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23 pages, 6337 KiB

Open AccessArticle

A New Protocol for Ash Wood Modification: Synthesis of Hydrophobic and Antibacterial Brushes from the Wood Surface

by Angelika Macior, Izabela Zaborniak, Paweł Chmielarz, Joanna Smenda, Karol Wolski, Ewa Ciszkowicz and Katarzyna Lecka-Szlachta

Molecules 2022, 27(3), 890; https://doi.org/10.3390/molecules27030890 - 28 Jan 2022

Cited by 11 | Viewed by 3232

Abstract

The article presents the modification of ash wood via surface initiated activators regenerated by electron transfer atom transfer radical polymerization mediated by elemental silver (Ag⁰ SI-ARGET ATRP) at a diminished catalyst concentration. Ash wood is functionalized with poly(methyl methacrylate) (PMMA) and poly(2-(dimethylamino)ethyl [...] Read more.

The article presents the modification of ash wood via surface initiated activators regenerated by electron transfer atom transfer radical polymerization mediated by elemental silver (Ag⁰ SI-ARGET ATRP) at a diminished catalyst concentration. Ash wood is functionalized with poly(methyl methacrylate) (PMMA) and poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) to yield wood grafted with PMMA-b-PDMAEMA-Br copolymers with hydrophobic and antibacterial properties. Fourier transform infrared (FT-IR) spectroscopy confirmed the covalent incorporation of functional ATRP initiation sites and polymer chains into the wood structure. The polymerization kinetics was followed by the analysis of the polymer grown in solution from the sacrificial initiator by proton nuclear magnetic resonance (¹H NMR) and gel permeation chromatography (GPC). The polymer layer covalently attached to the wood surface was observed by scanning electron microscopy (SEM). The hydrophobic properties of hybrid materials were confirmed by water contact angle measurements. Water and sodium chloride salt aqueous solution uptake tests confirmed a significant improvement in resistance to the absorption of wood samples after modification with polymers. Antibacterial tests revealed that wood-QPDMAEMA-Br, as well as wood-PMMA-b-QPDMAEMA-Br, exhibited higher antibacterial activity against Gram-positive bacteria (Staphylococcus aureus) in comparison with Gram-negative bacteria (Escherichia coli). The paper presents an economic concept with ecological aspects of improving wood properties, which gives great opportunities to use the proposed approach in the production of functional hybrid materials for industry and high quality sports equipment, and in furniture production. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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11 pages, 8235 KiB

Open AccessArticle

Deposition of Hybrid Photocatalytic Layers for Air Purification Using Commercial TiO₂ Powders

by Ewoud Cosaert, Cédric Wolfs, Stéphanie D. Lambert, Geraldine J. Heynderickx and Dirk Poelman

Molecules 2021, 26(21), 6584; https://doi.org/10.3390/molecules26216584 - 30 Oct 2021

Cited by 2 | Viewed by 1679

Abstract

Photocatalytic nanomaterials, using only light as the source of excitation, have been developed for the breakdown of volatile organic compounds (VOCs) in air for a long time. It is a tough challenge to immobilize these powder photocatalysts and prevent their entrainment with the [...] Read more.

Photocatalytic nanomaterials, using only light as the source of excitation, have been developed for the breakdown of volatile organic compounds (VOCs) in air for a long time. It is a tough challenge to immobilize these powder photocatalysts and prevent their entrainment with the gas stream. Conventional methods for making stable films typically require expensive deposition equipment and only allow the deposition of very thin layers with limited photocatalytic performance. The present work presents an alternative approach, using the combination of commercially available photocatalytic nanopowders and a polymer or inorganic sol–gel-based matrix. Analysis of the photocatalytic degradation of ethanol was studied for these layers on metallic substrates, proving a difference in photocatalytic activity for different types of stable layers. The sol–gel-based

{TiO}_{2}

layers showed an improved photocatalytic activity of the nanomaterials compared with the polymer

{TiO}_{2}

layers. In addition, the used preparation methods require only a limited amount of photocatalyst, little equipment, and allow easy upscaling. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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13 pages, 2057 KiB

Open AccessArticle

Conversion of Organic Dyes into Pigments: Extraction of Flavonoids from Blackberries (Rubus ulmifolius) and Stabilization

by Rossella G. Candela, Giuseppe Lazzara, Sonia Piacente, Maurizio Bruno, Giuseppe Cavallaro and Natale Badalamenti

Molecules 2021, 26(20), 6278; https://doi.org/10.3390/molecules26206278 - 17 Oct 2021

Cited by 16 | Viewed by 2899

Abstract

The blackberry’s color is composed mainly of natural dyes called anthocyanins. Their color is red–purple, and they can be used as a natural colorant. Anthocyanins are flavonoids, which are products of plants, and their colors range from orange and red to various shades [...] Read more.

The blackberry’s color is composed mainly of natural dyes called anthocyanins. Their color is red–purple, and they can be used as a natural colorant. Anthocyanins are flavonoids, which are products of plants, and their colors range from orange and red to various shades of blue, purple and green, according to pH. In this study, the chemical composition of an extract obtained from blackberries was defined by LC-ESI/LTQOrbitrap/MS in positive and negative ionization mode. Furthermore, we investigated the adsorption process of blackberry extract using several inorganic fillers, such as metakaolin, silica, Lipari pumice, white pozzolan and alumina. The pigments exhibit different colors as a function of their interactions with the fillers. The analysis of the absorption data allowed the estimation of the maximum adsorbing capacity of each individual filler tested. Through thermogravimetric measurements (TGA), the thermal stability and the real adsorption of the organic extract were determined. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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15 pages, 6285 KiB

Open AccessArticle

New Hybrid Polyurea-Polyurethane Elastomers with Antistatic Properties and an Influence of Various Additives on Their Physicochemical Properties

by Szymon Kosiński, Marcin Gonsior, Piotr Krzyżanowski and Iwona Rykowska

Molecules 2021, 26(19), 5778; https://doi.org/10.3390/molecules26195778 - 24 Sep 2021

Cited by 7 | Viewed by 3656

Abstract

Polyurea is a synthetic high-strength elastomeric material that can be sprayed as a coating over existing structures in order to protect against weathering effects. It is ideal for anti-corrosion protection and is characterized by excellent mechanical properties and adhesion to various surfaces. Further [...] Read more.

Polyurea is a synthetic high-strength elastomeric material that can be sprayed as a coating over existing structures in order to protect against weathering effects. It is ideal for anti-corrosion protection and is characterized by excellent mechanical properties and adhesion to various surfaces. Further development of this technology may allow obtaining new coatings with improved antistatic properties, which would be an excellent alternative compared to used antistatic epoxy paints. This paper will examine the influence of tetraalkylammonium salt (1), potassium hexafluorophosphate solution (2) and imidazolium-based ionic liquid (3) on the improvement of antistatic properties of the polyurea-polyurethane coatings. In addition, the modified samples were also verified in terms of changes in mechanical properties and the appearance of functional groups other than in the reference sample, as well as surface defects that may arise due to incompatibility of the antistatic additive with the polymer matrix. In order to obtain information about the properties mentioned above, the electrical resistance was determined, the tensile strength and elongation were measured, FT-IR spectra were made, and images were taken with the use of scanning electron microscopy. The conducted research showed that the antistatic properties of the tested hybrid coatings could be improved, but their use may be associated with certain limitations that should be taken into account when designing such materials. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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19 pages, 18443 KiB

Open AccessArticle

A Perfect Plastic Material for Studies on Self-Propelled Motion on the Water Surface

by Richard J. G. Löffler, Martin M. Hanczyc and Jerzy Gorecki

Molecules 2021, 26(11), 3116; https://doi.org/10.3390/molecules26113116 - 23 May 2021

Cited by 7 | Viewed by 2889

Abstract

We describe a novel plastic material composed of camphene, camphor, and polypropylene that seems perfectly suited for studies on self-propelled objects on the water surface. Self-motion is one of the attributes of life, and chemically propelled objects show numerous similarities with animated motion. [...] Read more.

We describe a novel plastic material composed of camphene, camphor, and polypropylene that seems perfectly suited for studies on self-propelled objects on the water surface. Self-motion is one of the attributes of life, and chemically propelled objects show numerous similarities with animated motion. One of important questions is the relationship between the object shape and its motility. In our paper published in 2019, we presented a novel hybrid material, obtained from the solution of camphor in camphene, that allowed making objects of various shapes. This hybrid material has wax-like mechanical properties, but it has a very high tackiness. Here, we report that a small amount of polypropylene removed this undesirable feature. We investigated the properties of camphor–camphene–polypropylene plastic by performing the statistical analysis of a pill trajectory inside a Petri dish and compared them with those of camphor-camphene wax. The plastic showed the stable character of motion for over an hour-long experiment. The surface activity of objects made of plastic did not significantly depend on the weight ratios of the compounds. Such a significant increase in usefulness came from the polypropylene, which controlled the dissipation of camphor and camphene molecules. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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12 pages, 2129 KiB

Open AccessCommunication

Fe(II) Spin Crossover/Polymer Hybrid Materials: Investigation of the SCO Behavior via Temperature-Dependent Raman Spectroscopy, Physicochemical Characterization and Migration Release Study

by Zoi G. Lada, Amaia Soto Beobide, Georgios N. Mathioudakis and George A. Voyiatzis

Molecules 2021, 26(1), 201; https://doi.org/10.3390/molecules26010201 - 3 Jan 2021

Cited by 3 | Viewed by 3441

Abstract

Polymeric composites constitute an appealing class of materials with applications in various fields. Spin crossover (SCO) coordination complexes are switchable materials with potential use in data storage and sensors. Their incorporation into polymers can be considered an effective method for their wider practical [...] Read more.

Polymeric composites constitute an appealing class of materials with applications in various fields. Spin crossover (SCO) coordination complexes are switchable materials with potential use in data storage and sensors. Their incorporation into polymers can be considered an effective method for their wider practical application. In this study, Fe(II) SCO/polylactic acid hybrid polymeric composites have been prepared by film casting. The mononuclear coordination complex [Fe{N(CN)₂}₂(abpt)₂] was incorporated into polylactic acid. The morphological, structural and thermoanalytical characterization of the composite films were performed via scanning electron microscopy (SEM), attenuated total reflectance (ATR/FTIR), Raman spectroscopy and differential scanning calorimetry (DSC). In addition, the migration release study (MRS) of the SCO compound from the polymeric matrix into the food simulant 50% v/v water/ethanol solution was also examined via UV/Vis absorption. Of particular interest was the investigation of the SCO behavior of the coordination complex after its incorporation into the polymer matrix; it was accomplished by temperature-dependent micro-Raman spectroscopy. The described attempt could be considered a preparatory step toward the development of SCO-based temperature sensors integrated into food packaging materials. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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13 pages, 2631 KiB

Open AccessArticle

An Effective Hybrid Heterogeneous Catalyst to Desulfurize Diesel: Peroxotungstate@Metal–Organic Framework

by Yan Gao, Fátima Mirante, Baltazar de Castro, Jianshe Zhao, Luís Cunha-Silva and Salete S. Balula

Molecules 2020, 25(23), 5494; https://doi.org/10.3390/molecules25235494 - 24 Nov 2020

Cited by 18 | Viewed by 2235

Abstract

A peroxotungstate composite comprising the chromium terephthalate metal–organic framework MIL-101(Cr) and the Venturello peroxotungstate [PO₄{WO(O₂)₂}₄]³⁻ (PW₄) has been prepared by the impregnation method. The PW₄@MIL-101(Cr) composite presents high catalytic efficiency [...] Read more.

A peroxotungstate composite comprising the chromium terephthalate metal–organic framework MIL-101(Cr) and the Venturello peroxotungstate [PO₄{WO(O₂)₂}₄]³⁻ (PW₄) has been prepared by the impregnation method. The PW₄@MIL-101(Cr) composite presents high catalytic efficiency for oxidative desulfurization of a multicomponent model diesel containing the most refractory sulfur compounds present in real fuels (2000 ppm of total S). The catalytic performance of this heterogeneous catalyst is similar to the corresponding homogeneous PW₄ active center. Desulfurization efficiency of 99.7% was achieved after only 40 min at 70 °C using H₂O₂ as an oxidant and an ionic liquid as an extraction solvent ([BMIM]PF₆, 2:1 model diesel/[BMIM]PF₆). High recycling and reusing capacity was also found for PW₄@MIL-101(Cr), maintaining its activity for consecutive oxidative desulfurization cycles. A comparison of the catalytic performance of this peroxotungstate composite with others previously reported tungstate@MIL-101(Cr) catalysts indicates that the presence of active oxygen atoms from the peroxo groups promotes a higher oxidative catalytic efficiency in a shorter reaction time. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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17 pages, 16748 KiB

Open AccessArticle

Deposition of Tetracoordinate Co(II) Complex with Chalcone Ligands on Graphene

by Jakub Hrubý, Šárka Vavrečková, Lukáš Masaryk, Antonín Sojka, Jorge Navarro-Giraldo, Miroslav Bartoš, Radovan Herchel, Ján Moncol, Ivan Nemec and Petr Neugebauer

Molecules 2020, 25(21), 5021; https://doi.org/10.3390/molecules25215021 - 29 Oct 2020

Cited by 17 | Viewed by 3831

Abstract

Studying the properties of complex molecules on surfaces is still mostly an unexplored research area because the deposition of the metal complexes has many pitfalls. Herein, we probed the possibility to produce surface hybrids by depositing a Co(II)-based complex with chalcone ligands on [...] Read more.

Studying the properties of complex molecules on surfaces is still mostly an unexplored research area because the deposition of the metal complexes has many pitfalls. Herein, we probed the possibility to produce surface hybrids by depositing a Co(II)-based complex with chalcone ligands on chemical vapor deposition (CVD)-grown graphene by a wet-chemistry approach and by thermal sublimation under high vacuum_. Samples were characterized by high-frequency electron spin resonance (HF-ESR), XPS, Raman spectroscopy, atomic force microscopy (AFM), and optical microscopy, supported with density functional theory (DFT) and complete active space self-consistent field (CASSCF)/N-electron valence second-order perturbation theory (NEVPT2) calculations. This compound’s rationale is its structure, with several aromatic rings for weak binding and possible favorable π–π stacking onto graphene. In contrast to expectations, we observed the formation of nanodroplets on graphene for a drop-cast sample and microcrystallites localized at grain boundaries and defects after thermal sublimation. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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16 pages, 3937 KiB

Open AccessArticle

Mesoporous Silica as a Drug Delivery System for Naproxen: Influence of Surface Functionalization

by Lukáš Žid, Vladimír Zeleňák, Miroslav Almáši, Adriana Zeleňáková, Jaroslava Szücsová, Jozef Bednarčík, Monika Šuleková, Alexander Hudák and Lucia Váhovská

Molecules 2020, 25(20), 4722; https://doi.org/10.3390/molecules25204722 - 15 Oct 2020

Cited by 17 | Viewed by 3153

Abstract

In this work we describe the relationship between surface modification of hexagonally ordered mesoporous silica SBA-15 and loading/release characteristics of nonsteroidal anti-inflammatory drug (NSAID) naproxen. Mesoporous silica (MPS) was modified with 3-aminopropyl, phenyl and cyclohexyl groups by grafting method. Naproxen was adsorbed into [...] Read more.

In this work we describe the relationship between surface modification of hexagonally ordered mesoporous silica SBA-15 and loading/release characteristics of nonsteroidal anti-inflammatory drug (NSAID) naproxen. Mesoporous silica (MPS) was modified with 3-aminopropyl, phenyl and cyclohexyl groups by grafting method. Naproxen was adsorbed into pores of the prepared MPS from ethanol solution using a solvent evaporation method. The release of the drug was performed in buffer medium at pH 2 and physiological solution at pH 7.4. Parent MPSs as well as naproxen loaded MPSs were characterized using physicochemical techniques such as nitrogen adsorption/desorption, thermogravimetric analysis (TG), Zeta potential analysis, Fourier transform infrared spectroscopy (FT-IR), and elemental analysis. The amount of naproxen released from the MPSs into the medium was determined by high-performance liquid chromatography (HPLC). It was shown that the adsorption and desorption characteristics of naproxen are dependent on the pH of the solution and the surface functionalization of the host. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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12 pages, 2170 KiB

Open AccessArticle

Dependence of the Optical Constant Parameters of p-Toluene Sulfonic Acid-Doped Polyaniline and Its Composites on Dispersion Solvents

by Fahad Usman, John Ojur Dennis, Fabrice Meriaudeau, Abdelaziz Yousif Ahmed, Khe Cheng Seong, Yap Wing Fen, Amir Reza Sadrolhosseini, Bashir Abubakar Abdulkadir, Ridwan Tobi Ayinla, Wan Mohd Ebtisyam Mustaqim Mohd Daniyal, Nur Alia Sheh Omar, Nissren Tamam and Abdelmoneim Sulieman

Molecules 2020, 25(19), 4414; https://doi.org/10.3390/molecules25194414 - 25 Sep 2020

Cited by 6 | Viewed by 2656

Abstract

The optical constants of Para-Toluene sulfonic acid-doped polyaniline (PANI), PANIchitosan composites, PANI-reduced graphene-oxide composites and a ternary composite comprising of PANI, chitosan and reduced graphene-oxide dispersed in diluted p-toluene sulfonic acid (PTSA) solution and N-Methyl-2-Pyrrolidone (NMP) solvent have been evaluated and compared. [...] Read more.

The optical constants of Para-Toluene sulfonic acid-doped polyaniline (PANI), PANIchitosan composites, PANI-reduced graphene-oxide composites and a ternary composite comprising of PANI, chitosan and reduced graphene-oxide dispersed in diluted p-toluene sulfonic acid (PTSA) solution and N-Methyl-2-Pyrrolidone (NMP) solvent have been evaluated and compared. The optical constant values were extracted from the absorbance spectra of thin layers of the respective samples. The potential utilization of the materials as the active sensing materials of surface plasmon resonance biosensors has also been assessed in terms of the estimated value of the penetration depth through a dielectric medium. The results show a reasonable dependence of the optical constant parameters on the solvent type. Higher real part refractive index (n) and real part complex dielectric permittivity (ε’) values were observed for the samples prepared using PTSA solution, while higher optical conductivity values were observed for the NMP-based samples due to their relatively higher imaginary part refractive index (k) and imaginary part complex dielectric permittivity (ε″) values. In addition, NMP-based samples show improvement in terms of the penetration depth through a dielectric medium by around 9.5, 1.6, 4.4 and 2.9 times compared to PTSA-based samples for the PANI, PANI-chitosan, PANI-RGO and the ternary composites, respectively. Based on these, it is concluded that preparation of these materials using different dispersion solvents could produce materials of different optical properties. Thus, the variation of the dispersion solvent will allow the flexible utilization of the PANI and the composites for diverse applications. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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21 pages, 2622 KiB

Open AccessArticle

Exciton Coupling and Conformational Changes Impacting the Excited State Properties of Metal Organic Frameworks

by Andreas Windischbacher, Luca Steiner, Ritesh Haldar, Christof Wöll, Egbert Zojer and Anne-Marie Kelterer

Molecules 2020, 25(18), 4230; https://doi.org/10.3390/molecules25184230 - 15 Sep 2020

Cited by 10 | Viewed by 3483

Abstract

In recent years, the photophysical properties of crystalline metal-organic frameworks (MOFs) have become increasingly relevant for their potential application in light-emitting devices, photovoltaics, nonlinear optics and sensing. The availability of high-quality experimental data for such systems makes them ideally suited for a validation [...] Read more.

In recent years, the photophysical properties of crystalline metal-organic frameworks (MOFs) have become increasingly relevant for their potential application in light-emitting devices, photovoltaics, nonlinear optics and sensing. The availability of high-quality experimental data for such systems makes them ideally suited for a validation of quantum mechanical simulations, aiming at an in-depth atomistic understanding of photophysical phenomena. Here we present a computational DFT study of the absorption and emission characteristics of a Zn-based surface-anchored metal-organic framework (Zn-SURMOF-2) containing anthracenedibenzoic acid (ADB) as linker. Combining band-structure and cluster-based simulations on ADB chromophores in various conformations and aggregation states, we are able to provide a detailed explanation of the experimentally observed photophysical properties of Zn-ADB SURMOF-2: The unexpected (weak) red-shift of the absorption maxima upon incorporating ADB chromophores into SURMOF-2 can be explained by a combination of excitonic coupling effects with conformational changes of the chromophores already in their ground state. As far as the unusually large red-shift of the emission of Zn-ADB SURMOF-2 is concerned, based on our simulations, we attribute it to a modification of the exciton coupling compared to conventional H-aggregates, which results from a relative slip of the centers of neighboring chromophores upon incorporation in Zn-ADB SURMOF-2. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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16 pages, 2009 KiB

Open AccessArticle

Second-Generation Lignocellulosic Supportive Material Improves Atomic Ratios of C:O and H:O and Thermomechanical Behavior of Hybrid Non-Woody Pellets

by Bruno Rafael de Almeida Moreira, Ronaldo da Silva Viana, Victor Hugo Cruz, Anderson Chagas Magalhães, Celso Tadao Miasaki, Paulo Alexandre Monteiro de Figueiredo, Lucas Aparecido Manzani Lisboa, Sérgio Bispo Ramos, Douglas Enrique Juárez Sánchez, Marcelo Carvalho Minhoto Teixeira Filho and André May

Molecules 2020, 25(18), 4219; https://doi.org/10.3390/molecules25184219 - 15 Sep 2020

Cited by 4 | Viewed by 2317

Abstract

Pellets refer to solid biofuels for heating and power. The pellet’s integrity is of great relevant to ensure safe and effective transportation and storage, and comfort to stakeholders. Several materials that are supportive, whether organic and inorganic, to pellets exist. However, no work [...] Read more.

Pellets refer to solid biofuels for heating and power. The pellet’s integrity is of great relevant to ensure safe and effective transportation and storage, and comfort to stakeholders. Several materials that are supportive, whether organic and inorganic, to pellets exist. However, no work in the literature is linking making hybrid non-wood pellets with addition of residual biomass from distillation of cellulosic bioethanol, and this requires further investigations. Figuring out how effective this challenging agro-industrial residue could be for reinforcing non-wood pellets is accordingly the scientific point of this study focusing on management of waste and valorization of biomass. The pilot-scale manufacturing of hybrid pellets consisted of systematically pressing sugarcane bagasse with the lignocellulosic reinforcement at the mass ratios of 3:1, 1:1, and 1:3 on an automatic pelletizer machine at 200 MPa and 125 °C. Elemental contents of C and H, durability, and energy density all increased significantly from 50.05 to 53.50%, 5.95 to 7.80%, 95.90 to 99.55%, and 28.20 to 31.20 MJ kg⁻¹, respectively, with blending the starting material with the reinforcement at 1:3. Preliminary evidence of residual biomass from distillation of second-generation bioethanol capable of highly improving molecular flammable/combustible properties, mechanical stability, and fuel power of composite non-wood pellets exist. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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19 pages, 4266 KiB

Open AccessArticle

Boron-Doped Reduced Graphene Oxide with Tunable Bandgap and Enhanced Surface Plasmon Resonance

by Muhammad Junaid, M. H. Md Khir, Gunawan Witjaksono, Nelson Tansu, Mohamed Shuaib Mohamed Saheed, Pradeep Kumar, Zaka Ullah, Asfand Yar and Fahad Usman

Molecules 2020, 25(16), 3646; https://doi.org/10.3390/molecules25163646 - 11 Aug 2020

Cited by 40 | Viewed by 4750

Abstract

Graphene and its hybrids are being employed as potential materials in light-sensing devices due to their high optical and electronic properties. However, the absence of a bandgap in graphene limits the realization of devices with high performance. In this work, a boron-doped reduced [...] Read more.

Graphene and its hybrids are being employed as potential materials in light-sensing devices due to their high optical and electronic properties. However, the absence of a bandgap in graphene limits the realization of devices with high performance. In this work, a boron-doped reduced graphene oxide (B-rGO) is proposed to overcome the above problems. Boron doping enhances the conductivity of graphene oxide and creates several defect sites during the reduction process, which can play a vital role in achieving high-sensing performance of light-sensing devices. Initially, the B-rGO is synthesized using a modified microwave-assisted hydrothermal method and later analyzed using standard FESEM, FTIR, XPS, Raman, and XRD techniques. The content of boron in doped rGO was found to be 6.51 at.%. The B-rGO showed a tunable optical bandgap from 2.91 to 3.05 eV in the visible spectrum with an electrical conductivity of 0.816 S/cm. The optical constants obtained from UV-Vis absorption spectra suggested an enhanced surface plasmon resonance (SPR) response for B-rGO in the theoretical study, which was further verified by experimental investigations. The B-rGO with tunable bandgap and enhanced SPR could open up the solution for future high-performance optoelectronic and sensing applications. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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13 pages, 17953 KiB

Open AccessArticle

Synthesis and Microwave Absorption Properties of Sulfur-Free Expanded Graphite/Fe₃O₄ Composites

by Jian Sun, Lijie Li, Rui Yu, Xianlong Ma, Shaohua Jin, Kun Chen, Shusen Chen, Xijuan Lv and Qinghai Shu

Molecules 2020, 25(13), 3044; https://doi.org/10.3390/molecules25133044 - 3 Jul 2020

Cited by 24 | Viewed by 3062

Abstract

In this study, sulfur-free expanded graphite (EG) was obtained by using flake graphite as the raw material, and EG/Fe₃O₄ composites with excellent microwave absorption properties were prepared by a facile one-pot co-precipitation method. The structure and properties of as-prepared EG/Fe [...] Read more.

In this study, sulfur-free expanded graphite (EG) was obtained by using flake graphite as the raw material, and EG/Fe₃O₄ composites with excellent microwave absorption properties were prepared by a facile one-pot co-precipitation method. The structure and properties of as-prepared EG/Fe₃O₄ were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Raman, X-ray photoelectron spectrometry (XPS), thermogravimetric (TG), and vibrating sample magnetometry (VSM) characterizations. The Fe₃O₄ intercalated between the layers of expanded graphite forms a sandwich-like structure which is superparamagnetic and porous. When applied as a microwave absorber, the reflection loss (R_L) of EG/Fe₃O₄ reaches −40.39 dB with a thickness of 3.0 mm (10 wt% loading), and the effective absorption bandwidth (EAB < −10 dB) with R_L exceeding −10 dB is 4.76–17.66 GHz with the absorber thickness of 1.5–4.0 mm. Considering its non-toxicity, easy operation, low cost, suitability for large-scale industrial production, and excellent microwave absorbing performance, EG/Fe₃O₄ is expected to be a promising candidate for industrialized electromagnetic absorbing materials. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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23 pages, 7914 KiB

Open AccessArticle

Magnetically Recoverable TiO₂/SiO₂/γ-Fe₂O₃/rGO Composite with Significantly Enhanced UV-Visible Light Photocatalytic Activity

by Reyhaneh Kaveh, Maryam Mokhtarifar, Mojtaba Bagherzadeh, Andrea Lucotti, Maria Vittoria Diamanti and MariaPia Pedeferri

Molecules 2020, 25(13), 2996; https://doi.org/10.3390/molecules25132996 - 30 Jun 2020

Cited by 24 | Viewed by 3579

Abstract

In this paper, we report the preparation of a new composite (TiO₂/SiO₂/γ-Fe₂O₃/rGO) with a high photocatalytic efficiency. The properties of the composite were examined by different analyses, including X-ray diffraction (XRD), field emission scanning electron [...] Read more.

In this paper, we report the preparation of a new composite (TiO₂/SiO₂/γ-Fe₂O₃/rGO) with a high photocatalytic efficiency. The properties of the composite were examined by different analyses, including X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), photoluminescence (PL), UV-Visible light diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman, vibrating-sample magnetometer (VSM), and nitrogen gas physisorption (BET) studies. The photocatalytic efficiency of the proposed composite was evaluated by the degradation of methylene blue under UV and visible light, and the results were compared with titanium dioxide (TiO₂), where degradation increased from 30% to 84% and 4% to 66% under UV and visible light, respectively. The significant increase in photocatalytic activity may be explained by the higher adsorption of dye on the surface of the composite and the higher separation and transfer of charge carriers, which in turn promote active sites and photocatalytic efficiency. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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Review

Jump to: Research

32 pages, 7323 KiB

Open AccessReview

A Review on Graphene-Based Light Emitting Functional Devices

by Muhammad Junaid, M. H. Md Khir, Gunawan Witjaksono, Zaka Ullah, Nelson Tansu, Mohamed Shuaib Mohamed Saheed, Pradeep Kumar, Lee Hing Wah, Saeed Ahmed Magsi and Muhammad Aadil Siddiqui

Molecules 2020, 25(18), 4217; https://doi.org/10.3390/molecules25184217 - 14 Sep 2020

Cited by 20 | Viewed by 4985

Abstract

In recent years, the field of nanophotonics has progressively developed. However, constant demand for the development of new light source still exists at the nanometric scale. Light emissions from graphene-based active materials can provide a leading platform for the development of two dimensional [...] Read more.

In recent years, the field of nanophotonics has progressively developed. However, constant demand for the development of new light source still exists at the nanometric scale. Light emissions from graphene-based active materials can provide a leading platform for the development of two dimensional (2-D), flexible, thin, and robust light-emitting sources. The exceptional structure of Dirac’s electrons in graphene, massless fermions, and the linear dispersion relationship with ultra-wideband plasmon and tunable surface polarities allows numerous applications in optoelectronics and plasmonics. In this article, we present a comprehensive review of recent developments in graphene-based light-emitting devices. Light emissions from graphene-based devices have been evaluated with different aspects, such as thermal emission, electroluminescence, and plasmons assisted emission. Theoretical investigations, along with experimental demonstration in the development of graphene-based light-emitting devices, have also been reviewed and discussed. Moreover, the graphene-based light-emitting devices are also addressed from the perspective of future applications, such as optical modulators, optical interconnects, and optical sensing. Finally, this review provides a comprehensive discussion on current technological issues and challenges related to the potential applications of emerging graphene-based light-emitting devices. Full article

(This article belongs to the Special Issue Hybrid Materials for Advanced Applications)

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