Aspects of high-performance and bio-acceptable magnetic nanoparticles for biomedical application

This review covers extensively the synthesis&surface modification,characterization,and application of magnetic nanoparticles.For biomedical applications,consideration should be given to factors such as design strategies,the synthesis process,coating,and surface passivation.The synthesis method regulates post-synthetic change and specific applications in vitro and in vivo imaging/diagnosis and pharmacotherapy/administration.Special insights have been provided on biodistribution,pharmacokinetics,and toxicity in a living system,which is imperative for their wider application in biology.These nanoparticles can be decorated with multiple contrast agents and thus can also be used as a probe for multi-mode imaging or double/triple imaging,for example,MRI-CT,MRI-PET.Similarly loading with different drug molecules/dye/fluorescent molecules and integration with other carriers have found application not only in locating these particles in vivo but simultaneously target drug delivery/hyperthermia inside the body.Studies are underway to collect the potential of these magnetically driven nanoparticles in various scientific fields such as particle interaction,heat conduction,imaging,and magnetism.Surely,this comprehensive data will help in the further development of advanced techniques for theranostics based on high-performance magnetic nanoparticles and will lead this research area in a new sustainable direction.

Detection of Breast Cancer 1 (BRCA1) Gene Using an Electrochemical DNA Biosensor Based on Immobilized ZnO Nanowires

Herein we report an electrochemical DNA biosensor for the rapid detection of sequence (5’ AAT GGA TTT ATC TGC TCT TCG 3’) specific for the breast cancer 1 (BRCA1) gene. The proposed electrochemical genosensor is based on short oligonucleotide DNA probe immobilized onto zinc oxide nanowires (ZnONWs) chemically synthesized onto gold electrode via hydrothermal technique. The morphology studies of the ZnONWs, performed by field emission scanning electron microscopy (FESEM), showed that the ZnO nanowires are uniform, highly dense and oriented perpendicularly to the substrate. Recognition event between the DNA probe and the target was investigated by differential pulse voltammetry (DPV) in 0.1 M acetate buffer solution (ABS), pH 7.00;as a result of the hybridization, an oxidation signal was observed at +0.8 V. The influences of pH, target concentration, and non-complimentary DNA on biosensor performance were examined. The proposed DNA biosensor has the ability to detect the target sequence in the range of concentration between 10.0 and 100.0 μM with a detection limit of 3.32 μM. The experimental results demonstrated that the prepared ZnONWs/Au electrodes are suitable platform for the immobilization of DNA.

Science Letters:Demonstration of a new biosensing concept for immunodiagnostic applications based on change in surface conductance of antibodies after biomolecular interactions

We report an important observation that the surface conductivity of antibody layer immobilized on polylysine-coated glass substrate decreases upon the formation of complex with their specific antigens. This change in conductivity has been ob- served for both monoclonal and polyclonal antibodies. The conductance of monoclonal mouse IgG immobilized on polylysine-coated glass substrate changed from 1.02×10?8 ??1 to 1.41×10?11 ??1 at 10 V when complex is formed due to the specific biomolecular interactions with rabbit anti-mouse IgG F(ab′)2. Similar behavior was observed when the same set up was tested in two clinical assays: (1) anti-Leishmania antigen polyclonal antibodies taken from Kala Azar positive patient serum interacting with Leishmania promastigote antigen, and (2) anti-p21 polyclonal antibodies interacting with p21 antigen. The pro- posed concept can represent a new immunodiagnostic technique and may have wide ranging applications in biosensors and nanobiotechnology too.

Comparative study of various methods for extraction of multi-quantum wells Schottky diode parameters

In this work,forward current voltage characteristics for multi-quantum wells Al_(0.33)Ga_(0.67)As Schottky diode were measured at temperature ranges from 100 to 300 K.The main parameters of this Schottky diode,such as the ideality factor,barrier height,series resistance and saturation current,have been extracted using both analytical and heuristics methods.Differential evolution(DE),particle swarm optimization(PSO)and artificial bee colony(ABC)have been chosen as candidate heuristics algorithms,while Cheung technic was selected as analytical extraction method.The obtained results show clearly the high performance of DE algorithms in terms of parameters accuracy,convergence speed and robustness.

Temperature and Magnetic Resonance Characteristics of Zinc, Manganese, Gadolinium, Gold, Iron Magnetic Nanoparticles and Cytokine Synergy in Hyperthermia

The temperature and magnetic moment depend-ence for assessing localized heating utilizing a new class of Manganese-Zinc-Gadolinium mag-netic nanoparticles was studied. These particles showed heating effect when subjected to alter-nating filed. Alternatively, a new approach was used to get disperse heating without spot heating by using the synthesis of particles at controlled Curie temperature of less than 44oC. The study reports a simple synthesis of Mn0.5Zn0.5GdxFe(2-x)O4 nanoparticles using chemical co- precipita-tion technique. The particles exhibited Curie temperature of 42篊 and high magnitude of mag-netic moments. The particles showed sigmoid behavior of dependence between temperature and magnetic moments. The Nuclear Magnetic Resonance spectroscopy showed T1 depend-ence on temperature in the range of 10-45篊. The particles may have high promise for self con-trolled magnetic hyperthermia application and its monitoring.

Thermal,infrared spectroscopy and molecular modeling characterization of bone:An insight in the apatite-collagen type I interaction

An insight into the interaction of collagen type I with apatite in bone tissue was performed by using differential scanning calorimetry, Fourier transform infrared spectroscopy, and molecular modeling. Scanning electron microscopy shows that bone organic content incinerate gradually through the different temperatures studied. We suggest that the amide regions of the type I collagen molecule (mainly C=O groups of the peptide bonds) will be important in the control of the interactions with the apatite from bone. The amide I infrared bands of the collagen type I change when interacting to apatite, what might confirm our assumption. Bone tissue results in a loss of thermal stability compared to the collagen studied apart, as a consequence of the degradation and further combustion of the collagen in contact with the apatite microcrystals in bone. The thermal behavior of bone is very distinctive. Its main typical combustion temperature is at 360°C with a shoulder at 550°C compared to the thermal behavior of collagen, with the mean combustion peak at ca. 500°C. Our studies with molecular mechanics (MM+ force field) showed different interaction energies of the collagen-like molecule and different models of the apatite crystal planes. We used models of the apatite (100) and (001) planes;additional two planes (001) were explored with phosphate-rich and calcium-rich faces;an energetic preference was found in the latter case. We preliminary conclude that the peptide bond of collagen type I is modified when the molecule interacts with the apatite, producing a decrease in the main peak from ca. 500°C in collagen, up to 350°C in bone. The combustion might be related to collagen type I, as the ΔH energies present only small variations between mineralized and non-mineralized samples. The data obtained here give a molecular perspective into the structural properties of bone and the change in collagen properties caused by the interaction with the apatite. Our study can be useful to understand the biological synthesis of minerals as well as the organic-inorganic interaction and the synthesis of apatite implant materials.

Multi-mode microcavity frequency engineering through a shifted grating in a photonic crystal ring

Frequency engineering of whispering-gallery resonances is essential in microcavity nonlinear optics.The key is to control the frequencies of the cavity modes involved in the underlying nonlinear optical process to satisfy its energy conservation criterion.Compared to the conventional method that tailors dispersion by cross-sectional geometry,thereby impacting all cavity mode frequencies,grating-assisted microring cavities,often termed as photonic crystal microrings,provide more enabling capabilities through mode-selective frequency control.For example,a simple single period grating added to a microring has been used for single frequency engineering in Kerr optical parametric oscillation(OPO)and frequency combs.Recently,this approach has been extended to multifrequency engineering by using multi-period grating functions,but at the cost of increasingly complex grating profiles that require challenging fabrication.Here,we demonstrate a simple approach,which we term as shifted grating multiple mode splitting(SGMMS),where spatial displacement of a single period grating imprinted on the inner boundary of the microring creates a rotational asymmetry that frequency splits multiple adjacent cavity modes.This approach is easy to implement and presents no additional fabrication challenges compared to an unshifted grating,and yet is very powerful in providing multi-frequency engineering functionality for nonlinear optics.We showcase an example where SGMMS enables OPO across a wide range of pump wavelengths in a normal-dispersion device that otherwise would not support OPO.

Optical Microresonators feature issue introduction

Optical microresonators,which confine light in both the spatial and time domains,have advanced various research areas benefiting from significantly enhanced light-matter interactions,including integrated microlasers,nonlinear frequency conversion,Kerr frequency combs,and optomechanics.Over the past five years,the research interests in optical microresonators have rapidly expanded and combined with other disciplines,for example,optical chaos,non-Hermitian physics,and quantum materials.These cutting-edge research works have enabled the creation of optical microresonators with novel properties and capabilities.

Universal frequency engineering tool for microcavity nonlinear optics:multiple selective mode splitting of whispering-gallery resonances

Whispering-gallery microcavities have been used to realize a variety of efficient parametric nonlinear optical processes through the enhanced light–matter interaction brought about by supporting multiple high quality factor and small modal volume resonances.Critical to such studies is the ability to control the relative frequencies of the cavity modes,so that frequency matching is achieved to satisfy energy conservation.Typically this is done by tailoring the resonator cross section.Doing so modifies the frequencies of all of the cavity modes,that is,the global dispersion profile,which may be undesired,for example,in introducing competing nonlinear processes.Here,we demonstrate a frequency engineering tool,termed multiple selective mode splitting(MSMS),that is independent of the global dispersion and instead allows targeted and independent control of the frequencies of multiple cavity modes.In particular,we show controllable frequency shifts up to 0.8 nm,independent control of the splitting of up to five cavity modes with optical quality factors≳10^5,and strongly suppressed frequency shifts for untargeted modes.The MSMS technique can be broadly applied to a wide variety of nonlinear optical processes across different material platforms and can be used to both selectively enhance processes of interest and suppress competing unwanted processes.

Overcoming thermo-optical dynamics in broadband nanophotonic sensing

Advances in integrated photonics open up exciting opportunities for batch-fabricated optical sensors using high-quality-factor nanophotonic cavities to achieve ultrahigh sensitivities and bandwidths.The sensitivity improves with increasing optical power;however,localized absorption and heating within a micrometer-scale mode volume prominently distorts the cavity resonances and strongly couples the sensor response to thermal dynamics,limiting the sensitivity and hindering the measurement of broadband time-dependent signals.Here,we derive a frequency-dependent photonic sensor transfer function that accounts for thermo-optical dynamics and quantitatively describes the measured broadband optomechanical signal from an integrated photonic atomic force microscopy nanomechanical probe.Using this transfer function,the probe can be operated in the high optical power,strongly thermo-optically nonlinear regime,accurately measuring low-and intermediate-frequency components of a dynamic signal while reaching a sensitivity of 0.7fm/Hz^(1/2) at high frequencies,an improvement of=10x relative to the best performance in the linear regime.Counterintuitively,we discover that a higher transduction gain and sensitivity are achieved with lower quality-factor optical modes for low signal frequencies.Not limited to optomechanical transducers,the derived transfer function is generally valid for describing the small-signal dynamic responses of a broad range of technologically important photonic sensors subject to the thermo-optical effect.

Property mapping of polycrystalline diamond coatings over large area

Large-area polycrystalline diamond(PCD)coatings are important for fields such as thermal management,optical windows,tribological moving mechanical assemblies,harsh chemical environments,biological sensors,etc.Microwave plasma chemical vapor deposition(MPCVD)is a standard technique to grow high-quality PCD films over large area due to the absence of contact between the reactive species and the filament or the chamber wall.However,the existence of temperature gradients during growth may compromise the desired uniformity of the final diamond coatings.In the present work,a thick PCD coating was deposited on a 100-mm silicon substrate inside a 915-MHz reactor;the temperature gradient resulted in a non-uniform diamond coating.An attempt was made to relate the local temperature variation during deposition and the different properties of the final coating.It was found that there was large instability inside the system,in terms of substrate temperature(as high asΔT=212℃),that resulted in a large dispersion of the diamond coating’s final properties:residual stress(-15.8 GPa to+6.2 GPa),surface morphology(octahedral pyramids with(111)planes to cubo-octahedrals with(100)flat top surfaces),thickness(190μm to 245μm),columnar growth of diamond(with appearance of variety of nanostructures),nucleation side hardness(17 GPa to 48 GPa),quality(Raman peak FWHM varying from 5.1 cm^(-1) to 12.4 cm^(-1) with occasional splitting).This random variation in properties over large-area PCD coating may hamper reproducible diamond growth for any meaningful technological application.

Facile Growth of Porous Hierarchical Structure of ZnO Nanosheets on Alumina Particles via Heterogeneous Precipitation

ZnO nanosheets and nanoflakes were grown on alumina particles in the absence of surfactants via heterogeneous precipitation using urea, zinc acetate and bayerite as precursors. Thermo-gravimetric analysis （TGA）, X-ray diffraction （XRD） and Fourier transform infrared spectroscopy （FTIR） were used and the results indicated the formation of only two phases： wurtzite-type ZnO and γ-Al2O3. ZnO nanoflakes were grown on alumina particles in the samples with ZnO content of 40 and 60 wt%, By increasing the ZnO content to 80 wt%, a porous hierarchical structure of ZnO with nanosheet arrays appeared. Both of these nanoflakes and nanosheets were about 40-80 nm in thickness and about 1-2 μm in diameter. It was proposed that Zns（CO3）2（OH）6 nuclei undergo higher growth rates in thin sheets at edges of bayerite particles with a higher surface energy. The Brunauer-Emmett-Teller （BET） measurements proved a reachable high surface area for hierarchical structures of ZnO nanosheets, which could mainly be attributed to their unique growth on alumina particles. Also, UV absorption results revealed that ZnO--Al2O3 compositions still show the UV characteristic absorption of ZnO, which can evidence the presence of photocatalytic properties in ZnO-Al2O3 compositions.

Simulink Behavioral Modeling of a 10-bit Pipelined ADC

The increasing architecture complexity of data converters makes it necessary to use behavioral models to simulate their electrical performance and to determine their relevant data features. For this purpose, a specific data converter simulation environment has been developed which allows designers to perform time-domain behavioral simulations of pipelined analog to digital converters （ADCs）. All the necessary blocks of this specific simulation environment have been implemented using the popular Matlab simulink environment. The purpose of this paper is to present the behavioral models of these blocks taking into account most of the pipelined ADC non-idealities, such as sampling jitter, noise, and operational amplifier parameters （white noise, finite DC gain, finite bandwidth, slew rate, and saturation voltages）. Simulations, using a 10-bit pipelined ADC as a design example, show that in addition to the limits analysis and the electrical features extraction, designers can determine the specifications of the basic blocks in order to meet the given data converter requirements.

Novel ZnO-Al_2O_3 composite particles as sorbent for low temperature H_2S removal

Received 28 September 2012 Received in revised form 13 December 2012 Accepted 24 December 2012 Available online 4 February 2013