The lateral transport of four single-strand homooligonucleotides on a microscopically flat silica surface chemically modified with chlorodimethyloctadecylsilane, in contact with 0.01 M KCI, was investigated using single-molecule spectroscopy. The deoxynucleotides were 20-mers of poly A, poly C, poly T, and poly G, each labeled at the 5 ' end with tetramethylrhodamine. Autocorrelation of the burst data, for each homooligonucleotide, indicates a single diffusing species with no significant difference in the diffusion coefficient among the individual oligonucleotides (D = 3.2 +/- 0.3 x 10(-6) cm(2)/s). Examination of burst data for each homooligonucleotide reveals the presence of diffusing molecules occasionally stopping at strong adsorption sites. The frequency of strong adsorption correlates with the number of the amino and amide groups of the base. A histogram of duration times of the strong adsorption events shows that there are two different time scales for strong adsorption events. The autocorrelation decay for the strong adsorption events pooled from all four oligonucleotides fit well to a double-exponential decay with 80% and 20% of the strongly adsorbing molecules having an average desorption time of 16 and 220 ms, respectively.