Using the Box-Benkhen design (BBD) to minimize the diameter of electrospun titanium dioxide nanofibers

A response surface model (RSM) for predicting the diameter of electrospun titanium dioxide (TiO2) nanofibers was developed using the Box-Benkhen experimental design (BBD) technique. The three electrospinning factors in preliminary studies using the BBD design included the potential difference (kV), the infusion rate (ml h(-1)) and the separation distance between electrodes (cm). Verification of the model was accomplished through the analysis of residuals. The model was subsequently used to locate the optimal experimental values (electrospinning variables) which yielded the minimum TiO2 nanofiber diameter. A minimum diameter of 43.3 nm was predicted by the model when the potential difference was set at 40 kV, the electrodes were separated by 32.5 cm apart and the infusion rate was set at 0.6 ml h(-1). The average experimental observed fiber diameter (47.8 +/- 8.7 nm) was 9.5% greater than the predicted value (43.3 nm) under identical electrospinning settings. The nanofibers diameter was affected by the percent titanium (Ti) (by weight) in the electrospinning solution. Hence, in the final analysis, the model was refined to include a term representing the proportion of Ti in the electrospinning solution. A smaller nanofibers diameter of 39.0 +/- 6.6 nm with a specific surface area (SSA) of 259 +/- 23 m(2) g(-1) was produced using a solution containing 1.3% Ti. The SSA value was comparable with that for commercially available 5 nm TiO2 nanoparticles. The diameter of the immobilized TiO2 nanofibers was significantly less than the values reported in the literature. The model could serve as a tool for researchers. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.