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Temperature dependence of the 1/f noise intensity in Bi2Se3 features a weak structure of unknown origin. Comparing the noise structure with the Raman spectrum of Bi2Se3, we found that it is the image of the surface phonon spectrum of this topological insulator. It also revealed that the low intensity of both noise bands composing the structure in the topological regime is due to the weak interaction of the Dirac electrons with the surface phonons of Bi2Se3. One of these noise bands has been found to correspond to the boson peak of the amorphous Se surface atoms, while the other one is well fitted by the Eliashberg function of amorphous Bi. It indicates that the interaction of the Dirac electrons with the thermal motion of the Se and Bi atoms, in the first and second atomic layers of the first quintuple Se–Bi–Se–Bi–Se surface cell, respectively, is the microscopic source of the surface 1/f noise in this quantum material. A step-like noise increase observed at a surface-bulk transition in a Bi2Se3 film is assigned to a Fano resonance. This proves that the electron–phonon coupling is involved in the microscopic mechanism of 1/f noise in solids. [ABSTRACT FROM AUTHOR]

Temperature dependence of the 1/f noise intensity in Bi2Se3 features a weak structure of unknown origin. Comparing the noise structure with the Raman spectrum of Bi2Se3, we found that it is the image of the surface phonon spectrum of this topological insulator. It also revealed that the low intensity of both noise bands composing the structure in the topological regime is due to the weak interaction of the Dirac electrons with the surface phonons of Bi2Se3. One of these noise bands has been found to correspond to the boson peak of the amorphous Se surface atoms, while the other one is well fitted by the Eliashberg function of amorphous Bi. It indicates that the interaction of the Dirac electrons with the thermal motion of the Se and Bi atoms, in the first and second atomic layers of the first quintuple Se–Bi–Se–Bi–Se surface cell, respectively, is the microscopic source of the surface 1/f noise in this quantum material. A step-like noise increase observed at a surface-bulk transition in a Bi2Se3 film is assigned to a Fano resonance. This proves that the electron–phonon coupling is involved in the microscopic mechanism of 1/f noise in solids. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) is a label-free, real-time bio-sensing technique with high potential in the diagnostic area, especially when a signal amplification strategy is used to improve the detection limit. We report here a simple method for enhancing the detection limit of bovine serum albumin (BSA), by attaching gold nanorods (AuNRs). AuNRs were obtained by a seedless synthesis technique and characterized using scanning electron microscopy (SEM), UV-VIS spectroscopy, FT-IR spectroscopy and dynamic light scattering (DLS). Finite element method (FEM) simulations were employed to explore the enhancement of the SPR signal by adding AuNRs on the SPR sensor's metallic layer. SPR spectroscopy was used to analyze the changes in the refractive index brought by the immobilization of unconjugated BSA and BSA modified with AuNRs. The results confirmed that the AuNRs conjugated with the protein increase the SPR signal ~ 10 times, leading to a limit of detection of 1.081 × 10 -8  M (0.713 μg/mL)., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In this work, we report the development of self-powered photodetectors that integrate silicon nanoholes (SiNHs) and four different types of metal nanowires (AgNWs, AuNWs, NiNWs, PtNWs) applied on the SiNHs' surface using the solution processing method. The effectiveness of the proposed architectures is evidenced through extensive experimental and simulation analysis. The AgNWs/SiNHs device showed the highest photo-to-dark current ratio of 2.1 × 10 -4 , responsivity of 30 mA/W and detectivity of 2 × 10 11 Jones along with the lowest noise equivalent power (NEP) parameter of 2.4 × 10 -12 WHz -1/2 in the blue light region. Compared to the bare SiNHs device, the AuNWs/SiNHs device had significantly enhanced responsivity up to 15 mA/W, especially in the red and near-infrared spectral region. Intensity-modulated photovoltage spectroscopy (IMVS) measurements revealed that the AgNWs/SiNHs device generated the longest charge carrier lifetime at 470 nm, whereas the AuNWs/SiNHs showed the slowest recombination rate at 627 nm. Furthermore, numerical simulation confirmed the local field enhancement effects at the MeNWs and SiNHs interface. The study demonstrates a cost-efficient and scalable strategy to combine the superior light harvesting properties of SiNHs with the plasmonic absorption of metallic nanowires (MeNWs) towards enhanced sensitivity and spectral-selective photodetection induced by the local surface plasmon resonance effects.

We report a simple, scalable route to wafer-size processing for fabrication of tunable nanoporous gold (NPG) by the anodization process at low constant current in a solution of hydrofluoric acid and dimethylformamide. Microstructural, optical, and electrochemical investigations were employed for a systematic analysis of the sample porosity evolution while increasing the anodization duration, namely the small angle X-ray scattering (SAXS) technique and electrochemical impedance spectroscopy (EIS). Whereas the SAXS analysis practically completes the scanning electronic microscopy (SEM) investigations and provides data about the impact of the etching time on the nanoporous gold layers in terms of fractal dimension and average pore surface area, the EIS analysis was used to estimate the electroactive area, the associated roughness factor, as well as the heterogeneous electron transfer rate constant. The bridge between the analyses is made by the scanning electrochemical microscopy (SECM) survey, which practically correlates the surface morphology with the electrochemical activity. The results were correlated to endorse the control over the gold film nanostructuration process deposited directly on the substrate that can be further subjected to different technological processes, retaining its properties. The results show that the anodization duration influences the surface area, which subsequently modifies the properties of NPG, thus enabling tuning the samples for specific applications, either optical or chemical.

Gold nanoparticles of comparable size were synthetized using honey mediated green method (AuNPs@honey) and citrate mediated Turkevich method (AuNPs@citrate). Their colloidal behavior in two cell media DMEM and RPMI, both supplemented with 10% FBS, was systematically investigated with different characterization techniques in order to evidence how the composition of the media influences their stability and the development of protein/NP complex. We revealed the formation of the protein corona which individually covers the nanoparticles in RPMI media, like a dielectric spacer according to UV-Vis spectroscopy, while DMEM promotes more abundant agglomerations, clustering together the nanoparticles, according to TEM investigations. In order to evaluate the biological impact of nanoparticles, B16 melanoma and L929 mouse fibroblasts cells were used to carry out the viability assays. Generally, the L929 cells were more sensitive than B16 cells to the presence of gold nanoparticles. Measurements of cell viability, proliferation and apoptotic activities of B16 cells indicated that the effects induced by AuNPs@honey were slightly similar to those induced by AuNPs@citrate, however, the toxic response improved in the L929 fibroblast cells following the treatment with AuNPs@honey within the same concentration range from 1 μg/ml to 15 μg/ml for 48 h. Results showed that honey mediated synthesis generates nanoparticles with reduced toxicity trends depending on the cell type, concentration of nanoparticles and exposure time toward various biomedical applications., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Novel microarray platform for single nucleotide polymorphisms (SNPs) detection has been developed using silicon nanowires (SiNWs) as support and two different surface modification methods for attaining the necessary functional groups. Accordingly, we compared the detection specificity and stability over time of the probes printed on SiNWs modified with (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde (GAD), or coated with a simpler procedure using epoxy-based SU-8 photoresist. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used for comparative characterization of the unmodified and coated SiNWs. The hybridization efficiency was assessed by comprehensive statistical analysis of the acquired data from confocal fluorescence scanning of the manufactured biochips. The high detection specificity between the hybridized probes containing different mismatch types was demonstrated on SU-8 coating by one way ANOVA test (adjusted p value *** < .0001). The stability over time of the probes tethered on SiNWs coated with SU-8 was evaluated after 1, 4, 8 and 21 days of probe incubation, revealing values for coefficient of variation (CV) between 2.4% and 5.6%. The signal-to-both-standard-deviations ratio measured for SU-8 coated SiNWs platform was similar to the commercial support, while the APTES-GAD coated SiNWs exhibited the highest values., (Copyright © 2018 Elsevier B.V. All rights reserved.)