Synthesis of micro-crosslinked adamantane-containing matrix resins designed for deep-UV lithography resists and their application in nanoimprint lithography.

A certain type of photoresist used for deep-UV lithography (DUVL) can also be used for other types of photolithography. Thus, to meet the requirements of two or more lithography technologies simultaneously, it is necessary to design a variety of corresponding functional groups in the molecules of materials and obtain the required properties. Herein, we designed four matrix resins based on acrylate for DUVL, employing alkyl sulfide, adamantane, methyladamantane, and hydroxyl as dangling groups and a microcrosslinking network by adding a small amount of crosslinker. These polymers were used in the thermal nanoimprint lithography (NIL) process, and distinct patterns with a resolution of 100 nm were observed. The acrylate copolymers designed for DUVL in this work can be used as thermal NIL resists and to obtain good patterns. It was found that ethylene dimethacrylate (EDMA) and adamantane endowed the matrix resins with good thermal stability and that PMMHM demonstrated the best patterning performance among the four resins. These polymers can be applied in the manufacturing of high-density integrated circuits, nano-transistors, optoelectronic devices and other components in the future.

Eco-Friendly Silver Nanoparticles/Chitosan/Poly(vinyl alcohol) Composites Exhibit Remarkable EMI Shielding Capabilities and Outstanding Thermal Conductivities.

The integration and miniaturization of contemporary electronics have led to significant challenges in dealing with electromagnetic (EM) radiation and heat accumulation. Despite these issues, achieving high thermal conductivity (TC) and electromagnetic interference (EMI) shielding effectiveness (SE) in polymer composite films remains an exceptionally difficult task. In this work, we used a straightforward in situ reduction process and a vacuum-drying method to successfully prepare a flexible Ag NPs/chitosan (CS)/PVA nanocomposite with three-dimensional (3D) conductive and thermally conductive network architectures. The 3D silver pathways formed by attaching to the chitosan fibers endow the material with simultaneous exceptional TC and EMI capabilities. At a silver concentration of 25 vol %, the TC of Ag NPs/CS/PVA nanocomposites reaches 5.18 W·m-1·K-1, exhibiting an approximately 25 times increase compared to CS/PVA composites. The electromagnetic shielding performance of 78.5 dB significantly outperforms the specifications of standard commercial EMI shielding applications by a significant margin. Additionally, Ag NPs/CS/PVA nanocomposites have greatly benefited from microwave absorption (SEA), effectively impeding the transmission of EM waves and reducing the reflected secondary EM wave pollution. Meanwhile, the composite material still maintains good mechanical properties and bendability. This endeavor helped develop malleable and durable composites that possess superior EMI shielding capabilities and intriguing heat dissipation properties using innovative design and fabrication methods.

Biomimetic redox-responsive smart coatings with resistance-release functions for reverse osmosis membranes.

Membrane fouling induces catastrophic loss of separation performance and seriously restricts the applications of reverse osmosis (RO) membranes. Inspired by the mussel structure, polydopamine (PDA) and cystamine molecules (CA) with excellent anti-fouling properties were used to prepare accessible, biocompatible, and redox-responsive coatings for RO membranes. The PDA/CA-coated RO membranes exhibit a superior water flux of 65 L m-2 h-1 with a favourable NaCl rejection exceeding 99%. The water permeability through the PDA/CA-coated membrane is much higher than that of most membranes with similar rejection rates. Due to the formed protective hydration layers by PDA/CA coatings, anti-fouling properties against proteins, polysaccharides and surfactants were evaluated separately, and ultralow fouling properties were demonstrated. Moreover, the disulfide linkages in CA molecules can cleave in a reducing environment, yielding the degradation of PDA/CA coatings, thereby removing the foulants deposited on the coatings. The degradation endows the coated membranes with satisfying longtime anti-fouling properties, where the flux recovery reaches up to 90%. The construction of redox-responsive smart coatings not only provided a promising route to alleviate membrane fouling but can also be upscaled for use in numerous practical applications like sensors, medical devices, and drug delivery.

Donnan Effect-Engineered Covalent Organic Framework Membranes toward Size- and Charge-Based Precise Molecular Sieving.

Covalent organic frameworks (COFs), with ordered pores and well-defined topology, are ideal materials for nanofiltration (NF) membranes because of their capacity of transcending the permeance/selectivity trade-off predicament. However, most reported COF-based membranes are focused on separating molecules with different sizes, resulting in low selectivity to similar molecules with different charges. Here, the negatively charged COF layer was fabricated in situ on a microporous support for the separation of molecules with different sizes and charges. Ultrahigh water permeance (216.56 L m-2 h-1 bar-1) was obtained because of the ordered pores and excellent hydrophilicity, which exceeds that of most membranes with similar rejections. For the first time, we used multifarious dyes with different sizes and charges, for the investigation of the selectivity behavior caused by the Donnan effect and size exclusion. The obtained membranes represent superior rejections to negatively and neutrally charged dyes larger than 1.3 nm, while positively charged dyes with a size of 1.6 nm can pass through the membrane, resulting in the separation of negative/positive mixed dyes with similar molecular sizes. This strategy of combining the Donnan effect and size exclusion in nanoporous materials may evolve into a generic platform for sophisticated separation.

Site-specific sulfur-for-metal replacement in a silver nanocluster.

A new Ag36 nanocluster with a closed electronic structure and eight valence electrons is reported, which has a similar structure to that of an open-shell Ag34 nanocluster with three valence electrons, except that in the shell two (Ag-PPh3)+ cations replace two S2- anions specifically. The fine structural modulation leads to various levels of activity for singlet oxygen photogeneration due to the distinct optical gaps of the nanoclusters.

A Novel Hierarchical Porous 3D Structured Vanadium Nitride/Carbon Membranes for High-performance Supercapacitor Negative Electrodes.

Transition-metal nitrides exhibit wide potential windows and good electrochemical performance, but usually experience imbalanced practical applications in the energy storage field due to aggregation, poor circulation stability, and complicated syntheses. In this study, a novel and simple multi-phase polymeric strategy was developed to fabricate hybrid vanadium nitride/carbon (VN/C) membranes for supercapacitor negative electrodes, in which VN nanoparticles were uniformly distributed in the hierarchical porous carbon 3D networks. The supercapacitor negative electrode based on VN/C membranes exhibited a high specific capacitance of 392.0 F g-1 at 0.5 A g-1 and an excellent rate capability with capacitance retention of 50.5% at 30 A g-1. For the asymmetric device fabricated using Ni(OH)2//VN/C membranes, a high energy density of 43.0 Wh kg-1 at a power density of 800 W kg-1 was observed. Moreover, the device also showed good cycling stability of 82.9% at a current density of 1.0 A g-1 after 8000 cycles. This work may throw a light on simply the fabrication of other high-performance transition-metal nitride-based supercapacitor or other energy storage devices.

Nanocomposites based on hierarchical porous carbon fiber@vanadium nitride nanoparticles as supercapacitor electrodes.

In this study, a hybrid electrode material for supercapacitors based on hierarchical porous carbon fiber@vanadium nitride nanoparticles is fabricated using the method of phase-separation mediated by the PAA-b-PAN-b-PAA tri-block copolymer. In the phase-separation procedure, the ionic block copolymer self-assembled on the surface of carbon nanofibers, and is used to adsorb NH4VO3. Thermal treatment at controlled temperatures under an NH3 : N2 atmosphere led to the formation of vanadium nitride nanoparticles that are distributed uniformly on the nanofiber surface. By changing the PAN to PAA-b-PAN-b-PAA ratio in the casting solution, a maximum specific capacitance of 240.5 F g-1 is achieved at the current density of 0.5 A g-1 with good rate capability at a capacitance retention of 72.1% at 5.0 A g-1 in an aqueous electrolyte of 6 mol L-1 KOH within the potential range of -1.10 to 0 V (rN/A = 1.5/1.0). Moreover, an asymmetric supercapacitor is assembled by using the hierarchical porous carbon fiber@vanadium nitride as the negative electrode and Ni(OH)2 as the positive electrode. Remarkably, at the power density of 400 W kg-1, the supercapacitor device delivers a better energy density of 39.3 W h kg-1. It also shows excellent electrochemical stability, and thus might be used as a promising energy-storage device.

Seasons, Searches, and Intentions: What The Internet Can Tell Us About The Bed Bug (Hemiptera: Cimicidae) Epidemic.

The common bed bug (Cimex lectularius L.) is once again prevalent in the United States. We investigated temporal patterns in Google search queries for bed bugs and co-occurring terms, and conducted in-person surveys to explore the intentions behind searches that included those terms. Searches for "bed bugs" rose steadily through 2011 and then plateaued, suggesting that the epidemic has reached an equilibrium in the United States. However, queries including terms that survey respondents associated strongly with having bed bugs (e.g., "exterminator," "remedies") continued to climb, while terms more closely associated with informational searches (e.g., "hotels," "about") fell. Respondents' rankings of terms and nonseasonal trends in Google search volume as assessed by a cosinor model were significantly correlated (Kendall's Tau-b P = 0.015). We find no evidence from Google Trends that the bed bug epidemic in the United States has reached equilibrium.

A door-to-door survey of bed bug (Cimex lectularius) infestations in row homes in Philadelphia, Pennsylvania.

We conducted a door-to-door survey in a residential census tract of Philadelphia to estimate the prevalence and spatial patterns of recent bed bug infestations. We interviewed 596 residents, of whom 66 (11.1%) reported recent bed bug infestations. We confirmed current infestations in a subset of 15 (68.2%) of 22 inspected households. Most residents reported that their infestation began within the past year (2012-2013). We found no correlation between property value and infestation status. Spatial analyses showed significant clustering of bed bug infestations only at fine scales, suggesting limited active dispersal of the insects. Residents used a large variety of treatment methods to eliminate bed bugs, but only 48.1% reported success. Our results provide a prevalence estimate of recent bed bug infestations and highlight the importance of passive rather than active dispersal of bed bugs even among dense urban row homes.