Salt-Responsive Fe₃O₄ Nanocomposites and Phase Behavior in Water

Abstract

The ability to achieve exquisite control over polymer building blocks within multicompartment magnetite nanocomposites (NCs) to afford predictable and ordered packing hierarchical structures remains a significant challenge for the design of NCs. Thus, there is an urgent need to develop new types of nano-dimensional assemblies that undergo responsive shape shift, size, phase, and morphological transitions, especially for processes that are triggered by biologically relevant stimuli such as ionic gradients to meet the demand for diverse applications. Accordingly, we report an unprecedented concept for the preparation of salt-responsive magnetite/polyaniline composite nanoassemblies with chemically distinct dual-compartment structures. The size, shape, and nano-dimensional phase separation of the PANI assemblies within NCs were adjusted in a facile manner with incremental changes in salt gradients using NaCl(aq). Composition effects bestow desirable diversiform shape, size, and phase behavior of the incorporated conductive polymer via dynamic H-bonding. The size, shape, and superparamagnetic character of iron oxide nanoparticles (IONPs) are unaffected by a "salting-in" process. The mechanism, gradual morphological evolution, interchangeable nanophase separation, and ion-stimulated disassembly of PANI building blocks for these magneto/ion-responsive polymer-composites at elevated ionic strength are strongly supported by DLS, Raman spectroscopy, TEM, and equilibrium dye (MB/MO) recognition studies.

Redox-Responsive Polymer Template as an Advanced Multifunctional Catalyst Support for Silver Nanoparticles

“…Aside from redox-switchable characteristics of PANI, the amine/imine groups, the quinoid (Q) and benzenoid (B) forms of PANI afford sites that have strong affinity for anchoring metals. The PANI binding sites can efficiently stabilize and adsorb NPs, in agreement with variable binding affinities reported for metal ions and by the removal of various cation and anion systems from water . In this regard, PANI is a suitable option to serve as nucleation sites for growth of AgNPs and as a multifunctional electro-active template for enhanced catalytic activity.…”

“…The PANI binding sites can efficiently stabilize and adsorb NPs, in agreement with variable binding affinities reported for metal ions and by the removal of various cation and anion systems from water. 24 In this regard, PANI is a suitable option to serve as nucleation sites for growth of AgNPs and as a multifunctional electro-active template for enhanced catalytic activity. The X-ray diffraction (XRD) pattern of AgNPs−CPs, shown in Figure 1a, comprised several reflections at 2θ values (44.7, 52.2, and 76.8°) that correspond to the typical (111), (200), and (220) planes of face-centered cubic silver that indicate the crystalline nature of the AgNPs.…”

“…In particular, a key consideration to afford enhanced catalytic activity of noble metal NPs is selection of an appropriate support or doping agent to create additional reaction sites for the catalyst to enhance the electron transport kinetics. PANI is a potential support for Au and AgNPs catalysis systems due to its low interfacial reactivity, electrical conductivity, ,, adsorbing surface, and electrochemical switchability. ,, The conductivity of a support material in a catalyst system is important to achieve rapid electron-transfer kinetics. , Herein, it is highly desirable to use the advantage of PANI as a functional support to construct an advanced low-cost catalyst with favorable catalytic performance. On the other hand, despite the recent developments , related to the design of metal/semiconductor catalyst systems, little is known about the interfacial electrical behavior of PANI nanocomposites with noble metal NPs with addressable nanointerface behavior.…”

“…In particular, a key consideration to afford enhanced catalytic activity of noble metal NPs is selection of an appropriate support or doping agent to create additional reaction sites for the catalyst to enhance the electron transport kinetics. PANI is a potential support for Au and AgNPs catalysis systems due to its low interfacial reactivity, electrical conductivity, 5,6,8 adsorbing surface, 24 and electrochemical switchability. 5,6,25 The conductivity of a support material in a catalyst system is important to achieve rapid electron-transfer kinetics.…”

Saline-Responsive and Hydrogen Bond Gating Effects in Self-Healing Polyaniline

“…In turn, the payload contents would be released in response to the salt (NaCl) dopant when the PANI shell is complexed with sodium cations (Na + ). 21 Polyaniline was polymerized in a dispersed phase that contains saturated levels of self-healing materials in an aqueous solution. The concentrations of guest materials in aqueous solution were 1 mg/mL (MBT), 0.43 mg/mL (MBI), and 1 mg/mL (BTA).…”