Quantitative Analysis of Trace Analytes with Highly Sensitive SERS Tags on Hydrophobic Interface

Surface-enhanced Raman scattering (SERS) presents a promising avenue for trace matter detection by using plasmonic nanostructures. To tackle the challenges of quantitatively analyzing trace substances in SERS, such as poor enrichment efficiency and signal reproducibility, this study proposes a novel approach using Au@internal standard@Au nanospheres (Au@IS@Au NSs) for realizing the high sensitivity and stability in SERS substrates. To verify the feasibility and stability of the SERS performances, the SERS substrates have exhibited exceptional sensitivity for detecting methyl blue molecules in aqueous solutions within the concentration range from 10-4 M to 10-13 M. Additionally, this strategy also provides a feasible way of quantitative detection of antibiotic in the range of 10-4 M to 10-10 M. Trace antibiotic residue on the surface of shrimp in aquaculture waters was successfully conducted, achieving a remarkably low detection limit of 10-9 M. The innovative approach has great potential for the rapid and quantitative detection of trace substances, which marks a noteworthy step forward in environmental detection and analytical methods by SERS.

Electropolymerisation Technologies for Next-Generation Lithium-Sulphur Batteries

Lithium-sulphur batteries (LiSBs) have garnered significant attention as the next-generation energy storage device because of their high theoretical energy density, low cost, and environmental friendliness. However, the undesirable "shuttle effect" by lithium polysulphides (LPSs) severely inhibits their practical application. To alleviate the shuttle effect, conductive polymers have been used to fabricate LiSBs owing to their improved electrically conducting pathways, flexible mechanical properties, and high affinity to LPSs, which allow the shuttle effect to be controlled. In this study, the applications of various conductive polymers prepared via the simple yet sophisticated electropolymerisation (EP) technology are systematically investigated based on the main components of LiSBs (cathodes, anodes, separators, and electrolytes). Finally, the potential application of EP technology in next-generation batteries is comprehensively discussed.

How Regiochemistry Influences Aggregation Behavior and Charge Transport in Conjugated Organosulfur Polymer Cathodes for Lithium-Sulfur Batteries

For lithium-sulfur (Li-S) batteries to become competitive, they require high stability and energy density. Organosulfur polymer-based cathodes have recently shown promising performance due to their ability to overcome common limitations of Li-S batteries, such as the insulating nature of sulfur. In this study, we use a multiscale modeling approach to explore the influence of the regiochemistry of a conjugated poly(4-(thiophene-3-yl)benzenethiol) (PTBT) polymer on its aggregation behavior and charge transport. Classical molecular dynamics simulations of the self-assembly of polymer chains with different regioregularity show that a head-to-tail/head-to-tail regularity can form a well-ordered crystalline phase of planar chains allowing for fast charge transport. Our X-ray diffraction measurements, in conjunction with our predicted crystal structure, confirm the presence of crystalline phases in the electropolymerized PTBT polymer. We quantitatively describe the charge transport in the crystalline phase in a band-like regime. Our results give detailed insights into the interplay between microstructural and electrical properties of conjugated polymer cathode materials, highlighting the effect of polymer chain regioregularity on its charge transport properties.

Fe Single-Atom Catalyst for Cost-Effective yet Highly Efficient Heterogeneous Fenton Catalysis

High energy consumption in pyrolyzing precursors for catalyst preparation would limit the application of nitrogen-doped carbon-based single-atom catalysts in actual pollutant remediation. Herein, we report an Fe single atom (7.67 wt %) loaded polyaniline catalyst (Fe-PANI) prepared via a simple impregnation process without pyrolysis. Both experimental characterizations and density functional theory calculations demonstrated that isolated -N═ group sites can fasten Fe atoms through Fe-N coordination in PANI, leading to a high stability of Fe atoms in a heterogeneous Fenton reaction. Highly dispersive yet dense -N═ groups in PANI can be protonated to be adsorption sites, which largely reduce the migration distance between reactive radicals and organics. More significantly, frontier molecular orbitals and spin-density distributions reveal that electrons can transfer from reduction groups of PANI to an Fe(III) site to accelerate its reduction. As a result, a remarkably boosted degradation behavior of organics under near-neutral conditions (pH 6), with low H₂O₂ concentration, was achieved. This cost-effective Fe-PANI catalyst with high catalytic activity, stability, and adsorption performance has great potential for industrial-level wastewater treatment.

Overoxidized poly(3,4-ethylenedioxythiophene)-gold nanoparticles-graphene-modified electrode for the simultaneous detection of dopamine and uric acid in the presence of ascorbic acid

An innovative, ternary nanocomposite composed of overoxidized poly(3,4-ethylenedioxythiophene) (OPEDOT), gold nanoparticles (AuNPs), and electrochemically reduced graphene oxide (ERGO) was prepared on a glassy carbon electrode (GCE) (OPEDOT–AuNPs–ERGO/GCE) through homogeneous chemical reactions and heterogeneous electrochemical methods. The morphology, composition, and structure of this nanocomposite were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The electrochemical properties of the OPEDOT–AuNPs–ERGO/GCE were investigated by cyclic voltammetry using potassium ferricyanide and hexaammineruthenium(III) chloride redox probe systems. This modified electrode shows excellent electro-catalytic activity for dopamine (DA) and uric acid (UA) under physiological pH conditions, but inhibits the oxidation of ascorbic acid (AA). Linear voltammetric responses were obtained when DA concentrations of approximately 4.0–100 μM and UA concentrations of approximately 20–100 μM were used. The detection limits (S/N=3) for DA and UA were 1.0 and 5.0 μM, respectively, under physiological conditions and in the presence of 1.0 mM of AA. This developed method was applied to the simultaneous detection of DA and UA in human urine, where satisfactory recoveries from 96.7% to 105.0% were observed. This work demonstrates that the developed OPEDOT–AuNPs–ERGO ternary nanocomposite, with its excellent ion-selectivity and electro-catalytic activity, is a promising candidate for the simultaneous detection of DA and UA in the presence of AA in physiological and pathological studies.

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Facile preparation of graphene-based hybrid composite OPEDOT–AuNPs–ERGO onto GCE.

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The OPEDOT–AuNPs–ERGO/GCE was endued with excellent electrocatalytic activity and ion-selectivity.

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The OPEDOT–AuNPs–ERGO/GCE was found highly selective and sensitive determination of DA and UA in the presence of AA.

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The method is expected to be applied to the detection of DA and UA under physiological and pathological conditions.

Microwave-promoted continuous flow synthesis of thermoplastic polyurethane–silver nanocomposites and their antimicrobial performance

The present study reports a reducing agent-free continuous manufacturing of ∼5 nm silver nanoparticles in a thermoplastic polyurethane matrix using a microwave-promoted fluidic system.

Large-Scale Synthesis of Functionalized Nanowires to Construct Nanoelectrodes for Intracellular Sensing

A strategy for one-pot and large-scale synthesis of functionalized core-shell nanowires (NWs) to high-efficiently construct single nanowire electrodes is proposed. Based on the polymerization reaction between 3,4-ethylenedioxythiophene (EDOT) and noble metal cations, manifold noble metal nanoparticles-polyEDOT (PEDOT) nanocomposites can be uniformly modified on the surface of any nonconductive NWs. This provides a facile and versatile approach to produce massive number of core-shell NWs with excellent conductivity, adjustable size, and well-designed properties. Nanoelectrodes manufactured with such core-shell NWs exhibit excellent electrochemical performance and mechanical stability as well as favorable antifouling properties, which are demonstrated by in situ intracellular monitoring of biological molecules (nitric oxide) and unraveling its relevant unclear signaling pathway inside single living cells.

Benzene Ring Knitting Achieved by Ambient-Temperature Dehalogenation via Mechanochemical Ullmann-Type Reductive Coupling

The current approaches capable of affording conjugated porous networks (CPNs) still rely on solution-based coupling reactions promoted by noble metal complexes or Lewis acids, on-surface polymerization conducted in ultrahigh-vacuum environment at very high temperatures (>200 °C), or mechanochemical Scholl-type reactions limited to electron-rich substrates. To develop simple and scalable approaches capable of making CPNs under neat and ambient conditions, herein, a novel and complementary method to the current oxidative Scholl coupling processes is demonstrated to afford CPNs via direct aromatic ring knitting promoted by mechanochemical Ullmann-type reactions. The key to this strategy lies in the dehalogenation of aromatic halides in the presence of Mg involving the formation of Grignard reagent intermediates. Products (Ph-CPN-1) obtained via direct CC bond formation between 1,2,4,5-tetrabromobenzene (TBB) monomer feature high surface areas together with mesoporous architecture. The versatility of this approach is confirmed by the successful construction of various CPNs via knitting of the corresponding aromatic rings (e.g., pyrene and triphenylene), and even highly crystalline graphite product was obtained. The CPNs exhibit good electrochemical performance as the anode material in lithium-ion batteries (LIBs). This approach expands the frontiers of CPN synthesis and provides new opportunities to their scalable applications.

Contrastive Study of In Situ Sensing and Swabbing Detection Based on SERS-Active Gold Nanobush-PDMS Hybrid Film

Surface-enhanced Raman scattering (SERS) with fast and intuitive property has been extensively utilized in the field of food safety. Here, we demonstrated a novel noble metal-polymer hybrid film as a SERS substrate for food fungicide analysis. Benefiting from its transparency and flexibility, poly(dimethylsiloxane) (PDMS) film was chosen as a versatile supporting matrix to grow gold nanobushes (Au NBs) through a seed-mediated process. The as-prepared AuNB-PDMS hybrid film performed satisfactorily in testing 4-nitrothiophenol (4NTP) and exhibited an enhancement factor (EF) of 2.56 × 10⁶. Moreover, the high sensitivity and elastic properties make the hybrid film a promising substrate in practical detection. Hence, the in situ sensing of TBZ, carbaryl, and their mixture was finally realized using the developed hybrid film, which exhibited higher sensitivity than that obtained by the swabbing method. This high-performance SERS substrate based on the flexible and transparent AuNB-PDMS hybrid film has great potential applications in the fast in situ monitoring of biochemical molecules.

Morphology control of Cu and Cu2O through electrodeposition on conducting polymer electrodes

Here we demonstrate the morphology control of Cu and Cu₂O through electrodeposition on conducting polymer surface.

Conducting Polymer-Based Nanohybrids for Fuel Cell Application

Carbon materials such as carbon graphitic structures, carbon nanotubes, and graphene nanosheets are extensively used as supports for electrocatalysts in fuel cells. Alternatively, conducting polymers displayed ultrahigh electrical conductivity and high chemical stability havegenerated an intense research interest as catalysts support for polymer electrolyte membrane fuel cells (PEMFCs) as well as microbial fuel cells (MFCs). Moreover, metal or metal oxides catalysts can be immobilized on the pure polymer or the functionalized polymer surface to generate conducting polymer-based nanohybrids (CPNHs) with improved catalytic performance and stability. Metal oxides generally have large surface area and/or porous structures and showed unique synergistic effects with CPs. Therefore, a stable, environmentally friendly bio/electro-catalyst can be obtained with CPNHs along with better catalytic activity and enhanced electron-transfer rate. The mass activity of Pd/polypyrrole (PPy) CPNHs as an anode material for ethanol oxidation is 7.5 and 78 times higher than that of commercial Pd/C and bulk Pd/PPy. The Pd rich multimetallic alloys incorporated on PPy nanofibers exhibited an excellent electrocatalytic activity which is approximately 5.5 times higher than monometallic counter parts. Similarly, binary and ternary Pt-rich electrocatalysts demonstrated superior catalytic activity for the methanol oxidation, and the catalytic activity of Pt24Pd26Au50/PPy significantly improved up to 12.5 A per mg Pt, which is approximately15 times higher than commercial Pt/C (0.85 A per mg Pt). The recent progress on CPNH materials as anode/cathode and membranes for fuel cell has been systematically reviewed, with detailed understandings into the characteristics, modifications, and performances of the electrode materials.

Effect of Light Intensity on the Aggregation Behavior of Primary Particles during In Situ Photochemical Synthesis of Gold/Polymer Nanocomposites

Metal/polymer nanocomposites have attracted much attention in recent years due to their exceptional properties and wide range of potential applications. A key challenge to obtain these materials is to stabilize the metal nanoparticles in the matrix, avoiding uncontrolled aggregation processes driven by the high surface free energy of nanosized particles. Here, we investigate the aggregation mechanism of primary particles in gold-epoxy nanocomposites prepared via light-assisted in situ synthesis, under different irradiation conditions. The growth and aggregation of gold nanoparticles were monitored in situ by time-resolved small-angle X-ray scattering experiments, whereas spectroscopic measurements were performed to interpret how matrix polymerization influences the aggregation process. It was found that light intensity has a greater influence on the reduction rate than on the polymerization rate. Under irradiation, gold nanostructures evolve through five time-defined stages: nuclei-mass fractals-surface fractals-spherical nanoparticles-aggregates. If the maximum in the polymerization rate is reached before the aggregation step, individual primary nanoparticles will be preserved in the polymer matrix due to diffusional constraints imposed by the reaction medium. Because the light intensity has a different influence on the reduction rate than on the polymerization rate, this parameter can be used as a versatile tool to avoid aggregation of gold nanoparticles into the polymer matrix.

A universal strategy: Rational construction of noble metal nanoparticle-shell/conducting polymer nanofiber-core electrodes with enhanced electrochemical performances

To address a challenge for decoration of noble metal nanoparticles (NMNPs)-shell on conducting polymer nanofiber (CPNF) electrodes (i.e. NMNP-shell/CPNF-core electrodes) for boosting electrochemical performances, a two-step strategy comprising chemical pre-deposition and electrochemical deposition is designed. The strategy shows a high universality in terms of the diversity of NMNP-shell elements (single-element: AgNP-shell, AuNP-shell, PtNP-shell, PdNP-shell; multi-element: Au/Pt/PdNP-shell) and the independence of conductive substrates of electrodes. The shells are composed of high-density NMNPs and have strong adhesion to CPNF-cores. It is demonstrated that in response to a specific applied electrical stimulus, the resulting low doping level of CPNFs facilitates the generation of high-density nucleation sites (small NMNPs) by chemical pre-deposition (as high capability of electron transfer and low resistance to electron transfer from CP chains to NM ions), which is indispensable for the formation of NMNP-shells on CPNF-cores by electrochemical deposition. The decoration of NMNP-shells can significantly enhance the electrochemical performances of CPNF electrodes. Moreover, the great practicality and reliability of NMNP-shell/CPNF-core electrodes in use as an electrocatalytic platform are confirmed. This universal strategy opens up a new avenue to construct high-dimension shell/core-nanostructured electrodes.

A simple electrochemical approach to fabricate functionalized MWCNT-nanogold decorated PEDOT nanohybrid for simultaneous quantification of uric acid, xanthine and hypoxanthine

Medical diagnostics and detection of food spoilage require estimation of hypoxanthine (HX), xanthine (XN), and uric acid (UA). A selective sensing platform has been proposed for simultaneous detection of all these species. Functionalized multi-walled carbon nanotube (fMWCNT) stabilized nanogold decorated PEDOT:TOS polymeric nanocomposite (Au-PEDOT-fMWCNT) was synthesized through rapid one-step electropolymerization to enhance conductivity and active surface area by several folds. Electrochemical activities of the proposed sensing platform were analyzed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS). Analyses through SEM, FESEM and TEM were performed to explore the surface morphology and elemental analysis of the polymeric nanohybrid was investigated by XPS, Raman, FTIR, XRD spectroscopy. Electro-catalysis of UA, XN and HX occurred at low oxidation potentials i.e. 0.082, 0.463 and 0.808 V, respectively in the optimized conditions. The uniquely designed simple, interference free Au-PEDOT-fMWCNT/GCE sensor exhibited high selectivity, good reproducibility, reusability (∼180 times) and stability (∼3 month) with excellent sensitivity of 1.73, 14.31 and 3.82 μA μM^-1 cm^-2 for UA, XN and HX, respectively. The sensor exhibited linear ranges of detection as 0.1-800, 0.05-175 and 0.1-150 μM with detection limits of 199.3, 24.1 and 90.5 nM for quantification of UA, XN and HX respectively. The performance of the proposed sensor was validated by addition of UA, XN and HX in human serum, urine and fish samples by comparing to those using HPLC. The results indicated good applicability of the proposed sensor for simultaneous detection of UA, XN, HX in real biological fluids.

Formation of Copper(I) Oxide- and Copper(I) Cyanide-Polyacetonitrile Nanocomposites through Strong-Field Laser Processing of Acetonitrile Solutions of Copper(II) Acetate Dimer

Irradiation studies of acetonitrile solutions of copper(II) acetate dimer ([Cu(OAc)₂]₂) using high energy, simultaneously spatially and temporally focused (SSTF) ultrashort laser pulses are reported. Under ambient conditions, irradiation for relatively short periods of time (10-20 s) selectively produces relatively small, narrowly size-dispersed (3.5 ± 0.7 nm) copper(I) oxide nanoparticles (Cu₂O NPs) embedded in CuCN-polyacetonitrile polymers generated in situ by the laser. The Cu₂O NPs become embedded in a CuCN-polyacetonitrile network as they form, stabilizing them and protecting the air-sensitive material from oxygen. Laser irradiation of acetonitrile causes fragmentation into transient radicals that initiate and terminate polymerization of acetonitrile. Control and mechanistic investigations reveal that HCN formed during laser irradiation reacts rapidly to reduce the Cu(II) centers in [Cu(OAc)₂]₂, leading to the formation of CuCN or, in the presence of water, Cu₂O nanoparticles that bind and cross-link CuCN-polyacetonitrile chains. The acetate-bridged Cu(II) dimer unit is a required structural feature that functions to preorganize and direct the Cu(II) reduction and selective formation of CuCN and Cu₂O nanoparticles. This study illustrates how rapid deposition of energy using shaped, ultrashort laser pulses can initiate multiple photolytic and thermal processes that lead to the selective formation of composite nanoparticle/polymer materials for applications in electronics and catalysis.

An efficient thin-walled Pd/polypyrrole hybrid nanotube biocatalyst for sensitive detection of ascorbic acid

Controllable fabrication of novel and uniform noble metal nanoparticles on a specific support with a superior catalytic or electrocatalytic performance is of significantly importance for practical applications. In this report, we demonstrated an effective way to fabricate uniform thin-walled Pd/polypyrrole (PPy) hollow nanotubes. The prepared Pd/PPy hybrid nanotubes exhibited an excellent peroxidase-like activity to oxidize a typical peroxidase substrate such as 3,3',5,5'-tetramethylbenzidine in comparison with traditional Pd/C and Pd black catalysts. The outstanding catalytic activity of the Pd/PPy hybrid nanotubes for peroxidase mimicking could be resulting from their unique hollow characteristic and an interfacial effect between PPy and Pd components. Based on the favorable catalytic property of the Pd/PPy hybrid nanotubes, a convenient and rapid colorimetric way to sensitively determine ascorbic acid has been presented. The detection limit was around 0.062 μM and an excellent selectivity was also achieved. The developed detection system in this study could be extended to the fields of bioscience and biotechnology with promising prospects.

In situ synthesis of low-cost and large-scale flexible metal nanoparticle–polymer composite films as highly sensitive SERS substrates for surface trace analysis

Surface-enhanced Raman spectroscopy (SERS) has been one of the most promising analytical tools. Despite many efforts in the design of SERS substrates, it remains a great challenge for creating a general flexible substrate that could in situ detect analytes on diverse objects. Herein, we report our attempt to address this issue by developing a facile and versatile method capable of generating silver/gold nanoparticles in situ on the surface of a cellulose acetate (CA) polymer in a simple, cheap, practical, and capping agent-free way. The as-prepared substrates exhibit excellent sensitivity, which enabled detection of Rhodamine 6G at concentrations as low as 10⁻¹² M. Taking advantage of the excellent flexibility and optical transparency of the CA matrix, the highly SERS-active substrate was applied for in situ identification and detection of pesticide residues on fruits. The results indicated that tetramethylthiuram disulfide (TMTD) and thiabendazole (TBZ) can be clearly identified at concentrations as low as 18.05 ng cm⁻² and 15.1 ng cm⁻², respectively, which were much lower than the maximum permitted residue doses with respect to food safety.

Facile and large-scale synthesis of flexible metal nanoparticle–polymer composite films as highly sensitive SERS substrates for in situ food inspection.

Hollow transition metal hydroxide octahedral microcages for single particle surface-enhanced Raman spectroscopy

Single M(OH)_x (M = Fe, Co, Ni) hollow octahedral microcage particles are explored as novel SERS-active substrates for sensitive dye molecule detection.

Graphene-based nanoplatforms for surface-enhanced Raman scattering sensing

Surface-enhanced Raman scattering (SERS) is one of the important techniques for sensing applications in biological analysis, disease diagnosis, environmental science, and food safety. Graphene provides an excellent nanoplatform for SERS sensing due to its two-dimensional flat structure, uniform electronic and photonic properties, excellent mechanical stability, atomic uniformity, and high biocompatibility. In this review, we summarize recent advances in the fabrication of various graphene-based nanoplatforms for SERS sensing. We present the strategies, such as self-assembly, in situ synthesis, one-pot synthesis, liquid phase reduction, and biomimetic synthesis, for the fabrication of graphene-based hybrid metallic and alloy nanoplatforms, and then demonstrate the potential applications of graphene-based nanoplatforms for the SERS sensing of ions, organic dyes, pesticides, bacteria, DNA, proteins, cells, and other chemicals in great detail. In addition, we also discuss the future development of this interesting research field and provide several perspectives. This work will be helpful for readers to understand the fabrication and sensing mechanisms of graphene-based SERS sensing nanoplatforms; meanwhile, it will promote the development of new materials and novel methods for high performance sensing and biosensing applications.

Rapid in situ synthesis of polymer-metal nanocomposite films in several seconds using a CO2 laser

We demonstrate the rapid in situ synthesis of polymer-metal nanocomposite films using a CO2 laser at 10.6 μm. The mechanism of our method is that the precursor of the metal nanoparticles, i.e., the metallic ions, is very rapidly reduced in the laser-heated polymer matrix without any reducing agent. Unlike other known laser-induced reduction methods using UV lasers, which produce radicals to promote reduction, the CO2 laser energy is mainly absorbed by the glass substrate, and the laser-heated substrate heats the polymer matrix through heat diffusion to promote reduction. The superiority of the use of CO2 lasers over nanosecond visible~UV lasers is also demonstrated in terms of the damage to the film. The developed method can be a new alternative to quickly synthesize a variety of polymer-metal nanocomposite films.

Programmable Negative Differential Resistance Effects Based on Self-Assembled Au@PPy Core-Shell Nanoparticle Arrays

The negative differential resistance (NDR) effect observed in conducting polymer/Au nanoparticle composite devices is not yet fully clarified due to the random and disordered incorporation of Au nanoparticles into conducting polymers. It remains a formidable challenge to achieve the sequential arrangement of various components in an optimal manner during the fabrication of Au nanoparticle/conducting polymer composite devices. Here, a novel strategy for fabricating Au nanoparticle/conducting polymer composite devices based on self-assembled Au@PPy core-shell nanoparticle arrays is demonstrated. The interval between the two Au nanoparticles can be precisely programmed by modulating the thickness of the shell and the size of the core. Programmable NDR is achieved by regulating the spacer between two Au nanoparticles. In addition, the Au/conducting polymer composite device exhibits a reproducible memory effect with read-write-erase characteristics. The sequentially controllable assembly of Au@PPy core-shell nanoparticle arrays between two microelectrodes will simplify nanodevice fabrication and will provide a profound impact on the development of new approaches for Au/conducting polymer composite devices.

Synthesis of Poly(3,4-ethylenedioxythiophene)-Platinum and Poly(3,4-ethylenedioxythiophene)-Poly(styrenesulfonate) Hybrid Fibers by Alternating Current Bipolar Electropolymerization

Alternating current (ac) bipolar electropolymerization of 3,4-ethylenedioxythiophene (EDOT) was performed in the presence of hexachloroplatinate ([PtCl₆]^2-) or poly(styrenesulfonate) (PSS). We demonstrated that both [PtCl₆]^2- and PSS were successfully incorporated into electrogenerated poly(3,4-ethylenedioxythiophene) (PEDOT) as dopants to offer hybrid fibers composed of (i) PEDOT and platinum nanoparticles (PtNPs) (PEDOT-Pt hybrid fibers) and (ii) PEDOT and PSS (PEDOT-PSS hybrid fibers), respectively, in one step, grown from the very edges of Au wires used as bipolar electrodes (BPEs).

One pot synthesis of dandelion-like polyaniline coated gold nanoparticles composites for electrochemical sensing applications

In this work, we report a facile and green strategy for one pot and in-situ synthesis of a dandelion-like conductive polyaniline coated gold nanoparticle nanocomposites (Au@PANI). The Au@PANI was characterized by SEM, TEM, XRD, TGA, FTIR, UV-vis and conductivity measurement, respectively. Newly-designed Au@PANI materials possessed a significantly high conductivity and strong adsorption capability. Thus, the Au@PANI modified glassy carbon electrode (GCE) was utilized for construct a novel electrochemical sensor for the simultaneous assay of Pb²⁺ and Cu²⁺ using square wave anodic stripping voltammetry (SWASV). Under the optimized conditions, an excellent electrochemical response in the simultaneous of Pb²⁺ and Cu²⁺ with detection limit of 0.003 and 0.008 μM (S/N = 3), respectively. Moreover, the prepared sensors realized an excellent reproducibility, repeatability and long term stability, as well as reliable practical assays in real water samples. Besides, the possible formation mechanism and sensing mechanism of Au@PANI nanocomposites have been discussed in detail. We believe this study provides a novel method of fabrication of noble metal nanoparticles decorated conducting polymer materials for the electrochemical sensing applications.

Unraveling the Raman Enhancement Mechanism on 1T'-Phase ReS2 Nanosheets

2D transition metal dichalcogenides materials are explored as potential surface-enhanced Raman spectroscopy substrates. Herein, a systematic study of the Raman enhancement mechanism on distorted 1T (1T') rhenium disulfide (ReS₂ ) nanosheets is demonstrated. Combined Raman and photoluminescence studies with the introduction of an Al₂ O₃ dielectric layer unambiguously reveal that Raman enhancement on ReS₂ materials is from a charge transfer process rather than from an energy transfer process, and Raman enhancement is inversely proportional while the photoluminescence quenching effect is proportional to the layer number (thickness) of ReS₂ nanosheets. On monolayer ReS₂ film, a strong resonance-enhanced Raman scattering effect dependent on the laser excitation energy is detected, and a detection limit as low as 10^-9 m can be reached from the studied dye molecules such as rhodamine 6G and methylene blue. Such a high enhancement factor achieved through enhanced charge interaction between target molecule and substrate suggests that with careful consideration of the layer-number-dependent feature and excitation-energy-related resonance effect, ReS₂ is a promising Raman enhancement platform for sensing applications.

Swollen hexagonal liquid crystals as smart nanoreactors: implementation in materials chemistry for energy applications

Materials are the key roadblocks for the commercialization of energy conversion devices in fuel cells and solar cells. Significant research has focused on tuning the intrinsic properties of materials at the nanometer scale. The soft template mediated controlled fabrication of advanced nanostructured materials is attracting considerable interest due to the promising applications of these materials in catalysis and electrocatalysis. Swollen hexagonal lyotropic liquid crystals (SLCs) consist of oil-swollen surfactant-stabilized 1D, 2D or 3D nanometric assemblies regularly arranged in an aqueous solvent. Interestingly, the characteristic size of the SLCs can be controlled by adjusting the volume ratio of oil to water. The non-polar and/or polar compartments of the SLCs can be doped with guest molecules and used as nanoreactors for the synthesis of various metals (Pt, Pd, Au, etc.), conducting polymers and composite nanostructures with controlled size and shape. 1D, 2D and 3D mono- and bimetallic nanostructures of controlled composition and porosity can also be fabricated. These materials have demonstrated impressive enhancements of their electrochemical properties as compared to their bulk counterparts and have been identified as promising for further implementation in energy harvesting applications. In this review article, recent research materials are described regarding the development of functional materials with much improved performances for catalysis applications. This review addresses a brief overview of swollen hexagonal mesophases as nanoreactors, describes examples of nanostructured materials synthesized in these nanoreactors, shows several examples of the energy conversion applications in solar light harvesting, fuel cells etc. and also summarizes the associated reaction mechanisms developed in the recent literature for enhanced catalytic activity.

Smart construction of palladium@polypyrrole nanocomposite coating on a magnetic support as a highly efficient and recyclable catalyst

Herein is reported a facile and smart approach to fabricating polystyrene/Fe₃O₄/palladium@polypyrrole nanocomposite particles with high catalytic activity and stability for the degradation of methylene blue by NaBH₄.

Ultrasmall MnO Nanoparticles Supported on Nitrogen-Doped Carbon Nanotubes as Efficient Anode Materials for Sodium Ion Batteries

Sodium ion batteries (SIBs) have attracted increasing attentions as promising alternatives to lithium ion batteries (LIBs). Herein, we design and synthesize ultrasmall MnO nanoparticles (∼4 nm) supported on nitrogen-doped carbon nanotubes (NDCT@MnO) as promising anode materials of SIBs. It is revealed that the carbonization temperature can greatly influence the structural features and thus the Na-storage behavior of the NDCT@MnO nanocomposites. The synergetic interaction between MnO and NDCT in the NDCT@MnO nanocomposites provides high rate capability and long-term cycling life due to high surface area, electrical conductivity, enhanced diffusion rate of Na⁺ ions, and prevented agglomeration and high stability of MnO nanoparticles. The resulting SIBs provide a high reversible specific capacity of 709 mAh g^-1 at a current density of 0.1 A g^-1 and a high capacity of 536 mAh g^-1 almost without loss after 250 cycles at 0.2 A g^-1. Even at a high current density of 5 A g^-1, a capacity of 273 mAh g^-1 can be maintained after 3000 cycles.

Highly Catalytic Pt Nanoparticles Grown in Two-Dimensional Conducting Polymers at the Air-Water Interface

We report a new approach to the synthesis of uniform, high areal density Pt nanocrystals supported by conducting polymers. The key strategy is the use of ice-templated, two-dimensional polyaniline nanosheets at the air-water interface as a platform for expediting Pt nucleation. Highly crystalline Pt nanoparticles with a narrow size distribution of 2.7 ± 0.3 nm and a high electrochemically active surface area of 94.57 m² g^-1 were obtained. Pt NPs were strongly anchored to the polyaniline nanosheets, and demonstrated high current densities, good durability for the methanol oxidation reaction, and excellent carbon monoxide tolerance, all of which are unprecedented. The idea established in this study could be applied to the production of a wide range of other catalysts with enhanced activities.

Ultrasensitive SERS performance in 3D "sunflower-like" nanoarrays decorated with Ag nanoparticles

Low-cost, stabilized and ultrasensitive three-dimensional (3D) hierarchical surface-enhanced Raman scattering substrates ("sunflower-like" nanoarrays decorated with Ag nanoparticles, denoted as SLNAs-Ag) have been obtained by fabricating binary colloidal crystals and then decorating with Ag nanoparticles. In order to provide a larger density of hot spots within the laser-illumination area, the silica sphere arrays were chosen as the island-type platform for the polystyrene (PS) nanosphere deposition, and the distances between the PS nanospheres were tuned by etching for different durations. Compared with conventional 2D planar systems, the as-fabricated 3D SLNAs-Ag exhibited extremely high SERS sensitivity ascribed to the larger SERS active regions. Quantitative detection of molecules with an extremely low incident laser power was achieved on the "sunflower-like" nanoarrays in which the PS nanospheres were etched for 5 minutes and decorated with Ag nanoparticles, and the corresponding analytical enhancement factor is calculated to be 2 × 10¹⁴ with the concentration of rhodamine 6G down to 10^-15 M. Based on the achieved SERS substrates, we have further demonstrated the highly sensitive detection of molecules such as melamine for food safety inspection.