Novel Plasmonic Nanostructures for Applications in Sensing, Imaging, and Controlled Release

This research placed emphasis on engineering the properties of novel plasmonic nanostructures, especially silver: Ag) and gold: Au) nanostructures with well-defined shapes, for biomedical applications in sensing, imaging and drug delivery. The first part of this work focused on the development of novel dimeric nanostructures of Ag for surface-enhanced Raman scattering: SERS) applications. In this section, I successfully demonstrated the synthesis of well-defined Ag dimers consisting of nanospheres with a broad range of sizes by using two methods. The first method was based on polyol process and the second was based on wet etching. The key for the dimerization process is to control the colloidal stability by adding appropriate amount of ionic species. I then investigated the SERS properties of the dimers of Ag nanospheres with various sizes and the application of using these dimers as SERS tags for Raman mapping of cancer cells. The second part of this work systematically investigated the use of Au nanocages as a novel class of optical tracers for noninvasive sentinel lymph node: SLN) imaging by photoacoustic: PA) tomography. The transport kinetics of Au nanocages in a lymphatic system was evaluated by PA imaging on the axillary region of a rat. Several experimental parameters, including the injection concentration, particle size, and surface charge were systematically studied. Quantification of the amount of nanocages accumulated in the lymph nodes was achieved by correlating the data from PA imaging with the results from inductively-coupled plasma mass spectrometry. In the final part of this work, I focused on the development of Au nanocages as a new platform for controlled drug release. Two temperature-regulated systems were developed by combining Au nanocages with high-intensity focused ultrasound: HIFU). Because it can penetrate more deeply into soft tissues than near-infrared light, HIFU is a potentially more effective external stimulus for rapid, on-demand drug release. The first system was based on nanocages covered with smart, thermally-responsive polymers, and the second was based on nanocages filled with a biocompatible phase-change material. The released dosage could be remotely controlled by manipulating the power of HIFU and/or the duration of exposure. Localization and depth capability of the HIFU-controlled release have also been investigated

Image Encryption Performance Evaluation Based on Poker Test

The fast development of image encryption requires performance evaluation metrics. Traditional metrics like entropy do not consider the correlation between local pixel and its neighborhood. These metrics cannot estimate encryption based on image pixel coordinate permutation. A novel effectiveness evaluation metric is proposed in this paper to address the issue. The cipher text image is transformed to bit stream. Then, Poker Test is implemented. The proposed metric considers the neighbor correlations of image by neighborhood selection and clip scan. The randomness of the cipher text image is tested by calculating the chi-square test value. Experiment results verify the efficiency of the proposed metrics

KCRC-LCD: Discriminative Kernel Collaborative Representation with Locality Constrained Dictionary for Visual Categorization

We consider the image classification problem via kernel collaborative representation classification with locality constrained dictionary (KCRC-LCD). Specifically, we propose a kernel collaborative representation classification (KCRC) approach in which kernel method is used to improve the discrimination ability of collaborative representation classification (CRC). We then measure the similarities between the query and atoms in the global dictionary in order to construct a locality constrained dictionary (LCD) for KCRC. In addition, we discuss several similarity measure approaches in LCD and further present a simple yet effective unified similarity measure whose superiority is validated in experiments. There are several appealing aspects associated with LCD. First, LCD can be nicely incorporated under the framework of KCRC. The LCD similarity measure can be kernelized under KCRC, which theoretically links CRC and LCD under the kernel method. Second, KCRC-LCD becomes more scalable to both the training set size and the feature dimension. Example shows that KCRC is able to perfectly classify data with certain distribution, while conventional CRC fails completely. Comprehensive experiments on many public datasets also show that KCRC-LCD is a robust discriminative classifier with both excellent performance and good scalability, being comparable or outperforming many other state-of-the-art approaches

Root-MUSIC Based Angle Estimation for MIMO Radar with Unknown Mutual Coupling

Direction of arrival (DOA) estimation problem for multiple-input multiple-output (MIMO) radar with unknown mutual coupling is studied, and an algorithm for the DOA estimation based on root multiple signal classification (MUSIC) is proposed. Firstly, according to the Toeplitz structure of the mutual coupling matrix, output data of some specified sensors are selected to eliminate the influence of the mutual coupling. Then the reduced-dimension transformation is applied to make the computation burden lower as well as obtain a Vandermonde structure of the direction matrix. Finally, Root-MUSIC can be adopted for the angle estimation. The angle estimation performance of the proposed algorithm is better than that of estimation of signal parameters via rotational invariance techniques (ESPRIT)-like algorithm and MUSIC-like algorithm. Furthermore, the proposed algorithm has lower complexity than them. The simulation results verify the effectiveness of the algorithm, and the theoretical estimation error of the algorithm is also derived

Dilute magnetic semiconductor and half metal behaviors in 3d transition-metal doped black and blue phosphorenes: a first-principles study

We present first-principles density-functional calculations for the structural, electronic, and magnetic properties of substitutional 3d transition metal (TM) impurities in two-dimensional black and blue phosphorenes. We find that the magnetic properties of such substitutional impurities can be understood in terms of a simple model based on the Hund's rule. The TM-doped black phosphorenes with Ti, V, Cr, Mn, Fe and Ni impurities show dilute magnetic semiconductor (DMS) properties while those with Sc and Co impurities show nonmagnetic properties. On the other hand, the TM-doped blue phosphorenes with V, Cr, Mn and Fe impurities show DMS properties, those with Ti and Ni impurities show half-metal properties, whereas Sc and Co doped systems show nonmagnetic properties. We identify two different regimes depending on the occupation of the hybridized electronic states of TM and phosphorous atoms: (i) bonding states are completely empty or filled for Sc- and Co-doped black and blue phosphorenes, leading to non-magnetic; (ii) non-bonding d states are partially occupied for Ti-, V-, Cr-, Mn-, Fe- and Ni-doped black and blue phosphorenes, giving rise to large and localized spin moments. These results provide a new route for the potential applications of dilute magnetic semiconductor and half-metal in spintronic devices by employing black and blue phosphorenes.Comment: 9 pages, 7 figure