title: Time-dependent pH sensing phenomena using CdSe/ZnS quantum dots in EIS structure.
abstract: Time-dependent pH sensing phenomena of the core-shell CdSe/ZnS quantum dot (QD) sensors in EIS (electrolyte insulator semiconductor) structure have been investigated for the first time. The quantum dots are immobilized by chaperonin GroEL protein, which are observed by both atomic force microscope and scanning electron microscope. The diameter of one QD is approximately 6.5 nm. The QDs are not oxidized over a long time and core-shell CdSe/ZnS are confirmed by X-ray photon spectroscopy. The sensors are studied for sensing of hydrogen ions concentration in different buffer solutions at broad pH range of 2 to 12. The QD sensors show improved sensitivity (38 to 55 mV/pH) as compared to bare SiO2 sensor (36 to 23 mV/pH) with time period of 0 to 24 months, owing to the reduction of defects in the QDs. Therefore, the differential sensitivity of the QD sensors with respect to the bare SiO2 sensors is improved from 2 to 32 mV/pH for the time period of 0 to 24 months. After 24 months, the sensitivity of the QD sensors is close to ideal Nernstian response with good linearity of 99.96%. Stability and repeatability of the QD sensors show low drift (10 mV for 10 cycles) as well as small hysteresis characteristics (<10 mV). This QD sensor is very useful for future human disease diagnostics.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Kumar
authors.affiliation: Thin Film Nano Technology Laboratory, Department of Electronic Engineering, Chang Gung University, Tao-Yuan, Taiwan 333, Taiwan. sidhu@mail.cgu.edu.tw.
authors.forename: Siddheswar
authors.initials: S
authors.lastname: Maikap
authors.forename: Amit
authors.initials: A
authors.lastname: Prakash
authors.forename: Ta-Chang
authors.initials: TC
authors.lastname: Tien
references.citation: Mol Cell. 2007 May 11;26(3):415-26
references.pmid: 17499047
references.citation: ACS Appl Mater Interfaces. 2013 May;5(9):3514-8
references.pmid: 23611583
references.citation: Anal Biochem. 2011 Oct 1;417(1):1-16
references.pmid: 21703222
references.citation: ACS Nano. 2012 Apr 24;6(4):2917-24
references.pmid: 22443420
references.citation: Science. 2002 May 3;296(5569):892-5
references.pmid: 11988570
references.citation: Chem Soc Rev. 2012 May 21;41(10):4067-85
references.pmid: 22481608
references.citation: Nanoscale Res Lett. 2011 Feb 14;6(1):142
references.pmid: 21711634
references.citation: J Am Chem Soc. 2005 Mar 9;127(9):2800-1
references.pmid: 15740085
references.citation: Biosens Bioelectron. 2005 Nov 15;21(5):827-32
references.pmid: 16242624
references.citation: Chem Rev. 2010 Jan;110(1):389-458
references.pmid: 19958036
references.citation: Nanoscale. 2010 Jul;2(7):1112-4
references.pmid: 20648335
references.citation: Nanoscale Res Lett. 2012 Aug 28;7(1):480
references.pmid: 22929008
references.citation: Nanoscale Res Lett. 2011 May 31;6(1):402
references.pmid: 21711931
references.citation: Nano Lett. 2011 Jun 8;11(6):2334-41
references.pmid: 21526845
references.citation: Anal Chim Acta. 2006 May 24;568(1-2):248-58
references.pmid: 17761266
references.citation: Nat Mater. 2002 Dec;1(4):247-52
references.pmid: 12618787
references.citation: Nanoscale Res Lett. 2008 Jun 24;3(6):213-20
references.pmid: 21777485
references.citation: Biosens Bioelectron. 2004 May 15;19(10):1295-300
references.pmid: 15046762
references.citation: Nat Mater. 2005 Jun;4(6):435-46
references.pmid: 15928695