In situ Study of DNA Attachment and Hybridization at Silicon Surfaces by Infrared Absorption Spectroscopy

Abstract

In this study, we have investigated in situ the process of DNA immobilization and the subsequent hybridization on Si surfaces by using infrared (IR) absorption spectroscopy in the geometry of multiple internal reflection (MIR-IRAS). We use 3aminopropyl-triethoxysilane (APTES) to functionalize Si surfaces with the amine group for DNA attachment. MIR-IRAS data, together with ab initio calculations, demonstrate that the amine-terminated surfaces are covalently coupled to thiolmodified oligonucleotides using a crosslinker of sulfo-succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SSMCC). Hybridization experiments reveal that MIR-IRAS enables us to detect DNA hybridization through IR spectral changes in the frequency region around 1685 cm À1 where the vibrational modes of the bases appear. The present results show that MIR-IRAS is a promising tool for the label-free detection of DNA hybridization as well as the in situ (in vitro) characterization of the conformation changes of DNA molecules immobilized on Si surfaces.

A general and precise method to evaluate the series resistance of photovoltaic cells from I-V characteristics

“…widely used methods: the standard method recommended by the International Electrotechnical Commission 14 (referred to as the I.E.C. method), and the derivative method, including the more recent improvements due to Ishibashi et al 15 A. Comparison with the I.E.C.…”

“…15 Although the method has the great advantage of requiring only one I(V) curve and employing a relatively simple numerical application, it addresses the numerical evaluation of the derivative of an experimental curve which obviously has much greater fluctuations than that of the original data points.…”

“…We have also tried to obtain a lower dispersion in the data of the derivative dI/dV by fitting a polynomial function to the experimental I(V) curve and then performing the derivative, which was suggested in the Ishibashi paper. 15 Although, in this way, the data variation becomes negligible, the actual result depends heavily on the choice of the polynomial degree.…”

“…Some relevant improvements to this method have recently been proposed by Ishibashi et al 15 The "derivative method" is a simple method from an experimental point of view, but as we will discuss later in Sec. IV, it is limited by the assumption of the single diode approximation.…”

New insights into electrolyte-component biased and transfer- and transport-limited charge recombination in dye-sensitized solar cells

“…The concentration of TBP in electrolyte was respectively 0.5 M and 0.01 M in cell-1 and cell-2, which gives rise to the significantly different photovoltaic performances. In addition, based on the standard diode equation, 46,47 we have fitted the J-V curves previously and the fitting parameters indicated the faster recombination occurs in cell-2, which is another factor giving rise to the smaller V OC of cell-2. in electrolyte; as a result, the conduction band of TiO 2 is expected to be lowered.…”