[1] Univ Nottingham, Sch Pharm, Lab Biophys & Surface Anal, Nottingham NG7 2RD, England
[2] Cambridge CMOS Sensors, Cambridge CB2 3BZ, England
[3] Univ Nottingham, Queens Med Ctr, Sch Biomed Sci, Adv Microscopy Unit, Nottingham NG7 2UH, England
[4] Univ Cambridge, Dept Engn, Elect Engn Div, Cambridge CB3 0FA, England
[5] De Montfort Univ, Fac Technol, Leicester LE1 9BH, Leics, England