs,i.e.,phenanthrene,pyrene,benzo(a)pyrene,benzo(k)fluoranthene and their mixture,were detected at the different concentrations.Their limits of detection(LODs)are 8.3×10^-10(phenanthrene),2.1×10^-10(pyrene),3.8×10^-10(benzo(a)pyrene)and 1.7×10^-10 mol L^-1(benzo(k)fluoranthene),respectively.In addition,these four PAHs were also detected by fluorescence spectroscopy to evaluate the sensitivity of SERS technology using this optimal 3-D SERS substrate.The results showed that the sensitivity of SERS based on the 3-D SERS substrate even using the portable Raman system was closed to that of fluorescence spectroscopy.Therefore,the SERS technology using this optimal 3-D substrate is expected to be an in-situ method for the detection of environmental PAHs.
文摘In this study,a convenient method of preparing the substrate is proposed with one-pot synthesis of silver colloid under body heat,and the SERS detection uses the fresh substrate to avoid the drawback of substrates’short life of use.The synthesis of silver colloid is carried out in a 10 mL vial by using ascorbic acid as a reductant and trisodium citrate as a stabilizer.The vial is grasped with the palm of the experimenter for several minutes without shaking.The proposed method is simple,rapid,green energy and cost-effective.By adjusting the concentration of trisodium citrate,not only the particle size can be controlled from about 110 nm to 50 nm but also the homogeneity of nanoparticles can be improved.As a SERS substrate,the silver colloid has high batch reproducibility and showed good SERS activity.The relative standard deviation between different manufacturers is 5.51%when the substrate of silver colloid is used for the detection of rhodamine 6 G.Using the substrate,the lowest detection concentrations of rhodamine 6 G,crystal violet,enrofloxacin,melamine and leucomalachite green are 1.0×10-8,6.1×10-8,1.4×10-6,7.1×10-5 and 5.1×10-8 mol/L,respectively.Results demonstrate that the developed method has the advantage of convenience and high efficiency in the field preparation of reliable SERS substrate.
基金This work is supported by the National Natural Science Foundation of China(No.81801122)Natural Science Basic Research Program of Shaanxi(No.2020JQ-529)+4 种基金Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JK0658)The industry-University-Research collaborative innovation project of Keqiao Textile Industry Innovation Institute of Xi’an Polytechnic University(No.19KQZD01)Xi’an Science and Technology Project(GXYD7.3)Key R&D projects of Shaanxi(No.2020GY-273)Project of China National Textile Industry Association(No.2020047)。
文摘Plasmonic surface of flexible multilayered nanofibers possesses special superiority for the surface-enhanced Raman scattering(SERS)sensing of molecules and microbial cells.However,the fabrication of flexible plasmonic nanofibers with high sensitivity and reproducibility is difficult.Herein,we report a smart strategy for fabricating flexible plasmonic fibers,in which compact and homogeneous gold nanoparticles(Au NPs)are in-situ grown on the high-curvature surface of multilayered fibers of electrospun polyvinylidene fluoride(PVDF).Firstly,the surface of PVDF fibers is changed electrically,and Au seeds are deposited on the surface of PVDF fibers using electrostatic driving force.Secondly,a stable AuI_(4)−complex is formed employing coordination between I−and AuCl4−ions,which could decrease the reduction potential of AuCl4−and restrain the self-nucleation,and then the reduction reaction of AuI4−is initiated by introducing PVDF@Au seeds to pull down the barrier of potential energy.Finally,in-situ growth of AuNPs is generated on the high-curvature surface of PVDF nanofibers,and large-scale hotspots are generated by adjacent AuNPs coupling in the three-dimensional(3D)space of multilayered fibers.Membrane of PVDF@Au nanofibers also realizes the sensitive detection of thiram molecules(low limit of detection of 0.1 nM)and good reproducibility(relative standard deviation of 10.6%).Meanwhile,due to the multilayered construction of PVDF@Au nanofibers,a valid SERS signal on 3D surface of bacteria could be generated.3D distribution of hotspots on multilayered PVDF@Au nanofibers gives a clear advantage for SERS sensing of organic molecules and microbial cells.
