Two-dimensional assembly of nanoparticles grafted with charged-end-group polymers

{\bf Hypothesis:} Introducing charged terminal groups to polymers that graft nanoparticles enables Coulombic control over their assembly by tuning pH and salinity of aqueous suspensions. {\bf Experiments:} Gold nanoparticles (AuNPs) are grafted with poly(ethylene glycol) (PEG) terminated with CH3 (charge neutral), COOH (negatively charged), or NH2 (positively charged) groups. The nanoparticles are characterized using dynamic light scattering, {\zeta}-potential, and thermal gravimetric analysis. Liquid surface X-ray reflectivity (XR) and grazing incidence small-angle X-ray scattering (GISAXS) techniques are employed to determine the density profile and in-plane structure of the AuNP assembly across and on the aqueous surface. {\bf Findings:} The assembly of PEG-AuNPs at the liquid/vapor interface can be tuned by adjusting pH or salinity, particularly for COOH terminals. However, the effect is less pronounced for NH2 terminals. These distinct assembly behaviors are attributed to the overall charge of PEG-AuNPs and the conformation of PEG. The COOH-PEG corona is the most compact, resulting in smaller superlattice constants. The net charge per particle depends not only on the PEG terminal groups but also on the cation sequestration of PEG and the intrinsic negative charge of the AuNP surface. NH2-PEG, due to its closeness to overall charge neutrality and the presence of hydrogen bonding, enables the assembly of NH2-PEG-AuNPs more readily.Comment: Submitted to the Journal of Colloid and Interface Science, and it's under review currentl

Assessment of Open-Access Institutional Repositories of China on Directory of Open Access Repositories (OpenDOAR)

Present-day institutional repositories play a vital role in promoting higher education systems and research and development. Individual organisations showcase their intellectual works using the Open access institutional repository platform. The present study focuses on the current status of Chinese Open Access Institutional Repositories. Data were collected from the global Directory of Open Access Institutional Repositories (DOAR) website. And collected data have been analysed and represented in graphical and tabular formats to clearly understand the study results. The Authors also assessed the Chinese’ contribution to various parameters such as Year wise growth pattern, Nature of Institutional Repository, disciplines, Content, software and language used to build institutional repository

3 Bit Synchronous Up Counter

Electronic counters are of two types: Asynchronous and Synchronous. Here we will work on Synchronous counter. Synchronous counters use a common clock and logic between the flip-flops to encode the count sequence. Asynchronous counters are simpler because they do not require logic gates, but any latency will scale linearly with respect to the number of bits. Synchronous architecture is preferable. If the application is not sensitive to false errors produced by latency, however, an asynchronous counter alone or with overclocking (in the event that cumulative latency is greater than the cycle time) may be feasible. Alternatively, filters, such as a strobing circuit, can be used to remove erroneous outputs caused by latency from the output

Effect of different smoking processes on the nutritional and polycyclic aromatic hydrocarbons composition of smoked Clarias gariepinus and Cyprinus carpio

The effect of different smoking processes on the nutritional value and polycyclic aromatic hydrocarbon (PAHs) content of Clarias gariepinus and Cyprinus carpio has been assessed in this study. After smoking processes, the finish products were analyzed to determine the nutritional quality and the PAHs content. Different smoking processes significantly decreased (p < 0.05) lipids content of fish. The smoked fish with unfiltered Psidium guajava has revealed higher lipid contents of 14.17 ± 0.15% and 14.96 ± 0.05%, respectively, for SNE GSF and SE GSF. A significant reduction (p < 0.05) in protein content (% DM) has been observed in the two fish's species submitted to smoking processes. We found that evisceration of fish before smoking leads to increase the level of naphthalene, acenaphthene, and benzo (a) pyrene in smoked C. gariepinus and C. carpio. The use of metallic filter in the smoking of noneviscerated fish leads to the significant reduction (p < 0.05) of the PAHs content in smoked fishes. Higher levels of PAH such as naphthalene and acenaphthene with values of 1,451.54 ± 49.58 and 709.91 ± 8.12 ng/kg were found in smoked C. carpio and 1,841.1 ± 11.41 and 809.91 ± 1.10 ng/kg were found in smoked C. gariepinus obtained in the case of traditional smoking. The PAHs content was higher in fish smoked using traditional ovens. Therefore, the quality of smoked fish was improved using a metallic filter during different smoking processes

Assembling PNIPAM-capped Gold Nanoparticles in Aqueous Solutions

Employing small-angle X-ray scattering (SAXS), we explore the conditions under which assembly of gold nanoparticles (AuNPs) grafted with the thermosensitive polymer poly(N-isopropylacrylamide) (PNIPAM) emerges. We find that short-range order assembly emerges by combining the addition of electrolytes or polyelectrolytes with raising the temperature of the suspensions above the lower-critical solution temperature (LCST) of PNIPAM. Our results show that the longer the PNIPAM chain is, the better organization in the assembled clusters. Interestingly, without added electrolytes, there is no evidence of AuNPs assembly as a function of temperature, although untethered PNIPAM is known to undergo a coil-to-globule transition above its LCST. This study demonstrates another approach to assembling potential thermosensitive nanostructures for devices by leveraging the unique properties of PNIPAM.This is a manuscript of an article published as Nayak, Binay P., Hyeong Jin Kim, Srikanth Nayak, Wenjie Wang, Wei Bu, Surya K. Mallapragada, and David Vaknin. "Assembling PNIPAM-Capped Gold Nanoparticles in Aqueous Solutions." ACS Macro Letters 12 (2023): 1659-1664. doi: https://doi.org/10.1021/acsmacrolett.3c00617. Posted with Permission. Copyright 2023 American Chemical Society

Tuning Self-Assembly of Gold Nanoparticles Grafted with Charged Polymers by Varying Temperature and Electrolytes

We report on the assembly of gold nanoparticles (AuNPs, 5 and 10 nm core diameters) grafted with poly(ethylene glycol) (PEG) terminated with either positively (−NH2) or negatively charged (−COOH) end groups. We employ synchrotron-based small-angle X-ray scattering (SAXS) techniques to investigate the effect of electrolytes and temperature on the assembly and crystallization behavior of these grafted AuNPs. Our studies reveal that −NH2-grafted AuNPs spontaneously assemble into a layered hexagonal structure that deteriorates upon adding K2CO3 to the suspension. The hexagonal structure recovers after heating the same suspension above 60 °C. On the other hand, the COOH-terminated AuNPs remain dispersed in the suspensions and assemble and crystallize into a face-centered cubic structure only in the presence of K2CO3 at temperatures above 60 °C. Varying the pH of the −NH2-terminated AuNP suspensions induces short-range order (SRO) structures with a single characteristic length scale that shrinks upon heating. Similarly, SRO for the −COOH-terminated AuNP is realized only by lowering the pH. This study demonstrates the use of electrolytes and temperature on the surface charge of grafted AuNPs as knobs to tune self-assembly and crystallization.This is a manuscript of an article published as Nayak, Binay P., Hyeong Jin Kim, Alex Travesset, David Vaknin, Surya K. Mallapragada, and Wenjie Wang. "Tuning Self-Assembly of Gold Nanoparticles Grafted with Charged Polymers by Varying Temperature and Electrolytes." The Journal of Physical Chemistry C (2023). doi: https://doi.org/10.1021/acs.jpcc.3c05722. Posted with Permission. Copyright © 2023 American Chemical Society

Inferiorly Based Fasciocutaneous Flaps In Leg - Our Experience

Inferiorly based fasciocutaneous flaps have emerged as an ideal material for the defects in lower leg and foot. We have used this flap in eleven patients since 1986 through 1989. The flaps have proved to be reliable over difficult areas of ankle and foot, either multistaged distant flaps or free flaps are the other alternative. Here inferiorly based fasciocutaneous flaps offer a much simpler and safer answer

Ionic-Like Superlattices by Charged Nanoparticles

Controlling interactions among nanoparticles is paramount to achieving assemblies vital to technologies seeking to exploit their novel collective properties. Although various techniques have been advanced, robust ones are necessary for upscaling nanoparticle assembly and crystallization. Here, we show that by grafting gold nanoparticles (AuNPs) with charge-end-group-thiolated polyethylene-glycol, we control the charge of each AuNP. Such control facilitates formation of various two-dimensional structures of oppositely charged binary constituents at vapor/liquid interfaces. Using surface-sensitive synchrotron X-ray diffraction techniques, we establish the formation of distinct checker-board square lattice structures at a range of pH and molar ratios of the constituents. By regulating pH the superlattices can transform from square to the hexagonal lattice or vice versa and, to a single component superstructure at the interface. Our recipe for the control of charges and their consequent interactions among nanoparticles can be readily exploited in the assembly of devices in two and three dimensions.This pre-print is published as Wang, W., Nayak, B., Zhang, H., Ocko, B., Bu, W., Travesset, A., Vaknin, D., Mallapragada, S.,Ionic-Like Superlattices by Charged Nanoparticles. https://doi.org/10.21203/rs.3.rs-3112594/v1. Posted with permission. This work is licensed under a CC BY 4.0 License<br

Two-dimensional assembly of nanoparticles grafted with charged-end-group polymers

Hypothesis: Introducing charged terminal groups to polymers that graft nanoparticles enables Coulombic control over their assembly by tuning pH and salinity of aqueous suspensions. Experiments: Gold nanoparticles (AuNPs) are grafted with poly (ethylene glycol) (PEG) terminated with CH3 (charge neutral), COOH (negatively charged) or NH2 group (positively charged), and characterized with dynamic light scattering, ζ-potential, and thermal gravimetric analysis. Liquid surface X-ray reflectivity (XR) and grazing incidence small-angle X-ray scattering (GISAXS) are used to determine the density profile and in-plane structure of the AuNP assembly across and on the aqueous surface. Findings: Assembly of PEG-AuNPs at the liquid/ vapor interface is tunable by adjusting pH or salinity for COOH but less for NH2 terminals. The distinct assembly behaviors are attributed to the overall charge of PEG-AuNPs as well as PEG conformation. COOH-PEG corona is the most compact and leads to smaller superlattice constants. The net charge per particle depends not only on the PEG terminal groups, but also on the cation sequestration of PEG and the intrinsic negative charge of AuNP surface. The closeness to overall charge neutrality, and the hydrogen bonding in play, brought by NH2-PEG, enables NH2-PEG-AuNPs assembly readily.This is a pre-print of the article Kim, Hyeong Jin, Binay P. Nayak, Honghu Zhang, Benjamin M. Ocko, Alex Travesset, David Vaknin, Surya K. Mallapragada, and Wenjie Wang. "Two-dimensional assembly of nanoparticles grafted with charged-end-group polymers." arXiv preprint arXiv:2305.16512 (2023). DOI: 10.48550/arXiv.2305.16512. Copyright 2023 The Authors. Posted with permission