A resonance cavity antenna (RCA) has been explored employing nontransparent solid metal sheet as superstrate which, to the best of our knowledge, is reported for the first time. The proposed configuration is much advantageous in terms of design, simplicity, structural stability, fabrication, and cost without compromising in gain, efficiency, and bandwidth. A probe-fed dielectric resonator antenna (DRA) with ε r =10 has been used as the primary radiator. Proposed RCA bearing overall size 1.1λ×1.1λ×0.6λ promises for large impedance bandwidth (23%) with considerably high gain (11.8 to 12.2 dBi). The superstrate size is relatively compact compared to its semi-transparent versions, investigated earlier. Present design has been experimentally validated indicating as much as 12 dBi peak gain with more than 96.5% efficiency.
In this work, a novel electrochemical immunosensor based on nitrogen doped graphene quantum dot (N-GQD) and single-walled carbon nanohorns (SWCNHs) was developed for the detection of α-fetoprotein (AFP), a cancer biomarker. Thus, to fabricate the platform of the immunosensor, nanocomposite architecture was developed by decorating N-GQD on the surface of the SWCNHs. The resulting hybrid architecture (N-GQD@ SWCNHs) functioned as an exceptional base for the immobilization of antibody (Anti-AFP) through carbodiimide reaction with good stability and bioactivity. The immunosensor was prepared by evenly distributing the bioconjugates (N-GQD@SWCNHs/Anti-AFP) dispersion on the surface of the glassy carbon electrode, and subsequently blocking the remaining active sites by bovine serum albumin to prevent the nonspecific adsorption. Cyclic voltammetry and electrochemical impedance spectroscopy technique was employed to investigate the assembly process of the immunosensor. Under optimal conditions, the immunosensor exhibited a broad dynamic range in between 0.001 ng/mL to 200 ng/mL and a low detection limit of 0.25 pg/mL. Furthermore, the sensor showed high selectivity, desirable stability, and reproducibility. Measurements of AFP in human serum gave outstanding recovery within 99.2% and 102.1%. Thus, this investigation and the amplification strategy exhibited a potential role of the developed nanocomposite based sensor for early clinical screening of cancer biomarkers.
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