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 orientation and structural characterization of the ultrathin film of azobenzene-containing amphiphilic compound, C_ 12AzoNaph(1,4)C_6N +Br -, were studied in the present study. The compound can form a stable m...The orientation and structural characterization of the ultrathin film of azobenzene-containing amphiphilic compound, C_ 12AzoNaph(1,4)C_6N +Br -, were studied in the present study. The compound can form a stable monolayer with sodium dextrin sulfate(SDS) by means of electrostatic interaction. Fourier-transform infrared(FT-IR) and near-infrared surface-enhanced Raman scattering(NIR-SERS) spectroscopies were used to study the orientation and characterize the structure of the Langmuir-Blodgett(LB) film and the dipping film. The FT-IR spectra indicate that the alkyl tail is nearly perpendicular to the substrate surface without any aggregation and adopts largely trans-zigzag conformation in the LB film. The NIR-SERS spectra demonstrate that the chromorphoric part in C_ 12AzoNaph(1,4)C_6N +Br is also nearly perpendicular to the surface of silver substrate both in the dipping film and the LB film. A new 'sandwiched system' model was designed to investigate the orientation and structural characterization of the chromophoric part in the multi-monolayer LB films on the non-SERS active substrate. The SERS mechanism of the 'sandwiched system' is discussed in the present paper.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Supported by the Major State Basic Research Development Program( G2 0 0 0 0 7810 2 ) and the National Natural ScienceFoundation of China( No.2 0 0 0 3 0 0 4)
文摘The orientation and structural characterization of the ultrathin film of azobenzene-containing amphiphilic compound, C_ 12AzoNaph(1,4)C_6N +Br -, were studied in the present study. The compound can form a stable monolayer with sodium dextrin sulfate(SDS) by means of electrostatic interaction. Fourier-transform infrared(FT-IR) and near-infrared surface-enhanced Raman scattering(NIR-SERS) spectroscopies were used to study the orientation and characterize the structure of the Langmuir-Blodgett(LB) film and the dipping film. The FT-IR spectra indicate that the alkyl tail is nearly perpendicular to the substrate surface without any aggregation and adopts largely trans-zigzag conformation in the LB film. The NIR-SERS spectra demonstrate that the chromorphoric part in C_ 12AzoNaph(1,4)C_6N +Br is also nearly perpendicular to the surface of silver substrate both in the dipping film and the LB film. A new 'sandwiched system' model was designed to investigate the orientation and structural characterization of the chromophoric part in the multi-monolayer LB films on the non-SERS active substrate. The SERS mechanism of the 'sandwiched system' is discussed in the present paper.
