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A Heuristic Automatic and Robust ROI Detection Method for Medical Image Warermarking

Mousavi SM, Naghsh A, Abu-Bakar SA

J Digit Imaging, 2015 Aug;28(4):417-27.
PMID: 25736857 DOI: 10.1007/s10278-015-9770-z

This paper presents an automatic region of interest (ROI) segmentation method for application of watermarking in medical images. The advantage of using this scheme is that the proposed method is robust against different attacks such as median, Wiener, Gaussian, and sharpening filters. In other words, this technique can produce the same result for the ROI before and after these attacks. The proposed algorithm consists of three main parts; suggesting an automatic ROI detection system, evaluating the robustness of the proposed system against numerous attacks, and finally recommending an enhancement part to increase the strength of the composed system against different attacks. Results obtained from the proposed method demonstrated the promising performance of the method.
A discrimination method for the detection of pneumonia using chest radiograph

Noor NM, Rijal OM, Yunus A, Abu-Bakar SA

Comput Med Imaging Graph, 2010 Mar;34(2):160-6.
PMID: 19758785 DOI: 10.1016/j.compmedimag.2009.08.005

This paper presents a statistical method for the detection of lobar pneumonia when using digitized chest X-ray films. Each region of interest was represented by a vector of wavelet texture measures which is then multiplied by the orthogonal matrix Q(2). The first two elements of the transformed vectors were shown to have a bivariate normal distribution. Misclassification probabilities were estimated using probability ellipsoids and discriminant functions. The result of this study recommends the detection of pneumonia by constructing probability ellipsoids or discriminant function using maximum energy and maximum column sum energy texture measures where misclassification probabilities were less than 0.15.
Fulltext Watermarking techniques used in medical images: a survey

Mousavi SM, Naghsh A, Abu-Bakar SA

J Digit Imaging, 2014 Dec;27(6):714-29.
PMID: 24871349 DOI: 10.1007/s10278-014-9700-5

The ever-growing numbers of medical digital images and the need to share them among specialists and hospitals for better and more accurate diagnosis require that patients' privacy be protected. As a result of this, there is a need for medical image watermarking (MIW). However, MIW needs to be performed with special care for two reasons. Firstly, the watermarking procedure cannot compromise the quality of the image. Secondly, confidential patient information embedded within the image should be flawlessly retrievable without risk of error after image decompressing. Despite extensive research undertaken in this area, there is still no method available to fulfill all the requirements of MIW. This paper aims to provide a useful survey on watermarking and offer a clear perspective for interested researchers by analyzing the strengths and weaknesses of different existing methods.
Suppressing growth, migration, and invasion of human hepatocellular carcinoma HepG2 cells by Catharanthus roseus‑silver nanoparticles

Azhar NA, Ghozali SZ, Abu Bakar SA, Lim V, Ahmad NH

Toxicol In Vitro, 2020 Sep;67:104910.
PMID: 32526345 DOI: 10.1016/j.tiv.2020.104910

Application of silver nanoparticles serves as a new approach in cancer treatment due to its unique features. Biosynthesis of silver nanoparticles using plant is advantageous since they are easily accessible, nontoxic and produce quicker reaction compared to other methods. To evaluate the cytotoxicity, mechanism of cell death and DNA damage of biosynthesized Catharanthus roseus-silver nanoparticles on human liver cancer (HepG2) cells. The antiproliferative activity of Catharanthus roseus‑silver nanoparticles was measured using MTT assay. The cytotoxic effects were further evaluated by measuring nitric oxide and reactive oxygen species (ROS). The mechanism of cell death was determined by annexin-FITC/propidium iodide, mitochondrial membrane potential (MMP) and cell cycle assays. The assessment of DNA damage was evaluated using Comet assay method. The uptake of the nanoparticles were evaluated by Transmission Electron Microscopy (TEM). Catharanthus roseus‑silver nanoparticles has inhibited the proliferation of HepG2 cells in a time-dependent manner with a median IC50 value of 3.871 ± 0.18 μg/mL. The concentration of nitrite and ROS were significantly higher than control. The cell death was due to apoptosis associated with MMP loss, cell cycle arrest, and extensive DNA damage. TEM analysis indicated the presence of free nanoparticles and endosomes containing the nanoparticles. The findings show that Catharanthus roseus‑silver nanoparticles have produced cytotoxic effects on HepG2 cells and thus may have a potential to be used as an anticancer treatment, particularly for hepatocellular carcinoma.
Fulltext mRNA transcriptome profiling of human hepatocellular carcinoma cells HepG2 treated with Catharanthus roseus-silver nanoparticles

Azhar NA, Abu Bakar SA, Citartan M, Ahmad NH

World J Hepatol, 2023 Mar 27;15(3):393-409.
PMID: 37034237 DOI: 10.4254/wjh.v15.i3.393

BACKGROUND: The demand for the development of cancer nanomedicine has increased due to its great therapeutic value that can overcome the limitations of conventional cancer therapy. However, the presence of various bioactive compounds in crude plant extracts used for the synthesis of silver nanoparticles (AgNPs) makes its precise mechanisms of action unclear.
AIM: To assessed the mRNA transcriptome profiling of human HepG2 cells exposed to Catharanthus roseus G. Don (C. roseus)-AgNPs.
METHODS: The proliferative activity of hepatocellular carcinoma (HepG2) and normal human liver (THLE3) cells treated with C. roseusAgNPs were measured using MTT assay. The RNA samples were extracted and sequenced using BGIseq500 platform. This is followed by data filtering, mapping, gene expression analysis, differentially expression genes analysis, Gene Ontology analysis, and pathway analysis.
RESULTS: The mean IC50 values of C. roseusAgNPs on HepG2 was 4.38 ± 1.59 μg/mL while on THLE3 cells was 800 ± 1.55 μg/mL. Transcriptome profiling revealed an alteration of 296 genes. C. roseusAgNPs induced the expression of stress-associated genes such as MT, HSP and HMOX-1. Cellular signalling pathways were potentially activated through MAPK, TNF and TGF pathways that are responsible for apoptosis and cell cycle arrest. The alteration of ARF6, EHD2, FGFR3, RhoA, EEA1, VPS28, VPS25, and TSG101 indicated the uptake of C. roseus-AgNPs via both clathrin-dependent and clathrin-independent endocytosis.
CONCLUSION: This study provides new insights into gene expression study of biosynthesised AgNPs on cancer cells. The cytotoxicity effect is mediated by the aberrant gene alteration, and more interestingly the unique selective antiproliferative properties indicate the C. roseusAgNPs as an ideal anticancer candidate.
Fulltext Effects of newcastle disease virus strains AF2240 and V4-UPM on cytolysis and apoptosis of leukemia cell lines

Alabsi AM, Bakar SA, Ali R, Omar AR, Bejo MH, Ideris A, et al.

Int J Mol Sci, 2011;12(12):8645-60.
PMID: 22272097 DOI: 10.3390/ijms12128645

Newcastle disease virus (NDV) is used as an antineoplastic agent in clinical tumor therapy. It has prompted much interest as an anticancer agent because it can replicate up to 10,000 times better in human cancer cells than in most normal cells. This study was carried out to determine the oncolytic potential of NDV strain AF2240 and V4-UPM on WEHI-3B leukemia cell line. Results from MTT cytotoxicity assay showed that the CD(50) values for both strains were 2 and 8 HAU for AF2240 and V4-UPM, respectively. In addition, bromodeoxyuridine (BrdU) and trypan blue dye exclusion assays showed inhibition in cell proliferation after different periods. Increase in the cellular level of caspase-3 and detection of DNA laddering using agarose gel electrophoresis on treated cells with NDV confirmed that the mode of cell death was apoptosis. In addition, flow-cytometry analysis of cellular DNA content showed that the virus caused an increase in the sub-G1 region (apoptosis peaks). In conclusion, NDV strains AF2240 and V4-UPM caused cytolytic effects against WEHI-3B leukemic cell line.
Fulltext LEP G2548A polymorphism is associated with increased serum leptin and insulin resistance among T2DM Malaysian patients

Ali LA, Jemon K, Latif NA, Bakar SA, Alwi SSS

Biomedicine (Taipei), 2022;12(3):1-11.
PMID: 36381191 DOI: 10.37796/2211-8039.1326

Background: Type 2 diabetes mellitus (T2DM) is a chronic metabolic syndrome that is rapidly increasing across the world, especially in Malaysia. Leptin plays a vital role in the regulation of metabolism through its effect on peripheral tissues. G2548A polymorphism in the LEP gene promoter has been associated with insulin resistance, leptin, and type 2 diabetes mellitus across different population, but has not been inclusively reported within the Malaysian population.
Objective: Thus, our study aimed to investigate the impact of G2548A polymorphism on serum leptin levels and insulin resistance among Malaysian T2DM patients.
Methods: This case-control study involved 150 T2DM patients and 150 non-diabetic volunteers from ethnic Malays, Chinese and Indians. Genotyping of G2548A polymorphism was carried out using PCR-RFLP. Serum leptin and insulin levels were determined via ELISA. ANOVA and Chi-square tests were used to determine the distribution of genotypes and allelic frequencies based on serum leptin and insulin levels.
Results: Frequency of AA genotype and A allele of G2548A variant were significantly (P < 0.05) higher in T2DM patients of Malay and Indian ethnicities (4%, 35%, and 36%, 57%, respectively) as compared to the control groups (0%, 22%, and 18%, 35%, respectively). Fasting serum leptin levels were significantly (P < 0.001) higher in T2DM patients compared to non-diabetic subjects (166.78 pg/ml, 101.94 pg/ml, respectively). Additionally, elevated serum leptin, insulin levels, and BMI in diabetic patients were found to be associated with the AA genotype of this variant, compared to GG, and GA genotypes (P < 0.05).
Conclusion: Our findings suggest a significant association between G2548A polymorphism among Malaysian T2DM subjects, particularly among Malay and Indian ethnic groups. Moreover, the A allele frequency of the G2548A variant significantly increased the risk of T2DM and is significantly associated with increased serum leptin, insulin levels, and elevated BMI.
Lower extremity joint reaction forces and plantar fascia strain responses due to incline and decline walking

Yamin NAAA, Basaruddin KS, Bakar SA, Salleh AF, Som MHM, Bakar AHA

Acta Bioeng Biomech, 2022;24(1):67-74.
PMID: 38314464

PURPOSE: The present study aims to investigate the effect of incline and decline walking on ground and joint reaction forces (JRF) of lower extremity and plantar fascia strain (PFS) under certain surface inclination angles.
METHODS: Twenty-three male subjects walked on a customized platform with four different surface inclinations (i.e., 0, 5, 7.5 and 10°) with inclined and declined directions. The motion of the ten reflective markers was captured using Qualysis motion capture system (Qualysis, Gothenburg, Sweden) and exported to a visual three-dimensional (3D) software (C-motion, Germantown, USA) in order to analyze the GRF, JRF and PFS.
RESULTS: The results found that the peak vertical GRF is almost consistent for 0 and 5° inclination slope but started to decrease at 7.5° onwards during decline walking. The most affected JRF was found on knee at medial-lateral direction even as low as 5 to 10° inclination for both walking conditions. Furthermore, the findings also show that the JRF of lower extremity was more affected during declined walking compared to inclined walking based on the number of significant differences observed in each inclination angle. The PFS was found increased with the increase of surface inclination.
CONCLUSIONS: The findings could provide a new insight on the relationship of joint reaction forces and strain parameter in response to the incline and decline walking. It would benefit in providing a better precaution that should be considered during hiking activity, especially in medial-lateral direction in order to prevent injury or fall risk.
High level expression of Glomerella cingulata cutinase in dense cultures of Pichia pastoris grown under fed-batch conditions

Seman WM, Bakar SA, Bukhari NA, Gaspar SM, Othman R, Nathan S, et al.

J Biotechnol, 2014 Aug 20;184:219-28.
PMID: 24910973 DOI: 10.1016/j.jbiotec.2014.05.034

A Pichia pastoris transformant carrying the cutinase cDNA of Glomerella cingulata was over-expressed in a 5L bioreactor (2.0L working volume) under fed-batch conditions. Bioreactor experiments rely on varying selected parameters in repeated rounds of optimisation: here these included duration of induction, pH and temperature. Highest cell densities (320gL(-1) wet cell weight) with a cutinase production of 3800mgL(-1) and an activity of 434UmL(-1) were achieved 24h after induction with methanol in basal salt medium (at pH 5 and 28°C). Characterisation of the cutinase showed that it was stable between pH 6 and pH 11, had an optimum pH of 8.0 and retained activity for 30min at 50°C (optimum temperature 25°C).The preferred substrates of G. cingulata cutinase were the medium- to long-chain ρ-nitrophenyl esters of ρ-nitrophenylcaprylate (C8), ρ-nitrophenyllaurate (C12) and ρ-nitrophenylmyristate (C14), with the highest catalytic efficiency, kcat/Km of 7.7±0.7mM(-1)s(-1) for ρ-nitrophenylcaprylate. Microscopic analyses showed that the G. cingulata cutinase was also capable of depolymerising the high molecular weight synthetic polyester, polyethylene terephthalate.
Immobilisation of Cu, Pb and Zn in Scrap Metal Yard Soil Using Selected Waste Materials

Kamari A, Putra WP, Yusoff SN, Ishak CF, Hashim N, Mohamed A, et al.

Bull Environ Contam Toxicol, 2015 Dec;95(6):790-5.
PMID: 26395356 DOI: 10.1007/s00128-015-1650-1

Immobilisation of heavy metals in a 30-year old active scrap metal yard soil using three waste materials, namely coconut tree sawdust (CTS), sugarcane bagasse (SB) and eggshell (ES) was investigated. The contaminated soil was amended with amendments at application rates of 0 %, 1 % and 3 % (w/w). The effects of amendments on metal accumulation in water spinach (Ipomoea aquatica) and soil metal bioavailability were studied in a pot experiment. All amendments increased biomass yield and reduced metal accumulation in the plant shoots. The bioconcentration factor and translocation factor values of the metals were in the order of Zn > Cu > Pb. The addition of ES, an alternative source of calcium carbonate (CaCO3), has significantly increased soil pH and resulted in marked reduction in soil metal bioavailability. Therefore, CTS, SB and ES are promising low-cost immobilising agents to restore metal contaminated land.
Fulltext An Emotion Assessment of Stroke Patients by Using Bispectrum Features of EEG Signals

Yean CW, Wan Ahmad WK, Mustafa WA, Murugappan M, Rajamanickam Y, Adom AH, et al.

Brain Sci, 2020 Sep 25;10(10).
PMID: 32992930 DOI: 10.3390/brainsci10100672

Emotion assessment in stroke patients gives meaningful information to physiotherapists to identify the appropriate method for treatment. This study was aimed to classify the emotions of stroke patients by applying bispectrum features in electroencephalogram (EEG) signals. EEG signals from three groups of subjects, namely stroke patients with left brain damage (LBD), right brain damage (RBD), and normal control (NC), were analyzed for six different emotional states. The estimated bispectrum mapped in the contour plots show the different appearance of nonlinearity in the EEG signals for different emotional states. Bispectrum features were extracted from the alpha (8-13) Hz, beta (13-30) Hz and gamma (30-49) Hz bands, respectively. The k-nearest neighbor (KNN) and probabilistic neural network (PNN) classifiers were used to classify the six emotions in LBD, RBD and NC. The bispectrum features showed statistical significance for all three groups. The beta frequency band was the best performing EEG frequency-sub band for emotion classification. The combination of alpha to gamma bands provides the highest classification accuracy in both KNN and PNN classifiers. Sadness emotion records the highest classification, which was 65.37% in LBD, 71.48% in RBD and 75.56% in NC groups.
Fulltext Traumatic transnasal penetrating injury with cerebral spinal fluid leak

Teng TS, Ishak NL, Subha ST, Bakar SA

EXCLI J, 2019;18:223-228.
PMID: 31217785 DOI: 10.17179/excli2018-1971

CSF leak in penetrating skull base injury is relatively rare compared to close head injury involving skull base fracture. We report a 5-year-old boy presented with epistaxis and impacted pencil into the left nostril. The child was hemodynamically stable without any neurological deficit. Intraoperatively, there was a nasal septal defect posteriorly with anterior skull base fracture associated with CSF leak. The pencil was removed from the left nostril and the CSF leak was repaired using harvested abdominal fat under the same setting. Computed Tomography (CT) of the brain showed right cribriform plate fracture with small pneumocranium. Postoperatively, a prophylactic antibiotic was given for seven days and he was discharged well. Subsequent clinic visits up to one-year postoperative period showed no recurrence of the CSF leak. History taking, physical examination and CT imaging give valuable diagnostic values in managing the penetrating skull base injury. Early intervention for removal of the foreign body and repair of the CSF leak is advocated to prevent catastrophic complication.
Fulltext Optimisation of GBFS, Fly Ash, and Nano-Silica Contents in Alkali-Activated Mortars

Algaifi HA, Mustafa Mohamed A, Alsuhaibani E, Shahidan S, Alrshoudi F, Huseien GF, et al.

Polymers (Basel), 2021 Aug 16;13(16).
PMID: 34451289 DOI: 10.3390/polym13162750

Although free-cement-based alkali-activated paste, mortar, and concrete have been recognised as sustainable and environmental-friendly materials, a considerable amount of effort is still being channeled to ascertain the best binary or ternary binders that would satisfy the requirements of strength and durability as well as environmental aspects. In this study, the mechanical properties of alkali-activated mortar (AAM) made with binary binders, involving fly ash (FA) and granulated blast-furnace slag (GBFS) as well as bottle glass waste nano-silica powder (BGWNP), were opti-mised using both experimentally and optimisation modelling through three scenarios. In the first scenario, the addition of BGWNP varied from 5% to 20%, while FA and GBFS were kept constant (30:70). In the second and third scenarios, BGWNP (5-20%) was added as the partial replacement of FA and GBFS, separately. The results show that the combination of binary binders (FA and GBFS) and BGWNP increased AAM's strength compared to that of the control mixture for all scenarios. In addition, the findings also demonstrated that the replacement of FA by BGWNP was the most significant, while the effect of GBFS replacement by BGWNP was less significant. In particular, the highest improvement in compressive strength was recorded when FA, GBFS, and BGWNP were 61.6%, 30%, and 8.4%, respectively. Furthermore, the results of ANOVA (p values < 0.0001 and high F-values) as well as several statistical validation methods (R > 0.9, RAE < 0.1, RSE < 0.013, and RRSE < 0.116) confirmed that all the models were robust, reliable, and significant. Similarly, the data variation was found to be less than 5%, and the difference between the predicted R2 and adj. R2 was very small (<0.2), thus confirming that the proposed non-linear quadratic equations had the capability to predict for further observation. In conclusion, the use of BGWNP in AAM could act as a beneficial and sustainable strategy, not only to address environmental issues (e.g., landfill) but to also enhance strength properties.
Fulltext Metabolic syndrome and cardiovascular risk among patients with schizophrenia receiving antipsychotics in Malaysia

Said MA, Sulaiman AH, Habil MH, Das S, Bakar AK, Yusoff RM, et al.

Singapore Med J, 2012 Dec;53(12):801-7.
PMID: 23268153

INTRODUCTION:This study aimed to determine the prevalence of metabolic syndrome and risk of coronary heart disease (CHD) in patients with schizophrenia receiving antipsychotics in Malaysia.
METHODS:This cross-sectional study, conducted at multiple centres, involved 270 patients who fulfilled the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV-TR diagnostic criteria for schizophrenia, were on antipsychotic medications for at least one year, and were screened for metabolic syndrome. Patients receiving mood stabilisers were excluded. Metabolic syndrome was defined according to the National Cholesterol Education Program ATP III criteria modified for Asian waist circumference. Risk for cardiovascular disease was assessed by using Framingham function (all ten-year CHD events).
RESULTS:The prevalence of metabolic syndrome was 46.7% (126/270). Among all the antipsychotics used, atypical antipsychotics (monotherapy) were most commonly used in both the metabolic and non-metabolic syndrome groups (50.8% vs. 58.3%). The ten-year risk for CHD was significantly higher in patients with metabolic syndrome. The proportion of patients with high/very high risk for CHD (Framingham ≥ 10%) was greater in patients with metabolic syndrome than in those with non-metabolic syndrome (31.5% vs. 11.0%, odds ratio 3.9, 95% confidence interval 2.0-7.6; p < 0.001). The mean body mass index was higher in patients with metabolic syndrome than in those without (29.4 ± 5.1 kg/m2 vs. 25.0 ± 5.6 kg/m2; p < 0.001).
CONCLUSION:Patients with schizophrenia receiving antipsychotics in Malaysia have a very high incidence of metabolic syndrome and increased cardiovascular risk. Urgent interventions are needed to combat these problems in patients.
Fulltext A stochastic simulation framework for the prediction of strategic noise mapping and occupational noise exposure using the random walk approach

Han LM, Haron Z, Yahya K, Bakar SA, Dimon MN

PLoS One, 2015;10(4):e0120667.
PMID: 25875019 DOI: 10.1371/journal.pone.0120667

Strategic noise mapping provides important information for noise impact assessment and noise abatement. However, producing reliable strategic noise mapping in a dynamic, complex working environment is difficult. This study proposes the implementation of the random walk approach as a new stochastic technique to simulate noise mapping and to predict the noise exposure level in a workplace. A stochastic simulation framework and software, namely RW-eNMS, were developed to facilitate the random walk approach in noise mapping prediction. This framework considers the randomness and complexity of machinery operation and noise emission levels. Also, it assesses the impact of noise on the workers and the surrounding environment. For data validation, three case studies were conducted to check the accuracy of the prediction data and to determine the efficiency and effectiveness of this approach. The results showed high accuracy of prediction results together with a majority of absolute differences of less than 2 dBA; also, the predicted noise doses were mostly in the range of measurement. Therefore, the random walk approach was effective in dealing with environmental noises. It could predict strategic noise mapping to facilitate noise monitoring and noise control in the workplaces.
Graphene-philic surfactants for nanocomposites in latex technology

Mohamed A, Ardyani T, Bakar SA, Brown P, Hollamby M, Sagisaka M, et al.

Adv Colloid Interface Sci, 2016 Apr;230:54-69.
PMID: 26888600 DOI: 10.1016/j.cis.2016.01.003

Graphene is the newest member of the carbon family, and has revolutionized materials science especially in the field of polymer nanocomposites. However, agglomeration and uniform dispersion remains an Achilles' heel (even an elephant in the room), hampering the optimization of this material for practical applications. Chemical functionalization of graphene can overcome these hurdles but is often rather disruptive to the extended pi-conjugation, altering the desired physical and electronic properties. Employing surfactants as stabilizing agents in latex technology circumvents the need for chemical modification allowing for the formation of nanocomposites with retained graphene properties. This article reviews the recent progress in the use of surfactants and polymers to prepare graphene/polymer nanocomposites via latex technology. Of special interest here are surfactant structure-performance relationships, as well as background on the roles surfactant-graphene interactions for promoting stabilization.
Enhanced dispersion of multiwall carbon nanotubes in natural rubber latex nanocomposites by surfactants bearing phenyl groups

Mohamed A, Anas AK, Bakar SA, Ardyani T, Zin WM, Ibrahim S, et al.

J Colloid Interface Sci, 2015 Oct 1;455:179-87.
PMID: 26070188 DOI: 10.1016/j.jcis.2015.05.054

Here is presented a systematic study of the dispersibility of multiwall carbon nanotubes (MWCNTs) in natural rubber latex (NR-latex) assisted by a series of single-, double-, and triple-sulfosuccinate anionic surfactants containing phenyl ring moieties. Optical polarising microscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Raman spectroscopy have been performed to obtain the dispersion-level profiles of the MWCNTs in the nanocomposites. Interestingly, a triple-chain, phenyl-containing surfactant, namely sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3-phenylpropoxy)carbonyl) pentane-2-sulfonate (TCPh), has a greater capacity the stabilisation of MWCNTs than a commercially available single-chain sodium dodecylbenzenesulfonate (SDBS) surfactant. TCPh provides significant enhancements in the electrical conductivity of nanocomposites, up to ∼10(-2) S cm(-1), as measured by a four-point probe instrument. These results have allowed compilation of a road map for the design of surfactant architectures capable of providing the homogeneous dispersion of MWCNTs required for the next generation of polymer-carbon-nanotube materials, specifically those used in aerospace technology.
Fabrication and application of composite adsorbents made by one-pot electrochemical exfoliation of graphite in surfactant ionic liquid/nanocellulose mixtures

Jamaluddin NA, Mohamed A, Bakar SA, Ardyani T, Sagisaka M, Saito H, et al.

Phys Chem Chem Phys, 2021 Sep 15;23(35):19313-19328.
PMID: 34524298 DOI: 10.1039/d1cp02206g

Previously, surfactant-assisted exfoliated graphene oxide (sEGO) formed with the triple-chain surfactant TC14 (sodium 1,4-bis(neopentyloxy)-3-(neopentylcarbonyl)-1,4-dioxobutane-2-sulfonate) was applied in wastewater treatment. The extent of dye-removal and the adsorption capacity of the sEGO formed with this triple-chain surfactant outperformed those of two other systems, namely, the di-chain version of TC14 (AOT14; sodium 1,2-bis-(2,2-dimethyl-propoxycarbonyl)-ethanesulfonate) and the single-chain surfactant sodium n-dodecylsulfate. In the present study, to further optimise the surfactant chemical structure, the sodium ion of TC14 was substituted with 1-butyl-3-methyl-imidazolium (BMIM) generating surfactant ionic liquids (SAILs; 1-butyl-3-imidazolium 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulfonate), hereafter denoted as BMIM-TC14. This SAIL, together with nanofibrillated kenaf cellulose (NFC), was used to electrochemically exfoliate graphite, yielding BMIM-TC14 sEGO/NFC composites. These highly hydrophobic polymer composites were then used for the removal of methylene blue (MB) from aqueous solution. 1H NMR spectroscopy was used to elucidate the structure of the synthesised SAILs. The morphologies of the resulting nanocomposites were investigated using Raman spectroscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. Analysis using small-angle neutron scattering was performed to examine the aggregation behaviour of sEGO and custom-made SAILs. Zeta potential, surface tension, and dynamic light-scattering measurements were used to study the aqueous properties and colloidal stability of the suspension. Amongst the surfactants tested, BMIM-TC14 sEGO/NFC exhibited the highest MB adsorption ability, achieving 99% dye removal under optimum conditions. These results highlight the importance of modifying the hydrophilic moieties of amphiphilic compounds to improve the performance of sEGO/NFC composites as effective adsorbents for wastewater treatment.
Preparation of conductive cellulose paper through electrochemical exfoliation of graphite: The role of anionic surfactant ionic liquids as exfoliating and stabilizing agents

Mohamed A, Ardyani T, Bakar SA, Sagisaka M, Umetsu Y, Hussin MRM, et al.

Carbohydr Polym, 2018 Dec 01;201:48-59.
PMID: 30241844 DOI: 10.1016/j.carbpol.2018.08.040

A facile electrochemical exfoliation method was established to efficiently prepare conductive paper containing reduced graphene oxide (RGO) with the help of single chain anionic surfactant ionic liquids (SAILs). The surfactant ionic liquids are synthesized from conventional organic surfactant anions and a 1-butyl-3-methyl-imidazolium cation. For the first time the combination of SAILs and cellulose was used to directly exfoliate graphite. The ionic liquid 1-butyl-3-methyl-imidazolium dodecylbenzenesulfonate (BMIM-DBS) was shown to have notable affinity for graphene, demonstrating improved electrical properties of the conductive cellulose paper. The presence of BMIM-DBS in the system promotes five orders of magnitude enhancement of the paper electrical conductivity (2.71 × 10-5 S cm-1) compared to the native cellulose (1.97 × 10-10 S cm-1). A thorough investigation using electron microscopy and Raman spectroscopy highlights the presence of uniform graphene incorporated inside the matrices. Studies into aqueous aggregation behavior using small-angle neutron scattering (SANS) point to the ability of this compound to act as a bridge between graphene and cellulose, and is responsible for the enhanced exfoliation level and stabilization of the resulting dispersion. The simple and feasible process for producing conductive paper described here is attractive for the possibility of scaling-up this technique for mass production of conductive composites containing graphene or other layered materials.
Surfactants with aromatic headgroups for optimizing properties of graphene/natural rubber latex composites (NRL): Surfactants with aromatic amine polar heads

Ardyani T, Mohamed A, Bakar SA, Sagisaka M, Umetsu Y, Mamat MH, et al.

J Colloid Interface Sci, 2019 Jun 01;545:184-194.
PMID: 30878784 DOI: 10.1016/j.jcis.2019.03.012

HYPOTHESIS: The compatibility of surfactants and graphene surfaces can be improved by increasing the number of aromatic groups in the surfactants. Including aniline in the structure may improve the compatibility between surfactant and graphene further still. Surfactants can be modified by incorporating aromatic groups in the hydrophobic chains or hydrophilic headgroups. Therefore, it is of interest to investigate the effects of employing anilinium based surfactants to disperse graphene nanoplatelets (GNPs) in natural rubber latex (NRL) for the fabrication of electrically conductive nanocomposites.
EXPERIMENTS: New graphene-philic surfactants carrying aromatic moieties in the hydrophilic headgroups and hydrophobic tails were synthesized by swapping the traditional sodium counterion with anilinium. 1H NMR spectroscopy was used to characterize the surfactants. These custom-made surfactants were used to assist the dispersion of GNPs in natural rubber latex matrices for the preparation of conductive nanocomposites. The properties of nanocomposites with the new anilinium surfactants were compared with commercial sodium surfactant sodium dodecylsulfate (SDS), sodium dodecylbenzenesulfonate (SDBS), and the previously synthesized aromatic tri-chain sodium surfactant TC3Ph3 (sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3phenylpropoxy)carbonyl) pentane-2-sulfonate). Structural properties of the nanocomposites were studied using Raman spectroscopy, field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). Electrical conductivity measurements and Zeta potential measurements were used to assess the relationships between total number of aromatic groups in the surfactant molecular structure and nanocomposite properties. The self-assembly structure of surfactants in aqueous systems and GNP dispersions was assessed using small-angle neutron scattering (SANS).
FINDINGS: Among these different surfactants, the anilinium version of TC3Ph3 namely TC3Ph3-AN (anilinium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3phenylpropoxy)carbonyl) pentane-2-sulfonate) was shown to be highly efficient for dispersing GNPs in the NRL matrices, increasing electrical conductivity eleven orders of magnitude higher than the neat rubber latex. Comparisons between the sodium and anilinium surfactants show significant differences in the final properties of the nanocomposites. In general, the strategy of increasing the number of surfactant-borne aromatic groups by incorporating anilinium ions in surfactant headgroups appears to be effective.

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