Displaying publications 81 - 100 of 337 in total

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  1. Fulltext Electrochemical Detection of Arsenite Using a Silica Nanoparticles-Modified Screen-Printed Carbon Electrode
    Ismail S, Yusof NA, Abdullah J, Abd Rahman SF
    Materials (Basel), 2020 Jul 16;13(14).
    PMID: 32708531 DOI: 10.3390/ma13143168
    Arsenic poisoning in the environment can cause severe effects on human health, hence detection is crucial. An electrochemical-based portable assessment of arsenic contamination is the ability to identify arsenite (As(III)). To achieve this, a low-cost electroanalytical assay for the detection of As(III) utilizing a silica nanoparticles (SiNPs)-modified screen-printed carbon electrode (SPCE) was developed. The morphological and elemental analysis of functionalized SiNPs and a SiNPs/SPCE-modified sensor was studied using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The electrochemical responses towards arsenic detection were measured using the cyclic voltammetry (CV) and linear sweep anodic stripping voltammetry (LSASV) techniques. Under optimized conditions, the anodic peak current was proportional to the As(III) concentration over a wide linear range of 5 to 30 µg/L, with a detection limit of 6.2 µg/L. The suggested approach was effectively valid for the testing of As(III) found within the real water samples with good reproducibility and stability.
    Matched MeSH terms: Silicon Dioxide
  2. Effect of extraction methods on the molecular structure and thermal stability of kenaf (Hibiscus cannabinus core) biomass as an alternative bio-filler for rubber composites
    Mohamad Aini NA, Othman N, Hussin MH, Sahakaro K, Hayeemasae N
    Int J Biol Macromol, 2020 Jul 01;154:1255-1264.
    PMID: 31765744 DOI: 10.1016/j.ijbiomac.2019.10.280
    Lignin from kenaf (Hibiscus cannabinus) core was investigated as an alternative filler for rubber. Three types of extraction methods were used to isolate lignin from kenaf, namely kraft, soda and organosolv process. The particle size, surface area, functionalities changes, molecular weight and thermal properties of the lignin were characterized. The results showed that Kraft lignin (KL) has the smallest particle size (40.41 μm) compared to soda lignin (SL) (63.85 μm) and organosolv lignin (OL) (66.85 μm). This is in good agreement with the BET surface area of 9.52 m2/g, 1.25 m2/g and 2.40 m2/g respectively. However, the smaller surface area of SL compared to OL is due to the smaller pore size and pore volume of SL. KL also showed high hydroxyl content with corresponding high thermal stability as confirmed by NMR and TGA. The thermal stability of the lignin correlates well with the molecular weight (MW). From the overall characteristics, it can be concluded that KL, SL and OL can be used as an alternative filler in rubber compounds to substitute common fillers like silica and carbon.
    Matched MeSH terms: Silicon Dioxide
  3. Fulltext Preparation and Characterization of Polyphenylsulfone (PPSU) Membranes for Biogas Upgrading
    Kujawski W, Li G, Van der Bruggen B, Pedišius N, Tonkonogij J, Tonkonogovas A, et al.
    Materials (Basel), 2020 Jun 25;13(12).
    PMID: 32630434 DOI: 10.3390/ma13122847
    Asymmetric polyphenylsulfone (PPSU) membranes were fabricated by a non-solvent induced phase inversion method. Glycerin and silica nanoparticles were added into the polymer solution to investigate their effects on the material properties and gas separation performance of prepared membranes. The morphology and structure of PPSU membranes were analyzed by scanning electron microscopy (SEM), the surface roughness of the selective layer was analyzed by atomic force microscopy (AFM), and the surface free energy was calculated based on the contact angle measurements by using various solvents. The gas separation performance of PPSU membranes was estimated by measuring the permeability of CO2 and CH4. The addition of glycerin as a nonsolvent into the polymer solution changed the cross-section structure from finger-like structure into sponge-like structure due to the delayed liquid-liquid demixing process, which was confirmed by SEM analysis. The incorporation of silica nanoparticles into PPSU membranes slightly increased the hydrophilicity, which was confirmed by water contact angle results. PPSU membrane fabricated from the polymer solution containing 10 wt.% glycerin showed the best CO2/CH4 selectivity of 3.86 and the CO2 permeability of 1044.01 Barrer. Mixed matrix PPSU membrane containing 0.1 wt.% silica nanoparticles showed the CO2/CH4 selectivity of 3.16 and the CO2 permeability of 1202.77 Barrer.
    Matched MeSH terms: Silicon Dioxide
  4. Fulltext Investigation of Fibers Reinforced Engineered Cementitious Composites Properties Using Quartz Powder
    Liew MS, Aswin M, Danyaro KU, Mohammed BS, Al-Yacouby AM
    Materials (Basel), 2020 May 26;13(11).
    PMID: 32466366 DOI: 10.3390/ma13112428
    In relation to the use of retrofit materials on damaged constructions, application on earthquake-resistant buildings, and for the strengthening and rehabilitation on weakened regions, there is a need for a more superior material than concrete. Application sites include beam-column joints, corbels, link-slabs, deep beams, support regions and dapped-end areas. Fiber reinforced engineered cementitious composites (FR-ECC) can address this issue, because FR-ECC is one of the composite materials that has high strength, ductility and durability. In order to develop FR-ECC, this study was done to investigate the effect of adding quartz powder on the compressive strength capacity and properties of FR-ECC through the use of polyvinyl alcohol (PVA) and steel fibers. The volume fraction of fiber was set to 0%-2%. To support the friendly environment, FR-ECC uses by-product materials such as fly ash and silica fume, with a cement content less than 600 kg/m3. In terms of the experimental investigation on FR-ECC, this work conducted the fresh property tests showing that PVA fibers have quite an influence on ECC workability, due to their hydrophilic behavior. By adjusting the superplasticizer (SP) content, the consistency and high workability of the ECC mixes have been achieved and maintained. The test results indicated that the PVA and steel fibers-based ECC mixes can be classified as self-compacting composites and high early compressive strength composites. Significantly, addition of quartz powder into the ECC mixes increased the compressive strength ratio of the ECC samples up to 1.0747. Furthermore, the steel fiber-based ECC samples exhibited greater compressive strength than the PVA fibers-based ECC samples with the strength ratio of 1.1760. Due to effect of the pozzolanic reaction, the fibers dispersion and orientation in the fresh ECC mixes, so that the cementitious matrices provided the high strength on the FR-ECC samples. During the compression loading, the bulging effect always occurred before the failures of the fibers-based ECC samples. No spalling occurred at the time of rupture and the collapse occurred slowly. Thus, FR-ECC has provided unique characteristics, which will reduce the high cost of maintenance.
    Matched MeSH terms: Silicon Dioxide
  5. Fulltext Surface Energy Mapping of Modified Silica Using IGC Technique at Finite Dilution
    Ngeow YW, Williams DR, Chapman AV, Heng JYY
    ACS Omega, 2020 May 12;5(18):10266-10275.
    PMID: 32426583 DOI: 10.1021/acsomega.9b03920
    The reinforcing silica filler, which can be more than 40% of an elastomer composite, plays a key role to achieve the desired mechanical properties in elastomer vulcanizates. However, the highly hydrophilic nature of silica surface causes silica particle aggregation. It remained a challenge for many tire manufacturers when using silica-filled elastomer compounds. Here, the silica surface energy changes when the surface is modified with coupling or noncoupling silanes; coupling silanes can covalently bond the silica to the elastomers. The surface energy of silica was determined using inverse gas chromatography (IGC) at finite dilution (FD-IGC) and found to be reduced by up to 50% when the silica surface was silanized. The spatial distribution of silica aggregates within the tire matrix is determined by transmission electron microscopy (TEM) and a direct correlation between aggregate size (silica microdispersion) and work of cohesion from IGC is reported, highlighting surface energy and work of cohesion being excellent indicators of the degree of dispersion of silica aggregates.
    Matched MeSH terms: Silicon Dioxide
  6. Papain grafted into the silica coated iron-based magnetic nanoparticles 'IONPs@SiO2-PPN' as a new delivery vehicle to the HeLa cells
    Nasiri R, Dabagh S, Meamar R, Idris A, Muhammad I, Irfan M, et al.
    Nanotechnology, 2020 May 08;31(19):195603.
    PMID: 31978907 DOI: 10.1088/1361-6528/ab6fd4
    The present study aims at engineering, fabrication, characterization, and qualifications of papain (PPN) conjugated SiO2-coated iron oxide nanoparticles 'IONPs@SiO2-PPN'. Initially fabricated iron oxide nanoparticles (IONPs) were coated with silica (SiO2) using sol-gel method to hinder the aggregation and to enhance biocompatibility. Next, PPN was loaded as an anticancer agent into the silica coated IONPs (IONPs@SiO2) for the delivery of papain to the HeLa cancer cells. This fabricated silica-coated based magnetic nanoparticle is introduced as a new physiologically-compatible and stable drug delivery vehicle for delivering of PPN to the HeLa cancer cell line. The IONPs@SiO2-PPN were characterized using FT-IR, AAS, FESEM, XRD, DLS, and VSM equipment. Silica was amended on the surface of iron oxide nanoparticles (IONPs, γ-Fe2O3) to modify its biocompatibility and stability. The solvent evaporation method was used to activate PPN vectorization. The following tests were performed to highlight the compatibility of our proposed delivery vehicle: in vitro toxicity assay, in vivo acute systemic toxicity test, and the histology examination. The results demonstrated that IONPs@SiO2-PPN successfully reduced the IC50 values compared with the native PPN. Also, the structural alternations of HeLa cells exposed to IONPs@SiO2-PPN exhibited higher typical hallmarks of apoptosis compared to the cells treated with the native PPN. The in vivo acute toxicity test indicated no clinical signs of distress/discomfort or weight loss in Balb/C mice a week after the intravenous injection of IONPs@SiO2 (10 mg kg-1). Besides, the tissues architectures were not affected and the pathological inflammatory alternations detection failed. In conclusion, IONPs@SiO2-PPN can be chosen as a potent candidate for further medical applications in the future, for instance as a drug delivery vehicle or hyperthermia agent.
    Matched MeSH terms: Silicon Dioxide/chemistry*
  7. Fulltext Targeted DNA complementation on a 1,1'-carbonyldiimidazole-functionalized surface for identifying Mycobacterium tuberculosis
    Xu S, Xue Y, Guo F, Xu M, Gopinath SCB, Mao X
    3 Biotech, 2020 May;10(5):227.
    PMID: 32373419 DOI: 10.1007/s13205-020-02216-2
    Herein, a rapid and sensitive current-volt measurement was developed for identifying the IS6110 DNA sequence to diagnose Mycobacterium tuberculosis (TB). An aminated capture probe was immobilized on a 1,1'-carbonyldiimidazole-functionalized interdigitated electrode (IDE) silica substrate, and the target sequence was detected by complementation. It was found that all tested concentrations displayed a higher response in current changes than the control, and the limit of detection was 10 fM. The sensitivity ranged from 1 to 10 fM. The control sequences with single-, triple-mismatch and noncomplementary sequences showed great discrimination. This rapid and easy DNA detection method helps to identify M. tuberculosis for early-stage diagnosis of TB.
    Matched MeSH terms: Silicon Dioxide
  8. Silica colloids as non-carriers facilitate Pb2+ transport in saturated porous media under a weak adsorption condition: effects of Pb2+ concentrations
    Dai C, Zhou H, You X, Duan Y, Tu Y, Liu S, et al.
    Environ Sci Pollut Res Int, 2020 May;27(13):15188-15197.
    PMID: 32072419 DOI: 10.1007/s11356-020-08064-0
    Transport of environmental pollutants in groundwater systems can be greatly influenced by colloids. In this study, the cotransport of Pb2+ and silica (SiO2) colloids at different Pb2+ concentrations was systematically investigated by batch adsorption and saturated sand column experiments. Results showed that SiO2 colloids had low adsorption capacity for Pb2+ (less than 1% of the input) compared with sands. In saturated porous media, SiO2 colloids showed a high mobility; however, with the increase of Pb2+ concentration in the sand column, the mobility of SiO2 colloids gradually decreased. Notably, SiO2 colloids could facilitate Pb2+ transport, although they did not serve as effective carriers of Pb2+. Under the condition of low Pb2+ concentration, SiO2 colloids promoted the Pb2+ transport mainly through the way of "transport channel," while changing the porosity of the medium and masking medium adsorption sites were the main mechanisms of SiO2 colloid-facilitated Pb2+ transport under the condition of high Pb2+ concentration. The discovery of this non-adsorption effect of colloids would improve our understanding of colloid-facilitated Pb2+ transport in saturated porous media, which provided new insights into the role of colloids, especially colloids with weak Pb2+ adsorption capacity, in Pb2+ occurrence and transport in soil-groundwater systems.
    Matched MeSH terms: Silicon Dioxide*
  9. Fulltext Influence of N6-Benzyladenine and Sucrose on In Vitro Direct Regeneration and Microrhizome Induction of Kaempferia parviflora Wall. Ex Baker, An Important Ethnomedicinal Herb of Asia
    Labrooy C, Abdullah TL, Stanslas J
    Trop Life Sci Res, 2020 Apr;31(1):123-139.
    PMID: 32963715 DOI: 10.21315/tlsr2020.31.1.8
    Kaempferia parviflora is an ethnomedicinally important plant. Conventional propagation of K. parviflora is hindered by slow growth rate, long dormancy periods and dual use of rhizomes for seeds as well as marketable produce. In our study, we developed a promising dual-phase micropropagation protocol to increase number of plantlets, survivability, biomass and quality plantlets for mass production. Multiple shoot regeneration was found most successful on Murashige and Skoog (MS) media supplemented with 35.52 μM N6-benzyladenine (BA) in terms of highest number of shoots (22.4 ± 1.84), leaves (29.27 ± 1.30), and roots (17.8 ± 1.72) per explant. High survivability was observed with an acclimatisation percentage of 100% in sterile perlite medium. This method was shown to be preferable compared to conventional propagation in terms of propagation time and number of plantlets. Regenerated in vitro plantlets were then successfully induced to form microrhizomes in MS media with an optimal concentration of 6% (w/v) sucrose. Increase in microrhizome biomass (35.7 ± 2.59 g per flask), number of microrhizomes (5.2 ± 0.78), shoots (8.5 ± 1.58) and roots (8.5 ± 1.58) were observed for this treatment. This investigation successfully highlights the manipulation of single factors in short time frame to produce a simple and efficient alternative propagation method for K. parviflora.
    Matched MeSH terms: Silicon Dioxide
  10. Mineral carbonation of sedimentary mine waste for carbon sequestration and potential reutilization as cementitious material
    Kusin FM, Hasan SNMS, Hassim MA, Molahid VLM
    Environ Sci Pollut Res Int, 2020 Apr;27(11):12767-12780.
    PMID: 32008190 DOI: 10.1007/s11356-020-07877-3
    This study highlights the importance of mineralogical composition for potential carbon dioxide (CO2) capture and storage of mine waste materials. In particular, this study attempts to evaluate the role of mineral carbonation of sedimentary mine waste and their potential reutilization as supplementary cementitious material (SCM). Limestone and gold mine wastes were recovered from mine processing sites for their use as SCM in brick-making and for evaluation of potential carbon sequestration. Dominant minerals in the limestone mine waste were calcite and akermanite (calcium silicate) while the gold mine waste was dominated by illite (iron silicate) and chlorite-serpentine (magnesium silicate). Calcium oxide, CaO and silica, SiO2, were the highest composition in the limestone and gold mine waste, respectively, with maximum CO2 storage of between 7.17 and 61.37%. Greater potential for CO2 capture was observed for limestone mine waste as due to higher CaO content alongside magnesium oxide. Mineral carbonation of the limestone mine waste was accelerated at smaller particle size of
    Matched MeSH terms: Silicon Dioxide*
  11. Fulltext Developing Conductive Highly Ordered Zinc Oxide Nanorods by Acetylacetonate-Assisted Growth
    A Karim SS, Takamura Y, Tue PT, Tung NT, Kazmi J, Dee CF, et al.
    Materials (Basel), 2020 Mar 04;13(5).
    PMID: 32143385 DOI: 10.3390/ma13051136
    Highly ordered vertically grown zinc oxide nanorods (ZnO NRs) were synthesized on ZnO-coated SiO2/Si substrate using zinc acetylacetonate hydrate as a precursor via a simple hydrothermal method at 85 °C. We used 0.05 M of ZnO solution to facilitate the growth of ZnO NRs and the immersion time was varied from 0.5 to 4 h. The atomic force microscopy revealed the surface roughness of ZnO seed layer used to grow the ZnO NRs. The morphology of vertically grown ZnO NRs was observed by field emission scanning electron microscopy. X-ray diffraction examination and transmission electron microscopy confirmed that the structure of highly ordered ZnO NRs was crystalline with a strong (002) peak corresponded to ZnO hexagonal wurtzite structure. The growth of highly ordered ZnO NRs was favorable due to the continuous supply of Zn2+ ions and chelating agents properties obtained from the acetylacetonate-derived precursor during the synthesis. Two-point probe current-voltage measurement and UV-vis spectroscopy of the ZnO NRs indicated a resistivity and optical bandgap value of 0.44 Ω.cm and 3.35 eV, respectively. The photoluminescence spectrum showed a broad peak centered at 623 nm in the visible region corresponded to the oxygen vacancies from the ZnO NRs. This study demonstrates that acetylacetonate-derived precursors can be used for the production of ZnO NRs-based devices with a potential application in biosensors.
    Matched MeSH terms: Silicon Dioxide
  12. Fulltext The role of silica-containing agro-industrial waste as reinforcement on physicochemical and thermal properties of polymer composites
    Rizal S, Fizree HM, Hossain MS, Ikramullah, Gopakumar DA, Wan Ni EC, et al.
    Heliyon, 2020 Mar;6(3):e03550.
    PMID: 32190763 DOI: 10.1016/j.heliyon.2020.e03550
    This study was conducted to determine the influence of the oil palm boiler ash (OPBA) reinforcement on the microstructural, physical, mechanical and thermal properties of epoxy polymer composites. The chemical composition analysis of OPBA revealed that it contains about 55 wt.% of SiO2 along with other metallic oxides and elements. The surface morphology of OPBA showed angular and irregular shapes with porous structures. The influence of OPBA as a reinforcement in epoxy composite was studied with varying filler loadings (10-50 wt.%) and different particle sizes (50-150 μm). The result showed that the incorporation of OPBA in composites has improved the physical, mechanical and thermal properties of the epoxy matrix. The highest physical and mechanical properties of fabricated composites were attained with 30 wt.% loading and size of 50 μm. Also, thermal stability and the percentage of char residue of the composite increased with increasing filler loading. Furthermore, the contact angle of OPBA reinforced epoxy composites increased with the increase of filler loading. The lowest value of the contact angle was obtained at 30 wt.% of filler loading with the OPBA particle size of 50 μm. The finding of this study reveals that the OPBA has the potential to be used as reinforcement or filler as well as an alternative of silica-based inorganic fillers used in the enhancement of mechanical, physical and thermal properties of the epoxy polymer composite.
    Matched MeSH terms: Silicon Dioxide
  13. Fulltext A Highly Sensitive Impedimetric DNA Biosensor Based on Hollow Silica Microspheres for Label-Free Determination of E. coli
    Yuhana Ariffin E, Heng LY, Tan LL, Abd Karim NH, Hasbullah SA
    Sensors (Basel), 2020 Feb 26;20(5).
    PMID: 32111092 DOI: 10.3390/s20051279
    A novel label-free electrochemical DNA biosensor was constructed for the determination of Escherichia coli bacteria in environmental water samples. The aminated DNA probe was immobilized onto hollow silica microspheres (HSMs) functionalized with 3-aminopropyltriethoxysilane and deposited onto a screen-printed electrode (SPE) carbon paste with supported gold nanoparticles (AuNPs). The biosensor was optimized for higher specificity and sensitivity. The label-free E. coli DNA biosensor exhibited a dynamic linear response range of 1 × 10-10 µM to 1 × 10-5 µM (R2 = 0.982), with a limit of detection at 1.95 × 10-15 µM, without a redox mediator. The sensitivity of the developed DNA biosensor was comparable to the non-complementary and single-base mismatched DNA. The DNA biosensor demonstrated a stable response up to 21 days of storage at 4 ℃ and pH 7. The DNA biosensor response was regenerable over three successive regeneration and rehybridization cycles.
    Matched MeSH terms: Silicon Dioxide/chemistry*
  14. Deoxygenation of pyrolysis vapour derived from durian shell using catalysts prepared from industrial wastes rich in Ca, Fe, Si and Al
    Tan YL, Hameed BH, Abdullah AZ
    Sci Total Environ, 2020 Feb 10;703:134902.
    PMID: 31753498 DOI: 10.1016/j.scitotenv.2019.134902
    Catalysts prepared from industrial wastes rich in Fe, Ca, Si, and Al were used in catalytic upgrading of pyrolysis vapour derived from durian shell and their effect on product yield and properties were compared. With same silica-to-alumina ratio, catalyst prepared from oil palm ash (AS-OPA) with lower Fe and Ca contents gave higher liquid yield (8.32 wt%) with alcohols (28.90%), hydrocarbons (46.00%), and nitrogen-containing compounds (21.46%) while catalyst prepared from electric arc furnace slag (AS-EAF) with higher Fe and Ca contents produced lower liquid yield (50.21 wt%) with high amount of esters (25.80%) and hydrocarbons (72.82%). The presence of AS-OPA and AS-EAF catalysts enhanced deoxygenation degree of bio-oil to 81.13% and 85.49%, respectively. The catalytic performance of AS-EAF at different temperatures (400-600 °C) and AS-EAF/durian shell ratios (1:30, 2:30, 3:30) was investigated. Increasing catalytic temperature enhanced production of bio-oil, reduced oxygenates and enhanced formation of esters. The liquid yield and yield of esters decreased with increasing catalyst loading. Hydrocarbons (mainly neopentane) were the major chemical compounds found in bio-oil produced over AS-EAF. Besides that, AS-EAF showed good deoxygenation performance with highest selectivity of hydrocarbons at 500 °C and AS-EAF/durian shell ratio of 2:30. Catalytic fast pyrolysis of durian shell using waste-derived catalysts is an effective waste management strategy as the bio-oil produced can be a potential alternative source of energy or chemical feedstocks.
    Matched MeSH terms: Silicon Dioxide
  15. Arsenic adsorption mechanism on palm oil fuel ash (POFA) powder suspension
    Yusof MSM, Othman MHD, Wahab RA, Jumbri K, Razak FIA, Kurniawan TA, et al.
    J Hazard Mater, 2020 02 05;383:121214.
    PMID: 31546216 DOI: 10.1016/j.jhazmat.2019.121214
    The contribution of palm oil fuel ash (POFA), an agricultural waste as a low cost adsorbent for the removal of arsenite (As(III)) and arsenate (As(V)) was explored. Investigation on the adsorbency characteristics of POFA suspension revealed that the surface area, particle size, composition, and crystallinity of the SiO2 rich mullite structure were the crucial factors in ensuring a high adsorption capacity of the ions. Maximum adsorption capacities of As(III) and As(V) at 91.2 and 99.4 mg g-1, respectively, were obtained when POFA of 30 μm particle size was employed at pH 3 with the highest calcination temperature at 1150 °C. An optimum dosage of 1.0 g of dried POFA powder successfully removed 48.7% and 50.2% of As(III) and As(V), respectively. Molecular modeling using the density functional theory consequently identified the energy for the proposed reaction routes between the SiO- and As+ species. The high stability of the POFA suspension in water in conjunction with good adsorption capacity of As(III) and As(V) seen in this study, thus envisages its feasibility as a potential alternative absorbent for the remediation of water polluted with heavy metals.
    Matched MeSH terms: Silicon Dioxide
  16. Reflectance aptasensor based on metal salphen label for rapid and facile determination of insulin
    Taib M, Tan LL, Abd Karim NH, Ta GC, Heng LY, Khalid B
    Talanta, 2020 Jan 15;207:120321.
    PMID: 31594568 DOI: 10.1016/j.talanta.2019.120321
    An optical aptasensor-based sensing platform for rapid insulin detection was fabricated. Aminated porous silica microparticles (PSiMPs) were synthesized via a facile mini-emulsion method to provide large surface area for covalent immobilization of insulin-binding DNA aptamer (IGA3) by glutaraldehyde cross-linking protocol. A Nickel-salphen type complex with piperidine side chain [Ni(II)-SP] was synthesized with a simple one-pot reaction, and functionalized as an optical label due to strong π-π interaction between aromatic carbons of G-quadruplex DNA aptamer and planar aromatic groups of Ni(II)-SP to form the immobilized IGA3-Ni(II)-SP complex, i.e. the dye-labeled aptamer, thereby bringing yellow colouration to the immobilized G-quartet plane. Optical characterization of aptasensor towards insulin binding was carried out with a fiber optic reflectance spectrophotometer. The maximum reflectance intensity of the immobilized IGA3-Ni(II)-SP complex at 656 nm decreased upon binding with insulin as aptasensor changed to brownish orange colouration in the background. This allows optical detection of insulin as the colour change of aptasensor is dependent on the insulin concentration. The linear detection range of the aptasensor is obtained from 10 to 50 μIU mL-1 (R2 = 0.9757), which conformed to the normal fasting insulin levels in human with a limit of detection (LOD) at 3.71 μIU mL-1. The aptasensor showed fast response time of 40 min and long shelf life stability of >3 weeks. Insulin detection using healthy human serums with informed consent provided by participants suggests the DNA aptamer biosensor was in good agreement with ELISA standard method using BIOMATIK Human INS (Insulin) ELISA Kit.
    Matched MeSH terms: Silicon Dioxide/chemistry
  17. New effective 3-aminopropyltrimethoxysilane functionalized magnetic sporopollenin-based silica coated graphene oxide adsorbent for removal of Pb(II) from aqueous environment
    Hassan AM, Wan Ibrahim WA, Bakar MB, Sanagi MM, Sutirman ZA, Nodeh HR, et al.
    J Environ Manage, 2020 Jan 01;253:109658.
    PMID: 31666209 DOI: 10.1016/j.jenvman.2019.109658
    A new effective adsorbent, 3-aminopropyltrimethoxysilane functionalized magnetic sporopollenin (MSp@SiO2NH2) based silica-coated graphene oxide (GO), (GO@SiO2-MSp@SiO2NH2) was successfully synthesized and applied for the first time in the removal of hazardous Pb(II) ions from aqueous solution. The properties of the composite were characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX) and vibrating-sample magnetometery (VSM). Evaluation of GO@SiO2-MSp@SiO2NH2 adsorption performance at optimum conditions revealed that the adsorbent has a maximum adsorption capacity of 323.5 mg/g for Pb(II) using 50-200 mg/L initial Pb(II) ions concentrations. Initial and final concentrations of Pb(II) ions in aqueous solution were analyzed using graphite furnace atomic absorption spectroscopy (GF-ASS). The adsorption behavior of Pb(II) ions onto GO@SiO2-MSp@SiO2NH2 was studied using Langmuir, Freundlich and Temkin isotherms models. The values of coefficient of determination showed that the adsorption best fitted the Langmuir model (R2 = 0.9994). Kinetic studies suggested that the adsorption of Pb(II) ion followed a pseudo-second-order rate model (R2 = 1.00) and thermodynamic studies revealed that the adsorption process is endothermic and spontaneous. The effect of co-existing ions on Pb(II) ion adsorption were also studied and found to have considerable effects only at higher matrix concentration. The adsorbent can be reused up to ten times and retain its good adsorption capacity. In addition, GO@SiO2-MSp@SiO2NH2 showed great potential for Pb(II)removal from industrial wastewater samples.
    Matched MeSH terms: Silicon Dioxide
  18. Fulltext Effect on Physical and Mechanical Properties of Conventional Glass Ionomer Luting Cements by Incorporation of All-Ceramic Additives: An In Vitro Study
    Saran R, Upadhya NP, Ginjupalli K, Amalan A, Rao B, Kumar S
    Int J Dent, 2020;2020:8896225.
    PMID: 33061975 DOI: 10.1155/2020/8896225
    Introduction: Glass ionomer cements (GICs) are commonly used for cementation of indirect restorations. However, one of their main drawbacks is their inferior mechanical properties.

    Aim: Compositional modification of conventional glass ionomer luting cements by incorporating two types of all-ceramic powders in varying concentrations and evaluation of their film thickness, setting time, and strength. Material & Methods. Experimental GICs were prepared by adding different concentrations of two all-ceramic powders (5%, 10, and 15% by weight) to the powder of the glass ionomer luting cements, and their setting time, film thickness, and compressive strength were determined. The Differential Scanning Calorimetry analysis was done to evaluate the kinetics of the setting reaction of the samples. The average particle size of the all-ceramic and glass ionomer powders was determined with the help of a particle size analyzer.

    Results: A significant increase in strength was observed in experimental GICs containing 10% all-ceramic powders. The experimental GICs with 5% all-ceramic powders showed no improvement in strength, whereas those containing 15% all-ceramic powders exhibited a marked decrease in strength. Setting time of all experimental GICs progressively increased with increasing concentration of all-ceramic powders. Film thickness of all experimental GICs was much higher than the recommended value for clinical application.

    Conclusion: 10% concentration of the two all-ceramic powders can be regarded as the optimal concentration for enhancing the glass ionomer luting cements' strength. There was a significant increase in the setting time at this concentration, but it was within the limit specified by ISO 9917-1:2007 specifications for powder/liquid acid-base dental cements. Reducing the particle size of the all-ceramic powders may help in decreasing the film thickness, which is an essential parameter for the clinical performance of any luting cement.

    Matched MeSH terms: Silicon Dioxide
  19. Fulltext Application of Plasmonic Metal Nanoparticles in TiO2-SiO2 Composite as an Efficient Solar-Activated Photocatalyst: A Review Paper
    Joseph CG, Taufiq-Yap YH, Musta B, Sarjadi MS, Elilarasi L
    Front Chem, 2020;8:568063.
    PMID: 33628762 DOI: 10.3389/fchem.2020.568063
    Over the last decade, interest in the utilization of solar energy for photocatalysis treatment processes has taken centre-stage. Researchers had focused on doping TiO2 with SiO2 to obtain an efficient degradation rate of various types of target pollutants both under UV and visible-light irradiation. In order to further improve this degradation effect, some researchers resorted to incorporate plasmonic metal nanoparticles such as silver and gold into the combined TiO2-SiO2 to fully optimize the TiO2-SiO2's potential in the visible-light region. This article focuses on the challenges in utilizing TiO2 in the visible-light region, the contribution of SiO2 in enhancing photocatalytic activities of the TiO2-SiO2 photocatalyst, and the ability of plasmonic metal nanoparticles (Ag and Au) to edge the TiO2-SiO2 photocatalyst toward an efficient solar photocatalyst.
    Matched MeSH terms: Silicon Dioxide
  20. Fulltext Morphological and compositional changes exhibited by rice husk when subjected to synergistic thermochemical treatments
    Revathi Rajan, Yusmazura Zakaria, Shaharum Shamsuddin, Nik Fakhuruddin Nik Hassan
    Malaysian Journal of Medicine and Health Sciences, 2020;16(101):1-7.
    MyJurnal
    Introduction: Rice husk has portrayed great potential in becoming a sustainable biomass source in producing silica, cellulose and carbon materials, which garnered widespread interest among researchers. The objective of the current study is to determine the morphological and compositional changes in rice husk due to the synergistic effects of ther- mochemical treatment. Methods: Washed and dried rice husk was blended into a fine powder and then subjected to step-wise heat treatment and acid digestion to produce white ash. The intermittent products, as well as the original rice husk and the final ash product, were characterised using analytical instruments to document the morphologi- cal and chemical composition changes. Results: This report highlights the production of pure rice husk ash using a step-wise treatment using a combination of thermochemical treatment and carbonisation. The results showed that a partial breakdown of the lignocellulose components was achieved using directed thermal treatment at low tem- perature. The ionic impurities were leached out in subsequent heated acid treatment. Thereafter, the carbonaceous organic matter was completely converted to carbon during the carbonisation of the sample and the remaining carbon residue was removed during calcination. High purity ash contained agglomerated and nanostructured silica in the dimensions of 20 to 50 nm in the amorphous form. Conclusion: The step-wise treatment allowed systematic removal of each compound while maintaining the amorphous mineral phase of silica and avoiding carbon fixation. Under- standing the effect of each treatment offers insight to produce purer silica from rice husk.
    Matched MeSH terms: Silicon Dioxide
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