Soft lithographic printing of titanium dioxide and the resulting silica contamination layer

Soft lithographic printing techniques can be used to print nanoparticle dispersions with relative ease while allowing for a measureable degree of controllability of printed feature size. In this study, a Polydimethylsiloxane (PDMS) stamp was used to print multi-layered, porous, nanoparticle dispersions of titanium dioxide (Ti02), for use in a dye-sensitized solar cell application. The gelled patterns were then sintered and the surface of the printed sample was chemically analyzed. X-ray photoelectron spectroscopy (XPS) was used to determine the surface constituents of the printed sample. The presence of a secondary peak feature located approximately 2.8 eV above the high resolution Ols core level binding energy peak was attributed to a contamination layer. Fourier transform infrared spectra (FTIR) of the printed sample revealed the presence of vibrational modes characteristic of the asymmetric bond stretching of silica, located at approximate wavenumbers of 1260 and 1030 cm^-1. Soft lithographic techniques are a viable manufacturing technique in a number of disciplines and sintered nano-oxide dispersions are readily used as reaction centers in a number of technologies. The presence of a residual, bonded silicate contamination layer may preclude the soft lithographic printing of chemically active oxide surfaces.