Functionalized iron oxide nanoparticles (IONPs) are of great interest due to wide range applications, especially in nanomedicine. However, they face challenges preventing their further applications ...such as rapid agglomeration, oxidation, etc. Appropriate surface modification of IONPs can conquer these barriers with improved physicochemical properties. This review summarizes recent advances in the surface modification of IONPs with small organic molecules, polymers and inorganic materials. The preparation methods, mechanisms and applications of surface-modified IONPs with different materials are discussed. Finally, the technical barriers of IONPs and their limitations in practical applications are pointed out, and the development trends and prospects are discussed.
In the recent era, the nanofluid's transportation due to the Jeffrey-Hemal flow phenomenon (i.e., carrying fluid through a converging/diverging channel) has significant applications in numerous ...engineering and science technologies. Therefore, multi-disciplinary evolution and research motivated us to present current attempt. The aim of this attempt is to present Jeffrey-Hamel mechanism of the nanofluid through non-parallel channel under thermally balance non-Darcy permeable medium impacts. The nanomaterial is represented using the Buongiorno nanofluid model. The investigation also includes zero mass flux impacts as well as variable rheological fluid properties. The influences of temperature jump are also encountered in the current analysis. The governing flow expressions under the Jeffrey-Hemal analysis are made dimensionless utilizing the similarity variables. The dimensionless equations are then solved using the analytical scheme (homotopy method) and the obtained series solutions are convergent. The influences of the involved parameters on concerned profiles are investigated through graphs. Force of drag, Nusselt and Sherwood numbers are elaborated graphically. In this analysis, intensification in Prandtl number enhances the heat transfer rate whereas decrement is seen in heat transfer rate for larger thermal slip parameter. Further, mass diffusivity parameter adversely affects the mass transfer rate. The current analysis incorporates numerous industrial and technological processes including transportation, material synthesis, microfluidics, high-power Xrays, biomedical, solid-state lighting, microelectronics, scientific measurement, medicine, molten polymers extrusion via converging dies, cold drawing operation related to polymer industry etc.
The problem of attitude tracking in the presence of disturbances is addressed by combining inverse optimality and
disturbance attenuation. Conditions are provided which ensure that an inverse optimal ...nonlinear
attitude control problem is solved and a meaningful cost function is minimised. The approach results in a PD-type attitude control law on the Special Orthogonal Group
which guarantees that, for almost all initial conditions, the energy gain from an exogenous disturbance to a specified error signal respects a given upper bound. For numerical simulations, a satellite attitude tracking problem from literature is considered. The controller gains are tuned using a decoupled linearised single-axis model and the structured
control synthesis method. Results indicate that the proposed controller has good tracking and disturbance attenuation capability. In particular, for the problem under consideration, the
inverse optimal
controller is seen to have better transient performance than its continuous-time quaternion counterpart. Moreover, for initial errors up to
radians, it has comparable performance to the shortest-path quaternion PD controller.
•High throughput and high efficiency chiral separations are reviewed.•The date range covers 21st century advances in chiral separations.•High throughput screening strategies are reviewed.•New high ...efficiency column technologies are discussed.•Instrumental considerations that should be taken into account are addressed.
The need for improved liquid chromatographic chiral separations has led to the advancement of chiral screening techniques as well as the development of new, high efficiency chiral separation methods and stationary phases. This review covers these advancements, which primarily occurred over the last 15 years. High throughput techniques include multi-column screening units, multiple injection sequences, and fast gradient SFC screening. New separation methods and column technologies that aim at high efficiency chiral separations include the use of achiral UHPLC (i.e. sub-2μm) columns for separating derivatized chiral analytes or using chiral additives in the run buffer, UHPLC chiral stationary phases, and superficially porous particle based chiral stationary phases. Finally, the enhancement of chiral separations through these new technologies requires that certain instrumental considerations be made. Future directions in continuing to improve chiral separations are also discussed.
An emerging electronic material as one of transition metal dichalcogenides (TMDCs), tungsten disulfide (WS2) can be exfoliated as an atomically thin layer and can compensate for the drawback of ...graphene originating from a gapless band structure. A direct bandgap, which is obtainable in single-layer WS2, is an attractive characteristic for developing optoelectronic devices, as well as field-effect transistors. However, its relatively low mobility and electrical characteristics susceptible to environments remain obstacles for the use of device materials. Here, we demonstrate remarkable improvement in the electrical characteristics of single-layer WS2 field-effect transistor (SL-WS2 FET) using chemical vapor deposition (CVD)-grown hexagonal BN (h-BN). SL-WS2 FET sandwiched between CVD-grown h-BN films shows unprecedented high mobility of 214 cm(2)/Vs at room temperature. The mobility of a SL-WS2 FET has been found to be 486 cm(2)/Vs at 5 K. The ON/OFF ratio of output current is ~10(7) at room temperature. Apart from an ideal substrate for WS2 FET, CVD-grown h-BN film also provides a protection layer against unwanted influence by gas environments. The h-BN/SL-WS2/h-BN sandwich structure offers a way to develop high-quality durable single-layer TMDCs electronic devices.
•Synthesis of flower-like MoS2-based hybrid photocatalyst and electronic structure engineering•The flower like MoS2 is coupled with conduction-band edge matched SnO2 and decorated•with Ag ...nanoparticles.•Photocatalytic activities was measured for CO2 conversion and pollutants degradation.
With recently increasing environmental issues and foreseeable energy crisis, it is desirable to design cheap, efficient, and visible-light responsive nano-photocatalyst for CO2 conversion and pollutant degradation. Herein, we report a flower-like of MoS2-based hybrid photocatalyst with high efficiency through nanostructure and electronic structure engineering. Nanostructure control is used to fabricate MoS2 in to flower-like nanosheets (NSs) with large surface active area. Then MoS2 is coupled with conduction-band edge matched tin dioxide (SnO2) and decorated with Ag nanoparticles for suitable work function to create a unique cascade band alignment electronic structure to facilitate photoexcited charge transfer. It is shown that the amount-optimized nanocomposite of SnO2/Ag/MoS2 exhibits exceptional visible-light photocatalytic activities for conversion of carbon dioxide (CO2) to methane (CH4), approximately one order of magnitude enhancement than original MoS2 with the apparent quantum efficiency 2.38% at 420 nm. Similarly, the optimized sample also shows high activities for 2,4-diclorophenol, Methylene-Blue, Rhodamine-B and Methyl-Orange degradation as compared to pure MoS2. It is clearly demonstrated through combination of hydroxyl radical evaluation, photoelectrochemical and electrochemical impedance, that the enhanced photoactivities are attributed to the increased specific surface area, optimized band alignment for charge transfer and suppressed recombination. Our current work provides feasible routes for further research.
This attempt addresses the simultaneous characteristics of thermal radiation and melting heat transfer effects in stagnation point flow of carbon nanotubes due to a stretching cylinder. Velocity slip ...phenomenon is also retained. Two types of carbon nanotubes (single and multi-walls) are homogeneously dispersed in the base fluid (water). The governing physical problem is modeled and converted into set of coupled nonlinear ODE’s utilizing transformations. Resulting problems are computed numerically by fifth order Range–Kutta Fehlberg scheme. The physical characteristics of various variables on the velocity and thermal fields are examined. Numerical data for skin friction and Nusselt number have been prepared and deliberated. It is explored that velocity is increased for larger ratio of rate constants. The increasing values of melting parameter correspond to higher velocity and less temperature. Besides this the accuracy of present results is also affirmed. It is noted that the computed numerical solutions have excellent match with previous published materials in a limiting sense.
•Thermally radiative stagnation point flow due to stretched cylinder in presence of velocity slip is investigated.•Both single and multi wall carbon nanotubes are considered.•Melting phenomenon characterizes the heat transfer process.•Range–Kutta Fehlberg scheme is utilized for computations of nonlinear systems.
Analytical and preparative separation techniques, although perceived as less detrimental compared to industrial manufacturing processes, present a substantial concealed environmental threat. Green ...analytical chemistry has seen major advances in the past five years in terms of proposing metrics for measuring the greenness of separation methods. One such comprehensive measure is the Analytical Method Greenness Score (AMGS), which was used to benchmark current enantiomeric separation methods in the literature. In this work, we propose pragmatic and mathematical strategies to minimize AMGSs in high-performance liquid chromatographic enantioseparations. A case study of more than 456 chromatograms from the enantiomers of 38 proteo- and non-proteogenic amino acids was generated and assessed. A sustainable method of generating carbonated water-based eluents was introduced, and the H
2
CO
3
* additive was shown to improve the chromatographic figures of merit (resolution and efficiency) while lowering the AMGS. We show that narrow diameter columns with superficially porous particles reduced the solvent waste 12-fold compared to traditional analyses. The AMGS formula was modified to incorporate the "cycle time" of the chromatograph, which provides a more accurate picture of solvent waste generation in high throughput chemical analyses. Using the principles of mathematical optimization, the AMGS was minimized with respect to flow rate to show that the ideal separation speed differs depending on the solvent composition. The AMGS reached values as low as 1.2 for ultrafast (<15 s) amino acid chiral separations, where 79% was contributed by the cycle time. This AMGS minimization adds a new optimization problem to future method development, with widespread implications for drug development research and other production fields reliant on separation sciences.
Analytical and preparative separation techniques, although perceived as less detrimental compared to industrial manufacturing processes, present a substantial concealed environmental threat.
New stationary phases are continuously developed for achieving higher efficiencies and unique selectivities. The performance of any new phase can only be assessed when the columns are effectively ...packed under high pressure to achieve a stable bed. The science of packing columns with stationary phases is one of the most crucial steps to achieve consistent and reproducible high-resolution separations. A poorly packed column can produce non-Gaussian peak shapes and lower detection sensitivities. Given the ever larger number of stationary phases, it is impossible to arrive at a single successful approach. The column packing process can be treated as science whose unified principles remain true regardless of the stationary phase chemistry. Phenomenologically, the column packing process can be considered as a constant pressure or constant flow high-pressure filtration of a suspension inside a column with a frit at the end. This process is dependent on the non-Newtonian suspension rheology of the slurry in which the particles are dispersed. This perspective lays out the basic principles and presents examples for researchers engaged in stationary phase development. This perspective provides an extensive set of slurry solvents, hardware designs, and a flowchart, a logical approach to optimal column packing, thus eliminating the trial and error approach commonly practiced today. In general, nonaggregating but high slurry concentrations of stationary phases tend to produce well packed analytical columns with small particles. Conversely, C18 packed capillary columns are best packed using agglomerating solvents.
In this article, the behavior of MHD hybrid nanofluid passing through a stretching sheet is examined. The current consideration also flashes the thermal radiation effects on hybrid nanofluid. Hybrid ...nanofluid is the new class of nanofluids which is very famous nowadays. Graphene oxide and silver as nanoparticles and water as a host fluid are considered. We presume low magnetic Reynolds number, and the magnetic field is enforced in the vertical direction. Features of heat transfer are assessed first time by exploiting the graphene oxide-Ag/H
2
O hybrid nanofluid with thermal radiation. By utilizing suitable transformations, governing equations are incorporated for heat and flow. Corresponding ordinary differential equations are solved by the homotopic procedure. The disparity of unlike parameters on flow and heat is revealed graphically. Resistive force is incorporated mathematically. The nanoparticle volume fraction of graphene oxide enhances both the velocity and temperature of the fluid. It is noticed that the thermal stratification parameter decays the temperature field while the opposite trend is observed for the radiation parameter. The heat transfer rate is disclosed by 3D graphs. It is observed that the temperature profile diminishes for enhanced thermal stratification parameters. Also, the heat transfer rate diminishes for radiation number and stratification parameter.
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