Browsing by Author "Agyei-Tuffour, B."

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Activated cashew carbon-manganese oxide based electrodes for supercapacitor applications
(Scientific African, 2023) Boamah, R.; Agyei-Tuffour, B.; Dodoo-Arhin, D.; Nyankson, E.; Brobbey, K.J.; et al.
The current global energy challenge which affects most developing countries in particular, is of major source of concern today. The availability of less expensive techniques of storing excess generated energy is critical to the success of the renewable energy roadmaps implementation. In this study, hydrothermal and chemical leaching methods have been used to synthesize MnO2 nanoparticles using KMnO4 and MnSO4 as precursors at 140 °C and from natural local manganese ore. Activated Carbon (ACF) have also been produced from agricultural Cashew biomass waste, through a physical carbonization and KOH activation process using temperatures of 700 °C – 900 °C for periods between 1 and 2 h. The as-prepared materials have been characterized via XRD, Raman, FTIR, SEM. Electrochemical performance measurements (CV, EIS and GCD) were carried out on the prepared electrodes. The specific capacitance values obtained were in the range of 2.8 F/g - 6.5 F/g at different scan rates of 20 mV -50 mV respectively in a potential range of -0.4 to +0.4 V and -0.4 to +0.6 V for the various types of electrodes
Ag2CO3-halloysite nanotubes composite with enhanced removal efficiency for water soluble dyes
(Heliyon, 2019-06-13) Nyankson, E.; Agyei-Tuffour, B.; Annan, E.; Yaya, A.; Mensah, B.; Onwona-Agyeman, B.; Amedalor, R.; Kwaku-Frimpong, B.
The release of water soluble dyes into the environment is an utmost concern in many countries. This paper presents the effects of Ag2CO3-halloysite composites on the efficient removal of water soluble dyes. In this study, NaHCO3 solution was added dropwisely to halloysite nanotubes (HNTs) dispersed in aqueous AgNO3 to form Ag2CO3-HNTs composite. The synthesized Ag2CO3-HNTs composite was characterized with Diffused Reflectance Spectroscopy (DRS), X-ray Diffraction (XRD), Thermogravimetric analysis (TGA), Scanning Electron Microscopy- Energy Dispersive Spectroscopy (SEM-EDX) and Fourier Transform Infra-Red (FT-IR) spectroscopy. The photocatalytic activity and the adsorption capacity of Ag2CO3-HNTs on methylene blue and rhodamine b dyes were dependent on pH and the amount of HNTs used in the synthesis. The photodegradation efficiency of Ag2CO3 was lower when compared with that of the composite material. This observation is due to the reduction in the electron-hole recombination with the HNTs acting as electron trapping site and the enhanced aqueous dispersity of Ag2CO3-HNTs. The enhanced adsorption of water soluble dyes by the Ag2CO3-HNTs resulted from the electrostatic attraction of cationic dyes to the surface of the HNTs (negatively charged). The Ag2CO3-HNTs therefore removed dye pollutants through a combination of photocatalytic and adsorption processes. The results obtained during the study confirmed the potential application of Ag2CO3-HNTs composite in water treatment technologies.
Annealing effects on interdiffusion in layered FA-rich perovskite solar cells
(AIP Advances, 2021) Oyewole, D.O.; Koech, R.K.; Ichwani, R.; Ahmed, R.; Tamayo, J.H.; Adeniji, S.A.; Cromwell, J.; Ulloa, E.C.; Oyewole, O.K.; Agyei-Tuffour, B.; Titova, L.V.; Burnham, N. A.; Soboyejo, W. O.
Annealing is one of the processing methods that are used for the fabrication of defect-free, photoactive perovskite films with compact grains in highly efficient and stable perovskite solar cells (PSCs). Thus, the annealing temperature is a key parameter for the control of the interdiffusion (of constituent elements) in photoactive films. In this paper, we present the results of a systematic study of the effects of annealing on the interdiffusion of constituent elements in efficient formamidinium-based PSCs. We also explore the effects of annealing-induced interdiffusion on layer microstructures, local strains, and the optoelectronic properties of perovskite films. We observe a dramatic upward diffusion of tin (Sn) and titanium (Ti) from fluorine-doped tin oxide and titanium dioxide (TiO2) to the perovskite films. We also observe a downward diffusion of lead (Pb) and iodine (I) from the perovskite films to the mesoporous layer of the electron transporting layer (ETL), after annealing at temperatures between 100 and 150 ○C. The diffused I substitutes for Ti in the ETL, which improves the optoelectronic properties of the films, for annealing temperatures between 100 and 130 ○C. The annealing-induced interdiffusion that occurs at higher temperatures (between 140 and 150 ○C) results in higher levels of interdiffusion, along with increased local strains that lead to the nucleation of pores and cracks. Finally, the implications of the results are discussed for the design of PSCs with improved photoconversion efficiencies and stability.
Application of clay ceramics and nanotechnology in water treatment: A review
(Cogent Engineering, 2018-07) Annan, E.; Agyei-Tuffour, B.; Bensah, Y.D.; Konadu, D.S.; Yaya, A.; Onwona-Agyeman, B.; Nyankson, E.
The increasing demand to provide clean water for drinking has brought to the fore the importance of seeking other materials with the ability or combined effect with other materials to purify water. Clay ceramics are known to be natural and also easily engineered porous-structured materials. Review papers on water filtration over the last decade have been on specific mechanisms or technologies. This review paper presents a single platform which provides information encapsulating all these technologies. This paper highlights water contaminants, and their various treatment technologies. The effectiveness of these technologies are evaluated via scholarly documented peer-reviewed papers. Moreover, the discussions are interspersed with the World Health Organization’s (WHO) standard for various contaminants along with the exploration of the efficiency of clay minerals as potent water filtration material. Finally, current trends in application of nanotechnology in water purification systems are also highlighted. These technologies include adsorption, microbial disinfection, and photocatalysis.
Awaso bauxite red mud-cement based composites: Characterisation for pavement applications
(Case Studies in Construction Materials, 2017-12) Dodoo-Arhin, D.; Nuamah, R.A.; Agyei-Tuffour, B.; Obada, D.O.; Yaya, A.
This paper presents the development of Bauxite residue (red mud) based cement composite mortar blocks for applications in pavement construction. The experimental techniques considered include the structural, thermal, morphological and microscopy analysis of the raw bauxite and red mud samples calcined at 800 °C. Composite mortar blocks of different batch formulations were produced and their physicochemical properties were investigated. The results show that the compressive strength of the as-prepared composite mortar blocks increased by ∼40% compared to the type M mortar strength of ∼2500 N/mm2. The load bearing applications of the composites are discussed to influence the adoption of the calcined red mud as supplement in the production of low-cost Portland cement based composite mortar blocks for the construction industry. © 2017
Characteristics Of Stabilized Shrink-Swell Deposits Using Eggshell Powder
(2013) Nyankson, E.; Agyei-Tuffour, B.; Annan, E.; et al.
Shrink-swell soils expand and heave or contract and crack during periods of high and low moisture content. The expansion and contraction cause the lifting and or sinking of structures, crack development, and eventual collapse of engineering structures. The need to stabilize such plastic soils to improve their load-carrying capacities cannot be overemphasized. Therefore in this article, the effect of lime contained in eggshells and its application in the stabilization of shrink-swell soils have been explored. 4wt% and 8wt% of eggshell powder were mixed with equal masses of two different soil samples from Dodowa (DD) and Adalekope (AD) in Ghana. The samples were characterized with X-ray fluorescence (XRF), Plasticity Index analysis (PI), Free Swell Index (FSI), pH test, and a grading test. The x-ray fluorescence results showed that eggshell contains about 52wt% of CaO, which is largely responsible for soil stabilization. The sample mixed with 8wt% eggshell powder showed a decreased PI, FSI, and a high silt/clay fraction. The results obtained have been discussed and can influence the application of eggshell powders for large-scale stabilization of expansive soils.
Chicken Feather Protein Dispersant for Effective Crude Oil Dispersion in the Marine Environment
(American Chemical Society, 2023) Adofo, Y.K.; Nyankson, E.; Agyei-Tuffour, B.; et al.
Various studies report that aside from the adverse impact of crude oil on the marine environment, there is the likelihood that chemical dispersants used on the surface of water as oil-treating agents themselves possess a degree of toxicity, which have additional effects on the environment. To eliminate the subject of toxicity, there are several materials in nature that have the ability to form good emulsions, and such products include protein molecules. In In this study, chicken feathers, which are known to contain ≥90% protein, were used to formulate a novel dispersant to disperse crude oil in seawater (35 ppt). Protein from chicken feathers was extracted and synthesized into the chicken feather protein (CFP) dispersant using deionized water as a solvent. Emulsions formed from CFP-synthesized dispersants were stable over a considerably long period of time, whereas the droplet sizes of the emulsion formed were on the average very small in diameter, making droplet coalescence very slow. The CFP dispersants exhibited moderate surface and interfacial activity at normal seawater salinity. Using the US EPA’s baffled flask test, at 800 and 1000 mg/ml CFP surfactant-to-oil ratios, dispersion effectiveness values of 56.92 and 68.64 vol % were obtained, respectively, which show that CFP has a great potential in crude oil dispersion. Moreover, the acute toxicity test performed on Nile tilapia showed that CFP was practically nontoxic with an LC50 value of more than 100 mg/L after 96 hours of exposure. The results obtained showed that the CFP dispersant is environmentally friendly.
Chitosan-Coated Halloysite Nanotubes As Vehicle for Controlled Drug Delivery to MCF-7 Cancer Cells In Vitro
(MDPI, 2021) Nyankson, E.; Aboagye, S.O.; Efavi, J.K.; Agyei-Tuffour, B.; Paemka, L.; Asimeng, B.O.; Balapangu, S.; Arthur, P.K.; Tiburu, E.K.
The aim of the work is to improve the release properties of curcumin onto human breast cancer cell lines using coated halloysite nanotubes (HNTs) with chitosan as a polycation. A loading efficiency of 70.2% (w/w) was attained for loading 4.9 mg of the drug into 0.204 g bed volume of HNTs using the vacuum suction method. Results acquired from Brunauer-Emmett-Teller (BET), Fourier-transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), scanning electron spectroscopy (SEM), zeta potential, and thermogravimetric analysis (TGA) indicated the presence of the drug and the biopolymer in and around the nanotubes. The release properties of drug-loaded HNTs (DLHNTs) and chitosan-coated drug-loaded HNTs (DLHNTs-CH) were evaluated. The release percentages of DLHNTs and DLHNTs-CH after 6 h were 50.7 and 37%, respectively. Based on the correlation coefficients obtained by fitting the release nature of curcumin from the two samples, the Korsmeyer-Peppas model was found to be the best-fitted model. In vitro cell viability studies were carried out on the human breast cancer cell line MCF-7, using the MTT and trypan blue exclusion assays. Prior to the Trypan blue assay, the IC50 of curcumin was determined to be ∼30 µM. After 24 h of incubation, the recorded cell viability values were 94, 68, 57, and 51% for HNTs, DLHNTs-CH, DLHNTs, and curcumin, respectively. In comparison to the release studies, it could be deducted that sustained lethal doses of curcumin were released from the DLHNTs-CH within the same time. It is concluded from this work that the “burst release” of naked drugs could be slowly administered using chitosan-coated HNTs as potential drug carriers.
Comparative analyses of rice husk cellulose fiber and kaolin particulate reinforced thermoplastic cassava starch biocomposites using the solution casting technique
(Wiley, 2021) Agyei-Tuffour, B.; Asante, J.T.; Nyankson, E.; Dodoo-Arhin, D.; Oteng-Peprah, M.; Azeko, S.T.; Azeko, A.S.; Oyewole, O.K.; Yaya, A.
he potential of biodegradable packaging materials from thermoplastic cassava starch (TPS) reinforced with rice husk cellulose fibers (RHCF) and kaolin particulates (KP) using the solution casting method has been presented. This involved the blending of TPS and RHCF/KP in a plasticizer of ~4 ml of glycerol and ~45 ml of distilled water at 125°C and stirred at 60 rpm until a gel was formed. The gel was cast into sheets and bone-shaped tensile specimens and allowed to dry for 5 days and characterized. The results show a semicrystalline structure for TPS with an ~36% increase in crystallinity after reinforcement. The O-H bond stretching and the C-H bending bonds due to starch–glycerol reactions were the common functional groups in TPS–RHCF biocomposites, and Si-O-C bonds were characteristics of the silica phase in the kaolin. The water vapor transmission rate (WVTR) reduced to ~34% with KP reinforcements from ~238 g/m.day to 177 g/m.day and to ~74 g/m.day and ~164% for TPS–RHCF. The strength increased with up to 50 wt% kaolin content; ~0.96 MPa yield strength and ~2.60 MPa ultimate tensile strength (UTS) were recorded. For the RHCF reinforced composites, TPS-50 wt% also showed high strengths of ~0.96 MPa yield strength and ~3.50 MPa UTS. The WVTR reduced as content of kaolin was increased. Typically, from 0 to 30 wt% volume fraction of kaolin, the WVTR was reduced by ~34% to 177 g/m.day for TPS–kaolin and by ~164% to ~74 g/m.day in TPS–RHCF. The as-prepared biocomposites have potential as good packaging materials.
Curcumin loaded Ag–TiO2-halloysite nanotubes platform for combined chemo-photodynamic therapy treatment of cancer cells†
(Royal Society of Chemistry, 2022) Nyankson, E.; Awuzah, D.; Tiburu, E.K.; Efavi, J.K.; Agyei-Tuffour, B.; Paemka, L.
The use of naturally occurring anticancer materials in combination with doped metal oxide has emerged as one of the most promising ways for improving anticancer treatment efficacy. In this study, the anticancer potential of curcumin-loaded Ag–TiO2-halloysite nanotubes (curcumin-loaded Ag–TiO2-HNTs) was examined. Ag–TiO2-HNTs with different wt% of Ag–TiO2 were synthesized and characterized using XRD, TGA, FT-IR, UV-Vis spectroscopy, and SEM-EDX. The XRD results revealed the presence of crystalline TiO2. However, the presence of Ag was detected through the SEM-EDX analysis. Cyclic voltammetry measurements suggested the enhancement of the release of ROS from TiO2 upon deposition with Ag. FT-IR and TGA analysis confirmed the successful loading of curcumin inside the nanotubes of the halloysite. In vitro drug released studies revealed the release of approximately 80–99% curcumin within 48 hours. Kinetic model studies revealed that the release of curcumin from HNT and Ag–TiO2-HNT followed the first-order and Higuchi models, respectively. The light irradiated curcumin-loaded Ag– TiO2-HNTs samples exhibited considerable anticancer potential as compared to the free curcumin, irradiated Ag–TiO2 NPs samples, and unirradiated curcumin loaded Ag–TiO2-HNTs samples. The obtained results revealed that combined chemo- and photodynamic therapy using curcumin-loaded Ag–TiO2-HNTs nanomaterial has the potential as an effective anticancer treatment method
Dispersants as an oil spill clean-up technique in the marine environment: A review
(Heliyon, 2022) Adofo, Y.K.; Nyankson, E.; Agyei-Tuffour, B.
Oil is a major source of energy in the industrial world. Exploitation of oil and rigging activities, transportation via sea, and many other mechanical failures lead to oil spills into the marine environment. In view of these, the suitability and effectiveness of oil spill response methods have always been a topical discussion worldwide. It has become necessary, now than ever, for existing spill response methods used to remove oil from the environment to be improved upon and more importantly, develop new response materials that are sustainable and environmentally friendly. There exist surfactants in nature that are non-toxic and biodegradable, which can be explored to produce potential dispersants to help remove oil safely from the surface of marine water. This review comprises of the works and resourceful materials produced by various researchers and agencies in the field of oil spill response, placing emphasis on the use of dispersants in the marine environment.
Effects of blister formation on the degradation of organic light emitting devices
(AIP Advances, 2022) Cromwell, J.; Adeniji, S. A.; Oyewole, D. O.; Koech, R.; Ichwani, R.; Agyei-Tuffour, B.; Oyewole, O. K.; Soboyejo, W. O.
This paper presents the results of a combined experimental and computational study of the mechanisms of blister formation, and their effects on the degradation of organic light emitting devices (OLEDs). Blister formation is attributed to the effects of thermally induced mismatch stresses associated with applied bias. These result in interfacial cracking phenomena that are affected by the solvents that are used in OLED fabrication. The OLEDs are first fabricated using an electron transport layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) deposited on an active layer made from solutions of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] dissolved in different solvents (toluene, chloroform, and chlorobenzene). The formation of blisters and degradation is then studied under applied bias for devices fabricated using different solvents (toluene, chloroform, and chlorobenzene) and emissive layer thicknesses. The underlying layer mechanical properties are then incorporated into interfacial fracture mechanic models that explain the formation of blisters that degrade the performance of OLED structures.
Effects of Graphene Oxide and Reduced Graphene Oxide on the Mechanical and Dielectric Properties of Acrylonitrile-Butadiene Rubber and Ethylene-Propylene-Diene-Monomer Blend
(International Journal of Polymer Science, 2022) Mensah, B.; Konadu, D.S.; Agyei-Tuffour, B.
The composites of properties of ethylene-propylene-diene-monomer (E) and acrylonitrile butadiene-rubber (N) composites of graphene oxide (GO) and reduced graphene oxide (G) were prepared by a combination of solution and open-roll method. They include single matrices (EGO and EG) and blends N/E, 20 part of hundreds of rubber (phr)/80 phr (A), 80 phr/20 phr (B), and 50 phr/50 phr(C) blend containing GO and G. The physico-mechanical properties including vulcanization, tensile, glass transition temperature (Tg), and dielectric spectroscopic properties were evaluated. The N-rich systems reinforced with GO, cured faster than the E-rich systems. Also, N-rich systems obtained the highest dielectric constant ðɛ′Þ, especially when GO and G were incorporated, for example, NG and N-GO obtained 317 and 283% increment in ɛ′ than EG and EGO, respectively. In terms of tensile properties, AGO exhibited the highest strength and elongation at break properties (%). Therefore, solution mixing technique of rubber blends filled with nanoinclusion can be achieved with the tendency of reducing cost without the use of compatibilizer and still maintain the integrity of the physical properties of the final product. The result obtained therefore shows that the current compositions can find various applications in oil/gas sealants, heat-resistant applications, and energy storage materials with minimal losses.
Effects of substrates on the performance of optoelectronic devices: A review
(Cogent Engineering, 2020) Asare, J.; Agyei-Tuffour, B.; Amonoo, E.A.; Dodoo-Arhin, D.; Nyankson, E.; Mensah, B.; Oyewole, O.O.; Yaya, A.; Onwona-Agyeman, B.
This review discusses the effects of substrates on devices fabricated for optoelectronic applications. It includes the types and characteristics of substrates, synthesis and fabrication of substrates, and the influence of substrates on the optical properties, surface morphology and current-voltage behaviour of optoelectronic devices. The study showed that two main types of substrates: planar and textured are commonly used in the industry. Flexibility, semi-rigidity and rigidity are characteristics of the substrates and they vary in modulus, transparency and texture. Whereas glass and metal substrates can be produced via melt casting, polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), etc are produced by crosslinking polymer base materials with curing agents. The mechanical and current-voltage characteristics are also shown for planar and textured substrate-based devices. The textured substrates showed ridges, wrinkles, buckled surface morphology whereas the planar showed uniform and largely flat morphology. Textured substrates also recorded higher optical absorbance and improved device efficiencies compared with planar substrates. The molecular configuration of the polymer chains are edged-on for planar substrates and both edge-on and face-on for textured substrates. The findings and their implications have been discussed to highlight the importance of substrates in the fabrication and performance of optoelectronic devices.
A Hybrid Hole Transport Layer for Perovskite-Based Solar Cells
(MDPI, 2021) Asare, J.; Sanni, D.M.; Agyei-Tuffour, B.; Agede, E.; Oyewole, O.K.; Yerramilli, A.S.; Doumon, N.Y.
This paper presents the effect of a composite poly(3,4-ethylenedioxythiophene) polystyrene sulfonate PEDOT:PSS and copper-doped nickel oxide (Cu:NiOx) hole transport layer (HTL) on the performance of perovskite solar cells (PSCs). Thin films of Cu:NiOx were spin-coated onto fluorine doped tin oxide (FTO) glass substrates using a blend of nickel acetate tetrahydrate, 2-methoxyethanol and monoethanolamine (MEA) and copper acetate monohydrate. The prepared solution was stirred at 65 ◦C for 4 h and spin-coated onto the FTO substrates at 3000 rpm for 30 s in a nitrogen glovebox. The Cu:NiOx/FTO/glass structure was then annealed in air at 400 ◦C for 30 min. A mixture of PEDOT:PSS and isopropyl alcohol (IPA) (in 1:0.05 wt%) was spun onto the Cu:NiOx/FTO/glass substrate at 4000 rpm for 60 s. The multilayer structure was annealed at 130 ◦C for 15 min. Subsequently, the perovskite precursor (0.95 M) of methylammonium iodide (MAI) to lead acetate trihydrate (Pb(OAc)2 ·3H2O) was spin-coated at 4000 rpm for 200 s and thermally annealed at 80 ◦C for 12 min. The inverted planar perovskite solar cells were then fabricated by the deposition of a photoactive layer (CH3NH3PbI3), [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and a Ag electrode. The mechanical behavior of the device during the fabrication of the Cu:NiOx HTL was modeled with finite element simulations using Abaqus/Complete Abaqus Environment CAE. The results show that incorporating Cu:NiOx into the PSC device improves its density–voltage (J–V) behavior, giving an enhanced photoconversion efficiency (PCE) of ~12.8% from ~9.8% and ~11.5% when PEDOT:PSS-only and Cu:NiOx-only are fabricated, respectively. The short circuit current density Jsc for the 0.1 M Cu:NiOx and 0.2 M Cu:NiOx-based devices increased by 18% and 9%, respectively, due to the increase in the electrical conductivity of the Cu:NiOx which provides room for more charges to be extracted out of the absorber layer. The increases in the PCEs were due to the copper-doped nickel oxide blend with the PEDOT:PSS which enhanced the exciton density and charge transport efficiency leading to higher electrical conductivity. The results indicate that the devices with the copper-doped nickel oxide hole transport layer (HTL) are slower to degrade compared with the PEDOT:PSS-only-based HTL. The finite element analyses show that the Cu:NiOx layer would not extensively deform the device, leading to improved stability and enhanced performance. The implications of the results are discussed for the design of low-temperature solution-processed PSCs with copper-doped nickel oxide composite HTLs.
Industrial Applications of Clay Materials from Ghana - A Review
(Oriental Journal of Chemistry, 2018-08) Asamoah, R.B.; Nyankson, E.; Annan, E.; Agyei-Tuffour, B.; Efavi, J.K.; Kan-Dapaah, K.; Apalangya, V.A.; Damoah, L.N.W.; Dodoo-Arhin, D.; Tiburu, E.K.; Kwofie, S.K.; Onwona-Agyeman, B.; Yaya, A.
Clay minerals are phyllosilicate groups naturally found in soils in all parts of the world. They have proven to be among the most essential industrial minerals because of their unique physicochemical properties and versatile applications within a wide range of fields including ceramics, construction, and environmental remediation, biomedical as well as cosmetics. Clay minerals are also primary to the production of other materials such as composite for secondary applications. In Ghana, clay mineral deposits are commonly found in several areas including soil horizons as well as geothermal fields and volcanic deposits, and are formed under certain geological conditions. This review seeks to explore the geographical occurrence and discusses the current uses of various local clay materials in Ghana in order to highlight opportunities for the utilization of these materials for other applications.
Managing Excess Lead Iodide with Functionalized Oxo-Graphene Nanosheets for Stable Perovskite Solar Cells
(Angewandte Chemie International Edition, 2023) Li, G.; Li, M.; Agyei-Tuffour, B.; et al.
Stability issues could prevent lead halide perovskite solar cells (PSCs) from commercialization despite it having a comparable power conversion efficiency (PCE) to silicon solar cells. Overcoming drawbacks affecting their long-term stability is gaining incremental importance. Excess lead iodide (PbI2) causes perovskite degradation, although it aids in crystal growth and defect passivation. Herein, we synthesized functionalized oxo-graphene nanosheets (Dec-oxoG NSs) to effectively manage the excess PbI2. Dec-oxoG NSs provide anchoring sites to bind the excess PbI2 and passivate perovskite grain boundaries, thereby reducing charge recombination loss and significantly boosting the extraction of free electrons. The inclusion of Dec-oxoG NSs leads to a PCE of 23.7% in inverted (p-i-n) PSCs. The devices retain 93.8% of their initial efficiency after 1,000 hours of tracking at maximum power points under continuous one-sun illumination and exhibit high stability under thermal and ambient conditions. [*] Dr. G. Li,+ Prof. Dr. M. Li, Y. Tang, Z. Zhang Key Lab for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High efficiency Display and Lighting Technology, School of Materials Science and Engineering, Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University Kaifeng 475004 (China) E-mail: mengli@henu.edu.cn Dr. G. Li,+ Prof. Dr. M. Li, Dr. A. Musiienko, F. Akhundova, J. Li, K. Prashanthan, Dr. F. Yang, S. Trofimov, S. Zuo, L. Wu, L. Wang, Dr. Y. Yang, Dr. B. Agyei-Tuffour, Dr. R. W. MacQueen, Dr. B. Naydenov, Dr. T. Unold, Prof. Dr. E. Unger, Prof. Dr. A. Abate Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Hahn-Meitner-Platz 1, 14109 Berlin (Germany) E-mail: antonio.abate@helmholtz-berlin.de Dr. G. Li,+ Prof. Dr. A. Abate Department of Chemistry, Bielefeld University Universitätsstraße 25, 33615 Bielefeld (Germany) Dr. G. Li+ Present address: Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne (Switzerland) Dr. Y. Hu,+ Q. Cao, Prof. Dr. S. Eigler Institute of Chemistry and Biochemistry, Freie Universität Berlin Altensteinstraße 23a, 14195 Berlin (Germany) E-mail: siegfried.eigler@fu-berlin.de Dr. Y. Hu+ CNRS, Immunology, Immunopathology and Therapeutic Chemistry, UPR3572, University of Strasbourg, ISIS 67000 Strasbourg (France) K. Prashanthan Department of Physics, University of Jaffn
Mechanical Properties of Epoxy/Clay Composite Coatings on an X65 Steel Substrate
(Taylor & Francis Group, 2021) Ngasoh, O.F.; Anye, V.C.; Ojo, E.B.; Stanislas, T.T.; Bello, A.; Agyei-Tuffour, B.; Orisekeh, K.; Oyewole, O.K.; Rahbar, N.; Soboyejo, W.O.
This paper presents the results of a combined experimental and theoretical study of the interfacial and mechanical properties of epoxy/clay composites coatings on a mild steel substrate. This was studied using nano-indentation and Brazil Disk techniques to determine the Young’s moduli, hardness values and mode mixity characteristics of the composite coatings. The Young’s moduli of the rein forced composites comprising 1, 3, and 5 wt. % of montmorillonite clay particles are shown to improve, respectively, by about 23%, 58%, and 50% while the respective hardness values increased by about 46%, 80%, and 88%, relative to those of pristine epoxy. The measured mechanical properties have also shown to compare favorably with predictions from composite theories (rule-of-mixture and shear lag theories). The interfacial toughness between X65 steel and the epoxy/clay coatings increases with increasing mode mixity. This is associated with crack-tip shielding by crack deflection and crack bridging. The trends in the measured mode-mixity dependence of the interfacial fracture toughness values are consistent with predictions from the simplified zone, normal zone, and row models (at lower mode mixity). The insights from the observations and the measured crack profiles are incorporated into zone and row models for the estimation of crack-tip shielding. The implications of the results are discussed for the design of epoxy/clay composites with attractive combinations of mechanical properties.
Modified halloysite nanoclay as a vehicle for sustained drug delivery
(Heliyon, 2018-07) Bediako, E.G.; Nyankson, E.; Dodoo-Arhin, D.; Agyei-Tuffour, B.; Łukowiec, D.; Tomiczek, B.; Yaya, A.; Efavi, J.K.
This paper presents the effect of modified halloysite nanotubes on the sustained drug release mechanisms of sodium salicylate. Acid treatment and composite polymer-halloysite modification techniques were adopted in this study. After each modification, sodium salicylate drug was loaded, and in vitro release properties were evaluated and compared with the raw unmodified halloysite nanotubes. The results obtained from SEM, TEM and FTIR analyses indicate that both acid treatment and composite formation have no effect on the tubular structure and morphology of halloysite. However, modification of the halloysite nanotubes did influence the drug release rate. In the acid treatment modification, there was an improved loading of sodium salicylate drug which resulted in the sustain release of large amount of the sodium salicylate. In the polymer/halloysite composite formation, a consistent layer of polymer was formed around the halloysite during the composite formation and thus delayed release providing sustained release of sodium salicylate drug over a longer period of time as compared to the acid treated and unmodified halloysite. The results from the invitro release were best fitted with the Higuchi and the Koresymer-Peppas models.
Multicomponent Photocatalytic-Dispersant System for Oil Spill Remediation
(ACS Omega, 2024) Gbogbo, S.; Nyankson, E.; Agyei-Tuffour, B.; et al.
In the present work, the potential application of a fabricated halloysite nanotubes-Ag-TiO2 (HNT-Ag-TiO2) compo site loaded with a binary surfactant mixture made up of lecithin and Tween 80 (LT80) in remediating oil spillages was examined. The as-prepared Ag-TiO2 that was used in the fabrication of the HNT-Ag-TiO2-LT80 composite was characterized by X-ray diffraction, Raman spectroscopy, UV−vis and diffuse reflectance spectroscopy, CV analyses, and SEM-EDX. The synthesized composite was also characterized by thermogravimetric analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. The synthesized composite was active in both the UV and visible light regions of the electromagnetic spectrum. The oil-remediating potential of the as-prepared composite was examined on crude oil, and aromatics and asphaltene fractions of crude oil. The composite was able to reduce the surface tension, form stable emulsions and smaller oil droplet sizes, and achieve a high dispersion effectiveness of 91.5%. A mixture of each of the crude oil and its fractions and HNT-Ag-TiO2-LT80 was subjected to photodegradation under UV light irradiation. The results from the GC-MS and UV−vis analysis of the photodegraded crude oil revealed that the photocatal composite was able to photodegrade the crude oil, aromatics, and asphaltene fractions of crude oil with the formation of intermediate photodegradation products depicting that the HNT-Ag-TiO2-LT80 has a potential as an oil spill remediation material.