Improved surface properties and catalytic activity of anisotropic shapes of photoetched Au nanostructures formed by variable energy laser exposure

• Anisotropic Au morphologies are formed by laser exposure in a single step.
• NR distortion rate enhances on increasing laser energy; 2.41 eV < 2.50 eV< 2.71 eV.
• Electrokinetic properties of Au nanostructures are varied on laser energy exposure.
• Uneven surface and exposed atoms of photoetched particles offer more catalytic sites.
• Catalytic activity enhances ∼15–20% with photoetched particles relative to unetched.

Anisotropic Au nanostructures with versatile shapes have been prepared in a single step through cost effective laser irradiation approach with different laser energies (≈2.41, 2.50 and 2.71 eV) and investigated the changes in optoelectronic and catalytic properties. A variety of irregular Au nano-morphologies such as spheres (5–20 nm), low aspect ratio rods, nano-capsules, oval egg shaped particles, ice cubes (∼7 nm), truncated triangles (∼7–8 nm), pentagonal (∼12 nm), square shaped particles (∼8 nm) and polygonal nanospheres (∼8–12 nm) were formed after laser exposure. The modified surface morphology of photoetched Au nanoparticles was monitored by variable energy laser beam, follows an exponential (A = A0 e−kt) disintegration rate as a function of particle geometric size and shape. The percentage decomposition of Au nanorods (aspect ratio = 2.8) is found to increase as 59% > 69% > 72% with increased laser energy exposure; 2.41 eV (514.7 nm) > 2.50 eV (488 nm) > 2.71 eV (457.9 nm) as determined from the decrease in surface plasmon absorption band during laser illumination. The formation of small clusters on laser irradiation has resulted in the decrease of zeta potential from +49.79 (unetched particles) to +12.71 mV (etched particles) and also conductance values. Catalytic reduction of p-nitrophenol to p-aminophenol and m-dinitrobenzene to m-phenylenediamine with photofragmented Au nanostructures is found to be ∼15–20% higher than non-etched Au particles.

An aqueous suspension of Au nanorods (aspect ratio ≈ 2.8) are photoetched to pentagonal, triangular, ice cube, square and polygonal sphere shaped nanostructures as a function of laser energy and irradiation time. The higher surface exposed of photo-distorted Au nanoparticles and larger per-particle surface area displayed significant enhancement in catalytic activity for m-dinitrobenzene reduction to m-phenylenediamine (PDA) in comparison with bare Au nanorods without laser exposure.Figure optionsDownload high-quality image (176 K)Download as PowerPoint slide