Enhancing the adsorption of CdSe quantum dots on TiO2 nanotubes by tuning the solvent polarity

- Higher coverage of nanotubes with Qdots achieved by increasing solvent polarity.
- Qdots coat nanotubes further along the length when adsorbed from polar solvents.
- Photoanode efficiency increases more than expected by enhancing Qdots adsorbed.

The aim of this work is to report the effect of the solvent polarity on the adsorption of CdSe quantum dots (QDots) over the surface of TiO2 nanotubes and the influence of the coverage gained on the efficiency of photoanodes based on these materials. Particularly, it is shown that the amount of QDots adsorbed on TiO2 nanotubes can be tuned by using solvent mixtures of different polarity and volume ratios. An increase on QDots coverage was found when the polarity increases. What is noticeable is that the photoanode efficiency increased at a higher rate than the QDots coverage. For instance, a two-fold increase of coverage at a 50% acetone - 50% toluene ratio induces up to a seven-fold increase of the photocurrent values with respect to those obtained when the adsorption is performed from toluene. This effect is explained in terms of a different distribution of QDots along the nanotube walls depending on the solvent polarity used for the adsorption.