Core-shell distinguishing

It is noteworthy that the HRTEM cannot distinguish core and shell even by combining X-ray or electron diffraction techniques for some small nanoparticles. If the shell epitaxially grows on the core in the case of two kinds of metals with same crystal type and little difference of lattice constant, the precise structure of the bimetallic nanoparticles cannot be well characterized by the present technique. Hodak et al. [153] investigated Au-core/Ag-shell or Ag-core/Au-shell bimetallic nanoparticles. They confirmed that Au shell forms on Ag core by the epitaxial growth. In the TEM observations, the core/shell structures of Ag/Au nanoparticles are not clear even in the HRTEM images in this case (Figure 7). 

Theoretical calculations have demonstrated the feasibility of distinguishing a core-shell latex from a homogeneous latex. 

In these cases, the drug and matrix former are not clearly physically separated with a core-shell structure, but more or less homogeneously mixed (Fig. 2). Analogous to the reservoir systems, two types of devices can be distinguished according to the initial drug concentration/drug solubility ratio ... 

Alternatively, the level of stmctural complexity may be affected in a totally different manner employing co-assembly of chemically unlike molecules instead of self-assembly of chemically identical molecules [12-20]. We refer to the resultant micelles as mixed micelles or co-micelles to indicate that this type of micelle consists of more than one type of molecule, whereas classical micelles consist of identical molecules (polydispersity effects not taken into account). Consider two chemically distinguishable amphiphilic molecules A-B and C-D. Self-assembly into A/C or B/D micelles consisting of a core-shell structure, with a core solely consisting of A or C units and a shell solely consisting of B or D units, will only occur if the A or C units are solvophobic and the B or D units are solvophilic. However, if all units (A and B, or C and D) are solvophobic, phase separation will occur on a macroscopic level and result in a macroscopically inhomogeneous two-phase system. Conversely, if all units (A and B, or C and D) are solvophilic, phase separation... 

Figure 2 shows a high-resolution transmission electron micrograph (HRTEM) of core/shell LaP04 Yb,Er nanocrystals. The cores of these particles have been doped with 1% of Er " and the shells with approximately 1% of Yb ". The particles did crystallise in a monochnic monazite structure. Core and shell can be clearly distinguished in the HRTEM. It was observed that the upconversion luminescence intensity of core/shell nanoparticles is larger as compared with homogeneous mies. 

The yolk-shell nanostructure is a modified form of the core-shell configuration. The yolk-shell structure is distinguished from the core-shell structure in that the former has a hollow inner space between the core and the shell layers. Compared to... 

In order to basically interpret the aforementioned seed-promoted core-shell NC growth mechanism, Tsuji et al. examined the two-step synthesis of Au-Ag core-shell nanostructures [207, 253]. Based on the fact that Au and Ag show the same fee crystal structure with similar lattice constants, nanostructures exhibiting comparable shapes and sizes are expected to evolve. Furthermore Au-Ag core-shell S5 ems are ideal candidates to be investigated at TEM structural analyses as they own different mass contrast therefore easily distinguishable in TEM images [33,253]. 

Two wider ranging, more systematic investigations of conformational dependence have since been performed to establish whether the conformational sensitivity noted in the above PECD smdies may generally provide a means for identifying and distinguishing gas-phase structure of suitable chiral species. The B-spline method has been applied to the model system (l/f,2f )-l,2-dibromo-l,2-dichloro-l,2-difluoroethane [60]. Rotation around the C C bond creates three stable conformational possibilities for this molecule to adopt. The results for both core and valence shell ionizations reaffirm an earlier conclusion a and p are almost unaffected by the rotational conformation adopted, whereas the PECD varies significantly. Eor the C Ij ionization to show any sensitivity at aU to the relative disposition of the halogen atoms further reinforces the point made previously in connection with the core level PECD phenomenon. 

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