tailieunhanh - Crystalline Silicon Properties and Uses Part 13

Tham khảo tài liệu 'crystalline silicon properties and uses part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Porous Silicon Integrated Photonic Devices for Biochemical Optical Sensing 289 ipi N __ i -Si-OH P-O ODMT - RO V T . _ T -SI-O-p-O- ODMT Or r T T T O II -SI-O-P-O I OR O _ II _ O-Ộ-O- O O-P-O- OH y OR V 1 R CH2CH2CN 4 Fig. 16. Scheme of the solid phase synthesis of the 10 bases oligonucleotide 4 on the PSi-OH surface 1 using 5 -dimethoxytrityl-thymidine-phosphoramidite 2 i standard automatic synthetic cycle Rea et al. 2010 . In order to quantify the surface functionalization we have removed the 5 -dimethoxytrityl DMT protecting group from the support-bound 5 -terminal nucleotide by using the deblocking solution of trichloroacetic acid in dichloromethane 3 w w . The release of the protecting group generates a bright red-orange colour solution in which the quantity of the DMT cation could be measured on-line by UV-VIS spectroscopy at 503 nm e 71700 M-1cm-1 . The Figure 17 shows the DMT analysis performed on the PSi device after each synthesis cycle the amount of DMT indicated reaction yields over 98 . These values resulted almost steady during the ON growing process confirming the stability of the chip surface and the high accessibility of ON 5 -OH end groups By averaging over these values we have estimated a functionalization degree of nmol cm2. The presence of ON chains bonded on the chip has been also verified by spectroscopic reflectometry. The biological molecules attached to the PSi pore walls induce an increase in the average refractive indexes of the layers causing a red-shift in the reflectivity spectrum of the Bragg mirror. The magnitude of the shift increases with the increase of the pores surface coverage with the organic matter. The reflectivity spectra of the PSi multilayered structure before and after the ON synthesis are reported in Figure 18. A red-shift of 11 nm has been measured. w o JI D _ __ _ _ __ _ __ _ _ __ T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 ON synthesis 3 5 Fig. 17. DMT measurements performed on the sample .