Fabrication of poly(aniline-co-pyrrole) hollow nanospheres with Triton X-100 micelles as templates

Linking atomic to mesoscopic scales in multilevel structural tailoring of single-atom catalysts for peroxide activation

A key challenge in designing single-atom catalysts (SACs) with multiple and synergistic functions is to optimize their structure across different scales, as each scale determines specific material properties. We advance the concept of a comprehensive optimization of SACs across different levels of scale, from atomic, microscopic to mesoscopic scales, based on interfacial kinetics control on the coupled metal-dissolution/polymer-growth process in SAC synthesis. This approach enables us to manipulate the multilevel interior morphologies of SACs, such as highly porous, hollow, and double-shelled structures, as well as the exterior morphologies inherited from the metal oxide precursors. The atomic environment around the metal centers can be flexibly adjusted during the dynamic metal-oxide consumption and metal-polymer formation. We show the versatility of this approach using mono- or bi-metallic oxides to access SACs with rich microporosity, tunable mesoscopic structures and atomic coordinating compositions of oxygen and nitrogen in the first coordination-shell. The structures at each level collectively optimize the electronic and geometric structure of the exposed single-atom sites and lower the surface *O formation barriers for efficient and selective peroxidase-type reaction. The unique spatial geometric configuration of the edge-hosted active centers further improves substrate accessibility and substrate-to-catalyst hydrogen overflow due to tunable structural heterogeneity at mesoscopic scales. This strategy opens up new possibilities for engineering more multilevel structures and offers a unique and comprehensive perspective on the design principles of SACs.

Platinum nanoparticles-embedded raspberry-liked SiO2 for the simultaneous electrochemical determination of eugenol and methyleugenol

Based on platinum nanoparticle-embedded raspberry-liked SiO₂, a sensitive and selective electrochemical sensor was developed for simultaneous determination of eugenol (EU) and methyleugenol (MEU). Raspberry-liked SiO₂ (RL-SiO₂) was characterized with open pores on the surface, which can be used as a path for utilizing the inner space fully. So, platinum nanoparticles (Pt NPs) could be embedded in the inner and outer surface of RL-SiO₂. As a carrier, RL-SiO₂ not only avoided the agglomeration of the Pt NPs but also improved the catalytic performance. Therefore, the prepared Pt NPs@RL-SiO₂/GCE exhibited excellent electrocatalytic activity for simultaneous determination of EU and MEU; the linearity ranges were 0.50 ~ 60 μmol/L for EU at a working potential of 0.65 V (vs. saturated calomel electrode) and 0.50 ~ 50 μmol/L for MEU at a working potential of 1.10 V; the detection limits were 0.12 μmol/L and 0.16 μmol/L (S/N=3); and the relative standard deviations (RSDs) were 3.2% and 4.5%, respectively. In addition, Pt NPs@RL-SiO₂/GCE was successfully applied to the analysis of fish samples; the obtained recoveries were between 92.0 and 107%. Notably, the results conducted on samples were highly consistent with those obtained from high-performance liquid chromatography. It can be concluded that the study provided a simple method for simultaneous electrochemical determination of EU and MEU in fish samples. Schematic illustration of the preparation of RL-SiO2@Pt NPs/GCE for simultaneous determination of eugenol and methyleugenol in fish samples.

Cu2+-modified hollow carbon nanospheres: an unusual nanozyme with enhanced peroxidase-like activity

A Cu²⁺-modified carboxylated hollow carbon nanospheres (Cu²⁺-HCNSs-COOH) was designed with enhanced peroxidase-like activity for the detection of hydrogen peroxide (H₂O₂) and degradation of methylene blue (MB). Hollow polymer nanospheres were fabricated from aniline, pyrrole, Triton-100, and ammonium persulfate via confined interfacial copolymerization reaction, which can be pyrolyzed to create HCNSs with the hollow gap diameter of about 20 nm under high temperature. Combining the synergistic effect of coordination and electrostatic interaction, Cu²⁺-HCNSs-COOH was constructed by anchoring Cu²⁺ on the surface of HCNSs-COOH. Furthermore, Cu²⁺-HCNSs-COOH has higher affinity for 3,3',5,5'-tetramethylbenzidine and H₂O₂ of 0.20 mM and 0.88 mM, respectively. Based on the rapid response of Cu²⁺-HCNSs-COOH to H₂O₂, we constructed a colorimetric sensing platform by detecting the absorbance of the 3,3',5,5'-tetramethylbenzidine-H₂O₂ system at 652 nm for quantifying H₂O₂, which holds good linear relationship between 1 and 150 μM and has a detection limit of 0.61 μM. We also investigated the degradation of MB in the presence of Cu²⁺-HCNSs-COOH and H₂O₂, which can degrade 80.7% pollutants within 30 min. This research developed an unusual nanozyme for bioassays and water pollution treatment, which broadened the way for the rapid development of clinical diagnostics and water pollution treatment.

3D ternary NixCo2-xP/C nanoflower/nanourchin arrays grown on HCNs: a highly efficient bi-functional electrocatalyst for boosting hydrogen production via the urea electro-oxidation reaction

Over the last few years, substantial efforts have been made to develop earth-abundant bi-functional catalysts for urea oxidation and energy-saving electrolytic hydrogen production due to their low cost and the potential to replace traditional noble-metal-based catalysts. Nevertheless, finding a straightforward and effective route to prepare efficient catalysts with unique structural features and optimal supports still is a big challenge. Among the various candidates, metal-organic framework (MOF)-derived materials show great advantages as new kinds of active non-precious catalysts. On the other hand, the controllable integration of MOFs and carbon-based nanomaterials leads to further enhancement in terms of the stability and electrical conductivity of catalysts. In this communication, we develop an MOF-carbon-based composite to synthesize a transition metal phosphide (TMP) catalyst for the electrocatalytic oxidation of urea. First, poly(pyrrole-co-aniline) (PPCA) hollow nanospheres were fabricated via the in situ emulsion polymerization of a mixture of aniline and pyrrole in the presence of Triton X-100. Then, the simple carbonization treatment of these PPCA hollow spheres led to the carbonized hollow carbon nanospheres (HCNs) with ultrahigh surface areas and uniform nano-morphologies. After that, bimetallic MM'/MOFs (M/M' = Ni, Co) were uniformly grown around the HCNs via a simple hydrothermal reaction (NiCo/MOF@HCNs). During the synthesis process, by adjusting Ni/Co ratios, the MOF morphology can be engineered so that by reducing the Ni/Co ratio, the flower-like structures change into urchin-like structures. Finally, this NiCo/MOF@HCNs precursor with different Ni/Co ratios during the in situ carbonization/phosphorization was chemically converted into Ni-Co mixed-metal phosphides (Ni_xCo_2-xP/C@HCNs). Finally, the electrocatalytic activity of the prepared catalysts was tested for the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER).

Fabrication of high-performance dual carbon Li-ion hybrid capacitor: mass balancing approach to improve the energy-power density and cycle life

Most lithium-ion capacitor (LIC) devices include graphite or non-porous hard carbon as negative electrode often failing when demanding high energy at high power densities. Herein, we introduce a new LIC formed by the assembly of polymer derived hollow carbon spheres (HCS) and a superactivated carbon (AC), as negative and positive electrodes, respectively. The hollow microstructure of HCS and the ultra large specific surface area of AC maximize lithium insertion/diffusion and ions adsorption in each of the electrodes, leading to individual remarkable capacity values and rate performances. To optimize the performance of the LIC not only in terms of energy and power densities but also from a stability point of view, a rigorous mass balance study is also performed. Optimized LIC, using a 2:1 negative to positive electrode mass ratio, shows very good reversibility within the operative voltage region of 1.5-4.2 V and it is able to deliver a specific cell capacity of 28 mA h-1 even at a high current density of 10 A g-1. This leads to an energy density of 68 W h kg-1 at an extreme power density of 30 kW kg-1. Moreover, this LIC device shows an outstanding cyclability, retaining more than 92% of the initial capacity after 35,000 charge-discharge cycles.

Free-standing polypyrrole/polyaniline composite film fabricated by interfacial polymerization at the vapor/liquid interface for enhanced hexavalent chromium adsorption

Interfacial polymerization is an innovative technique for the fabrication of polymeric films. However, the majority of studies on interfacial polymerization has focused on liquid/liquid interfaces, and little work has been done on vapor/liquid interfaces. In this paper, we present the fabrication of free-standing polypyrrole/polyaniline (PPy/PANI) composite films by interfacial polymerization at a vapor/liquid interface using FeCl₃ as an oxidant. The obtained PPy/PANI composite films were characterized using Fourier transform infrared spectroscopy, X-ray diffractometry, and scanning electron microscopy. It was found that the PPy/PANI composite films consist of PANI particles evenly distributed on porous PPy film. The influence of FeCl₃ concentration on the morphology of the resulting composite films was investigated. The PPy/PANI composite films show an excellent Cr(vi) adsorption capacity of 256.41 mg g⁻¹, much higher than that of PPy-based absorbents prepared from chemical and electrochemical polymerization routes. This work thus suggests a new route for the fabrication of PPy/PANI films with highly enhanced Cr(vi) adsorption capacity for practical applications.

Free-standing polypyrrole/polyaniline composite film fabricated by interfacial polymerization at vapor/liquid interface.

Pt-C Interfaces Based on Electronegativity-Functionalized Hollow Carbon Spheres for Highly Efficient Hydrogen Evolution

The hydrogen evolution reaction activity of carbon-supported Pt catalyst is highly dependent on Pt-C interfaces. Herein, we focus on the relationships between Pt activity and N/O-functionalized hollow carbon sphere (HCS) substrate in acidic media. The electrochemical dissolution of Pt counter electrode is performed to prepare Pt nanoparticles in low loading. The N groups are beneficial for homogeneously sized Pt nanoparticles, whereas the O groups lead to aggregated nanoparticles. Moreover, the proper electronegativity of the N groups may enable capturing of protons to create proton-rich Pt-C interfaces and transfer them onto the Pt sites. The O groups may also capture protons by hydrogen bonding, but the subsequent release of protons is more difficult due to a stronger electronegativity and result in an inferior Pt activity. Consequently, the N-doped HCS with a low Pt loading (1.7 μg cm^-2 and 0.05 wt %) possesses a higher intrinsic activity compared with Pt on O-doped HCS. Moreover, it outperforms the commercial 20% Pt/C with a stable operation for 12 h. This work may provide suggestions for constructing the advantageous Pt-C interfaces by proper functional groups for high catalytic efficiencies.

Microwave-assisted rapid preparation of hollow carbon nanospheres@TiN nanoparticles for lithium-sulfur batteries

Highly conductive titanium nitride (TiN) has a strong anchoring ability for lithium polysulfides (LiPSs). However, the complexity and high cost of fabrication limit their practical applications. Herein, a typical structure of hollow carbon nanospheres@TiN nanoparticles (HCNs@TiN) was designed and successfully synthesized via a microwave reduction method with the advantages of economy and efficiency. With unique structural and outstanding functional behavior, HCN@TiN-S hybrid electrodes display not only a high initial discharge capacity of 1097.8 mA h g^-1 at 0.1C, but also excellent rate performance and cycling stability. After 200 cycles, a reversible capacity of 812.6 mA h g^-1 is still retained, corresponding to 74% capacity retention of the original capacity and 0.13% decay rate per cycle, which are much better than those of HCNs-S electrodes.

Light-weight 3D Co-N-doped hollow carbon spheres as efficient electrocatalysts for rechargeable zinc-air batteries

Rational design of cost-effective, nonprecious metal-based catalysts with a desirable oxygen reduction reaction (ORR) performance by a simple and economical synthesis route is a great challenge for the commercialization of future fuel cell and metal-air batteries. Herein, light-weight 3D Co-N-doped hollow carbon spheres (Co-NHCs) have been fabricated via a facile emulsion approach followed by carbonization. The prepared 0.1-Co-NHCs catalyst with suitable Co doping content exhibits favorable ORR catalytic activity (onset potential of 0.99 V and half-wave potential of 0.81 V vs. RHE), comparable to that of commercial Pt-C (onset potential of 1.02 V and half-wave potential of 0.83 V vs. RHE) and rivals that of Pt-C with better cycling stability. The excellent performance of the catalyst is attributed to the synergetic effect of Co and N doping with a high total ratio of active sites, high surface area and good conductivity of the material. More impressively, the assembled rechargeable zinc-air batteries based on the 0.1-Co-NHCs catalyst outperform those afforded by commercial Pt-C. The progress presented in this reported work is of great importance in the development of outstanding non-noble metal based electrocatalysts for the fuel cell and metal-air battery industry.

Hydrogen Evolution Activity of Ruthenium Phosphides Encapsulated in Nitrogen- and Phosphorous-Codoped Hollow Carbon Nanospheres

RuP_x nanoparticles (NPs) encapsulated in uniform N,P-codoped hollow carbon nanospheres (RuP_x @NPC) have been synthesized through a facile route in which aniline-pyrrole copolymer nanospheres are used to disperse Ru ions followed by a gas phosphorization process. The as-prepared RuP_x @NPC exhibits a uniform core-shell hollow nanospherical structure with RuP_x NPs as the core and N,P-codoped carbon (NPC) as the shell. This strategy integrates many advantages of hollow nanostructures, which provide a conductive substrate and the doping of a nonmetal element. At high temperatures, the obtained thin NPC shell can not only protect the highly active phase of RuP_x NPs from aggregation and corrosion in the electrolyte but also allows variation in the electronic structures to improve the charge-transfer rate greatly by N,P codoping. The optimized RuP_x @NPC sample at 900 °C exhibits a Pt-like performance for the hydrogen evolution reaction (HER) and long-term durability in acidic, alkaline, and neutral solutions. The reaction requires a small overpotential of only 51, 74, and 110 mV at 10 mA cm^-2 in 0.5 m H₂ SO₄ , 1.0 m KOH, and 1.0 m phosphate-buffered saline, respectively. This work provides a new way to design unique phosphide-doped carbon heterostructures through an inorganic-organic hybrid method as excellent electrocatalysts for HER.

Activation-free fabrication of high-surface-area porous carbon nanosheets from conjugated copolymers

Porous carbon nanosheets with a high surface area of 1606 m² g⁻¹ have been successfully prepared by direct carbonization of graphene oxide sandwiched poly(aniline-co-pyrrole).

Reactive Oxygen Species-Regulating Polymersome as an Antiviral Agent against Influenza Virus

Reactive oxygen species (ROS) produced during mitochondrial oxidative phosphorylation play an important role as signal messengers in the immune system and also regulate signal transduction. ROS production, initiated as a consequence of microbial invasion, if generated at high levels, induces activation of the MEK (mitogen-activated protein kinase kinase)/ERK (extracellular signal-regulated kinase) pathway to promote cell survival and proliferation. However, viruses hijack the host cells' pathways, causing biphasic activation of the MEK/ERK cascade. Thus, regulation of ROS leads to concomitant inhibition of virus replication. In the present study, poly(aniline-co-pyrrole) polymerized nanoregulators (PASomes) to regulate intracellular ROS levels are synthesized, exploiting their oxidizing-reducing characteristics. Poly(aniline-co-pyrrole) embedded within an amphiphilic methoxy polyethylene glycol-block-polyphenylalanine copolymer (mPEG-b-pPhe) are used. It is demonstrated that the PASomes are water soluble, biocompatible, and could control ROS levels successfully in vitro, inhibiting viral replication and cell death. Furthermore, the effects of homopolymerized nanoregulators (polypyrrole assembled with mPEG-b-pPhe or polyaniline assembled with mPEG-b-pPhe) are compared with those of the PASomes. Consequently, it is confirmed that the PASomes can regulate intracellular ROS levels successfully and suppress viral infection, thereby increasing the cell survival rate.

Nitrogen and sulfur co-doping of 3D hollow-structured carbon spheres as an efficient and stable metal free catalyst for the oxygen reduction reaction

Three-dimensional, hollow-structured carbon sphere nanocomposites (N,S-hcs) doped with nitrogen and sulfur were prepared using a soft template approach followed by a high-temperature treatment. The synthesized N,S-hcs nanomaterials exhibited favourable catalytic activity for the oxygen reduction reaction (ORR) compared to carbon spheres doped solely with nitrogen (N-hcs), polypyrrole (PPY) solid nanoparticles and irregular fragments of polyaniline (PAN). These results demonstrated the co-doping of N/S and the relatively large surface area of the mesoporous carbon structure that enhanced the catalytic activity of the resulting material. Notably, the prepared N,S-hcs electrocatalysts provided four electron oxygen reduction selectivity, long-term durability and high resistance to methanol poisoning, all of which represented improvements over the conventional Pt/C electrocatalyst. The progress represented by this reported work is of great importance in the development of outstanding non-metal based electrocatalysts for the fuel cell industry.

A simple method to fabricate poly(aniline-co-pyrrole) with highly improved electrical conductivity via pre-polymerization

The electrical conductivity of poly(aniline-co-pyrrole) by proper pre-polymerization achieved the same order of magnitude (10⁻¹ S cm⁻¹) with their homopolymers, or even slightly higher, which was not affected by the molar ratio of two monomers.

Facile synthesis of ultrahigh-surface-area hollow carbon nanospheres for enhanced adsorption and energy storage

Exceptionally large surface area and well-defined nanostructure are both critical in the field of nanoporous carbons for challenging energy and environmental issues. The pursuit of ultrahigh surface area while maintaining definite nanostructure remains a formidable challenge because extensive creation of pores will undoubtedly give rise to the damage of nanostructures, especially below 100 nm. Here we report that high surface area of up to 3,022 m(2) g(-1) can be achieved for hollow carbon nanospheres with an outer diameter of 69 nm by a simple carbonization procedure with carefully selected carbon precursors and carbonization conditions. The tailor-made pore structure of hollow carbon nanospheres enables target-oriented applications, as exemplified by their enhanced adsorption capability towards organic vapours, and electrochemical performances as electrodes for supercapacitors and sulphur host materials for lithium-sulphur batteries. The facile approach may open the doors for preparation of highly porous carbons with desired nanostructure for numerous applications.

Multilayered electromagnetic bionanocomposite based on alginic acid: Characterization and biological activities

Poly(aniline-co-pyrrole)@Fe3O4@alginic acid (PACP@Fe3O4@AA) bionanocomposite was synthesized by a two-step method. In the first step, the AA@Fe3O4 nanocomposite was synthesized via the in-situ co-precipitation technique. In the second step, the PACP@Fe3O4@AA bionanocomposite was synthesized through the emulsion polymerization. Several techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, ultraviolet visible spectroscopy, scanning electron microscopy, and thermogravimetric analysis were utilized for the characterization of the synthesized materials. The presence of AA@Fe3O4 in the bionanocomposite enhanced the electrical conductivity as well as the thermal stability of the PACP@Fe3O4@AA bionanocomposite. The scanning electron micrograph of the PACP@Fe3O4@AA bionanocomposite demonstrated a nanosphere structure. The vibrating sample magnetometer analysis displayed that both AA@Fe3O4 and PACP@Fe3O4@AA bionanocomposites were super-paramagnetic at room temperature. The PACP@Fe3O4@AA bionanocomposite had good antioxidant and antibacterial activities. Furthermore, a synergistic effect was observed for the antifungal activity.

Enhanced cycling stability of silicon anode by in situ polymerization of poly(aniline-co-pyrrole)

Poly(aniline-co-pyrrole)-encapsulated Si nanoparticles composite anode material were prepared by an in situ chemical oxidation polymerization method.

Molecular template approach for evolution of conducting polymer nanostructures: tracing the role of morphology on conductivity and solid state ordering

Here, we report a unique molecular template approach, for the first time, to study the evolution of the different types of nanomaterial morphologies such as nanofiber, nanorod, nanosphere, and nanotube in a single system without changing their chemical composition or polymerization route. A renewable resource surfactant was self-organized with aniline (95%) and pyrrole (5%) in water to produce white emulsion consisting of long-range cylindrical micellar aggregates. The dilution of the emulsion with water resulted in the transformation of cylindrical to vesicular aggregates without any phase separation. The size and shape of the cylindrical and vesicular template aggregates were confirmed by dynamic light scattering and electron microscopic analysis. The chemical oxidation of the cylindrical templates produced nanofibers and nanorods, whereas hollow spheres and nanotubes were produced by vesicular templates. The nanofibers were found as long as 4-5 microm length with 200 nm widths, whereas the nanorods were shorter in length (0.5-0.7 microm) with 80-120 nm diameter. The hollow spheres were obtained in 1 mum diameter with wall thickness of approximately 80 nm. The length of the nanotubes was found to vary from 1.2 to 1.8 microm. The average wall thickness and inner pore diameter of the nanotubes were found as approximately 30 nm and approximately 60 nm, respectively. The size and shape of the template aggregates match very well with that of the synthesized nanomaterials and provide direct evidence for the template-assisted evolution of the nanostructure morphology. NMR, FT-IR and UV-visible spectroscopies were utilized to confirm the structure and electronic properties of the nanomaterials. Wide angle X-ray diffraction and transmission electron microscopy-electron diffraction analysis revealed that the nanotubes possessed three-dimensional lamellar-type solid states ordering with high percent crystallinity up to 60%. Variable temperature four-probe conductivity measurements of all samples showed typical I-V plots. The conductivity of the nanofibers was found one order higher than that of nanorod, hollow sphere, and nanotubes at all temperatures. The present investigation enabled us to establish the role of various types of nanomorphologies on properties of nanomaterials such as conductivity and solid state ordering without change in their chemical composition.