FRET‐Integrated Polymer Brushes for Spatially Resolved Sensing of Changes in Polymer Conformation

Abstract

Polymer brush surfaces that alter their physical properties in response to chemical stimuli have the capacity to be used as new surface-based sensing materials.F or such surfaces,d etecting the polymer conformation is key to their sensing capabilities.H erein, we report on FRET-integrated ultrathin (< 70 nm) polymer brush surfaces that exhibit stimuli-dependent FRET with changing brush conformation. Poly(N-isopropylacrylamide) polymers were chosen due their exceptional sensitivity to liquid mixture compositions and their ability to be assembled into well-defined polymer brushes.The brush transitions were used to optically sense changes in liquid mixture compositions with high spatial resolution (tens of micrometers), where the FRET coupling allowed for noninvasive observation of brush transitions around complex interfaces with real-time sensing of the liquid environment. Our methods have the potential to be leveraged towards greater surface-based sensing capabilities at intricate interfaces.

Membranotronics: Bioinspired Nonlinear Ion Transport with Negative Differential Resistance Based on Elastomeric Membrane System

“…ethanol (EtOH) in 1 m KCl also significantly affected the ionic current passing through the hole of the functionalized membrane (Figure 4h), which is the point of the co‐nonsolvency‐induced collapse of the PNIPAM brushes. [ 46 ] In the collapsed state, we observed substantially increased nonlinearity in the I – V (Figure 4h,i) curves when compared to the swollen state. This result is consistent with the co‐nonsolvency‐induced transitions of the PNIPAM chains from one state to the other, which influences ionic transport through the membrane at different biases (electrostatic compression states).…”

“…Furthermore, the PNIPAM brushes anchored to the soft PDMS surface have the ability to actuate or bend the PDMS as a function of conformation, [61] meaning this could lead to selective closure of the pore, if the geometry permits it. Figure 4b,g shows the operational principle of the functionalized hole in the elastomeric membrane where the walls and surrounding surface of the hole were covered with PNIPAM brushes that can be activated by temperature [62,63] or stimulated by exploring so-called co-nonsolvency [46] effects (i.e., a mixture of two good solvents causes the collapse or demixing for the polymer). More details on the functionalization and the operation principle can be found in Figures S9 and S10 and Note S6 (Supporting Information).…”

“…The hydrophilic and hydrophobic interactions in the polymer chain is the reason of this behavior. [ 46 ] PNIPAM brushes show the lowest height of polymer chain (collapsed state) at around 20% ethanol/water mixture. The height of the polymer chain is higher when the ethanol percentage is lower or higher than 20%.…”

Advances in design of polymer brush functionalized inorganic nanomaterials and their applications in biomedical arena

“…Grafting, a covalent functionalization technique, is widely used for grafting various polymers or other materials onto the surface of NMs to produce polymer‐coated nanostructures which can be used for a large set of applications like sensing and drug delivery (Besford et al, 2021; Braga et al, 2021; Kim, Kwak, et al, 2020; Krasnopeeva et al, 2021; Oliveira et al, 2021; Simonova et al, 2021; Smook et al, 2020). Chemical grafting techniques can be divided into two broad classifications, namely the “grafting from” and “grafting onto” approaches (see Figure 1).…”

Machine Learning-assisted Exploration of a Universal Polymer Platform with Charge Transfer-dependent Full-color Emission

“…In general, color-tunable fluorescence in polymer systems can be achieved either by direct emission spectra combination [17][18][19] or Förster resonance energy transfer (FRET) 20,21 . By modulation of energy transfer efficiency, the latter can generate more tunable emission properties, and is therefore widely used in stimuli-responsive materials 22,23 , ratiometric sensors 24,25 multicolor bioimaging agents 26,27 , security inks 28 , and light-harvesting systems 29 . The precise emission tuning of FRET polymers requires careful selection of donor (D) and acceptor (A) fluorophore pairs and extensive optimization of their energy transfer efficiency that depends on the inverse 6 th power of the donor-to-acceptor separation distance 30 .…”