Nanoparticle patterning

It was found that citrate-stabilised gold nanoparticles have a higher coverage onto NH2-terminated surfaces at pH values between 4.0 and 5.5 compared with acrylate-stabilised ones (Fig. 3a). Moreover, citrate-stabilised gold nanoparticles show very low affinity for the NO2-terminated surfaces within the aforementioned pH interval (Fig. 3b), resulting in the highest NH2 to NO2 selectivity between pH 5.0 and 5.5. These studies demonstrate that the quality of the gold nanoparticle patterns can be improved by optimization of the pH, and presumably other self-assembly related factors. 

Scholten, E., H. Dhamankar, L. Bromberg, G.C. Rutledge, and T Alan Hatton. Electrospray as a tool for drug micro-and nanoparticle patterning. Langmuir 27(11) (2011) 6683-6688. 

The nanoparticle patterning techniques described above are veiy powerful but they have some limitations. Nanoparticles affect the optical properties, but not, for example, the mechanical properties or hydrophilicity. In addition, nanoparticles can clog the matrix pores and limit diffusion of fluids and analytes through the monoliths [4]. 

In selected cases, it is desired to pattern the nanoparticles into nanoarrays rather than to arrange them into a continuous film. Polleux et al. reported the synthesis of titania nanoparticles and their arrangement in one step by combining the benzyl alcohol route with micellar nanolithography [196]. TiClj dissolved in benzyl alcohol in the presence of a diblock copolymer was aged and dip coated, upon which different titania nanoparticle patterns formed, ranging from quasi-hexagonally ordered nanodots to curved and parallel oriented nanowires. 

Horechyy A, Nandan B, Zafeiropoulos NE, Formanek P, Oertel U, Bigall NC, Eychmiiller A, Stamm M (2013) A step-wise approach for dual nanoparticle patterning via block copolymta-self-assembly. Adv Funct Mater 23(4) 483 90... 

Wang.Y., Liu,Y., Liang, H., Mei, Z., Du, X., 2013. Broadband antireflection on the sihcon surface realized by ag nanoparticle-patterned black sihcon. Phys. Chem. Chem. Phys. 15 (7), 2345-2350. 

A similar procedure was adopted for synthesis of nanoparticles of cellulose (CelNPs). The polysaccharide nanoparticles were derivatised under ambient conditions to obtain nanosized hydrophobic derivatives. The challenge here is to maintain the nanosize even after derivatisation due to which less vigorous conditions are preferred. A schematic synthesis of acetyl and isocyanate modified derivatives of starch nanoparticles (SNPs) is shown in scheme 3. The organic modification was confirmed from X-ray diffraction (XRD) pattern which revealed that A- style crystallinity of starch nanoparticles (SNPs) was destroyed and new peaks emerged on derivatisation. FT-IR spectra of acetylated derivatives however showed the presence of peak at 3400 cm- due to -OH stretching indicating that the substitution is not complete. 

The XRD pattern of the as-prepared ZnSe nanoparticles (Figure 3) exhibited predominantly wurtzite crystal structure with distinct diffraction peaks corresponding to the crystalline planes of hexagonal ZnSe and lattice constant of 0.397 nm, which was... 

Fig. 3. XRD patterns of (a) pure starch and (b) starch -capped ZnSe nanoparticles.

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