Controlled assembly of CdSe/MWNT hybrid material and its fast photoresponse with wavelength selectivity.

We report the novel assembly method of CdSe quantum dot (QD)/pyridine/multi-walled carbon nanotube (CdSe-py-MWNT) hybrid material between electrodes using two-step dielectrophoresis (DEP). At the first step, we assembled the individual MWNT between electrodes by the DEP method. At the second step, the CdSe-py materials were assembled onto the MWNT by DEP method again, which enables site specific and density controlled assembly of QDs. As the photoresponse results, the recovery time of the device fabricated was about 250 times faster than that of a similar CdSe-py-SWNT device using a single-walled carbon nanotube (SWNT) instead of a MWNT. Moreover, it was demonstrated that the optoelectronic property of the device could be modulated by the size of CdSe NQD assembled on a MWNT. We characterized the material and the device by using SEM, TEM, absorption spectroscopy, and optoelectronic instruments.