
110 Nanosensors: Physical, Chemical, and Biological
For CdS,
r
m m
CdS
12
e e
8.854 10 8.4
=
× × × ×
× ×
−−
( . )
. ( . . )/(
6 626 10
3 14 0 14 0 51
34 2
00 14 0 51 1 60219 10
10
9 1095 10
19 2
39
31
. . ) ( . )
.
m m
e e
3.688
+
( )
×
=
×
×
=
−
−
−
44 0485 10
9
. ×
−
m
(2.34)
For CdSe,
r
m m
CdSe
12
e e
8.854 10 9
=
× × × ×
× ×
−−
. ( . )
. ( . . )/
7 6 626 10
3 14 0 11 0 44
34 2
(( . . ) ( . )
.
.
0 11 0 44 1 60219 10
5 31586 10
9 1095 10
19 2
39
m m
e e
+
( )
×
=
×
×
−
−
−
331
9
5 84 10= ×
−
. m
(2.35)
2.11.3 Bandgap Energies
How does the bandgap in a bulk semiconductor differ from that in a small nanosize
crystal? In a bulk semiconductor, the bandgap is centered about the atomic
energy levels with a width proport