Phenylacetylene-Terminated Poly(Ethylene Glycol) as Ligands for Colloidal Noble Metal Nanoparticles: a New Tool for "Grafting to" Approach.

We report a new design of polymer phenylacetylene (PA) ligands and the ligand exchange methodology for colloidal noble metal nanoparticles (NPs). PA-terminated poly(ethylene glycol) (PEG) can bind to metal NPs through acetylide (M-C≡C-R) that affords a high grafting density. The ligand-metal interaction can be switched between σ bonding and extended π backbonding by changing grafting conditions. The σ bonding of PEG-PA with NPs is strong and it can compete with other capping ligands including thiols, while the π backbonding is much weaker. The σ bonding is also demonstrated to improve the catalytic performance of Pd for ethanol oxidation and prevent surface absorption of the reaction intermediates. Those unique binding characteristics will enrich the toolbox in the control of colloidal surface chemistry and their applications using polymer ligands.

Polyvinylpyrrolidone-Coated Cubic Hollow Nanocages of PdPt3 and PdIr3 as Highly Efficient Self-Cascade Uricase/Peroxidase Mimics.

Uricase-catalyzed uric acid (UA) degradation has been applied for hyperuricemia therapy, but this medication is limited by H2O2 accumulation, which can cause oxidative stress of cells, resulting in many other health issues. Herein, we report a robust cubic hollow nanocage (HNC) system based on polyvinylpyrrolidone-coated PdPt3 and PdIr3 to serve as highly efficient self-cascade uricase/peroxidase mimics to achieve the desired dual catalysis for both UA degradation and H2O2 elimination. These HNCs have hollow cubic shape with average wall thickness of 1.5 nm, providing desired synergy to enhance catalyst's activity and stability. Density functional theory calculations suggest the PdIr3 HNC surface tend to promote OH*/O* desorption for better peroxidase-like catalysis, while the PdPt3 HNC surface accelerates the UA oxidation by facilitating O2-to-H2O2 conversion. The dual catalysis power demonstrated by these HNCs in cell studies suggests their great potential as a new type of nanozyme for treating hyperuricemia.

Enabling Pd Catalytic Selectivity via Engineering Intermetallic Core@Shell Structure.

Core@shell nanoparticles (NPs) have been widely explored to enhance catalysis due to the synergistic effects introduced by their nanoscale interface and surface structures. However, creating a catalytically functional core@shell structure is often a synthetic challenge due to the need to control the shell thickness. Here, we report a one-step synthetic approach to core-shell CuPd@Pd NPs with an intermetallic B2-CuPd core and a thin (∼0.6 nm) Pd shell. This core@shell structure shows enhanced activity toward selective hydrogenation of Ar-NO2 and allows one-pot tandem hydrogenation of Ar-NO2 to Ar-NH2 and its condensation with Ar-CHO to form Ar-N═CH-Ar. DFT calculations indicate that the B2-CuPd core promotes the Pd shell binding to Ar-NO2 more strongly than to Ar-CHO, thereby selectively activating Ar-NO2. The chemoselective catalysis demonstrated by B2-CuPd@Pd can be extended to a broader scope of substrates, allowing green chemistry synthesis of a wide range of functional chemicals and materials.

Why surface hydrophobicity promotes CO2 electroreduction: a case study of hydrophobic polymer N-heterocyclic carbenes.

We report the use of polymer N-heterocyclic carbenes (NHCs) to control the microenvironment surrounding metal nanocatalysts, thereby enhancing their catalytic performance in CO2 electroreduction. Three polymer NHC ligands were designed with different hydrophobicity: hydrophilic poly(ethylene oxide) (PEO-NHC), hydrophobic polystyrene (PS-NHC), and amphiphilic block copolymer (BCP) (PEO-b-PS-NHC). All three polymer NHCs exhibited enhanced reactivity of gold nanoparticles (AuNPs) during CO2 electroreduction by suppressing proton reduction. Notably, the incorporation of hydrophobic PS segments in both PS-NHC and PEO-b-PS-NHC led to a twofold increase in the partial current density for CO formation, as compared to the hydrophilic PEO-NHC. While polymer ligands did not hinder ion diffusion, their hydrophobicity altered the localized hydrogen bonding structures of water. This was confirmed experimentally and theoretically through attenuated total reflectance surface-enhanced infrared absorption spectroscopy and molecular dynamics simulation, demonstrating improved CO2 diffusion and subsequent reduction in the presence of hydrophobic polymers. Furthermore, NHCs exhibited reasonable stability under reductive conditions, preserving the structural integrity of AuNPs, unlike thiol-ended polymers. The combination of NHC binding motifs with hydrophobic polymers provides valuable insights into controlling the microenvironment of metal nanocatalysts, offering a bioinspired strategy for the design of artificial metalloenzymes.

Au/Pt Bimetallic Nanowires with Stepped Pt Sites for Enhanced C-C Cleavage in C2+ Alcohol Electro-oxidation Reactions.

Efficient C-C bond cleavage and oxidation of alcohols to CO2 is the key to developing highly efficient alcohol fuel cells for renewable energy applications. In this work, we report the synthesis of core/shell Au/Pt nanowires (NWs) with stepped Pt clusters deposited along the ultrathin (2.3 nm) stepped Au NWs as an active catalyst to effectively oxidize alcohols to CO2. The catalytic oxidation reaction is dependent on the Au/Pt ratios, and the Au1.0/Pt0.2 NWs have the largest percentage (∼75%) of stepped Au/Pt sites and show the highest activity for ethanol electro-oxidation, reaching an unprecedented 196.9 A/mgPt (32.5 A/mgPt+Au). This NW catalyst is also active in catalyzing the oxidation of other primary alcohols, such as methanol, n-propanol, and ethylene glycol. In situ X-ray absorption spectroscopy and infrared spectroscopy are used to characterize the catalyst structure and to identify key reaction intermediates, providing concrete evidence that the synergy between the low-coordinated Pt sites and the stepped Au NWs is essential to catalyze the alcohol oxidation reaction, which is further supported by DFT calculations that the C-C bond cleavage is indeed enhanced on the undercoordinated Pt-Au surface. Our study provides important evidence that a core/shell structure with stepped core/shell sites is essential to enhance electrochemical oxidation of alcohols and will also be central to understanding electro-oxidation reactions and to the future development of highly efficient direct alcohol fuel cells for renewable energy applications.

Metal-Ligand Interactions and Their Roles in Controlling Nanoparticle Formation and Functions.

ConspectusFunctional nanoparticles (NPs) have been studied extensively in the past decades for their unique nanoscale properties and their promising applications in advanced nanosciences and nanotechnologies. One critical component of studying these NPs is to prepare monodisperse NPs so that their physical and chemical properties can be tuned and optimized. Solution phase reactions have provided the most reliable processes for fabricating such monodisperse NPs in which metal-ligand interactions play essential roles in the synthetic controls. These interactions are also key to stabilizing the preformed NPs for them to show the desired electronic, magnetic, photonic, and catalytic properties. In this Account, we summarize some representative organic bipolar ligands that have recently been explored to control NP formation and NP functions. These include aliphatic acids, alkylphosphonic acids, alkylamines, alkylphosphines, and alkylthiols. This ligand group covers metal-ligand interactions via covalent, coordination, and electrostatic bonds that are most commonly employed to control NP sizes, compositions, shapes, and properties. The metal-ligand bonding effects on NP nucleation rate and growth can now be more thoroughly investigated by in situ spectroscopic and theoretical studies. In general, to obtain the desired NP size and monodispersity requires rational control of the metal/ligand ratios, concentrations, and reaction temperatures in the synthetic solutions. In addition, for multicomponent NPs, the binding strength of ligands to various metal surfaces needs to be considered in order to prepare these NPs with predesigned compositions. The selective ligand binding onto certain facets of NPs is also key to anisotropic growth of NPs, as demonstrated in the synthesis of one-dimensional nanorods and nanowires. The effects of metal-ligand interactions on NP functions are discussed in two aspects, electrochemical catalysis for CO2 reduction and electronic transport across NP assemblies. We first highlight recent advances in using surface ligands to promote the electrochemical reduction of CO2. Several mechanisms are discussed, including the modification of the catalyst surface environment, electron transfer through the metal-organic interface, and stabilization of the CO2 reduction intermediates, all of which facilitate selective CO2 reduction. These strategies lead to better understanding of molecular level control of catalysis for further catalyst optimization. Metal-ligand interaction in magnetic NPs can also be used to control tunneling magnetoresistance properties across NPs in NP assemblies by tuning NP interparticle spacing and surface spin polarization. In all, metal-ligand interactions have yielded particularly promising directions for tuning CO2 reduction selectivity and for optimizing nanoelectronics, and the concepts can certainly be extended to rationalize NP engineering at atomic/molecular precision for the fabrication of sensitive functional devices that will be critical for many nanotechnological applications.

The built-in electric field across FeN/Fe3N interface for efficient electrochemical reduction of CO2 to CO.

Nanostructured metal-nitrides have attracted tremendous interest as a new generation of catalysts for electroreduction of CO2, but these structures have limited activity and stability in the reduction condition. Herein, we report a method of fabricating FeN/Fe3N nanoparticles with FeN/Fe3N interface exposed on the NP surface for efficient electrochemical CO2 reduction reaction (CO2RR). The FeN/Fe3N interface is populated with Fe-N4 and Fe-N2 coordination sites respectively that show the desired catalysis synergy to enhance the reduction of CO2 to CO. The CO Faraday efficiency reaches 98% at -0.4 V vs. reversible hydrogen electrode, and the FE stays stable from -0.4 to -0.9 V during the 100 h electrolysis time period. This FeN/Fe3N synergy arises from electron transfer from Fe3N to FeN and the preferred CO2 adsorption and reduction to *COOH on FeN. Our study demonstrates a reliable interface control strategy to improve catalytic efficiency of the Fe-N structure for CO2RR.

Progress in Microtopography Optimization of Polymers-Based Pressure/Strain Sensors.

Due to the wide application of wearable electronic devices in daily life, research into flexible electronics has become very attractive. Recently, various polymer-based sensors have emerged with great sensing performance and excellent extensibility. It is well known that different structural designs each confer their own unique, great impacts on the properties of materials. For polymer-based pressure/strain sensors, different structural designs determine different response-sensing mechanisms, thus showing their unique advantages and characteristics. This paper mainly focuses on polymer-based pressure-sensing materials applied in different microstructures and reviews their respective advantages. At the same time, polymer-based pressure sensors with different microstructures, including with respect to their working mechanisms, key parameters, and relevant operating ranges, are discussed in detail. According to the summary of its performance and mechanisms, different morphologies of microstructures can be designed for a sensor according to its performance characteristics and application scenario requirements, and the optimal structure can be adjusted by weighing and comparing sensor performances for the future. Finally, a conclusion and future perspectives are described.

Construction of a new smooth support vector machine model and its application in heart disease diagnosis.

Support vector machine (SVM) is a new machine learning method developed from statistical learning theory. Since the objective function of the unconstrained SVM model is a non-smooth function, a lot of fast optimization algorithms can't be used to find the solution. Firstly, to overcome the non-smooth property of this model, a new padé33 approximation smooth function is constructed by rational approximation method, and a new smooth support vector machine model (SSVM) is established based on the smooth function. Then, by analyzing the performance of the smooth function, we find that the smooth precision is significantly higher than existing smooth functions. Moreover, theoretical and rigorous mathematical analyses are given to prove the convergence of the new model. Finally, it is applied to the heart disease diagnosis. The results show that the Padé33-SSVM model has better classification capability than existing SSVMs.

Introduction to CO2 capture and conversion.

An introduction to the Nanoscale themed collection on CO2 capture and conversion, featuring exciting research on advanced nanoscale materials and reactions.

Magnetic Nanoparticles: Synthesis, Anisotropy, and Applications.

Anisotropy is an important and widely present characteristic of materials that provides desired direction-dependent properties. In particular, the introduction of anisotropy into magnetic nanoparticles (MNPs) has become an effective method to obtain new characteristics and functions that are critical for many applications. In this review, we first discuss anisotropy-dependent ferromagnetic properties, ranging from intrinsic magnetocrystalline anisotropy to extrinsic shape and surface anisotropy, and their effects on the magnetic properties. We further summarize the syntheses of monodisperse MNPs with the desired control over the NP dimensions, shapes, compositions, and structures. These controlled syntheses of MNPs allow their magnetism to be finely tuned for many applications. We discuss the potential applications of these MNPs in biomedicine, magnetic recording, magnetotransport, permanent magnets, and catalysis.

Consumers' coping strategies when they feel negative emotions in the face of forced deconsumption during the Covid-19 pandemic lockdowns.

Introduction: This paper explores consumers' coping strategies when they feel negative emotions due to forced deconsumption during the Covid-19 pandemic lockdowns. Methods: The tool used for data collection is the questionnaire. It was made using the LimeSurvey software. A total of 621 complete observations were analyzed. Results: The findings demonstrate that anger positively influences the activation of seeking social support, mental disengagement, and confrontive coping strategies. Besides, disappointment activates mental disengagement but only marginally confrontive coping and not behavioral disengagement. Furthermore, regret is positively related to confrontive coping, behavioral disengagement, acceptance, and positive reinterpretation. Finally, worry positively impacts behavioral disengagement, self-control, seeking social support, mental disengagement, and planful problem-solving. Discussion: The study's originality lies in its investigation of consumers' coping strategies when experiencing negative emotions due to forced deconsumption in the context of the Covid-19 pandemic.

Polymer N-Heterocyclic Carbene (NHC) Ligands for Silver Nanoparticles.

Polymer N-heterocyclic carbenes (NHCs) are a class of robust surface ligands to provide superior colloidal stability for metal nanoparticles (NPs) under various harsh conditions. We report a general method to prepare polymeric NHCs and demonstrate that these polymer NHC-AgNPs are stable against oxidative etching and show high peroxidase activity. We prepared three imidazolium-terminated poly(methyl methacrylate) (PMMA), polystyrene (PS), and poly(2-(2-methoxyethoxy)ethyl methacrylate) (PMEO2MA) through atom-transfer radical polymerization with an imidazole-containing initiator. The imidazolium end group was further converted to NHC-Ag(I) in the presence of Ag2O at room temperature. Polymer NHC-Ag(I) can transmetalate to AgNPs through ligand exchange at the interface of oil/water within 2 min. All the three polymers can modify metal NPs, such as AgNPs, Ag nanowires, and AuNPs, providing excellent thermal, oxidative, and chemical stabilities for AgNPs. As an example, in the presence of hydrogen peroxide, AgNPs modified by polymer NHCs were resistant against oxidative etching with a rate of ∼700 times slower than those grafted with thiolates. AgNPs modified by polymer NHCs also showed higher peroxidase activity, 4 times more active than those capped by citrate and polyvinylpyrrolidone (PVP) and 2 times more active than those with polymer thiolate. Our studies demonstrate a great potential of using polymer NHCs to stabilize metallic NPs for various applications.

Recent advances in CO2 capture and reduction.

Given the continuous and excessive CO2 emission into the atmosphere from anthropomorphic activities, there is now a growing demand for negative carbon emission technologies, which requires efficient capture and conversion of CO2 to value-added chemicals. This review highlights recent advances in CO2 capture and conversion chemistry and processes. It first summarizes various adsorbent materials that have been developed for CO2 capture, including hydroxide-, amine-, and metal organic framework-based adsorbents. It then reviews recent efforts devoted to two types of CO2 conversion reaction: thermochemical CO2 hydrogenation and electrochemical CO2 reduction. While thermal hydrogenation reactions are often accomplished in the presence of H2, electrochemical reactions are realized by direct use of electricity that can be renewably generated from solar and wind power. The key to the success of these reactions is to develop efficient catalysts and to rationally engineer the catalyst-electrolyte interfaces. The review further covers recent studies in integrating CO2 capture and conversion processes so that energy efficiency for the overall CO2 capture and conversion can be optimized. Lastly, the review briefs some new approaches and future directions of coupling direct air capture and CO2 conversion technologies as solutions to negative carbon emission and energy sustainability.

Cu2O nanoparticle-catalyzed tandem reactions for the synthesis of robust polybenzoxazole.

We report the synthesis of Cu2O nanoparticles (NPs) by controlled oxidation of Cu NPs and the study of these NPs as a robust catalyst for ammonia borane dehydrogenation, nitroarene hydrogenation, and amine/aldehyde condensation into Schiff-base compounds. Upon investigation of the size-dependent catalysis for ammonia borane dehydrogenation and nitroarene hydrogenation using 8-18 nm Cu2O NPs, we found 13 nm Cu2O NPs to be especially active with quantitative conversion of nitro groups to amines. The 13 nm Cu2O NPs also efficiently catalyze tandem reactions of ammonia borane, diisopropoxy-dinitrobenzene, and terephthalaldehyde, leading to a controlled polymerization and the facile synthesis of polybenzoxazole (PBO). The highly pure PBO (Mw = 19 kDa) shows much enhanced chemical stability than the commercial PBO against hydrolysis in boiling water or simulated seawater, demonstrating a great potential of using noble metal-free catalysts for green chemistry synthesis of PBO as a robust lightweight structural material for thermally and mechanically demanding applications.

A Heteroleptic Gold Hydride Nanocluster for Efficient and Selective Electrocatalytic Reduction of CO2 to CO.

It has been a long-standing challenge to create and identify the active sites of heterogeneous catalysts, because it is difficult to precisely control the interfacial chemistry at the molecular level. Here we report the synthesis and catalysis of a heteroleptic gold trihydride nanocluster, [Au22H3(dppe)3(PPh3)8]3+ [dppe = 1,2-bis(diphenylphosphino)ethane, PPh3 = triphenylphosphine]. The Au22H3 core consists of two Au11 units bonded via six uncoordinated Au sites. The three H atoms bridge the six uncoordinated Au atoms and are found to play a key role in catalyzing electrochemical reduction of CO2 to CO with a 92.7% Faradaic efficiency (FE) at -0.6 V (vs RHE) and high reaction activity (134 A/gAu mass activity). The CO current density and FECO remained nearly constant for the CO2 reduction reaction for more than 10 h, indicating remarkable stability of the Au22H3 catalyst. The Au22H3 catalytic performance is among the best Au-based catalysts reported thus far for electrochemical reduction of CO2. Density functional theory (DFT) calculations suggest that the hydride coordinated Au sites are the active centers, which facilitate the formation of the key *COOH intermediate.

Theory-Based Roadmap for Assessing Sustainability in the Collaborative Economy.

This study aims to investigate the current state of sustainability for the collaborative economy (CE). By utilizing the triple bottom line as a founding conceptual framework, the study summarizes and discusses the sustainability of the CE from three dimensions: environment, economy, and society. The study further proposes some targeted measures and suggestions to measure the level of sustainability of the CE and CE platforms. The result shows that the CE has partially fulfilled some of its initial promises pertaining to sustainability, such as creating new job opportunities, economic growth, the efficient use of space and physical resources, as well as social mixing. However, the current sustainability benefits remain much smaller than some claim and hope for. Therefore, governments, platforms, and the public should work together to solve current challenges pertaining to the CE to tap its sustainability potential.

A New Hexagonal Cobalt Nanosheet Catalyst for Selective CO2 Conversion to Ethanal.

We report a new form of catalyst based on ferromagnetic hexagonal-close-packed (hcp) Co nanosheets (NSs) for selective CO2RR to ethanal, CH3CHO. In all reduction potentials tested from -0.2 to -1.0 V (vs RHE) in 0.5 M KHCO3 solution, the reduction yields ethanal as a major product and ethanol/methanol as minor products. At -0.4 V, the Faradaic efficiency (FE) for ethanal reaches 60% with current densities of 5.1 mA cm-2 and mass activity of 3.4 A g-1 (total FE for ethanal/ethanol/methanol is 82%). Density functional theory (DFT) calculations suggest that this high CO2RR selectivity to ethanal on the hcp Co surface is attributed to the unique intralayer electron transfer, which not only promotes [OC-CO]* coupling but also suppresses the complete hydrogenation of the coupling intermediates to ethylene, leading to highly selective formation of CH3CHO.

To waste or not to waste? Empirical study of waste minimization behavior.

This study explores the key variables that influence overall waste minimization behaviors of consumers by augmenting the theory of planned behavior (TPB) with additional variables, including environmental concern, perceived consumer effectiveness, and perceived lack of facilities. Further, subjective norm is replaced by injunctive norm and descriptive norm. A questionnaire was administered to 455 consumers from North America, a region that faces acute waste production challenges. The findings suggest that perceived consumer effectiveness (PCE) constitutes the most influential variable to predict zero waste behavior (ZWB) intentions (ß = 0.380 p < 0.001), even surpassing perceived behavioral control (PBC) (ß = 0.232 p < 0.001), PBC also directly influences ZWB (ß = 0.321 p < 0.001), and injunctive norms (ß = 0.171 p < 0.05) exert a slightly greater influence than attitudes (ß = 0.122 p < 0.001). Importantly, environmental concern is a meaningful antecedent to all belief variables (i.e., control belief [ß = 0.689 p < 0.001], normative belief [ß = 0.378 p < 0.001], and behavioral belief [ß = 0.367p < 0.001]) while exerting an indirect effect on ZWB (ß = 0.474 [0.299, 0.523]), especially via attitudes and PBC. Albeit perceived lack of facilities negatively impacts intentions (ß = -0.073 p < 0.05), it positively relates ZWB (ß = 0.189 p < 0.001) or worsens the effect of intentions on ZWB (ß = -0.033 [-0.102, 0.036]). The results deliver crucial insights to devise impactful strategies and formulate sound policies to nudge consumers' ZWB.

Linking melem with conjugated Schiff-base bonds to boost photocatalytic efficiency of carbon nitride for overall water splitting.

Developing an efficient single component photocatalyst for overall water splitting under visible-light irradiation is extremely challenging. Herein, we report a metal-free graphitic carbon nitride (g-CxN4)-based nanosheet photocatalyst (x = 3.2, 3.6, or 3.8) with melem rings conjugated by Schiff-base bonds (N[double bond, length as m-dash]C-C[double bond, length as m-dash]N). The presence of the conjugated Schiff-base bond tunes the band gap of g-CxN4 and, more importantly, serves as an electron sink to suppress electron-hole pair recombination. The projected density of states (PDOS) calculations suggest that the melem ring and Schiff-base bond act as oxidizing and reducing centers, respectively, for photocatalytic water splitting. As a result, g-CxN4, in particular g-C3.6N4, can catalyze overall water splitting without the need for any co-catalyst or sacrificial donor. Under visible light (>420 nm wavelength) irradiation, g-C3.6N4 catalyzes the overall water splitting with H2 and O2 generation rates of 75.0 and 36.3 µmol h-1 g-1, respectively. g-C3.6N4 is the most efficient single-component photocatalyst ever reported for overall water splitting. Our studies demonstrate a new approach for tuning the bandgap and the electronic structure of graphitic carbon nitride for maximizing its photocatalytic performance for water splitting, which will be important for hydrogen generation and for energy applications.