. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. Fig. 3. Crystal habit ofcoppcr plitlialocsanine (after Robert- son, 1934). with intermediate molecular weights. Among these the phthalocyanines appeared a promising group to study and most of our work so far has been carried out on copper and platinum phthalocyanine. The metal phthalocyanines have a number of favourable properties. The molecule of platinum phthalocyanine is shown in figure I, and the unit cell of the crystal lattice in figure 2. From these it is apparent that we may idealise t
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956. Electron microscopy. Fig. 3. Crystal habit ofcoppcr plitlialocsanine (after Robert- son, 1934). with intermediate molecular weights. Among these the phthalocyanines appeared a promising group to study and most of our work so far has been carried out on copper and platinum phthalocyanine. The metal phthalocyanines have a number of favourable properties. The molecule of platinum phthalocyanine is shown in figure I, and the unit cell of the crystal lattice in figure 2. From these it is apparent that we may idealise the structure into widely spaced planes of heavy metal atoms (^^o,,, A) embedded in a matrix of the light elements carbon, nitrogen and hydrogen. We would expect to obtain strong diffracted beams from these planes even in very thin crystals since the scattering from the heavy metal atoms swamps that from the organic parts of the unit cell. The crystals grow as long thin ribbons with (001) as the habit plane of the ribbon surface as shown in figure 3, so that crystals sup- ported on a specimen grid will be oriented with (001) perpendicular to the electron beam and (20T) almost. Fig. 4. Schematic representation ol"(20T) planes in platinum phthalocyanine in relation to crystal habit. ABCD is a (001) plane. The almost vertical sheets such as ABEF arc (20T) planes. parallel to the beam, since (001)A(20T) =88". The (201) planes are thus in a favourable orientation for diffraction, which is essential in order to form an image of the planes. A schematic representation of the nearly vertical (20T) planes is shown in figure 4. In copper phthalocyanine the corresponding para- meters are (001)A(20T) 80 , f/201 = A. Preparation of specimens and method of examina- tion.—The crystals were prepared by sublimation from the powder after the method of Barrett, Dent & Linstead (I). After irechanical breaking down to reduce their size they v\ere suspended in ethyl alcohol,
Size: 1785px × 1400px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversity, bookleafnumber105
