Biology Reference
In-Depth Information
supporting films are generated. These films are in the centimeter size
range and can be manipulated with forceps (Lee
., 2002, 2003a,b).
Figure 7.6 shows such a film, consisting of M13 particles carrying ZnS
quantum dots at the terminal pIII protein. The VNPs are parallel aligned
in a zigzag pattern resulting in a smectic C phase liquid crystal (Lee
et al
.,
2002). The thickness of the film can be controlled by virus concentration;
the thickness is directly proportional to the film thickness. For example,
at a virus concentration ~10 mg/ml, an approximately 13-
et al
m-thick film
is assembled. Using a virus concentration of about 1.8 mg/ml, the film
thickness lies at about 1.6
µ
m. By varying the virus concentration, the
phase can also be tuned. At a M13 concentration of about 1.8 mg/ml, the
VNPs arrange in a nematic phase. At concentrations above, smectic liquid
crystals are formed (Lee
µ
→
et al
., 2003b). Phase changes (smectic
nematic)
can also be controlled by applying a magnetic field (Lee
et al
., 2002).
Figure 7.6
(a) Schematic diagram of the process used to generate nanocrystal
alignment by the phage display method. (b) Photograph of a M13-ZnS viral film. (c,
d) Smectic C liquid crystal. (c) Polarized optical microscopy: birefringent dark and
bright band patterns (periodic length 72.8 mm) were observed. These band patterns
are optically active, and their patterns reverse depending on the angles between
polarizer and analyzer. (d) Atomic force microscopic image of the free surface.
Smectic morphologies: the phage forms parallel-aligned herringbone patterns that
have almost right angles between the adjacent directors (arrows). (f, g) Nematic
liquid crystal. (f ) Polarized optical microscopy showing the crooked schlieren dark
brush patterns. (g) Atomic force microscopic image of the viral film surface showing
the nematic ordering. Reproduced with permission from Lee, S. W., Mao, C., Flynn, C.
E., and Belcher, A. M. (2002) Ordering of quantum dots using genetically engineered
viruses,
(5569), 892-895; and Lee, S. W., Woods, B. W., and Belcher, A. M.
(2003) Chiral smectic C structures of virus-based films.
Science
,
296
Langmuir
,
19
, 1592-1598.
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