SERS Substrates by the Assembly of Silver Nanocubes: High-Throughput and Enhancement Reliability Considerations

Small clusters of nanoparticles are ideal substrates for SERS measurements, but the SERS signal enhancement by a particular cluster is strongly dependent on its structural characteristics and the measurement conditions. Two methods for high-throughput assembly of silver nanocubes into small clusters at predetermined locations on a substrate are presented. These fabrication techniques make it possible to study both the structure and the plasmonic properties of hundreds of nanoparticle clusters. The variations in SERS enhancement factors from cluster to cluster were analyzed and correlated with cluster size and configuration, and laser frequency and polarization. Using Raman instruments with 633 nm and 785 nm lasers and linear clusters of nanocubes, an increase in the reproducibility of the enhancement and an increase in the average enhancement values were achieved by increasing the number of nanocubes in the cluster, up to 4 nanocubes per cluster. By examining the effect of cluster configuration, it is shown that linear clusters with nanocubes attached in a face-to-face configuration are not as effective SERS substrates as linear clusters in which nanocubes are attached along an edge

Practical Fully Secure Three-Party Computation via Sublinear Distributed Zero-Knowledge Proofs

Secure multiparty computation enables a set of parties to securely carry out a joint computation on their private inputs without revealing anything but the output. A particularly motivated setting is that of three parties with a single corruption (hereafter denoted 3PC). This 3PC setting is particularly appealing for two main reasons: (1) it admits more efficient MPC protocols than in other standard settings; (2) it allows in principle to achieve full security (and fairness). Highly efficient protocols exist within this setting with security against a semi-honest adversary; however, a significant gap remains between these and protocols with stronger security against a malicious adversary. In this paper, we narrow this gap within concretely efficient protocols. More explicitly, we have the following contributions: * Concretely Efficient Malicious 3PC. We present an optimized 3PC protocol for arithmetic circuits over rings with (amortized) communication of 1 ring element per multiplication gate per party, matching the best semi-honest protocols. The protocol applies also to Boolean circuits, significantly improving over previous protocols even for small circuits. Our protocol builds on recent techniques of Boneh et al.\ (Crypto 2019) for sublinear zero-knowledge proofs on distributed data, together with an efficient semi-honest protocol based on replicated secret sharing (Araki et al., CCS 2016). We present a concrete analysis of communication and computation costs, including several optimizations. For example, for 40-bit statistical security, and Boolean circuit with a million (nonlinear) gates, the overhead on top of the semi-honest protocol can involve less than 0.5KB of communication {\em for the entire circuit}, while the computational overhead is dominated by roughly 30 multiplications per gate in the field $F_{2^{47}}$. In addition, we implemented and benchmarked the protocol for varied circuit sizes. * Full Security. We augment the 3PC protocol to further provide full security (with guaranteed output delivery) while maintaining amortized 1 ring element communication per party per multiplication gate, and with hardly any impact on concrete efficiency. This is contrasted with the best previous 3PC protocols from the literature, which allow a corrupt party to mount a denial-of-service attack without being detected

Bismuth nanowire and antidot array studies motivated by thermoelectricity

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004.Vita.Includes bibliographical references (p. 187-200).Porous anodic alumina (PAA) films were utilized to template the fabrication of nanostructures of bismuth, antimony and bismuth-antimony alloys. The cylindrical template pores were used to synthesize nanowires by electrochemical methods. The porous surface of the template was used as a substrate for the e-beam deposition of antidot array thin films. Electrical transport measurements in bismuth nanowire arrays embedded in the templates were demonstrated to be highly sensitive to structural imperfections. Thin film studies compared the weak anti-localization effect in bismuth films with antidot array morphology versus continuous films. It is shown that the antidot array makes the weak anti-localization effect more pronounced in magnetoresistance measurements, and allows for a more detailed study of carrier scattering mechanisms in thin films. A new process is presented for the fabrication of PAA templates on rigid substrates. The substrate provides mechanical support for the generation of crack-free PAA films over areas of tens of cm2, while electrically-conducting substrates can serve as back-electrodes for the electrochemical growth of nanowires and for their electrical characterization. Various processing challenges were solved, including the deposition of thick aluminum films, the control over the adhesion between the layers of the structure, and the removal of the alumina barrier-layer at the interface between the porous film and the substrate. The use of the substrate to achieve non-planar and patterned PAA films is demonstrated.(cont.) A model is constructed to calculate the thermoelectric figure-of-merit Z of bismuth- antimony alloy nanowires as a function of diameter, composition, and carrier density. In this model, the band structure of the alloy in bulk form is modified by the quantization of k-space in the two dimensions perpendicular to the nanowire main-axis. Boltzmann's transport equations are solved with this one-dimensional band structure. The model predicts an enhancement in Z in alloy nanowires compared to the alloys in bulk form and to bismuth nanowires. The enhancement, which was found to be non- monotonic i diameter-composition space, was related to shifts in the populations and energies of the different carrier pockets.by Oded Rabin.Ph.D

An X-Ray Computed Tomography Imaging Agent Based On Long-Circulating Bismuth Sulphide Nanoparticles

The utilization of polymer-coated Bi2S3 nanoparticle preparation, as an injectable imaging agent in computed tomography (CT), was investigated. The polymer-coated bismuth sulfide nanoparticles (BPNP) were synthesized by a two-step protocol adapted to give homogeneous preparations which is more suitable for parenteral use. The application of nanoparticulate imaging probes to X-ray CT imaging have a significant impact on health care, owing to the ubiquitous nature of CT in the clinical setting. The results show that the lower volumes of BPNP can be used without confronting viscosity problems and they also have long vascular half-life

Remote Chemical Sensing by SERS with Self-Assembly Plasmonic Nanoparticle Arrays on a Fiber

Partial funding for Open Access provided by the UMD Libraries' Open Access Publishing Fund.An optical fiber was modified at the tip with a self-assembled plasmonic metamaterial that acts as a miniature surface-enhanced Raman spectroscopy (SERS) substrate. This optical fiber-based device co-localizes the laser probe signal and the chemical analyte at a distance remote from the spectrometer, and returns the scattered light signal to the spectrometer for analysis. Remote SERS chemical detection is possible in liquids and in dried samples. Under laboratory conditions, the analyte SERS signal can be separated from the background signal of the fiber itself and the solvent. An enhancement factor greater than 35,000 is achieved with a monolayer of the SERS marker 4-aminothiophenol.https://doi.org/10.3389/fphy.2021.75294

Plasmonic nanoarcs: a versatile platform with tunable localized surface plasmon resonances in octave intervals.

The tunability of the longitudinal localized surface plasmon resonances (LSPRs) of metallic nanoarcs is demonstrated with key relationships identified between geometric parameters of the arcs and their resonances in the infrared. The wavelength of the LSPRs is tuned by the mid-arc length of the nanoarc. The ratio between the attenuation of the fundamental and second order LSPRs is governed by the nanoarc central angle. Beneficial for plasmonic enhancement of harmonic generation, these two resonances can be tuned independently to obtain octave intervals through the design of a non-uniform arc-width profile. Because the character of the fundamental LSPR mode in nanoarcs combines an electric and a magnetic dipole, plasmonic nanoarcs with tunable resonances can serve as versatile building blocks for chiroptical and nonlinear optical devices