Nanorods

  • Product Details
  • Application
  • Case Study

Product Details

Nanorods are one morphology of nanoscale objects. Each of their dimensions ranges from 1–100 nm and standard aspect ratios (length divided by width) are 3-5. They can be produced by direct chemical synthesis from metals or semiconducting materials.

The combinations of ligands act as shape control agents and bond to different facets of the nanorod with different strengths. This allows different faces of the nanorod to grow at different rates, producing an elongated object.

Gold NanorodsFig 1 Gold Nanorods

Metal nanorods have unique optical properties. The localized surface plasmon resonance was generated by interaction of light at a specific wavelength with noble metal nanoparticles. The intense surface plasmon band enables nanorods to absorb and scatter light in the visible and near infra-red regions, and fluorescence and two-photon induced luminescence are also observed. These optical properties, with the reactivity towards binding events that induce changes in the refractive index of the surrounding solution, which makes nanorods a useful tool for tracking binding events in different applications.

Dark-field micrograph of gold nanorods immobilized on a glass substrate Fig 2 Dark-field micrograph of gold nanorods immobilized on a glass substrate
(Anal Bioanal Chem., 2010, 398, 2451–2469)

Application

  • Display technologies: By changing the orientation of the nanorods with respect to an applied electric field, the reflectivity of the rods can be altered, resulting in superior displays. Each picture element, known as pixel, is composed of a sharp-tipped device of the scale of a few nanometers.

  • Cancer therapeutics: Nanorods with near-infrared absorption peaks can be excited by a laser at the absorbance band wavelength to produce heat, potentially allowing for the selective thermal destruction of cancerous tissues.

  • Biological sensing: Gold nanorods are considered excellent candidates for biological sensing applications because the absorbance band changes with the refractive index of local material, allowing for extremely accurate sensing.

  • Gas sensing: ZnO nanorods have attracted considerable attention for solid-state gas sensors with great potential for overcoming fundamental limitations due to their ultrahigh surface-to-volume ratio.

  • Dye solar cells: The structures of ZnO nanorods solar cells can solve the carrier collection problem that face the conventional planar solar cells and can help in trapping light in the cell, which enables the solar cells to achieve high conversion efficiency with a relatively low cost.

Case Study

Functionalization Strategies of Gold Nanorods and Their Applications

Mannelli I, et al. Analytical and bioanalytical chemistry, 2010, 398, 2451-2469.

Gold nanorods have been used to develop various bioanalytical and biomedical systems because of their antioxidant properties and their ability to be surface functionalized using a variety of well-established chemical methods. Several functionalization strategies for gold nanorods have been proposed to make gold nanorods suitable for assembly and use as transducers in biosensing and as tracers for in vivo imaging and targeting.
Examples of functionalization of gold nanorods
• Hybrid gold-polymer core-shell nanorods were prepared by completely coating their surfaces with polystyrene chains via a CTAB-thiol exchange reaction.
• Hydrophilic polymers such as monofunctional and difunctional thiols polyethylene glycol (PEG, MW 5,000) can be used to stabilize nanorod suspensions and form controlled assemblies with nanospheres or biomolecules in aqueous solutions.
• The use of single plasmonic nanostructures as sensors for biomolecule binding events has been reported, with the ultimate goal of detecting single molecules from complex biomolecule mixtures. The gold nanorods used in bioassay experiments detected streptavidin at a concentration of 1 nmol/L.
• An example of specific molecular probe construction and application was presented by Eghedari and co-workers, who engineered gold nanorods for developing enhanced contrast agents for a laser optoacoustic imaging system (LOIS).

Synthesis and Photocatalytic Application of Zinc Oxide Nanorods Loaded with Silver Nanospheres

Saoud, Khaled, et al. Materials Research Bulletin, 2015, 63, 134-140.

Using a microwave-assisted deposition-precipitation (MAD) synthesis method, a silver nanosphere-loaded zinc oxide nanorod can be successfully prepared with photocatalytic activity under visible light irradiation. When the dosage of this heterogeneous Ag/ZnO photocatalyst was higher than 0.5 g/L, the contaminant methylene blue (MB) was almost completely removed in about 60 minutes.
Synthesis of ZnO nanorods and Ag/ZnO photocatalyst
• The precursor solution of zinc was prepared by dissolving 5 g of Zn(NO3)2 in 100 mL of ethanol in a 250 mL reaction flask. While stirring the solution, adjust the pH to 10 by adding dropwise 1 M NaOH.
• The solution was subsequently placed in a microwave chemical reactor (MCR-3). The solution was exposed to microwave irradiation for approximately 10–15 min and was removed upon onset of boiling. After cooling the obtained solution, it was washed and filtered several times to obtain ZnO nanorods.
• 4 g of the as prepared ZnO nanorods was dispersed in 100 mL aqueous solution containing 2 wt.% of reducing agent (glucose). The solutionwas vigorously stirred for 10 min.
• Silver nitrate solution was then added to the stirring solution drop wise until a pH value of seven was obtained. Finally, the solution was placed in a microwave oven and irradiated for 10 min and was removed before onset of boiling. After cooling the obtained solution, the Ag/ZnO photocatalyst was obtained by centrifugation and washing.

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