The label-free detection of oligonucleotides of 12-14 bases at a concentration of 10 −7 M (double helix) was achieved by using surface enhanced Raman scattering (SERS) and spermine as the aggregant of Ag sol. The wavenumbers of the produced SERS spectra of DNA are similar to those in the corresponding normal Raman spectra of free DNA, allowing the detailed assignment of the vibrational modes. The conformation of the adsorbed DNA, the adsorption geometry, and a molecular model of the interactions among DNA, spermine, and Ag nanoparticle are derived from the SERS spectra. The results show that the protonated amine groups of spermine interact with phosphodioxygens of DNA and N7s of dA and dG from the major groove. The protonated amines are also attracted to the negatively charged Ag surface and thus induce the adsorption of DNA on the metal surface. The DNA remains mostly in the B-conformation with a variation in the C5 -O dihedral angle. DNA lies flat with the bases perpendicular to the metal surface.

Novel Raman tags called nanoaggregate‐embedded beads (NAEBs) have been developed. NAEBs are silica‐coated, dye‐induced aggregates of a small number of metal nanoparticles. In this work, the Raman reporters used to induce aggregation of gold nanoparticles include strongly binding dyes such as XRITC, TRITC, and DTDC and weakly binding dyes such as R6G. Surface‐enhanced Raman scattering (SERS) signal from a single NAEB can be detected. This study also demonstrates that these SERS‐active beads can be used as Raman tags for bio‐detection.

We report temperature dependence of electrical c o n d u c t i v i t y a n d t h e r m o p o w e r f o r p o l y ( 3 , 4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films post-treated using a combination of an organic polar solvent of ethylene glycol (EG) and transition metal chlorides. The pristine and post-treated PEDOT:PSS films are characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), atomic force microscopy (AFM), Raman spectroscopy techniques, and Hall effect measurements. Structural changes are confirmed by crystallinity improvement and Raman shift of the PEDOT:PSS, which correlate with a significant enhancement in thermoelectric power factor. The large variation of electronic transport in these films post-treated with three different metal chlorides can be attributed to the complex contribution of different conduction pathways. Among post-treated films, the highest electrical conductivity and power factor are attained for the EG/1 M ZnCl 2 post-treated PEDOT:PSS film with 1979 S/cm and 132 μW/m K 2 at 375 K. In general, organic conductive polymers have very low thermal conductivity; a zT = 0.24 at 375 K could be attained by assuming a thermal conductivity of 0.2 W/m-K. These results indicate that a combination of polar organic solvent EG and metal chlorides to post-treat a PEDOT:PSS film is a promising approach to enhance the thermoelectric properties of the conductive polymers of PEDOT:PSS.

Thermoelectric materials capable of converting waste heat energy into electrical energy are enchanting for applications in wearable electronics and sensors by harvesting heat energy of the human body. Organic conducting polymers offer promise of thermoelectric materials for next-generation power sources of wearable devices due to their low cost in preparation, easy processing, low toxicity, low thermal conductivity, mechanical flexibility, light weight, and large area application. Generally, the pristine PEDOT:PSS film has low electrical conductivity, small Seebeck coefficient, and low thermal conductivity. The thermoelectric power factors of conducting polymers of p-type PEDOT:PSS films are considerably improved via synergistic effect by using ethylene glycol and reductants of EG/NaBH 4 or EG/NaHCO 3 . As such, the charge carrier concentration of PEDOT:PSS films is tuned. The synergistic effect might lead to enhanced variation of density of states at the Fermi level and hence enhanced Seebeck coefficient. The resulting PEDOT:PSS films were characterized by atomic force microscopy (AFM), Raman spectroscopy, and XPS spectroscopy. The electrical conductivity and Seebeck coefficient were measured between 325 and 450 K. The carrier concentration and mobility were obtained by Hall measurements. The pristine thin film treated with 0.05 M EG/NaHCO 3 solution exhibits the highest power factor of 183 μW m −1 K −2 at 450 K among these two series of films due to its significant enhanced Seebeck coefficient of 48 μV/K. The maximum output power of 121.08 nW is attained at the output voltage of 6.98 mV and the output current of 17.45 μA. The corresponding maximum power density is 98 μW/cm 2 for a power generation device made of four pairs of p-leg (EG/NaHCO 3 post-treated PEDOT:PSS) and n-leg (Cu 0.6 Ni 0.4 ) on the polyamide substrate with the size of 4 mm × 20 mm for each leg.

2021) Gold nanorods conjugated upconversion nanoparticles nanocomposites for simultaneous bioimaging, local temperature sensing and photothermal therapy of OML-1 oral cancer cells,