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We have fabricated graphene devices on lightly doped Si substrates and show that pronounced changes in resistance versus gate voltage, R(Vg), characteristics of these devices at 77 K are induced by the variation in the charge distribution in substrate with both gate voltage and illumination. The R(Vg) of the graphene devices in the dark shows remarkable changes as the carriers in the underlying substrate go through accumulation, depletion, and inversion regimes. We demonstrate the possibility of using a graphene device as an optical-latch.

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In this study, we develop a real-time PCR strategy to directly detect and quantify DNA aptamers on functionalized graphene surfaces using a Staphylococcus aureus aptamer (SA20) as demonstration case. We show that real-time PCR allowed aptamer quantification in the range of 0.05 fg to 2.5 ng. Using this quantitative technique, it was possible to determine that graphene functionalization with amino modified SA20 (preceded by a graphene surface modification with thionine) was much more efficient than the process using SA20 with a pyrene modification. We also demonstrated that the functionalization methods investigated were selective to graphene as compared to bare silicon dioxide surfaces. The precise quantification of aptamers immobilized on graphene surface was performed for the first time by molecular biology techniques, introducing a novel methodology of wide application.

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We initially reported the synthesis, characterization of structural, optical, morphological, and photocatalytic properties of Ag 1.98 Cu 0.02 WO 4 solid solution in this work. The results were compared with the same characterizations performed in pure silver tungstate. Both materials exhibited an orthorhombic structure, with a high degree of crystallinity and purity. Although, a small number of copper atoms in the orthorhombic unit cell of Ag 1.98 Cu 0.02 WO 4 were detected by changes in the X-ray diffraction peak intensity and shift in peak positions corroborates with changes observed in micro-Raman active modes. The decrease in the optical band gap, α-Ag 2 WO 4 (3.05 ± 0.03 eV) to α-Ag 1.98 Cu 0.02 WO 4 (2.93 ± 0.01 eV), determined by diffuse reflectance spectroscopy, confirms the insertion of intermediate levels between valence and conduction bands that could be associated with the Jahn−Teller effect of copper. Field-emission scanning electron microscopy images show several rod-like microcrystals for α-Ag 2 WO 4 , while there are heterogeneous microcrystals for Ag 1.98 Cu 0.02 WO 4 solid solution with an inherent polyhedral shape. The highest photocatalytic performance of α-Ag 1.98 Cu 0.02 WO 4 in the degradation of RhB molecules under visible blue light-emitting device irradiation was achieved at the end of 120 min, therefore 10.61 times faster than pure α-Ag 2 WO 4 and 37.77 times than the photolysis experiment. Through the photocatalytic experiments using the scavenger radicals, the contribution of holes (h + ), singlet oxygen ( 1 O 2 ), superoxide radicals (O 2•− ), and hydroxyl radicals ( • OH) were evaluated, where the holes (h + ), singlet oxygen ( 1 O 2 ), and superoxide radicals (O 2•− ) show the main contribution in the photocatalytic degradation of the RhB molecules to colorless organic compounds, carbon dioxide (CO 2 ), and water (H 2 O).