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Optically anisotropic substrates via wrinkle-assisted convective assembly of gold nanorods on macroscopic areas.

Tebbe M, Mayer M, Glatz BA, Hanske C, Probst PT, Müller MB, Karg M, Chanana M, König TA, Kuttner C, Fery A - Faraday Discuss. (2015)

Bottom Line: We characterise the optical response of the assemblies on ITO-coated glass via UV/vis/NIR spectroscopy and determine an optical order parameter of 0.91.The assemblies are thus plasmonic metamaterials, as their periodicity and building block sizes are well below the optical wavelength.The presented approach does not rely on lithographic patterning and provides access to functional materials, which could have applications in subwavelength waveguiding, photovoltaics, and for large-area metamaterial fabrication.

View Article: PubMed Central - PubMed

Affiliation: Physical Chemistry II, Universitätsstraße 30, 95440, Bayreuth, Germany. andreas.fery@uni-bayreuth.de.

ABSTRACT
We demonstrate the large-scale organisation of anisotropic nanoparticles into linear assemblies displaying optical anisotropy on macroscopic areas. Monodisperse gold nanorods with a hydrophilic protein shell are arranged by dip-coating on wrinkled surfaces and subsequently transferred to indium tin oxide (ITO) substrates by capillary transfer printing. We elucidate how tuning the wrinkle amplitude enables us to precisely adjust the assembly morphology and fabricate single, double and triple nanorod lines. For the single lines, we quantify the order parameter of the assemblies as well as interparticle distances from scanning electron microscopy (SEM) images. We find an order parameter of 0.97 and a mean interparticle gap size of 7 nm. This combination of close to perfect uni-axial alignment and close-packing gives rise to pronounced macroscopic anisotropic optical properties due to strong plasmonic coupling. We characterise the optical response of the assemblies on ITO-coated glass via UV/vis/NIR spectroscopy and determine an optical order parameter of 0.91. The assemblies are thus plasmonic metamaterials, as their periodicity and building block sizes are well below the optical wavelength. The presented approach does not rely on lithographic patterning and provides access to functional materials, which could have applications in subwavelength waveguiding, photovoltaics, and for large-area metamaterial fabrication.

No MeSH data available.


Amplitude dependency of linear assembly of BSA-functionalised gold nanorods into wrinkles using dip-coating. Organisation of gold nanorods into (A) triple lines, (B) double lines, and (C) single lines. From (A) to (C) the amplitude of the wrinkles decreases progressively. For all samples the withdrawal of the templates was performed with the wrinkles oriented perpendicular to the contact line with a withdrawing speed of 100, 10, and 10 μm min–1, respectively, and a gold concentration of 1 mg mL–1.
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fig3: Amplitude dependency of linear assembly of BSA-functionalised gold nanorods into wrinkles using dip-coating. Organisation of gold nanorods into (A) triple lines, (B) double lines, and (C) single lines. From (A) to (C) the amplitude of the wrinkles decreases progressively. For all samples the withdrawal of the templates was performed with the wrinkles oriented perpendicular to the contact line with a withdrawing speed of 100, 10, and 10 μm min–1, respectively, and a gold concentration of 1 mg mL–1.

Mentions: We found that the parameters listed in the experimental section in Table 1 provide crack-free substrates with wrinkle periodicities of 200 to 300 nm and wrinkle amplitudes in the range 20 to 30 nm.51 To render the prepared substrates hydrophilic and to gain an even higher control over surface topology, defined plasma post-treatment was employed. A variation of the plasma dose at low pressure (0.2 mbar) facilitates a precise adjustment of the wrinkle amplitude, which is tuneable from the initial amplitude down to a completely flat surface without affecting the wrinkle periodicity, as shown in Fig. 2B–D. This is a simple control parameter that enables a precise adjustment of the wrinkle aspect ratio to match the nanoparticle dimensions and directly regulates nanoparticle arrangement inside the grooves of the wrinkle-templates (template requirements). For the representative sample shown in Fig. 2 the amplitude was tuned starting from 26 nm down to 5 nm, keeping the periodicity constant at 300 nm. The presented process offers the possibility to tune the wrinkle aspect ratio (periodicity/amplitude) with a single experimental parameter, which is of great importance to match the wrinkle dimensions with building block sizes.


Optically anisotropic substrates via wrinkle-assisted convective assembly of gold nanorods on macroscopic areas.

Tebbe M, Mayer M, Glatz BA, Hanske C, Probst PT, Müller MB, Karg M, Chanana M, König TA, Kuttner C, Fery A - Faraday Discuss. (2015)

Amplitude dependency of linear assembly of BSA-functionalised gold nanorods into wrinkles using dip-coating. Organisation of gold nanorods into (A) triple lines, (B) double lines, and (C) single lines. From (A) to (C) the amplitude of the wrinkles decreases progressively. For all samples the withdrawal of the templates was performed with the wrinkles oriented perpendicular to the contact line with a withdrawing speed of 100, 10, and 10 μm min–1, respectively, and a gold concentration of 1 mg mL–1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4530594&req=5

fig3: Amplitude dependency of linear assembly of BSA-functionalised gold nanorods into wrinkles using dip-coating. Organisation of gold nanorods into (A) triple lines, (B) double lines, and (C) single lines. From (A) to (C) the amplitude of the wrinkles decreases progressively. For all samples the withdrawal of the templates was performed with the wrinkles oriented perpendicular to the contact line with a withdrawing speed of 100, 10, and 10 μm min–1, respectively, and a gold concentration of 1 mg mL–1.
Mentions: We found that the parameters listed in the experimental section in Table 1 provide crack-free substrates with wrinkle periodicities of 200 to 300 nm and wrinkle amplitudes in the range 20 to 30 nm.51 To render the prepared substrates hydrophilic and to gain an even higher control over surface topology, defined plasma post-treatment was employed. A variation of the plasma dose at low pressure (0.2 mbar) facilitates a precise adjustment of the wrinkle amplitude, which is tuneable from the initial amplitude down to a completely flat surface without affecting the wrinkle periodicity, as shown in Fig. 2B–D. This is a simple control parameter that enables a precise adjustment of the wrinkle aspect ratio to match the nanoparticle dimensions and directly regulates nanoparticle arrangement inside the grooves of the wrinkle-templates (template requirements). For the representative sample shown in Fig. 2 the amplitude was tuned starting from 26 nm down to 5 nm, keeping the periodicity constant at 300 nm. The presented process offers the possibility to tune the wrinkle aspect ratio (periodicity/amplitude) with a single experimental parameter, which is of great importance to match the wrinkle dimensions with building block sizes.

Bottom Line: We characterise the optical response of the assemblies on ITO-coated glass via UV/vis/NIR spectroscopy and determine an optical order parameter of 0.91.The assemblies are thus plasmonic metamaterials, as their periodicity and building block sizes are well below the optical wavelength.The presented approach does not rely on lithographic patterning and provides access to functional materials, which could have applications in subwavelength waveguiding, photovoltaics, and for large-area metamaterial fabrication.

View Article: PubMed Central - PubMed

Affiliation: Physical Chemistry II, Universitätsstraße 30, 95440, Bayreuth, Germany. andreas.fery@uni-bayreuth.de.

ABSTRACT
We demonstrate the large-scale organisation of anisotropic nanoparticles into linear assemblies displaying optical anisotropy on macroscopic areas. Monodisperse gold nanorods with a hydrophilic protein shell are arranged by dip-coating on wrinkled surfaces and subsequently transferred to indium tin oxide (ITO) substrates by capillary transfer printing. We elucidate how tuning the wrinkle amplitude enables us to precisely adjust the assembly morphology and fabricate single, double and triple nanorod lines. For the single lines, we quantify the order parameter of the assemblies as well as interparticle distances from scanning electron microscopy (SEM) images. We find an order parameter of 0.97 and a mean interparticle gap size of 7 nm. This combination of close to perfect uni-axial alignment and close-packing gives rise to pronounced macroscopic anisotropic optical properties due to strong plasmonic coupling. We characterise the optical response of the assemblies on ITO-coated glass via UV/vis/NIR spectroscopy and determine an optical order parameter of 0.91. The assemblies are thus plasmonic metamaterials, as their periodicity and building block sizes are well below the optical wavelength. The presented approach does not rely on lithographic patterning and provides access to functional materials, which could have applications in subwavelength waveguiding, photovoltaics, and for large-area metamaterial fabrication.

No MeSH data available.