Nanoshell

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Nanotoxicology Nanosensor Nanoshell Nanorobotics

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This box: view · gold).[1] These nanoshells involve a quasiparticle called plasmon which is a collective excitation or quantum plasma oscillation where the electrons simultaneously oscillate with respect to all the ions. The simultaneous oscillation can be called plasmon hybridization where the tunability of the oscillation is associated with mixture of the inner and outer shell where they hybridize to give a lower energy or higher energy. This lower energy couples strongly to incident light whereas, the higher energy is an anti-bonding and weakly combines to incident light. The hybridization interaction is stronger for thinner shell layers, hence, the thickness of the shell and overall particle radius determines which wavelength of light it couples with.[2] Nanoshells can be varied across a broad range of the light spectrum that spans the visible and near infrared regions. The interaction of light and nanoparticles affects the placements of charges which affects the coupling strength. Incident light polarized parallel to the substrate gives a s-polarization (Figure 1b), hence the charges are further from the substrate surface which gives a stronger interaction between the shell and core. Otherwise, a p-polarization is formed which gives a more strongly shifted plasmon energy causing a weaker interaction and coupling. Synthesis A nanoshell is synthesized in a multistep process [2] : Obtain gold nanoparticles in a solution (usually tetrachloroauric acid and a reducing agent) This solution phase synthesis of the gold nanoparticles uses a reduction using tetrachloroauric acid by a reducing agent. There are several different reducing agents used and all can greatly affect the uniformity of the nanoparticle. Attach a very small seed colloid onto the dielectric nanoparticles (such as: zinc selenide, sapphire, and glass) giving a discontinuous shell Grow a continuous shell by using a chemical reduction of the metal attached to the dielectric nanoparticles If a uniform shell is not obtained then it can greatly affect the optical properties of the nanoshell. A good example of this is a nanoegg, which is a metallic nanoshell that has a nonuniform thickness. This characteristic nonuniformity causes additional hybridized plasmon resonances in the spectrum making the coupling not as effective. Applications Since nanoshells possess highly favorable optical and chemical properties it is often used for biomedical imaging, therapeutic applications, fluorescence enhancement of weak molecular emitters, surface enhanced Raman spectroscopy and surface enhanced infrared absorption spectroscopy.[1] Cancer Treatment Gold nanoshells are shuttled into tumors by the use of phagocytosis where phagocytes engulf the nanoshells through the cell membrane to form an internal phagosome, or macrophage. After this it is shuttled into a cell and enzymes are usually used to metabolize it and shuttle it back out of the cell. These nanoshells are not metabolized so for them to be effective they just need to be within the tumor cells and photoinduced cell death is used to terminate the tumor cells. This scheme is shown in Figure 2. Nanoparticle-base therapeutics have been successfully delivered into tumors by exploiting the enhanced permeability and retention effect, a property that permits nanoscale structures to be taken up passively into tumors with out the assistance of antibodies.[4] Delivery of nanoshells into the important regions of tumors can be very difficult. This is where most nanoshells try to exploit the tumor’s natural recruitment of monocytes for delivery as seen in the above figure. This delivery system is called a "Trojan Horse".[3] This process works so well since tumors are about ¾ macrophages and once monocytes are brought into the tumor, it differentiates into macrophages which would also be need to maintain the cargo nanoparticles. Once the nanoshells are at the necrotic center, near-infrared illumination is used to destroy the tumor associated macrophages. References ^ a b Loo, C; Lin, A; Hirsch, L; Lee, Mh; Barton, J; Halas, N; West, J; Drezek, R (Feb 2004). "Nanoshell-enabled photonics-based imaging and therapy of cancer" (Free full text). Technology in cancer research & treatment 3 (1): 33–40. PMID 14750891. http://www.tcrt.org/index.cfm?d=3018&c=4130&p=12032&do=detail.  ^ a b Brinson, Be; Lassiter, Jb; Levin, Cs; Bardhan, R; Mirin, N; Halas, Nj (Nov 2008). "Nanoshells Made Easy: Improving Au Layer Growth on Nanoparticle Surfaces". Langmuir 24 (24): 14166. doi:10.1021/la802049p. PMID 19006344.  ^ Choi, Mr; Stanton-Maxey, Kj; Stanley, Jk; Levin, Cs; Bardhan, R; Akin, D; Badve, S; Sturgis, J; Robinson, Jp; Bashir, R; Halas, Nj; Clare, Se (Dec 2007). "A cellular Trojan Horse for delivery of therapeutic nanoparticles into tumors". Nano letters 7 (12): 3759–65. Bibcode 2007NanoL...7.3759C. doi:10.1021/nl072209h. PMID 17979310.  Wikimedia Foundation. 2010. Игры ⚽ Поможем решить контрольную работу Ovation Pharma Teknival Look at other dictionaries: nanoshell — noun A dielectric nanoparticle coated with a very thin metallic shell …   Wiktionary Nanomedicine — Part of a series of articles on Nanomedicine Nanotoxicology Nanosensor Nanoshell Nanorobotics See also Nanotechnology This box …   Wikipedia Nanosensor — Part of a series of articles on Nanomedicine Nanotoxicology Nanosensor Nanoshell Nanorobotics See also Nanotechnology This box …   Wikipedia Naomi Halas — is the Stanley C. Moore professor in Electrical and Computer Engineering and professor in Chemistry at Rice University. Her current work focuses on nanoshells which her nanophotonics group is developing at Rice University. 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