Creation of nanopatterns by local protonation of P4VP via dip pen nanolithography

Maedler, Carsten; Chada, Sailaja; Cui, Xiquan; Taylor, Michael; Yan, Mingdi; Rosa, Andrés H. La

doi:10.1063/1.2953090

Cited by 10 publications

(8 citation statements)

References 22 publications

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“…Several control experiments confirmed that an AFM tip, when coated with phosphate buffer solution of pH 4 and placed in contact with the substrate, delivers protons into the P4VP polymer film causing the latter to swell. [18] A similar result has been shown before in a macroscale setup, where an increase in film thickness of UV-cross-linked P4VP films under acidic stimulation was found. [19] This swelling is due to the protonation of pyridyl groups when adding Brønsted acids to form pyridinium ions, which was confirmed by infrared spectroscopy which showed a shift in the frequency band associated with the pyridyl ring-stretching modes to frequencies related to pyridinium ions.…”

Section: Introductionsupporting

confidence: 85%

Nanostructure formation driven by local protonation of polymer thin films

et al. 2009

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We report the creation of nano-structures via Dip Pen Nanolithography by locally exploiting the mechanical response of polymer thin films to an acidic environment. Protonation of cross linked poly(4-vinylpyridine) (P4VP) leads to a swelling of the polymer. We studied this process by using an AFM tip coated with a pH 4 buffer. Protons migrate through a water meniscus between tip and sample into the polymer matrix and interact with the nitrogen of the pyridyl group forming a pyridinium cation. The increase in film thickness, which is due to Coulomb repulsion between the charged centers, was investigated using Atomic Force Microscopy. The smallest structures achieved had a width of about 40 nm. Different control experiments support our claim that the protonation is the reason for the swelling and therefore the formation of the structures. Kelvin probe force microscopy measurements suggest the presence of counter ions which compensate the positively charged pyridinium ions. We investigated the influence of the water meniscus on the structure formation by varying the relative humidity in the range from 5% to 60% for different dwell times. The diffusion of protons and counter ions is humidity-dependent and requires a water meniscus.

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Section: Introductionsupporting

confidence: 85%

Nanostructure formation driven by local protonation of polymer thin films

et al. 2009

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“…To further support the claim that the presence of raised patterns were a consequence of the swelling response of the P4VP polymer film , , we demonstrated the reversibility of the patterning process by selectively erasing an existing swollen pattern. “Dot” features were initially generated using a tip coated with the acidic ink.…”

Section: Resultsmentioning

confidence: 71%

“…The factors that affect the dimensions of the patterned features can be attributed but not limited to a combination of several variables, such as the writing speed (14,34,35), the effects of temperature and humidity (19,34,36), and the geometry and wettability of the tip (36). The dimensions of dot features as a function of the dwell time and relative humidity has been demonstrated in our previous work (26,27). No structures could be created when the humidity was below 30%.…”

Section: Resultsmentioning

confidence: 76%

“…We have previously demonstrated the fabrication of patterns on P4VP thin films based on the DPN technique , . Differing from the conventional feature formation via a direct deposition of ink molecules onto substrates, the underlying working principle in our approach constitutes the delivery of hydronium ions from the sharp tip into the polymer thin film, which leads to the polymer swelling in response to the local protonation.…”

Section: Introductionmentioning

confidence: 99%

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Electric-Field-Assisted Dip-Pen Nanolithography on Poly(4-vinylpyridine) (P4VP) Thin Films

Wang

Fernandez

et al. 2010

ACS Appl. Mater. Interfaces

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Dip-pen nanolithography (DPN) has attracted increased attention for its ability to generate nanometer-scale patterns on solid surface using an “ink”-coated atomic force microscope (AFM) tip. In contrast to this conventional anchoring-molecules procedure, nanopatterns can also be created by triggering the structural response of the proper substrate. In one approach, the delivery of acidic buffer from the tip into a poly(4-vinylpyridine) (P4VP) thin film (while the tip is being laterally moved, in a raster fashion, along a preprogrammed pattern) leads to the polymer swelling in response to the local protonation. This practice, however, has suffered from a lack of consistency due to the potentially many factors influencing the pattern formation. Herein we report that a more reliable strategy for well controlling the protonation process results when applying an electric field between the AFM tip and the sample. We demonstrate the improved capabilities of the electric-field-assisted DPN method towards reproducibly and reliably fabricating nanostructures by taking advantage of the responsive characteristics (i.e. swelling) of P4VP. Our work includes a systematic study of pattern fabrication under different patterning parameters (mainly the applied bias and contact force) and, very important, provides evidence of the reversible characteristic of the pattern formation process.

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“…[10][11][12] We have developed a simple photochemical immobilization technique for the fabrication of polymer thin films on solid substrates. [13][14][15] The method is based on the photochemistry of polymers. Upon UV irradiation, free radicals are generated and can undergo crosslinking, degradation, and chain scission reactions.…”

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confidence: 99%

Photochemical Reactions of Poly(4‐vinylphenol) Thin Films

Uppalapati

Chada

Engelhard

et al. 2010

Macro Chemistry & Physics

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The mechanism involved in the photochemical immobilization of poly(4‐vinylphenol) (PVP) thin films was investigated. The films were fabricated by a simple procedure of UV irradiation and solvent extraction. A combination of ellipsometry, IR, and high‐resolution X‐ray photoelectron spectroscopy (XPS) was used to provide detailed and quantitative analysis of the composition of the photochemical reaction products. Upon irradiation at 260 nm, benzyl and phenoxy radicals are generated in the polymer. In the absence of oxygen, PVP films crosslinked via the combination of the benzyl radicals or phenoxy radicals. At lower irradiation doses, the photochemical process was dominated by crosslinking of the polymer backbone via the combination of benzyl radicals. At higher exposure doses, crosslinked quinoid structures were generated, and the concentration increased with the irradiation time. No oxidation or degradation products were observed. In the presence of oxygen, additional reactions of oxidation and degradation occurred. At lower doses, oxidation at the benzyl position produced the ketone structure evidenced by the drastic increase in the O content in the irradiated films. As the irradiation doses increased, further oxidation at the methylene position occurred, and in addition, volatile and degradation products were also generated. This photochemical process was successfully employed to fabricate patterned PVP structures.magnified image

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Creation of nanopatterns by local protonation of P4VP via dip pen nanolithography

Cited by 10 publications

References 22 publications

Nanostructure formation driven by local protonation of polymer thin films

Nanostructure formation driven by local protonation of polymer thin films

Electric-Field-Assisted Dip-Pen Nanolithography on Poly(4-vinylpyridine) (P4VP) Thin Films

Photochemical Reactions of Poly(4‐vinylphenol) Thin Films

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