Graphene-Based Sorbents for Multipollutants Removal in Water: A Review of Recent Progress

The coexistence of multiple toxic water pollutants (heavy metals, organic dyes, oils, and organic solvents) limits the sustainable supply of clean water worldwide and urges the development of advanced water purification technology that can remove these contaminants simultaneously. Since its discovery, graphene-based materials have gained substantial attention toward development of new-generation sorbents for water purification. Despite several recently published reviews on water purification technology using graphene and its derivatives, there is still a gap in the review considering multiple water-pollutant remediation using advanced graphene materials. In this review, in the first instance, a comparative structure–function–performance relationship between graphene-based sorbents and the multipollutants in water is established. A fundamental correlation is made between the sorption performance for diverse pollutants in water with the more specific adsorption properties (surface area, pore size, type of functional groups, C/O, C/N, and C/S atomic ratio) of advanced graphene sorbents. Second, the underlying interaction mechanisms are uncovered between different classes of water pollutants using single graphene-based sorbents. Third, the rational design of advanced multipollutant sorbents based on graphene is elaborated. The reality, challenges, and opportunities of advanced graphene materials as emerging sorbents for sustainable water purification technology are finally presented in the last section.     

Protonation of Nucleobases in Single‐ and Double‐Stranded DNA

Single‐stranded model oligodeoxyribonucleotides, each containing a single protonatable base—cytosine, adenine, guanine, or 5‐methylcytosine—centrally located in a background of non‐protonatable thymine residues, were acid‐titrated in aqueous solution, with UV monitoring. The basicity of the central base was shown to depend on the type of the central base and its nearest neighbours and to rise with increasing oligonucleotide length and decreasing ionic strength of the solution. More complex model oligonucleotides, each containing a centrally located 5‐methylcytosine base, were comparatively evaluated in single‐stranded and double‐stranded form, by UV spectroscopy and high‐field NMR. The N³ protonation of the 5‐methylcytosine moiety in the double‐stranded case occurred at much lower pH, at which the duplex was already experiencing general dissociation, than in the single‐stranded case. The central guanine:5‐methylcytosine base pair remained intact up to this point, possibly due to an unusual alternative protonation on O² of the 5‐methylcytosine moiety, already taking place at neutral or weakly basic pH, as indicated by UV spectroscopy, thus suggesting that 5‐methylcytosine sites in double‐stranded DNA might be protonated to a significant extent under physiological conditions.     

An energy efficiency grading system for mobile applications based on usage patterns

In selecting a mobile application, the absence of the power-related information obstructs the user from making the smart decision. To handle this problem, we propose an energy efficiency grading system for mobile applications. The system measures the power consumption of the applications over the test scenarios where the representative usage patterns of users are considered. After that, the system rates the grades of the applications based on the measured power consumption. Therefore, the user can refer to the appropriate energy efficiency grade of the applications by taking into account own usage pattern. Moreover, the proposed system provides a label for the energy efficiency grades, so the user can intuitively understand the power-related information of the applications. The evaluation of the system shows that it can help the user to select a better application among interchangeable applications.     

Numerical model of a nanoelectric line from a graphene component

The paper discusses the numerical model and provides the analysis of a graphene coaxial line suitable for sub-micron sensors and other applications utilized especially in biomedicine. In the wider perspective, the areas and disciplines targeted by the presented concept include biology, medicine, prosthetics, and microscopic solutions for modern actuators or SMART elements. The proposed hybrid numerical model is based on analyzing a periodic structure with high repeatability, and it exploits the conception of a graphene polymer having its basic dimension in nanometers. The model simulates both the transient analysis and the actual random motion of an electric charge in the structure as the source of spurious signals, and it also considers the harmonic signal propagation along the structure; moreover, the model examines whether and how the signal will be distorted at the beginning of the modeled electric line, given the various termination versions. The results of the analysis are necessary for further use of the designed sensing devices based on graphene structures.     

Graphene Oxide‐Based Lamella Network for Enhanced Sound Absorption

Noise is an environmental pollutant with recognized impacts on the psychological and physiological health of humans. Many porous materials are often limited by low sound absorption over a broad frequency range, delicacy, excessive weight and thickness, poor moisture insulation, high temperature instability, and lack of readiness for high volume commercialization. Herein, an efficient and robust lamella‐structure is reported as an acoustic absorber based on self‐assembled interconnected graphene oxide (GO) sheets supported by a grill‐shaped melamine skeleton. The fabricated lamella structure exhibits ≈60.3% enhancement over a broad absorption band between 128 and 4000 Hz (≈100% at lower frequencies) compared to the melamine foam. The enhanced acoustic absorption is identified to be structure dependent regardless of the density. The sound dissipation in the open‐celled structure is due to the viscous and thermal losses, whereas it is predominantly tortuosity in wave propagation and enhanced surface area for the GO‐based lamella. In addition to the enhanced acoustic absorption and mechanical robustness, the lamella provides superior structural functionality over many conventional sound absorbers including, moisture/mist insulation and fire retardancy. The fabrication of this new sound absorber is inexpensive, scalable and can be adapted for extensive applications in commercial, residential, and industrial building structures.     

Numerical simulation of the system “fixture–workpiece” for lever machining

In this article, the new configuration of fixture was proposed for ensuring the sufficient tool accessibility, which allows carrying out multiaxis machining of levers in one setup. The research based on numerical simulation was confirmed that the proposed fixture corresponds to all the accuracy parameters. Workpieces from steel, cast iron and aluminium alloy were investigated within the simulation. The values of displacements and stresses occurring during machining are less for proposed fixture in comparison with the existing fixtures that was confirmed by the deflected mode analysis. The modal analysis proved that the proposed fixture has much higher value of eigenfrequency than the other fixtures. To optimize the machining, the dependences for displacements and stresses on the cutting depth were determined. Oscillations of the system “fixture–workpiece” during machining were investigated for various manufacturing steps of levers machining of the fixtures from different fixture systems. The results of harmonic analysis showed that the dynamic stiffness of the proposed fixture was higher than that for the dedicated and modular fixtures. The oscillation amplitudes in the places of machined surfaces in the proposed fixture do not exceed the tolerance requirements for lever manufacturing.     

Principal tests and verification of a resonance-based solar harvester utilizing micro/nano technology

The authors propose an analysis of a model solar element based on the principle of a resonance system facilitating the transformation of the external form of incident energy into electrical energy. A similar principle provides the basis for harvesters designed to operate at lower frequencies, (Jirku et al. Microsyst Technol 16:677–690, 2010; Wen et al. In: Proceedings of World Automation Congress, Maui, 2000). In these harvesters, the efficiency of the energy form transformation can be controlled from the frequency spectrum of an external source.