Silica Core Research Articles

Design of simple circular photonic crystal fiber having high negative dispersion and ultra-low confinement loss

In this paper, we propose a simple circular photonic crystal fiber (SC-PCF) of silica core having six uniform air-holes and four uniform tiny air-holes arranged at the apexes of square inside the core. The finite element method is used for the numerical analysis of performance parameters. It is found that SC-PCF with four tiny air-holes, i.e., proposed SC-PCF has high negative dispersion of −600.3 ps/nm.km and −366.5 ps/nm.km at 1.3 µm and 1.55 µm operating wavelength, respectively, which is far higher than the previously reported PCFs. The obtained dispersion is highest negative among the air-hole based PCFs. Further, the proposed SC-PCF has ultralow confinement loss of 9.9 × 10−7 dB/cm and 5.13 × 10−5 dB/cm at 1.3 µm and 1.55 µm operating wavelength, respectively, which is far lower than the previously reported PCFs. However, proposed SC-PCF does not show significant improvement in birefringence, i.e. 0.00124 and 0.00145 at 1.3 µm and 1.55 µm operating wavelength, respectively, which is compensated for its high effective area, low coupling loss, and low effective material loss.

Mesoporous silica nanoparticles containing silver as novel antimycobacterial agents against Mycobacterium tuberculosis

Tuberculosis remains today a major public health issue with a total of 9 million new cases and 2 million deaths annually. The lack of an effective vaccine and the increasing emergence of new strains of Mycobacterium tuberculosis (Mtb) highly resistant to antibiotics, anticipate a complicated scenario in the near future. The use of nanoparticles features as an alternative to antibiotics in tackling this problem due to their potential effectiveness in resistant bacterial strains. In this context, silver nanoparticles have demonstrated high bactericidal efficacy, although their use is limited by their relatively high toxicity, which calls for the design of nanocarriers that allow silver based nanoparticles to be safely delivered to the target cells or tissues. In this work mesoporous silica nanoparticles are used as carriers of silver based nanoparticles as antimycobacterial agent against Mtb. Two different synthetic approaches have been used to afford, on the one hand, a 2D hexagonal mesoporous silica nanosystem which contains silver bromide nanoparticles distributed all through the silica network and, on the other hand, a core@shell nanosystem with metallic silver nanoparticles as core and mesoporous silica shell in a radial mesoporous rearrangement. Both materials have demonstrated good antimycobacterial capacity in in vitro test using Mtb, being lower the minimum inhibitory concentration for the nanosystem which contains silver bromide. Therefore, the interaction of this material with the mycobacterial cell has been studied by cryo-electron microscopy, establishing a direct connection between the antimycobactericidal effect observed and the damage induced in the cell envelope.

Rationale design of a layer-by-layer nanostructure for X-ray induced photodynamic therapy

X-ray induced Photodynamic Therapy (XPDT) is a proposed therapy for deep tumours. The idea is to use the X-ray beam of a standard radiotherapy facility to excite a scintillator which is coupled with a photosensitizing agent which in turn generates reactive oxygen species (ROS) which induce local oxidative stress. Alike in standard Photodynamic Therapy, this oxidative stress may be used to treat tumours. Preliminary results [F. Rossi et al. Sci. Rep. 5 (2015) 7606] demonstrated that can XPDT enhance the efficacy of standard radiotherapy, while reducing its unwanted side effects.This work reports the rationale development of a nanostructure incorporating nanoparticles (NP) for XPDT around a silica core by means of electrostatic adsorption. To this aim, scintillator CeF3 and photosensitizer ZnO, both in form of nanoparticles, have been adsorbed into a polyelectrolyte Layer-by-Layer (LbL) multilayer grown around a SiO2 core. This structure, in a future work, could be a platform for drug delivery.We optimized the growth of the structure basing on results from adsorption on planar substrates, as a function of incubation time, of particle concentration, and of the composition of the outer polyelectrolyte layer, having also in mind the need to avoid the formation of micrometric aggregates. This drove the rationale synthesis of the nanocapsules. The resulting structures are studied by Scanning Electron Microscopy, X-ray Microanalysis, Dynamic Light Scattering, and ζ-potential analysis.

Toxicity assessment of a novel oil dispersant based on silica nanoparticles using Fathead minnow

Oil spill accidents are a major concern for aquatic organisms. In recent history, the Deepwater Horizon blowout spilled 500 million liters of crude oil into the Gulf of Mexico. Corexit 9500A was used to disperse the oil since it was the method approved at that time, despite safety concerns about its use. A better solution is necessary for dispersing oil from spills that reduces the toxicity to exposed aquatic organisms. To address this challenge, novel engineered nanoparticles were designed using silica cores grafted with hyperbranched poly(glycidol) branches. Because the silica core and polymers are known to be biocompatible, we hypothesized that these particles are nontoxic to fathead minnows (Pimephales promelas) and would decrease their exposure to oil polyaromatic hydrocarbons. Fathead minnow embryos, juveniles and adult stages were exposed to the particles alone or in combination with a water-accommodated fraction of oil. Acute toxicity of nanoparticles to fish was tested by measuring mortality. Sub-lethal effects were also measured including gene expression of cytochrome P450 1a (cyp1a) mRNA and heart rate in embryos. In addition, a mixture of particles plus the water-accommodated fraction was directly introduced to adult female fathead minnows by gavage. Three different nanoparticle concentrations were used (2, 10, and 50 mg/L) in either artificial fresh water or the water-accommodated fraction of the oil. In addition, nanoparticle-free controls were carried out in the two solutions. No significant mortality was observed for any age group or nanoparticle concentration, suggesting the safety of the nanoparticles. In the presence of the water-accommodated fraction alone, juvenile and adult fathead minnows responded by increasing expression of cyp1a. The addition of nanoparticles to the water-accommodated fraction reduced cyp1a gene expression in treatments. Heart rate was also restored to normal parameters in embryos co-exposed to nanoparticles and to the water-accommodated fraction. Measurement of polyaromatic hydrocarbons confirmed their presence in the tested solutions and the reduction of available PAH in WAF treated with the nanoparticles. Our findings suggest the engineered nanoparticles may be protecting the fish by sequestering polyaromatic hydrocarbons from oil, measured indirectly by the induction of cypa1 mRNAs. Furthermore, chemical analysis showed a reduction in PAH content in the water accommodated fraction with the presence of nanoparticles.

Enhancement of interfacial catalysis in a triphase reactor using oxygen nanocarriers

Multiphase catalysis is used in many industrial processes; however, the reaction rate can be restricted by the low accessibility of gaseous reactants to the catalysts in water, especially for oxygen-dependent biocatalytic reactions. Despite the fact that solubility and diffusion rates of oxygen in many liquids (such as perfluorocarbon) are much higher than in water, multiphase reactions with a second liquid phase are still difficult to conduct, because the interaction efficiency between immiscible phases is extremely low. Herein, we report an efficient triphase biocatalytic system using oil core–silica shell oxygen nanocarriers. Such design offers the biocatalytic system an extremely large water-solid-oil triphase interfacial area and a short path required for oxygen diffusion. Moreover, the silica shell stabilizes the oil nanodroplets in water and prevents their aggregation. Using oxygen-dependent oxidase enzymatic reaction as an example, we demonstrate this efficient biocatalytic system for the oxidation of glucose, choline, lactate, and sucrose by substituting their corresponding oxidase counterparts. A rate enhancement by a factor of 10–30 is observed when the oxygen nanocarriers are introduced into reaction system. This strategy offers the opportunity to enhance the efficiency of other gaseous reactants involved in multiphase catalytic reactions.

Synthesis of tetrahedral patchy nanoparticles with controlled patch size

Silica nanoparticles with four circular surface patches made of polystyrene (PS) and arranged in a tetrahedral symmetry are synthesized through the multistep growth of the silica core of silica/PS tetrapods. Transmission electron microscopy and energy dispersive X-ray analysis studies indicate that, as the silica core regrows, its surface conforms to the shape of the polystyrene nodules, allowing good control of the size of the emerged fraction of these. Patches with an angular width as small as 49° were achieved, which is a prerequisite for their assembly in the form of a diamond crystal phase.

Surface-enhanced Raman scattering and photothermal effect of hollow Au nanourchins with well-defined cavities

We have prepared genuinely hollow Au nanourchins (HANUs) using SiO2 nanoparticles (NPs) as hard templates. Ag-SiO2 NPs were fabricated via amine-assisted reduction. Then, Au nanourchins (ANUs) were synthesized by the galvanic replacement reaction of Ag-SiO2 NPs using l-3,4-dihydroxyphenylalanine (DOPA) as a reductant and a capping agent. The silica cores of ANUs were etched using HF (aq) to produce HANUs. Measuring cross sections, we have found that HANUs have well-defined hollow morphologies. Compared with nanourchins made via DOPA-mediated reduction, HANUs hardly contain residual silver because very tiny silver seeds were used as the initiation sites of galvanic replacement. HANUs have revealed large surface-enhanced Raman scattering enhancement and a significant photothermal effect under a weak illumination.

Cascaded Fabry-Perot interferometer-regenerated fiber Bragg grating structure for temperature-strain measurement under extreme temperature conditions.

We demonstrated an optical fiber sensor based on a cascaded fiber Fabry-Perot interferometer (FPI)-regenerated fiber Bragg grating (RFBG) for simultaneous measurement of temperature and strain under high temperature environments. The FPI is manufactured from a ∼74 µm long hollow core silica tube (HCST) sandwiched between two single mode fibers (SMFs). The RFBG is inscribed in one of the SMF arms which is embedded inside an alundum tube, making it insensitive to the applied strain on the entire fiber sensor, just in case the temperature and strain recovery process are described using the strain-free RFBG instead of a characteristic due-parameter matrix. This feature is intended for thermal compensation for the FPI structure that is sensitive to both temperature and strain. In the characterization tests, the proposed device has exhibited a temperature sensitivity ∼ 18.01 pm/°C in the range of 100 °C - 1000 °C and excellent linear response to strain in the range of 300 °C - 1000 °C. The measured strain sensitivity is as high as ∼ 2.17 pm/µɛ for a detection range from 0 µɛ to 450 µɛ at 800 °C, which is ∼ 1.5 times that of a FPI-RFBG without the alundum tube.

Design of Highly Adhesive and Water-Resistant UV/Heat Dual-Curable Epoxy-Acrylate Composite for Narrow Bezel Display Based on Reactive Organic-Inorganic Hybrid Nanoparticles.

To attain the narrow bezel characteristic of information displays, functional sealing composite materials should possess high adhesion strength and water barrier performance due to their narrow line widths. In this study, highly adhesive UV/heat dual-curable epoxy–acrylate composites with outstanding water-resistant performance have been proposed using photoreactive organic–inorganic hybrid nanoparticles that can react with an acrylate resin, creating a crosslinked nanoparticle network within the sealing composite. The hybrid nanoparticles consisted of reactive methacrylate groups as a shell and an inorganic core of silica or aluminum oxide, and were facilely synthesized through sol–gel reaction and chemisorption process. The curing characteristics, adhesive strength, and moisture permeability of the proposed sealing composite have been compared to those of a conventional epoxy–acrylate composite containing inorganic silica particles. The composites including hybrid nanoparticles exhibited high UV and heat curing ratios owing to the numerous methacrylate groups on the nanoparticle surface and high compatibility with organic resins. Moreover, the proposed sealing composite showed high adhesion strength and extremely low water permeability due to the creation of densely photocrosslinked network with matrix resins. In addition, the sealing composite exhibited excellent narrow dispensing width as well as relatively low viscosity, suggesting the potential application in narrow bezel display.

Investigating the mechanism of uniform Ag@SiO2 core-shell nanostructures synthesis by a one-pot sol–gel method

Monodispersed Ag@SiO2 core-shell structure nanoparticles (NPs) are synthesized at room temperature via a one-pot sol–gel synthesis method, and the synthesizing procedure is observed over reaction time in order to investigate the formation mechanism. Ostwald ripening of silver (Ag) core NPs and silica (SiO2) shells during synthesis of core-shell NPs proceeds in parallel to reaction time. Uniform and stable Ag@SiO2 core-shell NPs are formed at 48 h of reaction time. The hydrolysis rate of tetraethyl orthosilicate (TEOS) plays a critical role in the growth of Ag NPs and the final structure of Ag@SiO2 core-shell NPs. The formation mechanisms of single-core and multicore Ag@SiO2 core-shell NPs are discussed in relation to synchronous Ag core and SiO2 shell growth. Optimal reaction conditions for critical parameters (water volume and TEOS and ascorbic acid concentrations) are also determined.

Radiation Resistance of Single-Mode Optical Fibers at λ = 1.55 μm Under Irradiation at IVG.1M Nuclear Reactor

Radiation-induced attenuation (RIA) at a wavelength of λ = 1.55 μm as well as the RIA spectra were investigated in optical fibers during and after irradiation at the IVG.1M nuclear reactor (Republic of Kazakhstan). The fibers studied were single mode at λ = 1.55 μm, had an undoped silica core and an-F-doped silica cladding [pure-silica fibers (PSFs)], and were provided by different manufacturers. In addition to five PSFs, a single-mode revolver hollow-core fiber was also studied. The PSFs had different coating materials: polyimide, copper, or aluminum. All fibers were exposed to three runs of reactor irradiation at enhanced temperature (155-355 °C) so that by the end of the third run, the fast-neutron fluence amounted to Φ = 4.46·10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sup> n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and y-dose to D = 2.91·10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> Gy. The total induced loss at λ = 1.55 μm was found to be composed of 1) RIA, 2) bending loss (BL), caused by thermal expansion of the copper cylinder the PSFs were wound on, and 3) thermo-induced microbending loss (ML) in Cu-coated PSFs. At the end of the irradiation campaign, the net RIA in PSFs proved to lie in the interval of 0.12-0.16 dB/m, which appears to be admissible to intrareactor transport fibers. It was confirmed that long-wavelength RIA tail is the only RIA origin at λ = 1.55 μm in PSFs in such strong radiation fields. The hollow-core fiber was found to feature zeroth RIA throughout the campaign.

Silica Nanoparticles in Transmucosal Drug Delivery.

Transmucosal drug delivery includes the administration of drugs via various mucous membranes, such as gastrointestinal, nasal, ocular, and vaginal mucosa. The use of nanoparticles in transmucosal drug delivery has several advantages, including the protection of drugs against the harsh environment of the mucosal lumens and surfaces, increased drug residence time, and enhanced drug absorption. Due to their relatively simple synthetic methods for preparation, safety profile, and possibilities of surface functionalisation, silica nanoparticles are highly promising for transmucosal drug delivery. This review provides a description of silica nanoparticles and outlines the preparation methods for various core and surface-functionalised silica nanoparticles. The relationship between the functionalities of silica nanoparticles and their interactions with various mucous membranes are critically analysed. Applications of silica nanoparticles in transmucosal drug delivery are also discussed.

Intense Brillouin amplification in gas using hollow-core waveguides.

Among all the nonlinear effects stimulated Brillouin scattering offers the highest gain in solid materials and has demonstrated advanced photonics functionalities in waveguides. The large compressibility of gases suggests that stimulated Brillouin scattering may gain in efficiency with respect to condensed materials. Here, by using a gas-filled hollow-core fibre at high pressure, we achieve a strong Brillouin amplification per unit length, exceeding by six times the gain observed in fibres with a solid silica core. This large amplification benefits from a higher molecular density and a lower acoustic attenuation at higher pressure, combined with a tight light confinement. Using this approach, we demonstrate the capability to perform large optical amplifications in hollow-core waveguides. The implementations of a low-threshold gas Brillouin fibre laser and a high-performance distributed temperature sensor, intrinsically free of strain cross-sensitivity, illustrate the potential for hollow-core fibres, paving the way to their integration into lasing, sensing and signal processing.

Development of dispersible radioluminescent silicate nanoparticles through a sacrificial layer approach

X-rays offer low tissue attenuation with high penetration depth when used in medical applications and when coupled with radioluminescent nanoparticles, offer novel theranostic opportunities. In this role, the ideal scintillator requires a high degree of crystallinity for an application relevant radioluminescence, yet a key challenge is the irreversible aggregation of the particles at most crystallization temperatures. In this communication, a high temperature multi-composite reactor (HTMcR) process was successfully developed to recrystallize monodisperse scintillating particulates by employing a core-multishell architecture. The core–shell morphology of the particles consisted of a silica core over-coated with a rare earth (Re = Y3+, Lu3+, Ce3+) oxide shell. This core–shell assembly was then encapsulated within a poly(divinylbenzene) shell which was converted to glassy carbon during the annealing & crystallization of the silica/rare earth oxide core–shell particle. This glassy carbon acted as a delamination layer and prevented the irreversible aggregation of the particles during the high temperature crystallization step. A subsequent low temperature annealing step in an air environment removed the glassy carbon and resulted in radioluminescent nanoparticles. Two monodisperse nanoparticle systems were synthesized using the HTMcR process including cerium doped Y2Si2O7 and Lu2Si2O7 with radioluminescence peaks at 427 and 399 nm, respectively. These particles may be employed as an in vivo light source for a noninvasive X-ray excited optogenetics.

Optical fiber temperature sensor with insensitive refractive index and strain based on phase demodulation

AbstractWe propose and experimentally demonstrate a temperature sensor based on a suspended‐core microstructure optical fiber (SCMF). The sensor is constructed by fusion splicing a piece of SCMF between two up‐tapers which act as light beam couplers. The Mach‐Zehnder interference (MZI) is formed by the silica core modes and the air cladding modes in the SCMF. The sensitivity of −0.011 rad/°C in the temperature range of 20°C to 90°C is achieved, which is more accurate and stable than conventional wavelength tracking method due to the phase demodulation method can avoid the effects of spectral noise, dip selection, and wavelength sampling rate on the wavelength tracking. In addition, our proposed sensor is inert to external environments such as strain and refractive index, which can well solve the problem of crosstalk during temperature sensing.

Distribution of Particles in Human Stem Cell-Derived 3D Neuronal Cell Models: Effect of Particle Size, Charge, and Density

Neurodegenerative diseases are generally characterized by a progressive loss of neuronal subpopulations, with no available cure to date. One of the main reasons for the limited clinical outcomes of new drug formulations is the lack of appropriate in vitro human cell models for research and validation. Stem cell technologies provide an opportunity to address this challenge by using patient-derived cells as a platform to test various drug formulations, including particle-based drug carriers. The therapeutic efficacy of drug delivery systems relies on efficient cellular uptake of the carrier and can be dependent on its size, shape, and surface chemistry. Although considerable efforts have been made to understand the effects of the physiochemical properties of particles on two-dimensional cell culture models, little is known of their effect in three-dimensional (3D) cell models of neurodegenerative diseases. Herein, we investigated the role of particle size (235-1000 nm), charge (cationic and anionic), and density (1.05 and 1.8 g cm-3) on the interactions of particles with human embryonic stem cell-derived 3D cell cultures of sensory neurons, called sensory neurospheres (sNSP). Templated layer-by-layer particles, with silica or polystyrene cores, and self-assembled glycogen/DNA polyplexes were used. Particles with sizes <280 nm effectively penetrated sNSP. Additionally, effective plasmid DNA delivery was observed up to 6 days post-transfection with glycogen/DNA polyplexes. The findings provide guidance in nanoparticle design for therapies aimed at neurodegenerative diseases, in particular Friedreich's ataxia, whereby sensory neurons are predominantly affected. They also demonstrate the application of 3D models of human sensory neurons in preclinical drug development.

Engineering of monosized lipid-coated mesoporous silica nanoparticles for CRISPR delivery

CRISPR gene editing technology is strategically foreseen to control diseases by correcting underlying aberrant genetic sequences. In order to overcome drawbacks associated with viral vectors, the establishment of an effective non-viral CRISPR delivery vehicle has become an important goal for nanomaterial scientists. Herein, we introduce a monosized lipid-coated mesoporous silica nanoparticle (LC-MSN) delivery vehicle that enables both loading of CRISPR components [145 µg ribonucleoprotein (RNP) or 40 µg plasmid/mg nanoparticles] and efficient release within cancer cells (70%). The RNP-loaded LC-MSN exhibited 10% gene editing in both in vitro reporter cancer cell lines and in an in vivo Ai9-tdTomato reporter mouse model. The structural and chemical versatility of the mesoporous silica core and lipid coating along with framework dissolution-assisted cargo delivery open new prospects towards safe CRISPR component delivery and enhanced gene editing. Statement of significanceAfter the discovery of CRISPR gene-correcting technology in bacteria. The translation of this technology to mammalian cells may change the face of cancer therapy within the next years. This was first made possible through the use of viral vectors; however, such systems limit the safe translation of CRISPR into clinics because its difficult preparation and immunogenicity. Therefore, biocompatible non-viral nanoparticulate systems are required to successfully deliver CRISPR into cancer cells. The present study presents the use of biomimetic lipid-coated mesoporous silica nanoparticles showing successful delivery of CRISPR ribonucleoprotein and plasmid into HeLa cervical and A549 lung cancer cells as well as successful gene editing in mice brain.

Targeted Delivery of Antibiotic Therapy to Inhibit Pseudomonas aeruginosa Using Lipid-Coated Mesoporous Silica Core-Shell Nanoassembly.

Pseudomonas aeruginosa (PA) is an opportunistic pathogen, which causes serious lung infections in immunocompromised patients. Traditional oral intake of large quantities of small-molecule antibiotics to treat bacterial infections leads to off-target toxicity and development of drug-resistant species. Improved delivery systems of antibiotics to the targeted site of bacterial infections would help reduce the need for a high intake of antibiotics. Colistin (Col), an antibacterial peptide, is considered the last resort treatment for multidrug resistant (MDR)-PA. To approach the problem of development of antibacterial resistance and off-target toxicity due to the use of excessive amounts of antibiotics, we have designed a targeted drug delivery nanoassembly, which delivers antibiotics to extracellular and intracellular bacteria. The nanoassembly is composed of (1) drug (Col)-loaded mesoporous silica (MSN) core (Col@MSN), (2) liposomal shell (Col@MSN@LL), and (3) PA-targeting LL-37 peptide (Col@MSN@LL-(LL-37)). The liposomal shell prevents premature drug release before the nanoassembly approaches the targeted bacteria. The liposome bilayer degrades upon excreted lipase present in the local environment of PA, releasing encapsulated Col. There is a significant increase in Col release (∼90% release within 40 h) in the presence of bacteria compared to the absence of bacteria (only ∼75% release after 80 h). A 6.7-fold increase in the antimicrobial efficacy of Col encapsulated in Col@MSN@LL-(LL-37) was seen compared to free Col. All studies were done using a clinical strain of PA14. Col@MSN@LL-(LL-37) successfully targets and inhibits intracellular PA14 within the lung epithelial cells. Only 7% PA14 viability is seen after treating the lung epithelial cells with Col@MSN@LL-(LL-37). No significant cytotoxicity was observed with Col@MSN@LL-(LL-37). Therefore, this discussed lipid-coated targeted nanoassembly can be considered as a successful antibiotic delivery platform.

Study of the optical parameters of a silica-polymeric optical fiber with a reflective coating made of a thermoplastic fluoropolymer

Silica optical fibers (OF) having a core diameter of 400 – 800 μm made of biocompatible materials are widely used in laser medicine. The results of studying the optical parameters of novel silica-polymeric optical fiber with a reflective thermoplastic copolymer coating (tetrafluoroethylene – ethylene) and the influence of coating conditions on these optical parameters are presented. Coatings from polymer melt were applied to the silica fiber surface by orifice drawing. The numerical aperture of the drawn OF was measured by distribution of the laser radiation emerging from OF in the far field. The optical losses were determined by the distribution of the radiation scattered by the reflective coating along the OF length. The scattering parameters of the laser radiation transmitted through OF were estimated by the intensity and indicatrix of scattering. We studied OF samples up to 50 m in length with a silica core of about 400 μm in diameter and reflective coating with a thickness of 70 – 90 μm, the reflective coating also performed a protective function. The quality of applied coating and optical parameters of the OF samples depended on the speed of fiber drawing (coating speed) Vd. A smooth coating was obtained at Vd ≤ 2 m/min. When Vd &gt; 2 m/min the coating became rough, turning into the so-called «shark skin» at Vd = 6 m/min. Observed scattering of radiation passing through the studied OF samples was attributed to the polymer structure which contained both crystalline and amorphous phases with different values of the refractive index. The smallest scattering was observed in a smooth-coated OF. The total optical loss at a wavelength λ = 532 nm amounted to 300 – 720 dB/km (a nominal numerical aperture was 0.44). Short (1.5 – 3 m) OF samples were shown to provide a transmission of 80 – 93% of the input power.

Silica-gold nanoshell@graphene: a novel class of plasmonic nanoagents for photothermal cancer therapy

In the current work, the optical properties of graphene-wrapped gold nanoshells (GGNSs) with a silica core for different sizes and geometries are investigated based on effective medium and Gans theories in tumor tissue. In addition, bioheat transfer equations are used to obtain the temperature distribution in the kidney tumor and its surrounding medium. The localized surface plasmon resonance peak of GGNSs can be easily tuned inside a large region of biological windows by controlling the thicknesses of gold and graphene layers and their aspect ratios for spheroidal nanoshells. Also, we show that oblate spheroidal GGNSs, due to a high temperature rise, are very effective for photothermal cancer therapy. Moreover, the rise in temperature for spherical nanoshells increases as the thickness of the graphene shell increases, while it is independent of the thickness of the graphene shell for spheroidal GNSs. Finally, the regions of tumor tissue with permanent thermal damage are determined by calculating thermal damage in tumor tissue. Our results demonstrate that GGNSs have a high potential for photothermal cancer therapy.