DNA at aqueous/solid interfaces: Chirality-based detection via second harmonic generation activity

We present electronic spectra of single-strand and duplex DNA oligonucleotides covalently attached to fused quartz/aqueous interfaces and demonstrate that a strong nonlinear optical linear dichroism response is obtained when adenine and thymine bases undergo Watson-Crick base pairing to form a double helix. Complementary χ ⁽³⁾ charge screening studies indicate that the signal originates from 5 × 10 ¹¹ strands per square centimeter, or 6 attomoles of surface-bound oligonucleotides. The label-free, molecular-specific nature afforded by nonlinear optical studies of DNA at aqueous/solid interfaces allows for the real-time tracking of interfacial DNA hybridization for the first time.