Abstract:Optical properties of polymer capped gold nanoparticles of various sizes (diameter 3-6 nm) have been studied. We present a new scheme to extract size dependent variation of total dielectric function of gold nanoparticles from measured UV-Vis absorption data. The new scheme can also be used, in principle, for other related systems as well. We show how quantum effect, surface atomic co -ordination and polymer -nanoparticle interface morphology leads to a systematic variation in inter band part of the dielectric … Show more
“…The ZnO-Nanorods are said to be in the wurtzite phases and exhibit excellent crystallinity since their XRD spectrum produce sharp, narrow peaks at 31.02°(100), 34.40°(002), 36.31°(101), 47.65°(102), 56.65°(110), 62.89°(103) and 68.00°(112). Similarly, the diffraction peaks at 38°(111) and 44°(200) were assigned to peaks that reflect face-centered cubic of AuNP’s 27,28 .Figure 6Diagram of structural analysis of ZnOAu-Nanorods. ( A ) EDX spectrum of Au doped ZnO-Nanorods.…”
Detection of host integrated viral oncogenes are critical for early and point-of-care molecular diagnostics of virus-induced carcinoma. However, available diagnostic approaches are incapable of combining both cost-efficient medical diagnosis and high analytical performances. To circumvent this, we have developed an improved IDE-based nanobiosensor for biorecognition of HPV-16 infected cervical cancer cells through electrochemical impedance spectroscopy. The system is fabricated by coating gold (Au) doped zinc oxide (ZnO) nanorods interfaced with HPV-16 viral DNA bioreceptors on top of the Interdigitated Electrode (IDE) chips surface. Due to the concurrently improved sensitivity and biocompatibility of the designed nanohybrid film, Au decorated ZnO-Nanorod biosensors demonstrate exceptional detection of HPV-16 E6 oncogene, the cancer biomarker for HPV infected cervical cancers. This sensor displayed high levels of sensitivity by detecting as low as 1fM of viral E6 gene target. The sensor also exhibited a stable functional life span of more than 5 weeks, good reproducibility and high discriminatory properties against HPV-16. Sensor current responses are obtained from cultured cervical cancer cells which are close to clinical cancer samples. Hence, the developed sensor is an adaptable tool with high potential for clinical diagnosis especially useful for economically challenged countries/regions.
“…The ZnO-Nanorods are said to be in the wurtzite phases and exhibit excellent crystallinity since their XRD spectrum produce sharp, narrow peaks at 31.02°(100), 34.40°(002), 36.31°(101), 47.65°(102), 56.65°(110), 62.89°(103) and 68.00°(112). Similarly, the diffraction peaks at 38°(111) and 44°(200) were assigned to peaks that reflect face-centered cubic of AuNP’s 27,28 .Figure 6Diagram of structural analysis of ZnOAu-Nanorods. ( A ) EDX spectrum of Au doped ZnO-Nanorods.…”
Detection of host integrated viral oncogenes are critical for early and point-of-care molecular diagnostics of virus-induced carcinoma. However, available diagnostic approaches are incapable of combining both cost-efficient medical diagnosis and high analytical performances. To circumvent this, we have developed an improved IDE-based nanobiosensor for biorecognition of HPV-16 infected cervical cancer cells through electrochemical impedance spectroscopy. The system is fabricated by coating gold (Au) doped zinc oxide (ZnO) nanorods interfaced with HPV-16 viral DNA bioreceptors on top of the Interdigitated Electrode (IDE) chips surface. Due to the concurrently improved sensitivity and biocompatibility of the designed nanohybrid film, Au decorated ZnO-Nanorod biosensors demonstrate exceptional detection of HPV-16 E6 oncogene, the cancer biomarker for HPV infected cervical cancers. This sensor displayed high levels of sensitivity by detecting as low as 1fM of viral E6 gene target. The sensor also exhibited a stable functional life span of more than 5 weeks, good reproducibility and high discriminatory properties against HPV-16. Sensor current responses are obtained from cultured cervical cancer cells which are close to clinical cancer samples. Hence, the developed sensor is an adaptable tool with high potential for clinical diagnosis especially useful for economically challenged countries/regions.
“…In the UV region in Fig. 1͑a͒, a prominent peak at 380 nm is observed for film S1, and the peak corresponds to the 5d → 6sp interband transition [13][14][15] of AuNPs. In the VIS region, the well-known surface plasmon ͑SP͒ peak [16][17][18] of AuNPs is centered at 620 nm.…”
Photocurrent generation and photodetection are usually based on semiconductor crystals including Si, CdS, and PbS. This work reports the enhanced photoabsorption and photodetection of close-packed metallic Au nanoparticles ͑NPs͒ in the UV-VIS ͑visible͒-NIR ͑near infrared͒ region. Photoabsorption in the UV-VIS regions is associated with the interband transition and surface plasmon resonance of AuNPs, while the enhanced NIR absorption is due to the collective effect of interacting AuNPs in the close-packed network. Consequently, the AuNPs exhibits photodetection behavior in the wavelength range of 300-1500 nm. It is proposed that the inter-AuNP photoejection and delocalization of electron-hole pairs changes the carrier lifetime and transit dynamics in favor of photocarrier conduction, thus significantly facilitating photocurrent generation in the metallic AuNP close-pack. Moreover, due to the power-law conduction mechanism in AuNP networks, the quantum yield of AuNPs can be tuned from 10 −6 to 10 −1 photoelectron/photon by increasing the bias voltage from 0 to 5 V. The AuNP quantum yield of 10 −1 at 5 V is as high as that of commercial Si photodetectors at 0 V, and this demonstrates the immediate applicability of AuNPs in photodetection. In view of the compatibility of AuNPs with wet-chemistry and inkjet printing processes at low temperatures, metallic AuNPs may provide a convenient alternative to semiconductor crystals in photodetection and perhaps photovoltaic applications.
“…Both theoretically and experimentally, shifts of surface plasmon energies in NPs have been shown to depend on the electronic properties of the particles. However, such energy shifts are mostly blue-shifts and their magnitudes rarely exceed 10 eV (Jain et al, 2007;Haridas et al, 2008). Hence, a shift of the surface plasmon energy of the Au core is not likely to be the source of the strong intensity in the shells observed in Fig.…”
Section: Eftem Contrast: Bulk or Surface Plasmons?mentioning
confidence: 89%
“…However, it can also result from electron irradiation due to hydrogen abstraction followed by a reaction between adjacent primary-chain carbon atoms. Surface plasmons in NPs, which feature in the sub-10-eV (optical) regions of EEL spectra, have been studied intensively as a result of their importance in plasmonics and biomedicine (Jain et al, 2007;Haridas et al, 2008). In contrast, there has not been an equivalent theoretical effort aimed at understanding bulk plasmons, which typically have energies above 10 eV.…”
Hybrid (organic shell-inorganic core) nanoparticles have important applications in nanomedicine. Although the inorganic components of hybrid nanoparticles can be characterized readily using conventional transmission electron microscopy (TEM) techniques, the structural and chemical arrangement of the organic molecular components remains largely unknown. Here, we apply TEM to the physico-chemical characterization of Au nanoparticles that are coated with plasma-polymerized-allylamine, an organic compound with the formula C3H5NH2. We discuss the use of energy-filtered TEM in the low-energy-loss range as a contrast enhancement mechanism for imaging the organic shells of such particles. We also study electron-beam-induced crystallization and amorphization of the shells and the formation of graphitic-like layers that contain both C and N. The resistance of the samples to irradiation by high-energy electrons, which is relevant for optical tuning and for understanding the degree to which such hybrid nanostructures are stable in the presence of biomedical radiation, is also discussed.
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