TAILIEUCHUNG - Microsensors Part 13

Tham khảo tài liệu 'microsensors part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 170 Microsensors Fig. 4. UV-Vis-NIR spectra for aqueous dispersions of different core-shell metal@pNIPAM nanocomposites. Data are recorded at 22 c solid lines and 44 c dash line which corresponds to the swollen and collapsed shell states respectively. A Sphere-coated particles a Au-sphere 64 nm b Au-sphere 103 nm c Au@Ag core-shell sphere. B Rod-coated particles a Au-nanorod b Au@Au nanorod c Au@Ag nanorod 10 time diluted to avoid scattering effects . Reprinted with permission from Contreras-Caceres Pastoriza-Santos et al. Copyright 2010 by Wiley-VSC Verlag GmbH Co. KGaA. 116 nm are prepared by seeded growth of the 67 nm coated gold cores through the addition of HAuCU and ascorbic acid as reducing agent. The SERS spectrum of goldpolystyrene particles is shown in Fig. 5. The peaks correspond to ring c c stretching 1615 cm4 CH2 scissoring 1461 cm4 ring breathing 1012 cm4 and radial ring stretching mode 646 cm-1 which are characteristic of polystyrene Hong Boerio et al. 1993 . Interestingly as particles polymerize with pNIPAM the bands disappear showing an effective replacement of PS by pNIPAM as also observed in Fig. 5 for both selected core sizes Au@pNIPAM 67 and 116 nm . Both spectra fit band to band being represented by NH bending 1447 cm-1 CN stretching 1210 CHY4 CH3 rocking 963 cm4 CH deformation 866 and 841 cm1 cc rocking 766 cm-1 CNO bending 655 cm-1 and cco out-of-plane deformation 413 cm-1 . There is an important increase in intensity for large gold cores as result of a considerable enhancement of the optical properties with increasing size in agreement with previous Surface-Enhanced Raman Scattering Sensors based on Hybrid Nanoparticles 171 reports Kelly Coronado et al. 2003 Njoki Lim et al. 2007 . The overall SERS intensity cross-section obtained from pNIPAM is low thus providing an excellent background for analytical applications. pNIPAM shell with thermoresponsive properties allows to entrap analyte molecules and approximate them to the metal core when .

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