Enhanced Lifetime Of Excitons In Nonepitaxial Au/cds Core/shell Nanocrystals

The ability of metal nanoparticles to capture light through plasmon excitations offers an opportunity for enhancing the optical absorption of plasmon-coupled semiconductor materials via energy transfer. This process, however, requires that the semiconductor component is electrically insulated to prevent a backward charge flow into metal and interfacial states, which causes a premature dissociation of excitons. Here we demonstrate that such an energy exchange can be achieved on the nanoscale by using nonepitaxial Au/CdS core/shell nanocomposites. These materials are fabricated via a multistep cation exchange reaction, which decouples metal and semiconductor phases leading to fewer interfacial defects. Ultrafast transient absorption measurements confirm that the lifetime of excitons in the CdS shell (tau approximate to 300 ps) is much longer than lifetimes of excitons in conventional, reduction-grown Au/CdS heteronanostructures. As a result, the energy of metal nanoparticles can be efficiently utilized by the semiconductor component without undergoing significant nonradiative energy losses, an important property for catalytic or photovoltaic applications. The reduced rate of exciton dissociation in the CdS domain of Au/CdS nanocomposites was attributed to the nonepitaxial nature of Au/CdS interfaces associated with low defect density and a high potential barrier of the interstitial phase

Sustained release from biodegradable metallic matrix—The entrapment of drugs within iron

Iron and its alloys have been widely used for variety of medical implants. These are used for long term applications as cheap implants with high inertness and low corrosion rate, and also as implants with high biocompatibility (the fourth-generation type). Such degrading implants can provide a temporary scaffold while the body heals. In addition to the needed mechanical support, it is highly desirable to provide local drug therapy, providing antibacterial properties, preventing rejection of the implant, and more. So far, the combination of a degradable metallic implant which serves also as a three-dimensional matrix for drug release, remained un-answered. Here we present, we believe for the first time realization of this concept: Entrapment of drugs within a 3D degradable metal matrix—iron—from which the entrapped drugs are sustain-released. This new type of material is based on the molecular metals entrapment materials methodology, resulting in drugs@Fe. Two drugs have been successfully entrapped and released: chlorhexidine - an antiseptic drug, and rapamycin—used for avoiding transplant rejection. The delivery profiles of the composites were studied in two forms—powders and pressed discs showing two different types of drug release profiles. The release of the drugs from the powder hasa first order release profile, while the pressed disk is a slower, zero-order release profile, which is highly desirable due to the constant rate of the release. Full characterization of the metallic biomaterials is provided, including XRD, SEM, TGA, elemental analysis, and surface area/porosity analysis

Multifunctional semiconductor nanoheterostructures via site-selective silica encapsulation

10.1002/smll.201202096Small9111908-1915SMAL

Asymmetric dumbbells from selective deposition of metals on seeded Semiconductor nanorods

10.1002/anie.200906783Angewandte Chemie - International Edition49162888-2892ACIE

Affecting an Ultra‐High Work Function of Silver

An ultra‐high increase in the WF of silver, from 4.26 to 7.42 eV, that is, an increase of up to circa 3.1 eV is reported. This is the highest WF increase on record for metals and is supported by recent computational studies which predict the potential ability to affect an increase of the WF of metals by more than 4 eV. We achieved the ultra‐high increase by a new approach: Rather than using the common method of 2D adsorption of polar molecules layers on the metal surface, WF modifying components, l‐cysteine and Zn(OH)_{2}, were incorporated within the metal, resulting in a 3D architecture. Detailed material characterization by a large array of analytical methods was carried out, the combination of which points to a WF enhancement mechanism which is based on directly affecting the charge transfer ability of the metal separately by cysteine and hydrolyzed zinc(II), and synergistically by the combination of the two through the known Zn‐cysteine finger redox trap effect

Engineering fluorescence in Au-tipped, CdSe-seeded CdS nanoheterostructures

10.1002/smll.201100976Small7202847-285