Dopamine-Mediated Graphene Bridging Hexagonal Boron Nitride for Large-Scale Composite Films with Enhanced Thermal Conductivity and Electrical Insulation.

Heat accumulation generated from confined space poses a threat to the service reliability and lifetime of electronic devices. To quickly remove the excess heat from the hot spot, it is highly desirable to enhance the heat dissipation in a specific direction. Herein, we report a facile route to fabricate the large-scale composite film with enhanced thermal conductivity and electrical insulation. The well-stacked composite films were constructed by the assembly of polydopamine (PDA)-modified graphene nanosheets (GNSPDA) and hexagonal boron nitride (BNPDA), as well as bacterial cellulose (BC). The introduction of the PDA layer greatly improves the interface compatibility between hybrid fillers and BC matrix, and the presence of GNSPDA-bridging significantly increases the probability of effective contact with BNPDA fillers, which is beneficial to form a denser and complete "BN-GNS-BN" heat conduction pathway and tight filler-matrix network, as supported by the Foygel model fitting and numerical simulation. The resulting BC/BNPDA/GNSPDA film shows the thermal conductivity and tensile strength of 34.9 W·m-1·K-1 and 30.9 MPa, which separately increases to 161% and 155% relative to the BC/BNPDA film. It was found that the low electrically conductive and high thermal conductive properties can be well balanced by tuning the mass ratio of GNSPDA at 5 wt%, and the electrical conductivity caused by GNSPDA can be effectively blocked by the BNPDA filler network, giving the low electrical conductivity of 1.8 × 10-10 S·cm-1. Meanwhile, the BC/BNPDA/GNSPDA composite films effectively transfer the heat and diminish the hot-spot temperature in cooling LED chip module application. Thus, the present study may pave the way to promoting the industrialization of scalable thermal management devices.

Hierarchical Superstructure of Plant Polyphenol and Arginine Surfactant for Long-Lasting and Target-Selective Antimicrobial Application.

Antimicrobial agents are massively used to disinfect the pathogen contaminated surfaces since the Corona Virus Disease 2019 (COVID-19) outbreak. However, their defects of poor durability, strong irritation, and high environmental accumulation are exposed. Herein, a convenient strategy is developed to fabricate long-lasting and target-selective antimicrobial agent with the special hierarchical structure through bottom-up assembly of natural gallic acid with arginine surfactant. The assembly starts from rodlike micelles, further stacking into hexagonal columns and finally interpenetrating into spherical assemblies, which avoid explosive release of antimicrobial units. The assemblies show anti-water washing and high adhesion on various surfaces; and thus, possess highly efficient and broad-spectrum antimicrobial activities even after using up to eleven cycles. Both in vitro and in vivo experiments prove that the assemblies are highly selective in killing pathogens without generating toxicity. The excellent antimicrobial virtues well satisfy the increasing anti-infection demands and the hierarchical assembly exhibits great potential as a clinical candidate.

Assembly of Hexagonal Column Interpenetrated Spheres from Plant Polyphenol/Cationic Surfactants and Their Application as Antimicrobial Molecular Banks.

Microbial infections have become a great threat to human health and one of the main risks arises from direct contact with the surfaces contaminated by pathogenic microbes. Herein, a kind of hexagonal column interpenetrated spheres (HCISs) are fabricated by non-covalent assembly of plant gallic acid with quaternary ammonium surfactants. Different from one-time burst release of conventional antimicrobial agents, the HCIS acts like a "antimicrobial molecular bank" and releases the antimicrobial ingredients in a multistage way, leading to long-lasting antimicrobial performance. Taking advantage of strong hydrophobicity and adhesion, HCISs are applicable to various substrates and endowed with anti-water washing property, thus showing high in vitro antimicrobial efficiency (>99 %) even after being used for 10 cycles. Meanwhile, HCISs exhibit broad-spectrum antimicrobial activity against bacteria and fungi, and have good biocompatibility with mammalian cells. Such a low-cost and portable long-lasting antimicrobial agent meets the growing anti-infection demand in public spaces.

Quantitative insights into tightly and loosely bound water in hydration shells of amino acids.

The hydration of amino acids closely correlates the hydration of peptides and proteins and is critical to their biological functions. However, complete and quantitative understanding about the hydration of amino acids is lacking. Here, tightly and loosely bound water of 20 zwitterionic amino acids are quantitatively distinguished and determined by Raman spectroscopy with multivariate curve resolution (Raman-MCR) and differential scanning calorimetry (DSC). The total hydration water obtained from Raman-MCR and the tightly bound water determined by DSC have certain relevance, but they do not exactly correspond. In particular, Pro, Arg and Lys exhibit larger number of tightly bound water molecules (4.02-6.59), showing a significant influence on the onset transition temperature and the melting enthalpy values of water molecules, which provides direct evidence for their unique functions associated with biological water. Asn, Ser, Thr, Met, His and Glu have a smaller number of tightly bound water molecules (0.30-1.31), whilst the other remaining 11 amino acids only contain loosely bound water molecules. Four exceptional amino acids Ile, Leu, Phe and Val show fewer tightly bound water molecules but a higher number of loosely bound water molecules. As for the hydration shell structure, most amino acids except Pro and Trp enhance tetrahedral water structure and H-bonds relative to pure water and at least 1.9% of the hydration water molecules associated with the amino acids show non-hydrogen-bonded OH defects. This work combines two effective experimental techniques to reveal the hydration water structure and quantitatively analyze two kinds of bound water molecules of 20 amino acids.

Trimeric Cationic Surfactant Coacervation as a Versatile Approach for Removing Organic Pollutants.

A versatile method to remove a broad spectrum of dye pollutants from wastewater rapidly and efficiently is highly desirable. Here, we report that the complex coacervation of cationic trimeric imine-based surfactants (TISn) with negatively charged hydrolyzed polyacrylamide (HPAM) can be used for this purpose. The coacervation occurs in a wide concentration and composition range and requires the HPAM and TISn concentrations as low as 0.1 g/L and 0.1 mM, respectively. Dye effluents treated by trimeric surfactants and HPAM complete phase separation within 30 s under turbulent conditions, which generates an exceedingly small volume fraction (0.4%) of viscoelastic coacervate and a clear supernatant with a dye removal efficiency of up to 99.9% for anionic and neutral dyes in dosages of up to 120 mg/L. Crowded molecular arrangement and thick framework in coacervate are responsible for the rapid phase separation rate and low volume fraction. The trimeric imine surfactant/polymer coacervation provides a simple, effective, and sustainable approach for the rapid removal of dyes and other organic pollutants.

Hydration Shell Changes in Surfactant Aggregate Transitions Revealed by Raman-MCR Spectroscopy.

Hydration states of many self-assemblies directly relate to their structures and functions. Here, we use Raman multivariate curve resolution (Raman-MCR) assisted by differential scanning calorimetry and nuclear magnetic resonance to explore the hydration properties of aggregates formed by three cationic ammonium surfactants, trimethylene-1,3-bis(dodecyldimethylammonium bromide) (12-3-12(Br)2), didodecyldimethylammonium bromide (DDAB), and dodecyltrimethylammonium bromide (DTAB). For 12-3-12(Br)2, the transitions from spherical to rodlike and wormlike micelles lead to about 20% and 60% dehydration and gradually weaken water tetrahedral order and H-bond in hydration shells for both headgroup and hydrophobic chain. As to DDAB, unilamellar vesicles contain two kinds of hydration water species, but multicompartment vesicles exhibit decreased water order and weaker H-bond. DTAB only forms spherical micelles and its hydration structure is similar to that of the 12-3-12(Br)2 spherical micelles. This work provides a basis to explore the hydration states of complex biological self-assemblies.