7 research outputs found
Superhydrophobic and Slippery Lubricant-Infused Flexible Transparent Nanocellulose Films by Photoinduced ThiolāEne Functionalization
Films
comprising nanofibrillated cellulose (NFC) are suitable substrates
for flexible devices in analytical, sensor, diagnostic, and display
technologies. However, some major challenges in such developments
include their high moisture sensitivity and the complexity of current
methods available for functionalization and patterning. In this work,
we present a facile process for tailoring the surface wettability
and functionality of NFC films by a fast and versatile approach. First,
the NFC films were coated with a layer of reactive nanoporous silicone
nanofilament by polycondensation of trichlorovinylsilane (TCVS). The
TCVS afforded reactive vinyl groups, thereby enabling simple UV-induced
functionalization of NFC films with various thiol-containing molecules
via the photo āclickā thiolāene reaction. Modification
with perfluoroalkyl thiols resulted in robust superhydrophobic surfaces,
which could then be further transformed into transparent slippery
lubricant-infused NFC films that displayed repellency against both
aqueous and organic liquids with surface tensions as low as 18 mNĀ·m<sup>ā1</sup>. Finally, transparent and flexible NFC films incorporated
hydrophilic micropatterns by modification with OH, NH<sub>2</sub>,
or COOH surface groups, enabling space-resolved superhydrophobicāhydrophilic
domains. Flexibility, transparency, patternability, and perfect superhydrophobicity
of the produced nanocellulose substrates warrants their application
in biosensing, display protection, and biomedical and diagnostics
devices
Reactive Superhydrophobic Surface and Its Photoinduced Disulfide-ene and Thiol-ene (Bio)functionalization
Reactive
superhydrophobic surfaces are highly promising for biotechnological,
analytical, sensor, or diagnostic applications but are difficult to
realize due to their chemical inertness. In this communication, we
report on a photoactive, inscribable, nonwettable, and transparent
surface (PAINTS), prepared by polycondensation of trichlorovinylsilane
to form thin transparent reactive porous nanofilament on a solid substrate.
The PAINTS shows superhydrophobicity and can be conveniently functionalized
with the photoclick thiol-ene reaction. In addition, we show for the
first time that the PAINTS bearing vinyl groups can be easily modified
with disulfides under UV irradiation. The effect of superhydrophobicity
of PAINTS on the formation of high-resolution surface patterns has
been investigated. The developed reactive superhydrophobic coating
can find applications for surface biofunctionalization using abundant
thiol or disulfide bearing biomolecules, such as peptides, proteins,
or antibodies
Reversible Surface Engineering via Nitrone-Mediated Radical Coupling
Efficient
and simple polymer conjugation reactions are critical
for introducing functionalities on surfaces. For polymer surface grafting,
postpolymerization modifications are often required, which can impose
a significant synthetic hurdle. Here, we report two strategies that
allow for reversible surface engineering via nitrone-mediated radical
coupling (NMRC). Macroradicals stemming from the activation of polymers
generated by copper-mediated radical polymerization are grafted via
radical trapping with a surface-immobilized nitrone or a solution-borne
nitrone. Since the product of NMRC coupling features an alkoxyamine
linker, the grafting reactions can be reversed or chain insertions
can be performed via nitroxide-mediated polymerization (NMP). PolyĀ(<i>n</i>-butyl acrylate) (<i>M</i><sub>n</sub> = 1570
gĀ·mol<sup>ā1</sup>, <i>DĢµ</i> = 1.12)
with a bromine terminus was reversibly grafted to planar silicon substrates
or silica nanoparticles as successfully evidenced via X-ray photoelectron
spectroscopy (XPS), time-of-flight secondary ion mass spectrometry,
and grazing angle attenuated total reflection Fourier-transform infrared
spectroscopy (GAATR-FTIR). NMP chain insertions of styrene are evidenced
via GAATR-FTIR. On silica nanoparticles, an NMRC grafting density
of close to 0.21 chains per nm<sup>2</sup> was determined by dynamic
light scattering and thermogravimetric analysis. Concomitantly, a
simple way to decorate particles with nitroxide radicals with precise
control over the radical concentration is introduced. Silica microparticles
and zinc oxide, barium titanate, and silicon nanoparticles were successfully
functionalized
Bioinstructive Coatings for Hematopoietic Stem Cell Expansion Based on Chemical Vapor Deposition Copolymerization
We
report the chemical vapor deposition (CVD) of dual-functional
polymer films for the specific and orthogonal immobilization of two
biomolecules (notch ligand delta-like 1 (DLL1) and an RGD-peptide)
that govern the fate of hematopoietic stem and progenitor cells. The
composition of the CVD polymer and thus the biomolecule ratio can
be tailored to investigate and optimize the influence of the relative
surface concentrations of biomolecules on stem cell behavior. Prior
to cell experiments, all surfaces were characterized by infrared reflection
adsorption spectroscopy, time-of-flight secondary ion mass spectrometry,
and X-ray photoelectron spectroscopy to confirm the presence of both
biomolecules. In a proof-of-principle stem cell culture study, we
show that all polymer surfaces are cytocompatible and that the proliferation
of the hematopoietic stem and progenitor cells is predominantly influenced
by the surface concentration of immobilized DLL1
Monolithic High Performance Surface Anchored MetalāOrganic Framework Bragg Reflector for Optical Sensing
We report the fabrication of monolithic
dielectric mirrors by stacking
layers of metalāorganic frameworks (MOFs) and indium tin oxide
(ITO). Such Hybrid Photonic Band-Gap (PBG) Materials exhibit high
optical quality (reflectivities of 80%) and are color tunable over
the whole visible range. While the ITO deposition is accomplished
by using a conventional sputter process, the highly porous MOF layers
are deposited using liquid-phase epitaxy (LPE), therefore yielding
crystalline, continuous, and monolithic HKUST-1 SURMOF thin films
with high optical performance. We demonstrate the optical sensing
capabilities of these monolithic and porous Bragg stacks by investigating
the chemo-responsive optical properties (PBG shift and modulation
of the intensity of the PBG maximum) upon the exposure to different
organic solvents
Interaction of Human Plasma Proteins with Thin Gelatin-Based Hydrogel Films: A QCMāD and ToF-SIMS Study
In
the fields of surgery and regenerative medicine, it is crucial
to understand the interactions of proteins with the biomaterials used
as implants. Protein adsorption directly influences cell-material
interactions in vivo and, as a result, regulates, for example, cell
adhesion on the surface of the implant. Therefore, the development
of suitable analytical techniques together with well-defined model
systems allowing for the detection, characterization, and quantification
of protein adsorbates is essential. In this study, a protocol for
the deposition of highly stable, thin gelatin-based films on various
substrates has been developed. The hydrogel films were characterized
morphologically and chemically. Due to the obtained low thickness
of the hydrogel layer, this setup allowed for a quantitative study
on the interaction of human proteins (albumin and fibrinogen) with
the hydrogel by Quartz Crystal Microbalance with Dissipation Monitoring
(QCM-D). This technique enables the determination of adsorbant mass
and changes in the shear modulus of the hydrogel layer upon adsorption
of human proteins. Furthermore, Secondary Ion Mass Spectrometry and
principal component analysis was applied to monitor the changed composition
of the topmost adsorbate layer. This approach opens interesting perspectives
for a sensitive screening of viscoelastic biomaterials that could
be used for regenerative medicine
Photoinduced CāC Reactions on Insulators toward Photolithography of Graphene Nanoarchitectures
On-surface chemistry for atomically
precise sp<sup>2</sup> macromolecules
requires top-down lithographic methods on insulating surfaces in order
to pattern the long-range complex architectures needed by the semiconductor
industry. Here, we fabricate sp<sup>2</sup>-carbon nanometer-thin
films on insulators and under ultrahigh vacuum (UHV) conditions from
photocoupled brominated precursors. We reveal that covalent coupling
is initiated by CāBr bond cleavage through photon energies
exceeding 4.4 eV, as monitored by laser desorption ionization (LDI)
mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS).
Density functional theory (DFT) gives insight into the mechanisms
of CāBr scission and CāC coupling processes. Further,
unreacted material can be sublimed and the coupled sp<sup>2</sup>-carbon
precursors can be graphitized by e-beam treatment at 500 Ā°C,
demonstrating promising applications in photolithography of graphene
nanoarchitectures. Our results present UV-induced reactions on insulators
for the formation of all sp<sup>2</sup>-carbon architectures, thereby
converging top-down lithography and bottom-up on-surface chemistry
into technology