Promising Properties For Applications Research Articles

High surface area microporous carbon nanocubes from controlled processing of graphene oxide nanoribbons

A new, facile, and template-free method to prepare high surface area microporous carbon nanocubes (CNCs) from a mixture of graphene oxide nanoribbons (NRs), graphene oxide, and carbon dots is reported. The nanoribbons, approximately 30 nm wide and with lengths ranging from a few tens of nanometres up to several micrometres, were obtained from the oxidation of Black Pearls 2000 carbon black in nitric acid solution. The non-purified nanoribbons further contained additional fragments of graphene oxide, and of graphene oxide quantum dots. Slow pyrolysis of the nanoribbon mixture with slow heating rates, e.g., 3 °C/min, yielded carbon nanocubes approximately 250 nm in size with surface areas greater than 900 m2/g. Heating rates of 50 °C/min led to carbons with ∼800 m2/g surface area but bulk morphology. Precipitating the nanoribbons in potassium hydroxide solution, followed by carbonization, yielded microporous nanoparticle aggregates that were 20 nm in size with surface areas greater than 2000 m2/g. The particles exhibited complex, quasi-spherical morphology. Pyrolysis of other products obtained from oxidation in HNO3 of different grades of carbon black, specifically graphene oxide nanoparticles and quantum dots, yielded high surface area microporous carbons but with bulk morphology regardless of the processing conditions. Despite the lower surface area and pore volume of the CNCs in comparison to the nanospheres, the former contained ultramicropores that were highly accessible to CO2 as a molecular probe and had excellent selectivity of CO2 over N2. Hence, CNC materials have promising properties for applications where particle surface-to-volume ratios, high internal surface areas, and abundant super and ultramicropores are desired.

NIR-Emitting Gold Nanoclusters Encapsulated in PS-b-PEG Polymer Micelles.

Gold nanoclusters (AuNCs) are an emerging type of luminescent probe, featuring good biocompatibility, high photostability, and large Stoke shifts. Their lack of colloidal stability is, however, a drawback for many applications. Here, we report the stabilization of AuNCs emitting in the NIR by a thiol-terminated polystyrene chain (Mn = 5000 g mol-1). The optical properties of this nanocomposite remain invariant for 2 years in THF. To use the PS5k-AuNCs in an aqueous environment, these were encapsulated into polymer micelles using a polystyrene-b-poly(ethylene glycol) copolymer. The resulting hierarchical constructs, with diameters of ca. 125 to 215 nm, have promising properties for applications as luminescent probes such as contrast agents for biomedical imaging.

Doped Carbon Dots Enable Highly Efficient Multiple‐Color Room Temperature Phosphorescence

AbstractColloidal carbon dots (C‐dots) are considered as promising heavy‐metal‐free materials to achieve room‐temperature phosphorescence (RTP) properties for promising applications, such as photoelectronic devices, information encryption, and bio‐imaging. However, most of the current obtained RTP C‐dots have a short lifetime with a relatively low quantum yield (QY). In this work, the C‐dots large‐scale synthesized via a vacuum heating approach have multiple RTP emissions (blue, green, and yellow), a long RTP lifetime of as high as 1.92 s, and a high QY of 34.4% by selecting different types of precursors, which is superior to most of reported RTP C‐dots. The multiple atoms doping and strong bonding between neighbored C‐dots promoted by vacuum heating contributes to the excellent RTP properties. As a proof‐of‐concept, the as‐obtained RTP C‐dots are used as optical ink for flexible security codes, exhibiting a bright shape with a lifetime of 1.37 s. This work offers an efficient approach for producing large‐scale high‐quality RTP C‐dots, which can be applied to anti‐counterfeiting and information encryption systems.

Foray into the topology of poly‐bi‐[8]‐annulenylene

AbstractAnalyzing phase transitions using the inherent geometrical attributes of a system has garnered enormous interest over the past few decades. The usual candidate often used for investigation is graphene—the most celebrated material among the family of tri‐coordinated graphed lattices. We show in this report that other inhabitants of the family demonstrate equally admirable structural and functional properties that at its core are controlled by their topology. Two interesting members of the family are cyclooctatrene (COT) and COT‐based polymer: poly‐bi‐[8]‐annulenylene, both in one and two dimensions that have been investigated by polymer chemists over a period of 50 years for its possible application in batteries exploiting its conducting properties. A single COT unit is demonstrated herein to exhibit topological solitons at sites of a broken bond similar to an open one‐dimensional Su–Schrieffer–Heeger (SSH) chain. We observe that poly‐bi‐[8]‐annulenylene in one dimension mimics two coupled SSH chains in the weak coupling limit, thereby showing the presence of topological edge modes. In the strong coupling limit, we investigate the different parameter values of our system for which we observe zero‐energy modes. Further, the application of an external magnetic field and its effects on the band flattening of the energy bands has also been studied. In two dimensions, poly‐bi‐[8]‐annulenylene forms a square‐octagon lattice which upon breaking time‐reversal symmetry goes into a topological phase forming noise‐resilient edge modes. We hope our analysis would pave the way for synthesizing such topological materials and exploiting their properties for promising applications in optoelectronics, photovoltaics, and renewable energy sources.Key Points We show in this paper tri‐coordinated lattice systems: cylooctatrene (COT) and COT‐based polymer: poly‐bi‐[8]‐annulenylene exhibit exotic topological properties. Flat bands are generated upon application of tailored magnetic flux for poly‐bi‐[8]‐annulenylene in one dimension. Insights from this paper open the possibility of using these polymers as an experimental ground to observe many flat‐band and topology‐related phenomena.

Strontium-loaded magnesium phosphate bone cements and effect of polymeric additives

Magnesium phosphate-based cements (MPCs) are nowadays regarded as promising materials in the field of bone repair. The inclusion of Sr ions in the formulations may represent a valuable strategy to improve their bone regeneration performances, but the effect that such ion exerts on the physico-chemical properties of the material have not been investigated so far. In this work we describe the development of Sr-MPCs obtained including Sr ions in different forms, i.e., using Sr-substituted tri-magnesium phosphate precursor powder or including in the formulation Sr-based salts (SrCl2 and SrHPO4). The materials were characterized both in the form of pastes and hardened cements, finding that according to the type of Sr precursor used we can tune the setting time, the amount of binding phases in the cements, their morphology and thermal behavior. The dissolution behavior and the release kinetics of Mg2+ and Sr2+ can as well be modulated, and in particular the use of SrCl2 in the formulation leads to a higher dissolution and a faster release of a significant amount of both Mg2+ and Sr2+, compared to the other samples. Given the unsatisfying performances obtained during the injectability and anti-washout tests, we also included two polymeric additives, namely poly(N-isopropylacrylamide) and mucin, in the Sr-MPCs formulations. The results demonstrate that it is possible to obtain Sr-MPCs with promising properties for applications as bone cements, that can be tuned according to the form under which Sr is included in the formulation. In addition, mucin markedly improves the cohesion and injectability of the Sr-MPC pastes, providing a simple but effective strategy to develop materials of interest in the orthopedic field.

State of the art: non-invasive electrical stimulation for the treatment of chronic tinnitus.

Subjective tinnitus is the perception of sound in the absence of external stimulation. Neuromodulation is a novel method with promising properties for application in tinnitus management. This study sought to review the types of non-invasive electrical stimulation in tinnitus to provide the foothold for further research. PubMed, EMBASE, and Cochrane databases were searched for studies on the modulation of tinnitus by non-invasive electrical stimulation. Among the four forms of non-invasive electrical modulation, transcranial direct current stimulation, transcranial random noise stimulation, and transauricular vagus nerve stimulation yielded promising results, whereas the effect of transcranial alternating current stimulation in the treatment of tinnitus has not been confirmed. Non-invasive electrical stimulation can effectively suppress tinnitus perception in some patients. However, the heterogeneity in parameter settings leads to scattered and poorly replicated findings. Further high-quality studies are needed to identify optimal parameters to develop more acceptable protocols for tinnitus modulation.

Polyamide-Based Adhesive Lascaux 5350 in Textile Conservation—Properties, Stability and Use

Lascaux Polyamid-Textil-Schweisspulver 5350 is a hot-melt adhesive with promising properties for applications in textile conservation. The study presented aims at examining the properties and long-term stability of this adhesive. It also deals with the possibilities of its use for bonding proteinaceous and cellulosic textiles and describes particular methods of using the adhesive either in the form of powder or as a prepared adhesive film. The adhesion techniques are compared with conventional sewing methods commonly used to consolidate damaged textile objects. In addition, the study also deals with the reversibility of the adhesive treatments.

Multi-stage block freeze concentration via gravitational method applied to increase of the nutritional content of Morinda citrifolia L. tea

The processing of Morinda citrifolia fruit normally results in a large number of waste leaves that hold many bioactive compounds with nutritional and pharmacological properties. This work aimed to evaluate the effects of a multi-stage block freeze concentration (BFC) via gravitational method on the physicochemical properties of the leaf extract (noni tea). The results in solid retention showed fractions almost 7 times most concentrated than the initial feed. In addition, when compared to the initial content, the BFC process showed an efficiency higher than 90% in the retention of phenolic compounds. Assays in liquid chromatography allowed the detection and quantification of phenolic compounds, in which the total amount increased by more than 1000% in relation to the initial content after each BFC step. Finally, it was also possible to observe a significant increase in the antioxidant activity of the concentrated product after the simulated in vitro digestion process. It was concluded that using a non-thermal, sustainable, low-cost processing, promoted the obtaining of concentrated fractions with high biological and nutritional values with promising properties for application in the development of functional foods from agroindustrial wastes.

Reusable hydrogels based on lignosulfonate and cationic polymer for the removal of Cr(VI) from wastewater

In this investigation, absorbent materials based on the polymer poly ([2-(acryloyloxy)ethyl]trimethylammonium chloride) were synthesized by radical polymerization using varying amounts of sodium lignosulfonate (LS) (0.00–30.0 wt%). The chemical composition was corroborated by Fourier transform infrared spectroscopy, and thermogravimetric analysis showed an increase in the thermal stability of the materials with the incorporation of LS. A porous surface with grooves was observed by scanning electron microscopy. In addition, the hydration in water and the removal capacity of hexavalent chromium (Cr(VI)) were tested by evaluating different experimental parameters. A hydration capacity of over 2000% was obtained when the incorporated percentage of LS exceeded 20.0 wt%. A maximum Cr(VI) removal efficiency of 88.4% was obtained by the adsorbent prepared with 5.00 wt% LS. The obtained results were well fit by a pseudosecond-order kinetic model and the Langmuir isotherm model. The presence of chromium on the surfaces of the adsorbents was corroborated. It was also found that the presence of interfering species led to a decrease of up to 11.0% of the maximum retention of Cr(VI) and that the materials could be reused up to five times without a significant decrease in efficiency. The adsorbent material prepared in this research has promising properties for application in the removal of metal anions, which could be extended to various anionic pollutants present in wastewater.

Chemistry in a spinneret—Polydopamine functionalized hollow fiber membranes

In recent years, dopamine has stood out as an all-round talent in the field of membrane modification. Membranes post-modified with polydopamine or made out of materials pre-modified with polydopamine show applicability in almost all membrane processes. These approaches have in common that they require additional fabrication steps to accomplish the final membrane product. In this study, the first part presents the post-modification of hollow fiber membrane modules with polydopamine. The resulting coated membranes suit further functionalization and exhibit excellent properties. The successful coating of commercial dialysis membranes with polydopamine and heparin while maintaining their selectivities for proteins present in human blood is highlighted in this work. Further and most importantly, membranes are successfully in-situ modified with polydopamine using the ’chemistry-in-a-spinneret’ technology base. Flat sheet and hollow fiber membranes with polydopamine modification evolve in a single-step process. The polydopamine functionalized membranes exhibit increased anti-fouling properties and bind heparin on their surface. The ’chemistry-in-a-spinneret’ approach fabricates directly polydopamine-functionalized membranes. These membranes have promising properties for application in the field of hemodialysis and pave the way for applications in other membrane processes.

Control of spontaneous emission rate in lead halide perovskite film on hyperbolic metamaterial

Hyperbolic metamaterials represent a class of nanophotonic architectures with the possibility of controlling density of optical states. Due to this property, hyperbolic metamaterials can be employed as meta-electrodes in optoelectronic devices. On the other hand, lead halide perovskites have several promising properties for application in light-emitting devices. Moreover, a perovskite film is easily deposited on a hyperbolic metamaterial surface. Here, we theoretically show how to accelerate radiative recombination in a perovskite film with a hyperbolic metamaterial. This effect can be applied in light-emitting devices, where radiative recombination is extremely important.

NHC-CDI Betaine Adducts and Their Cationic Derivatives as Catalyst Precursors for Dichloromethane Valorization.

Zwitterionic adducts of N-heterocyclic carbene and carbodiimide (NHC-CDI) are an emerging class of organic compounds with promising properties for applications in various fields. Herein, we report the use of the ICyCDI(p-Tol) betaine adduct (1a) and its cationic derivatives 2a and 3a as catalyst precursors for the dichloromethane valorization via transformation into high added value products CH2Z2 (Z = OR, SR or NR2). This process implies selective chloride substitution of dichloromethane by a range of nucleophiles Na+Z– (preformed or generated in situ from HZ and an inorganic base) to yield formaldehyde-derived acetals, dithioacetals, or aminals with full selectivity. The reactions are conducted in a multigram-scale under very mild conditions, using dichloromethane both as a reagent and solvent, and very low catalyst loading (0.01 mol %). The CH2Z2 derivatives were isolated in quantitative yields after filtration and evaporation, which facilitates recycling the dichloromethane excess. Mechanistic studies for the synthesis of methylal CH2(OMe)2 rule out organocatalysis as being responsible for the CH2 transfer, and a phase-transfer catalysis mechanism is proposed instead. Furthermore, we observed that 1a and 2a react with NaOMe to form unusual isoureate ethers, which are the actual phase-transfer catalysts, with a strong preference for sodium over other alkali metal nucleophiles.

Mesomorphic Behavior of Symmetric Azomethine Dimers Containing Different Chromophore Groups.

A series of new azomethine dimers was synthesized by the condensation reaction of flexible bis-benzaldehydes with four aromatic amines containing phenyl, naphthyl, anthracene and pyrene groups. Their right structure was confirmed by FTIR and 1H-NMR spectroscopy and their thermal properties were investigated by thermogravimetric analysis, differential scanning calorimetry and polarized light optical microscopy. A view on their photophysical behavior was gained by UV-vis and photoluminescence spectroscopy. The dimers containing pyrene and anthracene presented liquid crystalline behavior, while the other dimers were crystalline compounds. Two dimers containing pyrene moieties formed mesomorphic glasses and had intense luminescence, promising properties for applications in building optoelectronic devices.

Effect of Modified Hydroxypropyl Tapioca Starch and Percentage of Drug Loading on Physical Property of Paracetamol Tablet

The objective of this study was to investigate the effect of modified hydroxypropyl tapioca starch (HPTS) and % drug loading on physical property of tablet. Paracetamol was used as model drug because of its poor compressibility. The filler ability of modified HPTS such as hydroxyl propyl oxidized tapioca starch (HPOTS), hydroxyl propyl crosslinked tapioca starch (HPCTS) and pregelatinized tapioca starch (PTS) were evaluated and compared with the commercial starch (Starch 1500®). Tablets were prepared by direct compression method and the percent drug loading were 15, 30, 45, 60, 75%. For modified HPTS, the hardness of the tablets tended to decrease when the concentration of paracetamol increased. At drug concentrations of 15-30%, HPOTS exhibited good performance of tablet as indicated by the high hardness, low friability and acceptable disintegration time. The obtained results were better than HPTS and comparable to Starch 1500®. Moreover, the results revealed that tablet containing PTS provided the highest hardness and prolonged disintegration time (>30 min) while tablet containing HPCTS showed rapid disintegration time (<2 min). Therefore, modified HPTS disclosed promising properties for application as tablet filler

In situ synthesis of epoxy nanocomposites with hierarchical surface-modified SiO2 clusters

Polymer nanocomposites are often produced using in situ approaches where an inorganic filler (as the dispersed phase) is synthesized directly in an organic matrix. Such an approach generally leads to improved dispersion and reduced agglomeration of the filler material. Epoxy-based nanocomposites have demonstrated promising properties for application as high-voltage insulation materials. In this work, a sol–gel based method has been adapted to synthesize surface-functionalized SiO2 in situ in epoxy. The synthesized SiO2 moieties were dispersed in clusters of 10–80 nm, and formed chemical bonds with the epoxy monomers via a silane coupling agent. Raman spectra show the formation of four-membered D1 rings, which may be part of a cage-like structure similar to that of polyhedral oligomeric silsesquioxanes (POSS). SAXS measurements indicate that the SiO2 clusters consist of a hierarchical structure with an increasing fractal dimension with increasing SiO2 content. The nanocomposites displayed improved thermal stability, while the glass transition behavior varied depending on the structure and content of the SiO2 moieties. While the relative permittivity showed no significant changes from that of pure epoxy, the onset of the dielectric relaxation changed with the SiO2 structure and content, similar to the behavior observed for the glass transition.The synthesis of surface-functionalized SiO2 in situ in an epoxy resin (DGEBA) resulted in a good dispersion and limited agglomeration of the SiO2 in the nanocomposite, with little deviation in the dielectric properties (i.e., complex permittivity). The SiO2 is suspected to have a hierarchical structure based on the SAXS measurements, with the primary structural level consisting of POSS-like cages, and an evolution in the structure from inorganic chains to cross-linked clusters with increasing SiO2 content.

Sb2Se3(100) : A strongly anisotropic surface

Interest in antimony selenide (Sb2Se3) has been constantly growing in the recent past, especially for its promising properties for applications in the field of solar energy technologies. Surprisingly, the surface properties of this material, which is built from van der Waals stacked one-dimensional (1D) ribbons, have not been studied in detail yet. Here we demonstrate that Sb2Se3 crystals cleave along the (100) planes. The resulting surface shows a pronounced 1D structure, reflecting the stacking of ribbons in the bulk crystal. The cleaving process leads to the formation of slightly tilted surface domains, with the tilt angles oriented invariably along the ribbon directions, suggesting a strong anisotropy of the internal friction forces. Our angle-resolved photoemission data reveal that the 1D character of the crystalline structure of this material is also reflected in its electronic band structure.

Degradation and bioactivity studies of Mg membranes for dental surgery

Bioresorbable materials are under investigation due to their promising properties for applications as implant material. This study is about the degradation and bioactivity behaviour of magnesium foils, which allegorize dental membranes. The degradation behaviour including pitting corrosion during immersion tests can be precisely observed using micro-computed tomography. Using the bioactivity test according to Kokubo, it is shown that magnesium has strong Ca-phosphate layer formation correlated with high degradation. Therefore, magnesium foils appear to hold a great potential for bone implant application.

Impedance spectroscopy of water splitting reactions on nanostructured metal-based catalysts

Hydrogen production by water splitting using nanomaterials as electrocatalysts is a promising route enabling replacement of fossil fuels by renewable energy sources. In particular, the development of inexpensive non-noble metal-based catalysts is necessary in order to replace currently used expensive Pt-based catalysts. We report a detailed impedance spectroscopy study of Ni-Mo and Ni-Fe based electrocatalytic materials deposited onto porous and compact substrates with different conductivities. The results were interpreted by a critical comparison with equivalent circuit models. The reaction resistance displays a strong dependence on potential and a lower substrate dependence. The impedance behaviour can also provide information on the dominating reaction mechanism. An optimized Ni-Fe based catalyst showed very promising properties for applications in water electrolysis.

Controlled Polymerization of Ethyl Glyoxylate Using Alkyllithium and Alkoxide Initiators

The synthesis of poly(ethyl glyoxylate)s (PEtGs) by anionic polymerization was explored. PEtGs are a subclass of stimulus-responsive self-immolative polymers with promising properties for applications as coatings, sensors, and drug delivery vehicles. In this paper, a new purification procedure for the preparation of highly pure ethyl glyoxylate (EtG), suitable for anionic polymerization reactions, and the first successful examples of controlled polymerization of EtG are described. n-BuLi, PhLi, and t-BuLi were employed as initiators under different experimental conditions, and their behavior was examined using NMR spectroscopy, size exclusion chromatography, and thermal analysis to develop an optimized procedure. As functional alkoxide initiators, propargyl alkoxide was employed in optimization studies and poly(ethylene glycol) (PEG) dialkoxide was utilized for the direct synthesis of PEtG–PEG–PEtG copolymers. The new polymerization method revealed many features of controlled polymerization reactions, yie...

Antibacterial activity of nickel and nickel hydroxide nanoparticles against multidrug resistance K. pneumonia and E. coli isolated urinary tract

Objective(s): Antibacterial materials are so significant in the textile industry, water disinfection, medicine, and food packaging. Unfortunately, organic compounds for sterilization show toxicity to the human body; therefore, the interest in inorganic disinfectants such as metal oxide nanoparticles (NPs) is increasing. Materials and Methods: Nickel and nickel hydroxide nanoparticles (NiNPs and Ni(OH)2-NPs) were prepared and characterized by DLS, SEM, AFM and ATR. Antibacterial activity assay was carried by Spot on lawn method against two selected standard pathogenic bacteria such as E. coli (as Gram negative), S. aureus (as Gram positive) and multidrug resistance K. pneumonia and E. coli. Also the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined against two selected standard pathogenic bacteria and multidrug resistance K. pneumonia and E. coli. Results: The formation of the NiNPs and Ni(OH)2-NPs were confirmed by DLS, SEM, AFM and ATR. Antibacterial activity of nanoparticles were confirmed against two selected standard pathogenic bacteria such as E. coli and S. aureus. And also, NiNPs and Ni(OH)2-NPs revealed fair antibacterial effect against multidrug resistance K. pneumonia and E. coli based on MIC and MBC data. As well, the experimental data presented that the antibacterial activity of NiNPs was more than Ni(OH)2-NPs. Conclusion: Based on the achieved results, NiNPs and Ni(OH)2-NPs show antibacterial activity against clinical patients bacteria (multidrug resistance K. pneumonia and E. coli(. Finally, the NPs evaluated in this study have promising properties for applications as antiseptic agent for environment; however, further studies are warranted such as study toxicity NPs on normal human cell line and other clinical bacteria.