Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The synthesis and characterization of silica nanoparticles (NPs) covalently modified with an aminonaphthoquinone are reported. The aminopropylsilicagelnaphthoquinone (APSGNQ) was obtained by nucleophilic substitution of 2-methoxy-1,4-naphthoquinone with aminopropylsilicalgel (APSG) NPs. Solid state C-13 and Si-29 nuclear magnetic resonance spectra confirmed that the naphthoquinone is covalently bonded to APSG. Due to the solubility of APSGNQ in common organic solvents, solution ultraviolet-visible spectroscopy was used to determine the amount of naphthoquinone on the NPs surface (0.56 mmol of incorporated naphthoquinone per gram of APSGNQ) by comparison with the spectrum of 2-aminobutyl-1,4-naphthoquinone (ABNQ). Elemental analysis indicated that about 8% of the surface propylamine remained unreacted in APSGNQ. These multifunctional silica NPs have potential in medical applications.225961U226Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Pronex-FAPERJ [E-26/171.512/2006]