Sheet Surface Research Articles

Thermal characterization of heat source (sink) on hybridized (Cu–Ag/EG) nanofluid flow via solid stretchable sheet

Abstract The goal of this research is to consider the thermal impact on varied convection flow in hybrid nanofluids with heat generation over a two-dimensional heated flat around a stretchable sheet. The flow is considered steady and incompressible while the stretchable sheet is assumed an impermeable. Two distinctive nano-level particles are considered, namely copper (Cu) and silver (Ag) with ethylene glycol base fluid. The boundary layer was generated on a stretchable sheet surface by mixed convection flow in hybrid nanofluids. Ideally, the sink and source are thermal reservoirs of internal thermal capacities. This means you can extract or reject heat from them without changing their temperature. To make a study of thermodynamic systems like heat engines and refrigerator systems, the governing equations were solved numerically with Keller-box methodology depending on the implicit finite-difference technique. Research findings were worked with the parameters of mixed convection, Prandtl number, nanoparticle volume fraction, through various non-dimensional parameters, and heat generation. Especially for thermal generation enhancement, the fluidity and thermal dispersal get elevated. Even though the flowing behavior and the thermal dispersal of hybridity fluids with the combinations of Cu and Ag nanoparticles were similar, their values are distinct, which reflect in graphical displays. The hybrid nanofluidity gets improved with the volume variation of nanoparticles if the ϕ \phi value is 0.01 ≤ ϕ ≤ 0.05 0.01\le \phi \le 0.05 and if the flow profile value decreases ϕ h {\phi }_{{\rm{h}}} , where 0.01 ≤ ϕ h ≤ 0.05 0.01\le {\phi }_{{\rm{h}}}\le 0.05 as the dispersal of temperature enhances when the nanoparticle nanofluid constraint is improved.

Snowmelt detection in Greenland ice sheet based on AMSR2 89GHz

The snowmelt on the surface of the Greenland ice sheet can show the climate change in the Arctic. In order to obtain high spatial resolution and high precision results for snowmelt detection on the polar ice sheet surface, a method of snowmelt detection based on an Advanced Microwave Scanning Radiometer-2 (AMSR-2) 89GHz channel is presented. Firstly, the stable relationship between the polarization ratio of 89GHz data and 36GHz data under clear and cloudless weather conditions is used to screen out the 89GHz data that is not affected by external factors such as clouds and water vapor. Then, the Nobuyuki Otsu (Otsu) method is used to obtain the freeze-thaw threshold, and the snowmelt detection results of the ice sheet surface are obtained from the unaffected data by cloud conditions. The areas affected by cloud cover are replaced by the snowmelt detection results of the ice sheet surface from the gradient ratio (GR) model based on 19GHz and 37GHz horizontal polarization data. Finally, we get the snowmelt detection results of the Greenland ice sheet surface. To verify the feasibility and rationality of the proposed method, the results are compared with those of the cross-polarized gradient ratio algorithm (XPGR) and the simple physical model algorithm. The snowmelt area obtained by our method is between the XPGR and the simple physical model, and the snowmelt trend of our method and the simple physical model algorithm is closer. Then the results of the three algorithms are compared and analyzed with the temperature data from the automatic weather stations showing that the results obtained by our method are closer to the measurement data.

Contrasting current and future surface melt rates on the ice sheets of Greenland and Antarctica: Lessons from in situ observations and climate models

Surface meltwater production impacts the mass balance of the Greenland and Antarctic ice sheets in several ways, both directly (e.g., through runoff in Greenland) and indirectly (e.g., through cryo-hydrologic warming and frontal melt of marine-terminating glaciers in Greenland and hydrofracturing of ice shelves in Antarctica). Despite its importance, the spatial and temporal patterns in melt rates on both ice sheets are still relatively poorly understood. In this contribution we review and contrast surface melt ‘weather ‘(i.e., short term, intra- and interdiurnal variability) and surface melt ‘climate’ (i.e., longer term, interannual variability and future melt) of both ice sheets. We find that in situ observations using suitably equipped (automatic or staffed) weather stations are invaluable for a complete understanding of the melt process, which represents the complex transport of energy by radiation, turbulence, and molecular conduction between the lower atmosphere, the ice/snow surface, and the subsurface ice/snow layers. We provide example time series of ice sheet melt ‘weather’ for the marginal Greenland ice sheet, where warm and humid air masses tend to increase surface melt rate, and for coastal East Antarctica, where the opposite happens. Apart from process understanding, these in situ observations, which especially in Antarctica are scarce in space and time, are also invaluable to validate, evaluate and calibrate satellite- and model-based estimates of ice sheet surface melt rate. We provide examples of modelled melt maps for both ice sheets, and melt projections for a high-warming, fossil-fuelled development scenario. Although important milestones in melt observations (both in-situ and remotely sensed) and melt models (both global and regional) have recently been reached, we identify multiple outstanding research questions pertaining to current and future ice sheet surface melt rates.

Photodegradation of methylene blue and photoproduction of hydrogen peroxide using magnesium ferrite-titanium dioxide/reduced graphene oxide as a photo-catalyst under visible light

In this study, the ternary composite material of magnesium ferrite-titanium dioxide/reduced graphene oxide (MgFe2O4–TiO2/rGO−MFOTG) was successfully synthesized via a simple hydrothermal method from MgFe2O4–TiO2 (MFOT) and graphene oxide (GO). In particular, the MFOT was fabricated via the co-precipitation method with chitosan as a stabilizer. Meanwhile, the GO was fabricated via the improved Hummers’ method. The characterization results indicated that the MFOT was successfully synthesized and evenly distributed onto the surface of the rGO sheets with the average size ranging from 50 to 100 nm. The prepared material possessed a photodegradation efficiency of 95% for methylene blue under the radiation of UV and visible light for 60 and 70 min, respectively. Besides, the MFOTG exhibited a good catalysis performance for the photoproduction of H2O2 under the illumination of visible light with a productivity of 153.63 ± 2.76 mM/g for 30 min. The aforementioned results confirmed the potential applications of the resulting MFOTG in the environmental treatment and production of H2O2.

Use of bacterial cellulose in paper document restoration

Показана эффективность применения суспензии бактериальной целлюлозы Komagataeibacter (Gluconacetobacter) rhaeticus при реставрации документов на бумаге аэродинамическим способом. Одной из проблем при реставрации документов на бумаге методом восполнения утраченных частей документа является прочность шва между реставрируемым документом и восполняющей частью. Для повышения прочности шва документ по контуру утрат обрабатывают связующими - растворами натриевой соли карбоксиметилцеллюлозы или крахмала. В данном исследовании при реставрации методом аэродинамического формования в качестве связующего была применена суспензия бактериальной целлюлозы Komagataeibacter (Gluconacetobacter) rhaeticus. Для создания прочного соединительного шва между реставрируемым документом и восполняющим волокнистым слоем по контуру утраты документа наносили суспензию бактериальной целлюлозы концентрацией 1,0 ± 0,1% масс., предварительно подготовленную в дезинтеграторе. Применение бактериальной целлюлозы в качестве связующего при аэродинамическом способе реставрации привело к повышению прочности сформованного шва в 1,5-2 раза, по сравнению с применением в качестве связующего растворов крахмала и натриевой соли карбоксиметилцеллюлозы. Искусственное тепло-влажное старение документа после реставрации в течение 12 суток показало, что прочность шва снижается после первых трех суток старения на 32% и затем стабилизируется. Это позволяет прогнозировать хорошую сохранность отреставрированного документа в процессе дальнейшего архивного хранения и пользования. С помощью программного комплекса, предназначенного для исследования памятников письменности путем анализа их цифровых изображений «Vestigium» показано, что рельеф поверхности листов документа после реставрации становится более сглаженным, что снижает возможность глубокого проникновения пыли в структуру листа и повышает срок использования документа. The effectiveness of the bacterial cellulose suspension Komagataeibacter (Gluconacetobacter) rhaeticus in the restoration of documents on paper using the aerodynamic method is shown. One of the problems in document restoration on paper using the method of replacing lost parts of a document is the strength of the seam between the document to be restored and the replacing part. To increase the strength of the seam the document is treated with binders - solutions of sodium salt of carboxymethylcellulose or starch on the contour of the loss. In this study, a suspension of bacterial cellulose Komagataeibacter (Gluconacetobacter) rhaeticus was used as a binder for the restoration by aerodynamic molding. In order to create a strong bonding seam between the restored document and the replenishing fibrous layer, a suspension of bacterial cellulose with a concentration of 1.0 ± 0.1 wt. %, previously prepared in a disintegrator, was applied along the contour of the lost document. The use of bacterial cellulose as a binder in the aerodynamic method of restoration led to an increase in the strength of the formed seam by 1.5-2.0 times compared to the use of starch solutions and sodium salt of carboxymethylcellulose as a binder. Artificial heat-moist aging of the document after restoration for 12 days showed that the suture strength decreased after the first three days of aging by 32% and then stabilized. This makes it possible to predict good preservation of the restored document during further archival storage and use. With the help of «Vestigium» software designed to study the monuments of writing by analyzing their digital images, it is shown that the relief of the document sheets surface after restoration becomes smoother, which reduces the possibility of deep penetration of dust into the sheet structure and increases the life of the document.

Tunable lipid-coated nanoporous silver sheet for characterization of protein-membrane interactions by surface-enhanced Raman scattering (SERS)

Membrane environments affect protein structures and functions through protein-membrane interactions in a wide range of important biological processes. To better study the effects from the lipid’s hydrophilic and hydrophobic interaction with protein on different membrane regions, we developed the lipid-coated nanoporous silver sheets to provide tunable supported lipid monolayer/bilayer environments for in situ surface-enhanced Raman vibrational spectroscopy (SERS) characterizations. Under the controllable surface pressure, lipid monolayer/bilayer was coated along the microscopic curved surface of nanoporous silver sheets to serve as a cell membrane mimic as well as a barrier to avoid protein denaturation while empowering the high SERS enhancements from the underlying metallic bases allowing detection sensitivity at low physiological concentrations. Moreover, we fine-tuned the lipid packing density and controlled the orientation of the deposited lipid bilayers and monolayers to directly monitor the protein structures upon interactions with various membrane parts/positions. Our results indicate that lysozyme adopted the α-helical structure in both hydrophilic and hydrophobic interaction with lipid membrane. Interestingly, alpha-synuclein folded into the α-helical structure on the negatively charged lipid heads, whereas the hydrophobic lipid tails induced the β-sheet structural conversion of alpha-synuclein originated from its unstructured monomers. These direct observations on protein hydrophilic and hydrophobic interaction with lipid membrane might provide profound insights into the formation of the β-sheet-containing alpha-synuclein oligomers for further membrane disruptions and amyloid genesis associated with Parkinson’s disease. Hence, with the controllability and tunability of lipid environments, our platform holds great promise for more general applications in investigating the influences from membranes and the correlative structures of proteins under both hydrophilic and hydrophobic effects.Graphical

Simultaneous impact of droplet pairs on solid surfaces

This study investigates the dynamics of the simultaneous impact of two droplets on a dry substrate. We develop a new micro-controlled droplet generator that releases two equally sized water droplets simultaneously on-demand, with no trailing droplets. The impact Weber number, based on impact droplet size and velocity, and the inter-droplet spacing relative to the impact droplet size are varied in the ranges of 54 to 155 and 1.32 to 2.25, respectively, leading to the strong interaction of the spreading lamellae that form a central uprising sheet, which eventually deposits or breaks into tiny droplets. We analyse the impact processes for both deposition and splashing of the uprising sheets. Simultaneous high-speed imaging from two orthogonal views of the droplet impacts quantifies the three-dimensional structure of the sheet morphology, including the temporal evolution of the rim-bounded ‘semilunar’ shape, surface waves, rim corrugations and finger formation, and deposition or splashing of the liquid sheet. The characteristics of the sheet surface waves and the rim instabilities are quantified. Novel scaling is developed for the maximum sheet height, sheet width and thickness, which considers the geometrical constraints and mass balance of the interacting lamellae to describe the temporal evolution of a ‘semilunar’ uprising sheet and is in good agreement with the measurements. The uprising sheet splashing generates larger droplets than those from splashing of single-droplet impacts, and it occurs due to the end-pinching of sheet fingers and at conditions that single-droplet impacts lead only to liquid deposition.

The drainage of glacier and ice sheet surface lakes

Supraglacial lakes play a central role in storing melt water, enhancing surface melt and ultimately in driving ice flow and ice shelf melt through injecting water into the subglacial environment and through facilitating fracturing. Here, we develop a model for the drainage of supraglacial lakes through the dissipation-driven incision of a surface channel. The model consists of the St Venant equations for flow in the channel, fed by an upstream lake reservoir, coupled with an equation for the evolution of channel elevation due to advection, uplift and downward melting. After reduction to a ‘stream power’-type hyperbolic model, we show that lake drainage occurs above a critical rate of water supply to the lake due to the backward migration of a shock that incises the lake seal. The critical water supply rate depends on advection velocity and uplift (or more precisely, drawdown downstream of the lake) as well as model parameters such as channel wall roughness and the parameters defining the relationship between channel cross-section and wetted perimeter. Once lake drainage does occur, it can either continue until the lake is empty, or terminate early, leading to oscillatory cycles of lake filling and draining, with the latter favoured by large lake volumes and relatively small water supply rates.

LiFePO4/rGO composite prepared from the leaching liquor of jarosite residue as a cathode material for lithium-ion batteries

The effective utilization of jarosite residue is of great significance for environmental protection and alleviates the pressure on resources. Herein, a LiFePO4/rGO composite is synthesized by selective precipitation and carbothermal reduction method using the leaching liquor of jarosite residue as the Fe source. In this composite, LiFePO4 nanoparticles are uniformly anchored on the surface of rGO sheets. As a cathode material for lithium-ion batteries (LIBs), the LiFePO4/rGO composite exhibits outstanding cycling stability (106.8 mA h g−1 after 1000 cycles at 1 C), excellent rate capability (91.5 mA h g−1 at 10 C), and fast kinetics. Furthermore, the LiFePO4/rGO composite still shows a good lithium storage property (76.9 mA h g−1 after 200 cycles at 1 C) in a LiFePO4/rGO//graphite full cell. The present work realizes the high-value utilization of the Fe resources in jarosite residue and the low-cost preparation of LiFePO4 cathode material for LIBs.

Constructing Fe2O3 particles uniformly grown on graphene oxide as additives for ethylene vinyl acetate copolymer thermal stability, thermal conductivity and anti‐static performance enhancement

AbstractEthylene‐vinyl acetate copolymer (EVA) has been widely used for packaging materials for decades. However, EVA was highly restricted due to the poor thermal stability and anti‐static performance. For enhancing thermal stability and anti‐static performances, a large number of additives were added to EVA, which seriously prejudice the processability and mechanical properties of the polymer. To address this problem, N‐doped reduced graphene oxide@Fe2O3 (RGF) was constructed as a heat and electronic conduction actor in EVA matrix in this work. As as‐prepared RGF composites shown, Fe2O3 particles well dispersed on the surface of RGO sheets, forming a point‐plane three‐dimensional structure. Therefore, the thermal conductivity and volume resistivity of the EVA composites reached 0.58 W/mK and 1.7 × 1010 ohm∙cm at 1.0 wt.% of RGF addition, which shows 284% folds increasement and 7 orders of magnitude decrement than neat EVA. Moreover, the storage modulus and thermal stability of EVA composites at 180°C were also improved. In sum, all those enhancements were attributed to the Fe2O3 particles well dispersed on RGO sheets, and amino groups from RGF provided mass of hydrogen bonds with EVA chains which provide more sites and path for heat and electronic conduction. In this work, RGF composites and its synthesis strategy show potential promising in the highly effective thermal and electrical exchange materials.

Optimization of response function on hydromagnetic buoyancy-driven rotating flow considering particle diameter and interfacial layer effects: Homotopy and sensitivity analysis

Alumina is one of the modern era and most utilized ceramic materials. One example of an electrical insulating substance is alumina. It has an enhanced temperature, chemical stability and higher thermal conductivity. It is mostly used in medical, industry, household items, military purposes, production of batteries and electrical parts. Therefore, the authors have formulated a mathematical model of the three-dimensional magnetohydrodynamic mixed convective flow of a nanofluid containing Alumina nanoparticles past a stretching surface. Preliminary assumptions bound the nanofluid flow to be rotational, electrically conducting, dissipative, buoyancy driven, thermally heated and convective. An important investigation based on the effects of nanoparticle diameter and nanolayer of the nanofluid makes the novelty of this investigation. The modeled problem is solved with a homotopic approach, which is suitable for the solution of the highly nonlinear differential equations and has quick convergence. The outcomes of the present analysis are shown with the help of Tables and Figures. The outcomes showed that the higher resistive force at the sheet surface caused by the higher solid volume fraction (varies from 1% to 4%), diminishes the primary velocity, while escalates the secondary velocity. Additionally, the greater solid volume fraction (which ranges from 1% to 4%) raises the thermal conductivity of the nanofluid flow, resulting in an increasing conduct in the thermal function. The enhancing nanolayer to base fluid conductivity ratio (which ranges from 1.1 to 65.25), results in an increase in both velocities and thermal functions, gives the nanofluid flow a higher thermal conductivity. Additionally, the local Nusselt number and skin friction increase as a result of the higher thermal conductivity. The primary velocity and temperature are reduced due to the decrease in thermal and momentum boundary layer thicknesses brought on by the rising nanoparticle diameter (which ranges from 1 nm to 50 nm). The rate of heat transfer is significantly achieved at the higher levels of the volume fraction and radiation factor while heat source is at lower level. The friction rate at the surface is dominant at higher level values of magnetic and volume fraction factor and medium level of rotation factor. The transport of heat has highest sentivity at the middle level of thermla radaition and volume fraction of the nanoparticle and low level of heat source, while the highest sensitivity of friction factor is observed at the middle level of thermal rotation and high level nanoparticle volume fraction and magnetic factor.

Comparative Analysis of Movements of Curved Ultrasonic Instruments

The paper presents a theoretical analysis of vibrations of a curvilinear rod in the form of a loop of low rigidity formed from a quarter of a circle with a constant radius, limited by an angle π/2 < γ < π and two rectilinear rods. It is indicated that in the practice of ultrasonic technology, some types of structures are known in which elastic elements are used as resonators, waveguides, oscillation transformers and instruments for influencing the processed materials. Their use makes it possible to obtain an additional impulse of force in the working area by using the potential energy caused by the action of the elastic properties of such elements. However, insufficient attention has been paid to the theoretical justification of the use of elastic elements in ultrasonic systems. In this regard, the present work is devoted to the theoretical substantiation of the use of an elastic tool made of a thin rod having the shape of a loop. The diagram and calculation of displacements of the free end of a curved rod under the action of forces directed along the longitudinal axis are given in the paper. It is shown that elastic displacements are caused by a curved shape in the form of an arc of a circle of a curved rod. For comparison, calculation schemes of two types of curved rod with an attached rod are given. In the first case, the free ends of the rectilinear rods, directed vertically downwards, make elastic movements along two coordinates. In the second case, the ends of rectilinear rods directed at a certain angle to the vertical axis and converging at the bottom point due to the symmetry of their location, make vertical movements only along one coordinate. The considered shape of the curved rod can be successfully used as a tool for performing technological tasks in the ultrasonic method of processing holes in brittle materials, spot welding, etc. Such a scheme, in contrast to the traditional ultrasonic treatment scheme based on the use of rectilinear rods, makes it possible to increase the magnitude of the vibration amplitude of the instrument due to elastic displacements of the curved section of the rod of low rigidity. The proposed form will increase the intensity of tool vibrations and increase process productivity and processing accuracy. The resulting calculation formula shows that the amount of elastic displacements of curved rods is affected by the cross-sectional stiffness and the radius of curvature of the curved part, as well as the angle of inclination of the rectilinear rod. The theoretical calculation is supplemented by a comparative experimental study of the Chladni forms for both schemes obtained on the sheet surface using abrasive particles.

Molecular modeling for sensing of cisplatin drug by graphdiyne: electronic study via DFT.

By utilizing first-principles calculations, we studied the electronic properties of graphdiyne nanosheet (GDY) and its Si-doped counterpart, Si-GDY. Both GDY and Si-GDY sheet surfaces were examined for the drug cisplatin (CP) adsorption using adsorption energy, charge transfer, and changes in electrical conductivity as indicators. Pure GDY has little affinity for CP, according to this study. Only 7.83% of the GDY surface's bandwidth energy changed after CP adsorption. CP on Si-GDY has a gaseous energy value of -18.75kcal/mol and an aqueous energy value of - 49.39kcal/mol. The prescribed medications' water-phase solubility is determined by their solvation energy value. These charges are transferred between CP and the Si-GDY sheet, which is extremely positively charged, and this gives CP the necessary binding energy. After CP adsorption, electrical conductivity of Si-GDY increased by approximately 19.01%.

Integratedin silico–in vitrorational design of oncogenic EGFR-derived specific monoclonal antibody-binding peptide mimotopes

Human epidermal growth factor receptor (EGFR) is strongly associated with malignant proliferation and has been established as an attractive therapeutic target of diverse cancers and used as a significant biomarker for tumor diagnosis. Over the past decades, a variety of monoclonal antibodies (mAbs) have been successfully developed to specifically recognize the third subdomain (TSD) of EGFR extracellular domain. Here, the complex crystal structures of EGFR TSD subdomain with its cognate mAbs were examined and compared systematically, revealing a consistent binding mode shared by these mAbs. The recognition site is located on the [Formula: see text]-sheet surface of TSD ladder architecture, from which several hotspot residues that significantly confer both stability and specificity to the recognition were identified, responsible for about half of the total binding potency of mAbs to TSD subdomain. A number of linear peptide mimotopes were rationally designed to mimic these TSD hotspot residues in different orientations and/or in different head-to-tail manners by using an orthogonal threading-through-strand (OTTS) strategy, which, however, are intrinsically disordered in Free State and thus cannot be maintained in a native hotspot-like conformation. A chemical stapling strategy was employed to constrain the free peptides into a double-stranded conformation by introducing a disulfide bond across two strand arms of the peptide mimotopes. Both empirical scoring and [Formula: see text]fluorescence assay reached an agreement that the stapling can effectively improve the interaction potency of OTTS-designed peptide mimotopes to different mAbs, with binding affinity increase by [Formula: see text]-fold. Conformational analysis revealed that the stapled cyclic peptide mimotopes can spontaneously fold into a double-stranded conformation that well threads through all the hotspot residues on TSD [Formula: see text]-sheet surface and exhibits a consistent binding mode with the TSD hotspot site to mAbs.

A new type of magnetising and magnetic flux leakage inspection system for the non-destructive testing of pit defects on the surface of a steel sheet

A new type of magnetising and magnetic flux leakage (MFL) inspection system is designed, in which an ARM microprocessor-based measuring circuit and a novel magnetising device developed by the authors are combined to detect the magnetic field around a pit defect in a steel sheet. Based on a series of careful detection experiments, the spatial distributions of the three-dimensional (3D) MFL components of some typical artificial defects are described and observation, comparison, feature extraction and analyses are then carried out. The results show that the 3D components of the MFL field produced by the newly proposed magnetising device present some distinctive properties compared to those made by the traditional magnetising device. They involve rich information that exhibits close correlations to the morphology and critical parameters of the pit defects on the near side of the steel sheet, demonstrating the feasibility, effectiveness and reliability of the newly proposed inspection system, as well as laying a good foundation for the testing, evaluation or reconstruction and inversion of the pit defect.

First BISTRO Observations of the Dark Cloud Taurus L1495A-B10: The Role of the Magnetic Field in the Earliest Stages of Low-mass Star Formation

We present BISTRO Survey 850 μm dust emission polarization observations of the L1495A-B10 region of the Taurus molecular cloud, taken at the James Clerk Maxwell Telescope (JCMT). We observe a roughly triangular network of dense filaments. We detect nine of the dense starless cores embedded within these filaments in polarization, finding that the plane-of-sky orientation of the core-scale magnetic field lies roughly perpendicular to the filaments in almost all cases. We also find that the large-scale magnetic field orientation measured by Planck is not correlated with any of the core or filament structures, except in the case of the lowest-density core. We propose a scenario for early prestellar evolution that is both an extension to, and consistent with, previous models, introducing an additional evolutionary transitional stage between field-dominated and matter-dominated evolution, observed here for the first time. In this scenario, the cloud collapses first to a sheet-like structure. Uniquely, we appear to be seeing this sheet almost face on. The sheet fragments into filaments, which in turn form cores. However, the material must reach a certain critical density before the evolution changes from being field dominated to being matter dominated. We measure the sheet surface density and the magnetic field strength at that transition for the first time and show consistency with an analytical prediction that had previously gone untested for over 50 yr.

Ternary CoFe2O4/g-C3N4/ZnO heterostructure as an efficient and magnetically separable visible-light photocatalyst: Characterization, dye purification, and mechanism

Recently, hybrid materials have received considerable attention due to the spatial dissociation of photogenerated electron-hole pairs, enabling them to harvest solar light from ultraviolet to visible regions. This study investigates the photocatalytic activity of magnetic CoFe2O4/g-C3N4/ZnO (CF-gCN/ZnO) nanocomposite as a visible-light photocatalyst. CoFe2O4 and ZnO were decorated on the surface of as-prepared g-C3N4 sheets using the precipitation technique. The structural, morphology, optical, and magnetic properties of the photocatalysts were investigated. Rietveld refinement confirmed the hexagonal wurtzite structure with the P63mc space group of ZnO. Diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) measurements showed that the optical properties and the electron-hole behavior of ZnO are affected by g-C3N4 nanosheets. The photocatalytic capability was assessed against methylene blue (MB) dye as a model pollutant under visible light irradiation. Compared to CoFe2O4/ZnO and CoFe2O4/gC3N4 composites, the heterojunction CF-gCN/ZnO photocatalyst achieved a photodegradation efficiency of 89% for degradation of MB after 100 min of irradiation. The formation of heterojunction structures at the interface of g-C3N4 and ZnO leads to improved photocatalytic activity due to the separation of the photo-generated electron-hole pairs. Additionally, the magnetic properties of the CoFe2O4 component provided the separation of the photocatalyst from the solution under an external magnetic field. The present study offers a facile method for designing CoFe2O4/g-C3N4/ZnO nanocomposite as a potential ternary photocatalyst with high efficiency and good separability for environmental remediation applications.

Photochromic cellulose nanofibers-reinforced polyacrylic acid self-healable hydrogel toward dual-mode security authentication stamp

Photochromic inks have displayed various disadvantages such as poor durability, high cost and limited efficiency. The self-healing inks have shown to be more durable and photostable. In order to create an authentication stamp, UV-induced photochromic hydrogel inks with self-healable capabilities were developed. Nanoparticles of rare-earth aluminate (NREA) were synthesized and dispersed in a combination of cellulose nanofibers (CNF) and polyacrylic acid (PAA) to create an organic-inorganic hybrid ink. NREA were produced and analyzed using transmission electron microscope (TEM), revealing diameters of 1–4 nm. CNF were synthesized to act as a nanofiller and dispersing agent to improve the mechanical strength of the polyacrylic acid bulk and to prevent the agglomerates of the NREA. In order to create transparent prints, NREA must be uniformly disseminated in the CNF/PAA hybrid hydrogel ink without clumping. A paper surface was effectively stamped with the photochromic ink, and then the ink was thermofixed. Transparency was achieved by direct stamping of a consistent photochromic layer on the sheet surface, and this film was shown to become green when exposed to ultraviolet light as verified by photoluminescence spectral and CIE Lab analysis. The luminous paper sheets had an emission wavelength at 519 nm when irradiated at 368 nm. Energy-dispersive X-ray (EDX), infrared spectroscopy (FT-IR), X-ray fluorescence and scanning electron microscope (SEM) were utilized to examine the morphology of the stamped sheets. The cellulose nanofibers displayed diameters of 9–17 nm. The printed hydrogel ink displayed highly reversible photochromic emission without fatigue. Mechanical testing of the printed sheets and examination of the rheology of the luminous hydrogel was explored. The current NREA@CNF/PAA hydrogel ink offers a competent method for anticounterfeiting that can be used in a variety of authentication industries.

Roles of Hydrogen, Halogen Bonding and Aromatic Stacking in a Series of Isophthalamides

The synthesis and spectroscopic characterisation of six bis(5-X-pyridine-2-yl)isophthalamides (X = H, F, Br, Cl, I, NO2) are reported, together with five crystal structure analyses (for X = H, F to I). The isophthalamides span a range of conformations as syn/anti (H-DIP; I-DIP), anti/anti- (F-DIP; Br-DIP) and with both present in ratio 2:1 in Cl-DIP. The essentially isostructural F-DIP and Br-DIP molecules (using strong amide…amide interactions) aggregate into 2D molecular sheets that align with either F/H or Br atoms at the sheet surfaces (interfaces), respectively. Sheets are linked by weak C-H⋯F contacts in F-DIP and by Br⋯Br halogen bonding interactions as a ‘wall of bromines’ at the Br atom rich interfaces in Br-DIP. Cl-DIP is an unusual crystal structure incorporating both syn/anti and anti/anti molecular conformations in the asymmetric unit (Z’ = 3). The I-DIP•½(H2O) hemihydrate structure has a water molecule residing on a twofold axis between two I-DIPs and has hydrogen and N⋯I (Nc = 0.88) halogen bonding. The hydrate is central to an unusual synthon and involved in six hydrogen bonding interactions/contacts. Contact enrichment analysis on the Hirshfeld surface demonstrates that F-DIP, Cl-DIP and Br-DIP have especially over-represented halogen···halogen interactions. With the F-DIP, Cl-DIP and Br-DIP molecules having an elongated skeleton, the formation of layers of halogen atoms in planes perpendicular to the long unit cell axis occurs in the crystal packings. All six DIPs were analysed by ab initio calculations and conformational analysis; comparisons are made between their minimized structures and the five crystal structures. In addition, physicochemical properties are compared and assessed.

Intra-seasonal variability in supraglacial stream sediment on the Greenland Ice Sheet

On the surface of the Greenland Ice Sheet, the presence of low-albedo features greatly contributes to ablation zone meltwater production. Some of the lowest albedo features on the Ice Sheet are water-filled supraglacial stream channels, especially those with abundant deposits of consolidated cryoconite sediment. Because these sediments enhance melting by disproportionately lowering albedo, studying their spatial extent can provide a better understanding of Greenland’s contribution to global sea level rise. However, little is known about the spatial distribution of supraglacial stream sediment, or how it changes in response to seasonal flow regimes. Here, we surveyed a supraglacial stream network in Southwest Greenland, collecting imagery from seven uncrewed aerial vehicle (UAV) flights over the course of 24 days in 2019. Using Structure-from-Motion-generated orthomosaic imagery and digital elevation models (DEMs), we manually digitized the banks of the supraglacial stream channels, classified the areal coverage of sediment deposits, and modeled how the terrain influences the amount of incoming solar radiation at the Ice Sheet surface. We used imagery classified by surface types andin-situspectrometer measurements to determine how changes in sediment cover altered albedo. We found that, within our study area, only 15% of cryoconite sediment was consolidated in cryoconite holes; the remaining 85% was located within supraglacial streams mostly concentrated on daily inundated riverbanks (hereafter termed floodplains). Sediment cover and stream width are highly correlated, suggesting that sediment influx into supraglacial drainage systems widens stream channels or darkens previously widened channels. This reduces albedo in floodplains that already receive greater solar radiation due to their flatness. Additionally, the areal extent of stream sediments increased in August following seasonal peak flow, suggesting that as stream power decreases, more sediment accumulates in supraglacial channels. This negative feedback loop for melting may delay Greenland’s runoff to the latter end of the melt season. This study shows in unprecedented detail where and when sediment is deposited and how these deposits potentially impact the Ice Sheet surface energy balance. These findings may allow for better prediction of how supraglacial floodplains, and the microbiomes they contain, might change in response to increased melting.