The timing of green product introduction in relation to technological evolution

<p>As a result of the rising awareness of environmental issues and increasingly stringent regulations, the ability of a business to manage environmentally friendly products represents an important competitive edge. This paper presents a study of the impacts of two types of technological solutions, namely, Zero Sum and Synergy, on strategies for timing the introduction of green products. We have developed mathematical models to determine the optimal price, traditional quality, and environmental quality required to maximize profit. In addition, we discuss how differentiation in environmental quality and customer patience impact the choice of product introduction strategies under the commitment and no-commitment scenarios. We also investigate how Zero Sum and Synergy interact with choice. The results show that a business tends to adopt a simultaneous introduction strategy when the differentiation in market condition for environmental quality is high, customer is patient, and/or the business employs the Synergy technology. In addition, we determine that this strategy change is less likely in the commitment scenario, when the technology changes from Zero Sum to Synergy.</p

Co₃O₄ Nanosheets with In-Plane Pores and Highly Active {112} Exposed Facets for High Performance Lithium Storage

Recently, two-dimensional transition metal oxide nanomaterials have been extensively investigated as promising candidates for the lithium-ion battery anode materials due to their elastic volume change, efficient ion/electrical pathways, and additional interfacial lithium storage sites. Herein, we report a simple wet-chemical method followed by thermal treatment to synthesize Co₃O₄ nanosheets with the in-plane pores. The as-prepared nanosheets are found to selectively expose the highly active {112} facets as the dominant surfaces. When fabricated into the anode configuration, a specific capacity of 1717 mA h g^–1 can be reliably retained after 100 cycles at a current density of 200 mA g^–1. While increasing the current density to 1 A g^–1 and prolonging the cycle life to 400 cycles, the nanosheets can still deliver a capacity of 1090 mA h g^–1 with a Coulombic efficiency of 99.5%. This excellent electrochemical performance can be attributed to the unique morphological structures of our porous nanosheets for the shortened lithium ion diffusion pathway, alleviated volume expansion, and enhanced active sites, indicating the technological potency of the nanosheets for high-performance lithium storage

Amine-Modulated/Engineered Interfaces of NiMo Electrocatalysts for Improved Hydrogen Evolution Reaction in Alkaline Solutions

The interface between electrolytes and electrocatalysts would largely determine their corresponding activity and stability. Herein, modulating the surface characteristics of NiMo nanoparticles by various adsorbed amines gives the tunability on their interfacial properties and subsequently improves their catalytic performance for hydrogen evolution reaction (HER) in alkaline solutions. Diamines can significantly improve their HER activity by decreasing the charge-transfer resistance and modulating the electronic structures of interfacial active sites. Importantly, among various amines, ethylenediamine facilitates the HER activity of NiMo with a remarkable decrease of 268 mV in the overpotential to reach 10 mA cm^–2 as compared with that of the unmodified NiMo in 1.0 M KOH. This method provides a novel strategy of regulating the interfacial properties to strengthen the catalytic performance of electrocatalysts

Mechanistic Characteristics of Metal-Assisted Chemical Etching in GaAs

Because of the unique physical properties, various GaAs micro- and nanostructures have attracted increasing research attention for many technical applications such as solar cells, light-emitting diodes, and field-effect transistors. In this regard, numerous fabrication techniques have been explored, and among all, metal-assisted chemical etching is successfully applied to GaAs in order to achieve cost-effective, large-scale, and complex structures. However, the detailed explanations as well as the corresponding etching mechanism have not been reported until now or simply relied on the hole injection model of Si in order to explain the phenomenon. In this work, we perform a more systematic study to further explore and assess the etching phenomenon of GaAs employing the Au catalyst and the [KMnO₄/H₂SO₄] etch system. It is revealed that the anisotropic etching behavior of GaAs is predominantly due to the Au-induced surface defects at the Au/GaAs interface, which makes the particular area more prone to oxidation and thus results in the simple directional wet etching; for that reason, more anisotropic etch is obtained for the Au pattern with higher edge-to-surface-area ratio. All these findings not only offer additional insight into the MacEtch process of GaAs but also provide essential information on different etching parameters in manipulating this anisotropic wet etching to achieve the fabrication of complex GaAs structures for technological applications

High-Index Faceted Porous Co₃O₄ Nanosheets with Oxygen Vacancies for Highly Efficient Water Oxidation

Because of sluggish kinetics of the oxygen evolution reaction (OER), designing low-cost, highly active, and stable electrocatalysts for OER is important for the development of sustainable electrochemical water splitting. Here, {112} high-index facet exposed porous Co₃O₄ nanosheets with oxygen vacancies on the surface have been successfully synthesized via a simple hydrothermal method followed by NaBH₄ reduction. As compared with the pristine and other faceted porous Co₃O₄ nanosheets (e.g., {110} and {111}), the as-prepared {112} faceted porous nanosheets exhibit a much lower overpotential of 318 mV at a current density of 10 mA cm^–2. Importantly, these nanosheets also give excellent electrochemical stability, displaying an insignificant change in the required overpotential at a current density of 10 mA cm^–2 even after a 14 h long-term chronoamperometric test. All these superior OER activity and stability could be attributed to their unique hierarchical structures assembled by ultrathin porous nanosheets, {112} high-index exposed facets with higher ratio of Co²⁺/Co³⁺ and oxygen vacancies on the surface, which can substantially enhance the charge transfer rate and increase the number of active sites. All these findings not only demonstrate the potency of our Co₃O₄ nanosheets for efficient water oxidation but also provide further insights into developing cost-effective and high-performance catalysts for electrochemical applications

Synthesis and Characterizations of Ternary InGaAs Nanowires by a Two-Step Growth Method for High-Performance Electronic Devices

InAs nanowires have been extensively studied for high-speed and high-frequency electronics due to the low effective electron mass and corresponding high carrier mobility. However, further applications still suffer from the significant leakage current in InAs nanowire devices arising from the small electronic band gap. Here, we demonstrate the successful synthesis of ternary InGaAs nanowires in order to tackle this leakage issue utilizing the larger band gap material but at the same time not sacrificing the high electron mobility. In this work, we adapt a two-step growth method on amorphous SiO₂/Si substrates which significantly reduces the kinked morphology and surface coating along the nanowires. The grown nanowires exhibit excellent crystallinity and uniform stoichiometric composition along the entire length of the nanowires. More importantly, the electrical properties of those nanowires are found to be remarkably impressive with <i>I</i>_ON/<i>I</i>_OFF ratio >10⁵, field-effect mobility of ∼2700 cm²/(V·s), and ON current density of ∼0.9 mA/μm. These nanowires are then employed in the contact printing and achieve large-scale assembly of nanowire parallel arrays which further illustrate the potential for utilizing these high-performance nanowires on substrates for the fabrication of future integrated circuits

High-Index Faceted Porous Co₃O₄ Nanosheets with Oxygen Vacancies for Highly Efficient Water Oxidation

Because of sluggish kinetics of the oxygen evolution reaction (OER), designing low-cost, highly active, and stable electrocatalysts for OER is important for the development of sustainable electrochemical water splitting. Here, {112} high-index facet exposed porous Co₃O₄ nanosheets with oxygen vacancies on the surface have been successfully synthesized via a simple hydrothermal method followed by NaBH₄ reduction. As compared with the pristine and other faceted porous Co₃O₄ nanosheets (e.g., {110} and {111}), the as-prepared {112} faceted porous nanosheets exhibit a much lower overpotential of 318 mV at a current density of 10 mA cm^–2. Importantly, these nanosheets also give excellent electrochemical stability, displaying an insignificant change in the required overpotential at a current density of 10 mA cm^–2 even after a 14 h long-term chronoamperometric test. All these superior OER activity and stability could be attributed to their unique hierarchical structures assembled by ultrathin porous nanosheets, {112} high-index exposed facets with higher ratio of Co²⁺/Co³⁺ and oxygen vacancies on the surface, which can substantially enhance the charge transfer rate and increase the number of active sites. All these findings not only demonstrate the potency of our Co₃O₄ nanosheets for efficient water oxidation but also provide further insights into developing cost-effective and high-performance catalysts for electrochemical applications

Controlled Growth of Heterostructured Ga/GaAs Nanowires with Sharp Schottky Barrier

Because of the inevitable Fermi level pinning on surface/interface states of nanowires, achieving high-performance nanowire devices with controllable nanoscale contacts is always challenging but important. Herein, single-crystalline heterostructured Ga/GaAs nanowires with sharp hetero-Schottky interfaces have been successfully synthesized on amorphous substrates by utilizing Au nanoparticles as catalytic seeds via chemical vapor deposition. These nanowires are found to grow with the hemispherical Au₇Ga₂ catalytic tips following the vapor–liquid–solid mechanism. During the growth, simply by manipulating the source and growth temperatures, the Ga precipitation rate from Au–Ga alloy tips as well as the reaction rate of Ga precipitates with As can be reliably controlled in order to tailor the length (0–170 nm) of Ga nanowire segments obtained in the heterostructure. When configured into field-effect transistors, these Ga/GaAs NWs exhibit the p-type conductivity with a sharp hetero-Schottky barrier of ∼1.0 eV at the atomically connected Ga segment/GaAs NW body interface, in which this barrier height is close to the theoretical difference between the GaAs Fermi level (5.1–5.3 eV) and the Ga work function (∼4.3 eV), suggesting the effective formation of nanoscale contact by minimizing the Fermi level pinning, being advantageous for advanced nanoelectronics

Controllable p–n Switching Behaviors of GaAs Nanowires <i>via</i> an Interface Effect

Due to the extraordinary large surface-to-volume ratio, surface effects on semiconductor nanowires have been extensively investigated in recent years for various technological applications. Here, we present a facile interface trapping approach to alter electronic transport properties of GaAs nanowires as a function of diameter utilizing the acceptor-like defect states located between the intrinsic nanowire and its amorphous native oxide shell. Using a nanowire field-effect transistor (FET) device structure, p- to n-channel switching behaviors have been achieved with increasing NW diameters. Interestingly, this oxide interface is shown to induce a space-charge layer penetrating deep into the thin nanowire to deplete all electrons, leading to inversion and thus p-type conduction as compared to the thick and intrinsically n-type GaAs NWs. More generally, all of these might also be applicable to other nanowire material systems with similar interface trapping effects; therefore, careful device design considerations are required for achieving the optimal nanowire device performances

Polymer-Confined Colloidal Monolayer: A Reusable Soft Photomask for Rapid Wafer-Scale Nanopatterning

We demonstrate the repeated utilization of self-assembled colloidal spheres for rapid nanopattern generations. Highly ordered micro-/nanosphere arrays were interlinked and confined by a soft transparent polymer (polydimethylsiloxane, PDMS), which can be used as light-focusing elements/photomasks for area-selective exposures of photoresist in contact. Because of the stiffness of the colloidal spheres, the photomasks do not encounter feature-deformation problems, enabling reliable production of highly uniform patterns over large areas. The geometrical feature of the patterns, including the size, pitch, and even the shape, can be finely tuned by adjusting the mask design and exposure time. The obtained patterns could be used as deposition or etching mask, allowing easy pattern transfer for various applications