Interaction of Graphene And Polycaprolactone at Atomic Level

The main goal of the present work is to examine the effect of graphene layers on the structural and dynamical properties of polymer systems. We study hybrid poly(methyl methacrylate) (PMMA)/ graphene interfacial systems, through detailed atomistic molecular dynamics simulations. In order to characterize the interface, various properties related to density, structure and dynamics of polymer chains are calculated, as a function of the distance from the substrate. A series of different hybrid systems, with width ranging between 2.60 and 13.35 nm, are being modeled. In addition, we compare the properties of the macromolecular chains to the properties of the corresponding bulk system at the same temperature. We observe a strong effect of graphene layers on both structure and dynamics of the PMMA chains. Furthermore, the PMMA/graphene interface is characterized by different length scales, depending on the actual property we probe: density of PMMA polymer chains is larger than the bulk value, for polymer chains close to graphene layers up to distances of about 1.0-1.5 nm. Chain conformations are perturbed for distances up to about 2-3 radius of gyration from graphene. Segmental dynamics of PMMA is much slower close to the solid layers up to about 2-3 nm. Finally, terminal-chain dynamics is slower, compared to the bulk one, up to distances of about 5-7 radius of gyration.

The Journal of Physical Chemistry B, 2020

Synthesis of graphene (GN) in 2004 stimulated wide interest in potential applications of 2D materials in catalysis, optoelectronics, biotechnology, and construction of sensing devices. In the presented study, interactions between GN sheets and phospholipid bilayers are examined using steered molecular dynamics simulations. GN sheets of different sizes were inserted into a bilayer and subsequently withdrawn from it at two different rates (1 and 2 m/s). In some cases, nanoindentation led to substantial damage of the phospholipid bilayer; however, an effective self-sealing process occurred even after significant degradation. The average force and work, deflection of the membrane during indentation, withdrawal processes, and structural changes caused by moving sheets are discussed. These quantities are utilized to estimate the suitability of GN sheets for targeted drug delivery or other nanomedicine tools. The results are compared with those obtained for other nanostructures such as homogeneous and heterogeneous nanotubes.

Physical Chemistry Chemical Physics, 2017

The structure and morphology of three polymer/graphene nanocomposites have been studied using classical molecular dynamics (MD) simulations. The simulations use 10-monomer oligomeric chains of three polymers: polyethylene (PE), polystyrene (PS) and polyvinylidene fluoride (PVDF). The structure of the polymer chains at the graphene surface have been investigated and characterized by pair correlation functions (PCF), g(r), g(θ) and g(r,θ). In addition, the influence of the temperature on the graphene/polymer interactions has been analysed for each of the three polymer/graphene nanocomposite systems. The results indicate that graphene induces order in both the PE and PVDF systems by providing a nucleation site for crystallisation, steering the growth of oligomer crystals according to the orientation of the graphene sheet, whereas the PS system remains disordered in the presence of graphene. The overall results are in line with the findings in a recent quantumchemical study by some of the present authors.

International Journal of Applied Mechanics

Graphene has potential applications in a variety of fields including electronics, photonics and chemical-biosensing. In this study, we perform molecular dynamics (MD) simulations to study the interactions between graphene sheets and biomolecules. The bending behavior of graphene induced by adsorption of peptides is investigated. The influence of peptide size, number, and alignment on the deflection of graphene sheets is studied in detail. The van der Waals (VDW) interaction plays a dominant role in the interaction between peptides and graphene. Our study provides valuable information for the experimental design of nanodevices incorporating graphene with biomolecules.

Scientific Reports

Composites of polymer and graphene-based nanomaterials (GBNs) combine easy processing onto porous 3D membrane geometries due to the polymer and cellular differentiation stimuli due to GBNs fillers. Aiming to step forward to the clinical application of polymer/GBNs composites, this study performs a systematic and detailed comparative analysis of the influence of the properties of four different GBNs: (i) graphene oxide obtained from graphite chemically processes (GO); (ii) reduced graphene oxide (rGO); (iii) multilayered graphene produced by mechanical exfoliation method (Gmec); and (iv) low-oxidized graphene via anodic exfoliation (Ganodic); dispersed in polycaprolactone (PCL) porous membranes to induce astrocytic differentiation. PCL/GBN flat membranes were fabricated by phase inversion technique and broadly characterized in morphology and topography, chemical structure, hydrophilicity, protein adsorption, and electrical properties. Cellular assays with rat C6 glioma cells, as mode...

Materials Research, 2020

In order to realize the macroscopic features of a number of chemically bonded multi-layer dielectric and composite materials, interactions of metal oxide surfaces, polymer surface atoms, and near-surface atoms are very beneficial. The simulation study of polymer-metal oxides interfaces is of great importance in investigating the adhesion and miscibility features of these systems that are inherently challenging to obtain experimentally or for which there is no experimental data, even if some low data exist, they are not reliable. Polycaprolactone (PCL) is biocompatible, biodegradable, non-toxic and hydrophobic polyester that has been used in tissue engineering, such as a bioactive implant. Hence, the molecular dynamics simulations of PCL are carried out to investigate its surface interaction with metal oxides as ZnO, CuO, Fe 2 O 3 , NiO and SiO 2. The force field of COMPASS is applied to simulations in order to compute interfacial and solubility parameters. Molecular dynamics approach to investigate the interaction and adsorption manner of PCL with metal oxides. Whereas investigations are useful in exploring polymer composites. Much better adhesion is achieved by the calculations between the PCL oligomer and the metal oxides under investigation. The negative values of interaction energy have to be forecasted despite the presence of acid-base or hydrogen-bonding interactions.

Molecules, 2021

Graphene and phospholipids are widely used in biosensing and drug delivery. This paper studies the mechanical and electronic properties of a composite based on two graphene flakes and dipalmitoylphosphatidylcholine (DPPC) phospholipid molecules located between them via combination of various mathematical modeling methods. Molecular dynamics simulation showed that an adhesion between bilayer graphene and DPCC increases during nanoindentation of the composite by a carbon nanotube (CNT). Herewith, the DPPC molecule located under a nanotip takes the form of graphene and is not destroyed. By the Mulliken procedure, it was shown that the phospholipid molecules act as a “buffer” of charge between two graphene sheets and CNT. The highest values of electron transfer in the graphene/DPPC system were observed at the lower indentation point, when the deflection reached its maximum value.

Biomedical applications of graphene have recently attracted intensive attention, with graphene-based nanomaterials being reported as promising candidates in, for example, drug delivery, biosensing and bioimaging. In this paper, mechanical properties and bioactivity of nanofibrous and porous membranes electrospun from graphene oxide (GO) nanoplatelets reinforced poly(ε-caprolactone) (PCL) were investigated. The results showed that the presence of 0.3 wt% GO increased the tensile strength, modulus and energy at break of the PCL membrane by 95%, 66% and 416%, respectively, while improving its bioactivity during biomineralization and maintaining the high porosity of over 94%. The mechanical enhancements were ascribed to the change in the fiber morphology and the reinforcing effect of GO on PCL nanofibers, whereas the improvements on the bioactivity stemmed from the anionic functional groups present on the GO surface that nucleated the formation of biominerals. Systematic studies on the PCL/GO nanocomposite films with varying GO concentrations revealed that the reinforcing effect of GO on PCL was due to the strong interfacial interactions between the two phases characterized by Fourier transform infrared spectroscopy, the good dispersion of GO in the matrix and the intrinsic properties of GO nanoplatelets. The strong and bioactive PCL/GO nanofibrous membranes with a high porosity have great potential for biomedical applications.

Supported phospholipid membrane patches stabilized on graphene surfaces have shown potential in sensor device functionalization, including biosensors and biocatalysis. Lipid dip-pen nanolithography (L-DPN) is a method useful in generating supported membrane structures that maintain lipid functionality, such as exhibiting specific interactions with protein molecules. Here, we have integrated L-DPN, atomic force microscopy, and coarse-grained molecular dynamics simulation methods to characterize the molecular properties of supported lipid membranes (SLMs) on graphene and graphene oxide supports. We observed substantial differences in the topologies of the stabilized lipid structures depending on the nature of the surface (polar graphene oxide vs nonpolar graphene). Furthermore, the addition of water to SLM systems resulted in large-scale reorganization of the lipid structures, with measurable effects on lipid lateral mobility within the supported membranes. We also observed reduced lipid ordering within the supported structures relative to free-standing lipid bilayers, attributed to the strong hydrophobic interactions between the lipids and support. Together, our results provide insight into the molecular effects of graphene and graphene oxide surfaces on lipid bilayer membranes. This will be important in the design of these surfaces for applications such as biosensor devices.

Chương 5. Kế toán các nguồn kinh phí Chương 5. KẾ TOÁN CÁC NGUỒN KINH PHÍ Mục tiêu chung: • Giúp cho người học nhận thức đối tượng kế toán là các loại kinh phí như nguồn vốn kinh doanh, kinh phí hoạt động sự nghiệp, kinh phí dự án, kinh phí theo đơn đặt hàng của Nhà nước, kinh phí đầu tư xây dựng cơ bản, quĩ cơ quan, kinh phí đã hình thành TSCĐ và các khoản chênh lệch thu chi chưa xử lý, chênh lệch đánh giá lại tài sản, chênh lệch tỷ giá hối đoái trong các đơn vị hành chính sự nghiệp. • Trang bị cho người học phương pháp kế toán các nguồn kinh phí trong các đơn vị hành chính sự nghiệp. 5.1. NỘI DUNG, NGUYÊN TẮC HẠCH TOÁN VÀ NHIỆM VỤ CỦA KẾ TOÁN NGUỒN KINH PHÍ 5.1.1. Nội dung và nguyên tắc hạch toán Nguồn kinh phí và vốn của các đơn vị hành chính sự nghiệp là nguồn tài chính mà các đơn vị được quyền sử dụng để phục vụ cho việc thực hiện nhiệm vụ chính trị, chuyên môn có tính chất HCSN hoặc có tính chất kinh doanh của mình. Như vậy, trong các đơn vị HCSN tất cả các loại kinh phí ngoài vốn đều được tiếp nhận theo nguyên tắc không bồi hoàn trực tiếp. Nguồn kinh phí và vốn của đơn vị HCSN thường gồm có:-Nguồn vốn kinh doanh-Chênh lệch tỷ giá-Chênh lệch đánh giá lại tài sản-Chênh lệch thu, chi chưa xử lý-Quỹ cơ quan-Nguồn kinh phí đầu tư XDCB-Nguồn kinh phí hoạt động-Nguồn kinh phí dự án-Nguồn kinh phí theo đơn đặt hàng của Nhà nước-Nguồn kinh phí đã hình thành TSCĐ Kinh phí các loại trong các đơn vị HCSN thường được hình thành các nguồn chủ yếu sau:-Ngân sách nhà nước hoặc cơ quan quản lý cấp trên cấp theo dự toán được phê duyệt (gọi tắt là Nguồn kinh phí Nhà nước)-Các khoản đóng góp hội phí, đóng góp của các hội viên, thành viên.-Thu sự nghiệp được sử dụng theo quy định và bổ sung từ kết quả của các hoạt động có thu theo chế độ tài chính hiện hành.-Điều chuyển bổ sung từ các quỹ dự trữ tài chính nội bộ.-Các khoản tài trợ của các tổ chức, cá nhân trong và ngoài nước-Vay nợ của Chính phủ-Các khoản kết dư Ngân sách năm trước. Nguồn kinh phí hoạt động là nguồn kinh phí nhằm duy trì và đảm bảo sự hoạt động theo chức năng của các cơ quan, đơn vị hành chính sự nghiệp. Kinh phí hoạt động được hình thành từ: 137