DNA Multilayers with Mono-, Hetero-, and Mixed-Type Plasmonic Nanoparticles for Broadband Absorption and Energy...

DNA incorporated with functional materials has led to development of hybrids with different functionalities. Among the functional materials, metal nanoparticles such as Au, Ag, and Cu (also known as plasmonic nanoparticles [PNPs]), which can exhibit surface plasmon resonance, are good candidates to fabricate useful optoelectronic devices and sensors. Here, we constructed PNP-assorted DNA (PNP-DNA) layers with mono-, hetero-, and mixed-type PNPs formed by successive spin-coating to obtain the required number of layers. Further, structural analysis of PNP-DNA was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The optical evaluation was carried out by Raman, UV-visible, and photoluminescence (PL) spectroscopies followed by measurement of capacitance. Cross-sectional SEM images of DNA single, DNA triple, and PNP-DNA triple layers indicated their thicknesses (i.e., 90, 280, and 395 nm, respectively), while the base pair distance of double helixes (∼0.4 nm) for the PNP-DNA multilayers was measured by XRD. The presence of Ag, Au, and Cu PNPs was confirmed by existence of spin-orbit coupling in the corresponding XPS spectra. The addition of PNPs in DNA multilayers caused significant enhancement in the intensities of Raman bands (especially in the range of 1200-1850 cm^-1) due to Raman resonance. UV-vis absorption and PL demonstrated stacking-order-dependent and layer-dependent light absorption and energy transfer (observed as quenching of fluorescence between PNPs and DNA), respectively. We observed n-type semiconducting behavior with a relatively higher dielectric constant for a PNP-assorted DNA single layer at a low frequency of 5 kHz. The dielectric constants of all samples decreased exponentially with increased frequency. Upon addition of PNPs, enhancement in the dielectric constant as well as capacitance was noted. Consequently, the simple fabrication method used in this study can be adopted to construct various nanomaterial-assorted DNA multilayers whose specific functionalities may be controlled with high efficiency.