Bi(III) ion detection The solutions of different concentrations of Bi(III) ions ranging from 0.001 to 1 ppm were prepared in a buffer solution of pH 4. The working solution of DZ was prepared by dissolving 10 mg of dithizone in 100 ml of ethanol. The buffer solution of 0.2 M KCl-HCl of pH 2, 0.1 M CH3COOH–CH3COONa of pH 4, sodium dihydrogen phosphate and disodium hydrogen phosphate BYL719 nmr solution of pH 7, and 0.1 M disodium hydrogen phosphate-HCl of pH 9 was used to study the effect of pH on the adsorption of the Bi(III) ions on the designed nanosensors. A series of experiments has been carried out for the different concentrations of Bi(III) ions ranging from 0.001 to 100 ppm. For the detection of the metal ions,

5 mg of mesoporous TiO2 was constantly stirred in 20 ml of metal-ion solution of desired pH for 5 min to achieve the heterogeneous solution. One milliliter ethanolic solution of DZ was added to the above solution at room temperature with constant stirring for 1 min. The solution was then filtered using Whatmann filter. The filtrate was then analyzed for metal ion and absorbance using UV-visible spectrophotometer (lambda 950

Perkin Elmer). Bi(III) sorption took place quantitatively as indicated from the analysis of the Bi(III) ions in effluent solutions by ICP-OES. After extraction, the ultratrace concentrations of the remained ions in the test aqueous solutions were estimated by ICP-MS. Also, the TiO2-DZ-Bi complex was analyzed by UV-visible diffuse reflectance spectra by collecting the FDA approved Drug Library screening material from Whatmann filter. Reflectance spectrum was taken at room temperature using UV-visible spectrophotometer (lambda 950 Perkin Elmer) fitted with universal reflectance accessory in the range of 200 to 800 nm. Results

and discussion The prepared mesoporous TiO2, TiO2-DZ, and TiO2-[(DZ)3-Bi] have been investigated. XRD pattern reflections from anatase phases with peaks characteristic for the (101), (004), (200), (211), and (213) lattice planes evince that TiO2 phase easily nucleates during heating and subsequently transforms into nanocrystals upon calcination at 450°C (see Additional file MG-132 cell line 1: Figure S1). Even upon the addition of DZ anchored on the mesoporous TiO2 (Additional file 1: Figure S1, curve b) and after the (Bi(DZ)3) complex was collected onto the surface of mesoporous TiO2, the intensity of the mean peak (101) for all the samples was similar and there is no significant change in the crystallinity of the TiO2 anatase phases. Nitrogen adsorption isotherms of the TiO2 mesoporous and TiO2-DZ are investigated (see Additional file 2: Figure S2). Typical reversible type-IV adsorption isotherms are found for both samples. The sharpness of the inflection resulting from capillary condensation at relative pressures p/p 0 between 0.45 and 0.7 is characteristic for mesostructures. The mesoporous TiO2 possesses high surface areas of 174 m2 g-1 and large pore volumes of 0.