International Journal of Nanomedicine (Aug 2019)
Synthesis of meso-tetra-(4-sulfonatophenyl) porphyrin (TPPS4) – CuInS/ZnS quantum dots conjugate as an improved photosensitizer
Abstract
Ncediwe Tsolekile,1–3 Vuyelwa Ncapayi,1,2 Gabriel K Obiyenwa,2,4 Mangaka Matoetoe,3 Sandile Songca,5 Oluwatobi S Oluwafemi1,21Department of Chemical Sciences (formerly Applied Chemistry), University of Johannesburg, Johannesburg 2028, South Africa; 2Centre for Nanomaterials Science Research, University of Johannesburg, Johannesburg 2028, South Africa; 3Department of Chemistry, Cape Peninsula University of Technology, Cape Town 2000, South Africa; 4Department of Chemistry, Federal University Lokoja, Lokoja, Nigeria; 5Department of Chemistry, University of Zululand, Kwadlangezwa 3886, South AfricaCorrespondence: Oluwatobi S OluwafemiDepartment of Chemical Sciences (formerly Applied Chemistry), University of Johannesburg, PO BOX 17011, Doornfontein2028, Johannesburg, South AfricaTel +27 11 559 9060Fax +27 11 559 6425Email [email protected]: Metal-free, water-soluble and highly stable meso-tetra-(4-sulfonatophenyl) porphyrin (TPPS4) has been studied for their singlet oxygen quantum yield. However, TPPS4 suffers from inherent shortcomings. To address these, TPPS4 was conjugated to ternary copper indium sulphide/ zinc sulphide (CuInS2/ZnS) quantum dots (QDs).Purpose: We herein report for the first time the synthesis of TPPS4–CuInS/ZnS QDs conjugate as an improved photosensitizer.Methods: Water-soluble TPPS4 was synthesized from tetraphenylporphyrin (TPPH2) after silica-gel purification. The CuInS/ZnS QDs were synthesized by hydrothermal method at a Cu:In ratio of 1:4. The porphyrin–QDs conjugate was formed via the daggling sulfonyl bond of the porphyrin and amine bond of the QDs. The effect of pH on the optical properties of TPPS4 was evaluated. The effect of Zn:Cu + In ratio on the ZnS shell passivation was examined to reduce structural defects on the as-synthesized QDs.Results: Various spectroscopic techniques were used to confirm the successful conversion of the organic TPPH2 to water-soluble TPPS4. The singlet oxygen generation evaluation shows an improved singlet oxygen quantum yield from 0.19 for the porphyrin (TPPS4) alone to 0.69 after conjugation (CuInS/ZnS-TPPS4) with an increase in the reaction rate constant (k (s-1)).Keywords: CuInS/ZnS, meso-tetra-(4-sulfonatophenyl) porphyrin, TTPS4, singlet oxygen, conjugation, quantum dots
