In this paper, we have experimentally demonstrated the engineering of semi-metal single layer CVD Graphene’s bandgap by decorating with randomly distributed ZnO nano-seed grown by sonication of Zinc acetate dehydrate. The proximity of nanoparticles and Graphene breaks Graphene’s sublattice symmetry and opens-up a bandgap. The 2-D/G ratio of Raman spectroscopy of decorated Graphene along with a peak at 432.39 cm-1 confirmed presence of ZnO on single layer Graphene. The introduced bandgap was measured from the slope of Arrhenius plot. Graphene with significant bandgap introduced by the proposed methods could be used for devices intended for digital and logic applications.
In this paper, we report on fabrication of a label free, highly sensitive and selective electrochemical cortisol
immunosensors using one dimensional (1D) ZnO nanorods (ZnO-NRs) and two dimensional nanoflakes (ZnO-NFs)
as immobilizing matrix. The synthesized ZnO nanostructures (NSs) were characterized using scanning electron
microscopy (SEM), selective area diffraction (SAED) and photoluminescence spectra (PL) which showed that both
ZnO-NRs and ZnO-NFs are single crystalline and oriented in [0001] direction. Anti-cortisol antibody (Anti-Cab) are
used as primary capture antibodies to detect cortisol using electrochemical impedance spectroscopy (EIS). The
charge transfer resistance increases linearly with increase in cortisol concentration and exhibits a sensitivity of 3.078
KΩ. M-1 for ZnO-NRs and 540 Ω. M -1 for ZnO-NFs. The developed ZnO-NSs based immunosensor is capable of
detecting cortisol at 1 pM. The observed sensing parameters are in physiological range. The developed sensors can
be integrated with microfluidic system and miniaturized potentiostat to detect cortisol at point-of-care.
We theoretically investigated and designed a tunable, compact THz source in 1-10 THz range based on a nonlinear
optical microdisk resonator. The lack of tunable THz source operating at room temperature is still one of the major
impediments for the applications of THz radiation. The proposed device on an insulated borosilicate glass substrate
consists of a nonlinear optical disk resonator on top of another disk capable of sustaining THz modes. A pair of Si
optical waveguides is coupled to the nonlinear microdisk in order to carry the two input optical waves. Another pair of Si
THz waveguides is placed beneath the input optical waveguides to couple out the generated THz radiation from the disk
to receiver antenna. Both optical and THz disks are engineered optimally with necessary effective mode indices in order
to satisfy the phase matching condition. We present the simulation results of our proposed device using a commercial
finite element simulation tool. A distinguished THz peak coincident exactly with the theoretical calculations involving
DFG is observed in frequency spectrum of electric field in the microdisk resonator. Our device has the potential to
enable tunable, compact THz emitters and on-chip integrated spectrometers.
We designed and theoretically investigated nonlinear optical micro-ring resonators for tunable terahertz (THz) emission
in 1-10 THz range by using difference frequency generation (DFG) phenomenon with large second order optical
nonlinearity (χ(2)). Our design consists of a nonlinear ring resonator and another ring underneath capable of sustaining high-Q resonant modes for infrared pump beams and the generated THz radiation, respectively. The nonlinear ring
resonator generates THz through DFG by mixing the input waves carried by a pair of waveguides. The proposed device
can be a viable platform for tunable, compact THz emitters and on-chip integrated spectrometers.
In this paper, we report on a new method of synthesis for ZnO nanowires on arbitrary substrates and nanowalls on
aluminum coated substrates at ambient conditions. Our method is based on sonochemical reaction of Zinc acetate
dihydrate (Zn(O2CCH3)2-2H2O) Zinc nitrate hexahydrate (Zn(NO3)2-6H2O) and hexamethylenetetramine (HMT,
(CH2).6N4) in aqueous solutions. Repetitive growth cycles resulted in synthesis of ZnO nanowires and nanowalls with
controlled dimensions and large aspect ratios. Extensive analysis by transmission electron microscopy (TEM), energy
dispersive x-ray spectroscopy (EDS) and UV-Visible spectroscopy revealed the crystalline ZnO composition of the
synthesized nanostructures. The proposed method is a rapid, inexpensive, low-temperature, catalyst-free, CMOS
compatible and environmentally benign alternative to existing growth techniques.
New energy harvesting technologies have drawn interest in recent years for both military
and commercial applications. We present complete analysis of a novel device technology
based on nanowire antennas and very high speed rectifiers (collectively called
nanorectenna) to convert infrared and THz electromagnetic radiation into DC power. A
nanowire antenna can receive electromagnetic waves and an integrated rectifier can
convert them into electrical energy. The induced voltage and current distributions of
nanowire antennas for different geometric parameters at various frequencies are
investigated and analyzed. Also, nanowire antenna arrays with different geometries and
distributions are examined. Moreover, novel nanoantennas are proposed for broadband
operation and power conversion. All numerical computations are conducted using Ansoft
HFSS. An incident plane wave was used to excite each device and simulations were carried out
for frequencies between 0 and 200 THz. A voltage is induced in each device and it is
measured in the thin oxide layer. Finally, optimum geometries of nanowires are proposed
in order to maximize the amount of infrared power that is harvested.
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