Optical Properties Of Au Nanoparticles Research Articles

Preparation and Thermoresponsive Properties of AuNPs/PNIPAM Composite Particles

A new composite of Au nanoparticles (AuNPs) adsorbed on thermoresponsive poly(N-isopropyl acrylamide) (PNIPAM) microgels that combines the thermoresponsive behavior of PNIPAM microgels with the optical properties of Au nanoparticles is reported. The LSPR (localized surface plasmon resonance) of the AuNPs could be changed by adjusting the temperature of the thermoresponsive PNIPAM microgels. An increase in temperature led to a red shift of the LSPR of the AuNPs and this change was found to be fully reversible. Optical properties of AuNPs were used to monitor the thermoresponsive behavior of PNIPAM microgels. The morphology, optical properties, and average particle size of AuNPs/PNIPAM particles were characterized by transmission electron microscopy (TEM), UV-Vis spectroscopy and dynamic light scattering.

Gold–silica nanocomposites for the detection of human ovarian cancer cells: a preliminarystudy

We report the structural and optical properties of Au nanoparticles embedded in a silicamatrix synthesized by atom beam co-sputtering. The presence of surface plasmon resonantabsorption indicates the formation of Au nanoparticles. Transmission electron microscopy(TEM) studies show the presence of Au nanoparticles with an average size ranging from∼1.8 to 5.4 nm with narrow size distributions depending on the relative areas of Au andSiO2. We discuss the process of nucleation and growth of Au nanoparticles in thenanocomposite films formed by co-sputtering. The present method of nanoparticle synthesisis compared with other ion beam based techniques such as ion implantation and ion beammixing. Preliminary experiments for the detection of human ovarian cancer cells usingthese Au nanoparticles are described.

Synthesis of Monodisperse FeAu Nanoparticles with Tunable Magnetic and Optical Properties

AbstractMonodisperse FeAu nanoparticles can be synthesized via the reduction of gold acetate by 1,2‐hexadecanediol and the thermal decomposition of iron pentacarbonyl in the presence of the stabilizers oleic acid and oleylamine. The effects of composition, reaction time, and reaction temperature on their size, structure, and optical and magnetic properties are studied. It is found that the incorporation of Au into Fe nanoparticles leads to a structural change from body‐centered cubic (bcc) to face‐centered cubic (fcc). The size of the particles decreases with increasing reaction time and temperature because of atom rearrangement, and varies with the Au/Fe molar ratio as a result of the faster reduction rate of gold acetate compared with the decomposition rate of iron pentacarbonyl and the associated changes in nucleation and growth processes. The resultant FeAu nanoparticles possess the optical properties of Au nanoparticles and the magnetic properties of Fe nanoparticles. Their characteristic absorption bands, in the visible light range, become broader with decreasing Au/Fe molar ratio or increasing reaction time and temperature. Also, they are red‐shifted with decreasing the Au content and blue‐shifted with increasing reaction time. In addition, the particles are nearly superparamagnetic. With the increase in the Au/Fe molar ratio, their blocking temperature and coercivity increase while the saturation magnetization and remnant magnetization decrease. They can be self‐assembled into parallel stripes in the direction of an applied magnetic field.

Changes in the Shape and Optical Properties of Gold Nanoparticles Contained within Alumina Membranes Due to Low-Temperature Annealing

The shape and optical properties of Au nanoparticles electrochemically deposited within the pores of porous alumina membranes have been studied as a function of the temperature to which the Au/alumina composite was heated. Low aspect ratio Au nanoparticles begin as thin skinned particles, essentially flakes of Au within the pores, but after heat treatment at low temperatures (<400 °C), they anneal to become dense, roughly spherical particles. Visually, the color of these membranes changes from blue to red after the thermal treatment. In contrast, the nanoparticles with an aspect ratio of ca. 3 exhibit essentially no change in either optical absorption characteristics or particle shape after exposure to the heating program. These membranes were initially red and did not change color with heating.