Displaying publications 41 - 60 of 317 in total

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  1. Nanostructured SnO2-Ge Multi-layer thin Films with Quantum Confinement Effects for Solar Cell
    Khan AF, Sajjad W, Rahim NA
    Recent Pat Nanotechnol, 2016;10(1):77-82.
    PMID: 27018275
    BACKGROUND: It is well-known that multi-layer films with nanostructure can give novel properties by interfacial phenomenon and quantum confinement effects. Nanostructured multi-layer thin films are presently being analyzed for their vast applications in the area of optoelectronics technology particularly photovoltaics. Hereof, two dimensional thin films with nanostructure are of prime importance due to their structure dependent optical, electrical, and opto-electronic properties. It has been revealed that these films exhibit quantum confinement effects with band gap engineering. The main focus of the research is to evaluate the effect on structural and optical properties with number of layers.

    METHODS: Nanostructured SnO2-Ge multi-layer thin films were fabricated using electron beam evaporation and resistive heating techniques. Alternate layers of SnO2 and Ge were deposited on glass substrate at a substrate temperature of 300 °C in order to obtain uniform and homogeneous deposition. The substrate temperature of 300 °C has been determined to be effective for the deposition of these multi-layer films from our previous studies. The films were characterized by investigating their structural and optical properties. The structural properties of the as-deposited films were characterized by Rutherford Backscattering Spectroscopy (RBS) and Raman spectroscopy and optical properties by Ultra-Violet-Near infrared (UV-VIS-NIR) spectroscopy.

    RESULTS: RBS studies confirmed that the layer structure has been effectively formed. Raman spectroscopy results show that the peaks of both Ge and SnO2 shifts towards lower wavenumbers (in comparison with bulk Ge and SnO2, suggesting that the films consist of nanostructures and demonstrate quantum confinement effects. UV-VIS-NIR spectroscopy showed an increase in the band gap energy of Ge and SnO2 and shifting of transmittance curves toward higher wavelength by increasing the number of layers. The band gap lies in the range of 0.9 to 1.2 eV for Ge, while for SnO2, it lies between 1.7 to 2.1 eV.

    CONCLUSION: Analysis of results suggests that the nanostructured SnO2-Ge multi-layer thin film can work as heterojunction materials with quantum confinement effects. Accordingly, the present SnO2-Ge multi-layer films may be employed for photovoltaic applications. Few relevant patents to the topic have been reviewed and cited.

    Matched MeSH terms: Spectrum Analysis, Raman
  2. Absolute Photoabsorption Cross-Sections of Methanol for Terrestrial and Astrophysical Relevance
    Lange E, Lozano AI, Jones NC, Hoffmann SV, Kumar S, Śmiałek MA, et al.
    J Phys Chem A, 2020 Sep 30.
    PMID: 32941031 DOI: 10.1021/acs.jpca.0c06615
    We investigate the methanol absorption spectrum in the range 5.5-10.8 eV to provide accurate and absolute cross-sections values. The main goal of this study is to provide a comprehensive analysis of methanol electronic-state spectroscopy by employing high-resolution vacuum ultraviolet (VUV) photoabsorption measurements together with state-of-the-art quantum chemical calculation methods. The VUV spectrum reveals several new features that are not previously reported in literature, for n > 3 in the transitions (nsσ(a') ← (2a″)) (1A' ← X̃1A') and (nsσ, npσ, npσ', ndσ ← (7a')) (1A' ← X̃1A'), and with particular relevance to vibrational progressions of the CH3 rocking mode, v11'(a″), mode in the (3pπ(a″) ← (2a″)) (21A' ← X̃1A') absorption band at 8.318 eV. The measured absolute photoabsorption cross-sections have subsequently been used to calculate the photolysis lifetime of methanol in the Earth's atmosphere from the ground level up to the limit of the stratosphere (50 km altitude). This shows that solar photolysis plays a negligible role in the removal of methanol from the lower atmosphere compared with competing sink mechanisms. Torsional potential energy scans, as a function of the internal rotation angle for the ground and first Rydberg states, have also been calculated as part of this investigation.
    Matched MeSH terms: Spectrum Analysis
  3. Fulltext Complex Chemical Data Classification and Discrimination Using Locality Preserving Partial Least Squares Discriminant Analysis
    Aminu M, Ahmad NA
    ACS Omega, 2020 Oct 20;5(41):26601-26610.
    PMID: 33110988 DOI: 10.1021/acsomega.0c03362
    Partial least squares discriminant analysis (PLS-DA) is a well-known technique for feature extraction and discriminant analysis in chemometrics. Despite its popularity, it has been observed that PLS-DA does not automatically lead to extraction of relevant features. Feature learning and extraction depends on how well the discriminant subspace is captured. In this paper, discriminant subspace learning of chemical data is discussed from the perspective of PLS-DA and a recent extension of PLS-DA, which is known as the locality preserving partial least squares discriminant analysis (LPPLS-DA). The objective is twofold: (a) to introduce the LPPLS-DA algorithm to the chemometrics community and (b) to demonstrate the superior discrimination capabilities of LPPLS-DA and how it can be a powerful alternative to PLS-DA. Four chemical data sets are used: three spectroscopic data sets and one that contains compositional data. Comparative performances are measured based on discrimination and classification of these data sets. To compare the classification performances, the data samples are projected onto the PLS-DA and LPPLS-DA subspaces, and classification of the projected samples into one of the different groups (classes) is done using the nearest-neighbor classifier. We also compare the two techniques in data visualization (discrimination) task. The ability of LPPLS-DA to group samples from the same class while at the same time maximizing the between-class separation is clearly shown in our results. In comparison with PLS-DA, separation of data in the projected LPPLS-DA subspace is more well defined.
    Matched MeSH terms: Spectrum Analysis
  4. A New Seco-Clerodane-Type Diterpenoid from Bornean Liverwort Schistochila acuminata
    Ng SY, Kamada T, Suleiman M, Vairappan CS
    Nat Prod Commun, 2016 Aug;11(8):1071-1072.
    PMID: 30725558
    A new compound, schistochilic acid D (1) and two known compounds (2 and 3) were isolated from MeOH extract of Bornean liverwort. Schistochila acuininata collected from Mount Trus Madi, Sabah. The structure of the new metabolite was established based on spectroscopic (ID NMR, 2D NMR, and IR). and HRESIMS data. In addition, another population of S. acuminata collected from Mount Alab (Sabah) yielded four known compounds, 2, 3, 4 and 5. These compounds were tested for their biological potential against the B 16-Fl0 cell line. Compounds 4 and 5 exhibited weak cytotoxic activity.
    Matched MeSH terms: Spectrum Analysis
  5. Fulltext Investigation of natural environmental radioactivity concentration in soil of coastaline area of Ado-Odo/Ota Nigeria and its radiological implications
    Joel ES, Maxwell O, Adewoyin OO, Olawole OC, Arijaje TE, Embong Z, et al.
    Sci Rep, 2019 03 12;9(1):4219.
    PMID: 30862825 DOI: 10.1038/s41598-019-40884-0
    Natural radioactivity in coastaline area soil of Ado-Odo/Ota has been carried out to ascertain the presence of radionuclides using gamma-ray spectroscopy (HPGe detector). The result showed that U-238, Th-232 and K-40 ranged from 24 ± 7-49 ± 10; 67 ± 6-120 ± 9 and 88 ± 17-139 ± 20 Bqkg-1 respectively. The radium equivalent for the samples ranged from 132.51 to 230.91 Bqkg-1 with mean value of 185.89 Bqkg-1. The mean value for the gamma dose rate for the soil samples was estimated to be 81.32 nGyh-1. The estimated values of annual effective dose equivalent ranged from 0.61 to 1.07 mSv y-1. The estimation of alpha index representative (Iα) ranged from 0.12 to 0.24 with mean value of 0.21 while the gamma representative index ranged between 0.465 and 0.810. The activity utilization index of the soil samples ranged from 1.09 to 1.89 with mean value of 1.53. The radiological implication in the study area has shown that the soil samples with gamma dose rate value of 89.99 nGyh-1, 94.39 nGyh-1, 97.40 nGyh-1 and 101.04 nGyh-1 respectively are higher than the recommended value of 80 nGyh-1 and may pose health implication for long term exposure.
    Matched MeSH terms: Spectrum Analysis
  6. Measuring Ultrafast Spectral Diffusion and Correlation Dynamics by Two-Dimensional Electronic Spectroscopy
    Do TN, Khyasudeen MF, Nowakowski PJ, Zhang Z, Tan HS
    Chem Asian J, 2019 Nov 18;14(22):3992-4000.
    PMID: 31595651 DOI: 10.1002/asia.201900994
    The frequency fluctuation correlation function (FFCF) measures the spectral diffusion of a state's transition while the frequency fluctuation cross-correlation function (FXCF) measures the correlation dynamics between the transitions of two separate states. These quantities contain a wealth of information on how the chromophores or excitonic states interact and couple with its environment and with each other. We summarize the experimental implementations and theoretical considerations of using two-dimensional electronic spectroscopy to characterize FFCFs and FXCFs. Applications can be found in systems such as the chlorophyll pigment molecules in light-harvesting complexes and CdSe nanomaterials.
    Matched MeSH terms: Spectrum Analysis
  7. Two closely related 2-(benzo-furan-2-yl)-2-oxoethyl benzoates: structural differences and C-H⋯O hydrogen-bonded supra-molecular assemblies
    Then LY, Chidan Kumar CS, Kwong HC, Win YF, Mah SH, Quah CK, et al.
    Acta Crystallogr E Crystallogr Commun, 2017 Jul 01;73(Pt 7):1087-1091.
    PMID: 28775889 DOI: 10.1107/S2056989017009422
    The compounds 2-(1-benzo-furan-2-yl)-2-oxoethyl 2-nitro-benzoate, C17H11NO6 (I), and 2-(1-benzo-furan-2-yl)-2-oxoethyl 2-amino-benzoate, C17H13NO4 (II), were synthesized under mild conditions. Their mol-ecular structures were characterized by both spectroscopic and single-crystal X-ray diffraction analysis. The mol-ecular conformations of both title compounds are generally similar. However, different ortho-substituted moieties at the phenyl ring of the two compounds cause deviations in the torsion angles between the carbonyl group and the attached phenyl ring. In compound (I), the ortho-nitro-phenyl ring is twisted away from the adjacent carbonyl group whereas in compound (II), the ortho-amino-phenyl ring is almost co-planar with the carbonyl group. In the crystal of compound (I), two C-H⋯O hydrogen bonds link the mol-ecules into chains propagating along the c-axis direction and the chains are inter-digitated, forming sheets parallel to [20-1]. Conversely, pairs of N-H⋯O hydrogen bonds in compound (II) link inversion-related mol-ecules into dimers, which are further extended by C-H⋯O hydrogen bonds into dimer chains. These chains are inter-connected by π-π inter-actions involving the furan rings, forming sheets parallel to the ac plane.
    Matched MeSH terms: Spectrum Analysis
  8. The effect of ammonia on carbon nanotube growth using simple thermal chemical vapour deposition
    Teh AA, Ahmad R, Kara M, Rusop M, Awang Z
    J Nanosci Nanotechnol, 2012 Oct;12(10):8201-4.
    PMID: 23421197
    We report the use of a new precursor as active agents to promote the growth of carbon nanotubes (CNT) in methane ambient using a simple thermal chemical vapour deposition method. The agents consist of ammonia and methanol mixed at different ratios and was found to enhance the growth of CNTs. The optimum methanol to ammonia ratio was found to be 8 to 5, whereby longer and denser CNTs were produced compared to other ratios. The result was found otherwise when the experiment was done solely in methane ambient. In addition, CNT growth on substrates coated with double layer Ni catalyst was improved in terms of quality and density compared to a single coated substrates. This finding is supported by Raman spectrometry analysis.
    Matched MeSH terms: Spectrum Analysis, Raman
  9. Fulltext Effects of 3.0 MeV electron irradiation on 4H-SiC wafer properties
    Yusof Abdullah, Mohd Reusmaazran Yusof, Megat Harun Al Rashid Megat Ahmad, Hafizal Yazid, Abdul Aziz Mohamed, Norazila Mat Sali, et al.
    Jurnal Sains Nuklear Malaysia, 2013;25(1):9-15.
    MyJurnal
    Effects of 3 MeV electron (10 mA) irradiation at room temperature on the phase, microstructure,
    electrical and life time properties of 4H-SiC wafer were investigated by scanning electron
    microscopy (SEM), X-ray diffraction (XRD), four point probe current-voltage measurements and
    positron annihilation spectroscopy. It was found that irradiation damage in SiC wafer is
    significantly increased with the increase of radiation dose as observed in SEM. Irradiation also
    resulted in modification of crystallite size as identified by XRD. The resistance of a sample before
    irradiation was found to be 0.8 MΩ, whereas for a sample irradiated at 200 kGy, the resistance as
    measured by four point probe was 5.2 MΩ. It seems that the increase of resistance hence, reduction
    in conductivities could be due to defects induced by the radiation dose received then created
    leakage currents at both reverse and low-forward biases and creation of traps in the SiC.
    Meanwhile positron annihilation spectroscopy (PAS) was used to analyse the life time of irradiated
    samples which nonetheless shows that all irradiated sample have similar life time of 151 ps. It was
    observed that that no degradation process of materials experienced by SiC wafer irradiated at 500
    kGy.
    Matched MeSH terms: Spectrum Analysis
  10. Fulltext Measurement of 226ra in iaea soil-6 using gamma spectrometry system: Comparison between manual and software calculation
    Mei-Wo, Yii, Kamarozaman Ishak, Nooruzainah Abu Hassan, Maziah Mahmud, Khairul Nizam Razali
    Jurnal Sains Nuklear Malaysia, 2012;24(1):102-112.
    MyJurnal
    IAEA Soil-6 is a reference material with a certified value for 226Ra fall between 69.6 – 93.4 Bq/kg at 95% confidence level. This material has been used as a sample and performed repeat measurement weekly between years 2006 – 2009 using a same gamma spectrometry system. The activity concentration of this material is calculated automatically using the operational commercial software and compared with activity obtained from the manual calculation. Study found that only 76.9%, 64.1%, 56.3%, and 79.3% of the results from the software calculation lie within the confidence level for year 2006, 2007, 2008 and 2009, respectively. However, u-score calculation revealed that 94.9 %, 89.7%, 79.2% and 84.9% data set have no significant bias (u < 2.58) for year 2006, 2007, 2008 and 2009, respectively. On the other hand, all manual calculation data were found to be within the 95 % confidence level. Factors suspected to cause differences between these two approaches were discussed here. Manually peak search, marking and calculation still remains as the preferred option for calculating the gamma radionuclides activity unless limitations of the spectrum analysis software, as described in this paper can be resolved/improved upon.
    Matched MeSH terms: Spectrum Analysis
  11. The occurrence of a furanoid fatty acid inHevea brasiliensis latex
    Hasma H, Subramaniam A
    Lipids, 1978 Dec;13(12):905-7.
    PMID: 27520427 DOI: 10.1007/BF02533847
    Methyl esters from the triglyceride fraction of the neutral lipids of natural rubber latex were found by gas liquid chromatography to contain about 90% of a furanoid acid. Spectroscopic analysis identified the acid as 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid.
    Matched MeSH terms: Spectrum Analysis
  12. Fulltext Revisiting uranium resources in Malaysia
    Mohd Azmi Ismail, Mohammad Roston Zakaria
    Jurnal Sains Nuklear Malaysia, 2012;24(1):1-8.
    MyJurnal
    An appraisal of the regional reconnaissance geophysical, geochemical and geological data obtained under the Central Belt Project in 1977 – 1978 appeared to constitute favourable uranium exploration targets. Follow-up surveys conducted until the year 1990 have proposed the exploration area to be divided into three transects. Transect 1 covers the western part of the state of Kelantan, northwest Pahang and the eastern half of Perak. Transect 2 covers southeastern tip of Perak, west Pahang, eastern half of Wilayah Persekutuan, eastern portion of Selangor, and the northwest portion of Negeri Sembilan. Transect 3 covers central Kelantan, northwestern of Terengganu and northern portion of Pahang. Results of the study indicate that the Main Range, Bujang Melaka, and Bukit Tinggi Plutons are most fertile with uranium spectrometric rock values range from 13 to 25 ppm. Further investigations to zero down the target areas for uranium mineralization are strongly recommended over these areas.
    Matched MeSH terms: Spectrum Analysis
  13. Fulltext Mimics and diagnostic pitfalls of intracranial lesions in conventional MRI: Clues on advanced MRI
    Peter, Alan Basil, Norlisah Ramli, Kartini Rahmat, Faizatul Izza Rozalli, Che Ahmad Azlan
    Neurology Asia, 2015;20(2):161-165.
    MyJurnal
    Objective: To delineate and differentiate between late subacute hemorrhage and intracranial lipomas in clinically available conventional and advanced MR sequences. Methods: Two cases of late subacute hemorrhage and two cases of intracranial lipoma were reviewed with CT scans and 3.0T scanner MRI. The sequences evaluated in MRI were T1-weighted (T1W) fast spin echo (FSE), T2-weighted (T2W) FSE, gradient echo T2*-weighted (GRE T2*W) images, diffusion weighted (DWI), apparent diffusion coefficient (ADC) and multivoxel spectroscopy. Results: Late subacute hemorrhage and intracranial lipoma have similar imaging features on T1W, T2W FSE with blooming artefact at the margins on GRE T2*W. However on GRE T2*W sequence, the central area of lipoma demonstrates low signal; while hemorrhage demonstrates high signal. In DWI, late subacute hemorrhage shows hyperintensity; while in lipoma there is loss of signal.
    Conclusion: Awareness of the potential pitfalls in standard sequence are important, as these entities appear to have similar T1W/ T2W characteristic with blooming artefact on T2*W. Knowing the distinctive central signal intensity pattern on GRE T2W* and DWI is therefore essential to differentiate between these lesions as there are differences to their clinical management.
    Matched MeSH terms: Spectrum Analysis
  14. Fulltext Faktor yang mempengaruhi paras kromium dalam kalangan petani di daerah Bachok dan Pasir Puteh, Kelantan
    Nurfariha Firdaus, Ismarulyusda Ishak, Syarif Husin Lubis, Nooraisyah Mansoor, Hidayatul Fathi Othman, Nihayah Mohammad, et al.
    Jurnal Sains Kesihatan Malaysia, 2014;12(2):27-31.
    MyJurnal
    Kromium merupakan mineral yang penting dan kofaktor insulin yang memainkan peranan penting sebagai hormon yang membantu dalam regulasi gula dalam darah. Penduduk Kelantan sering dikaitkan dengan pengambilan makanan berasaskan gula. Petani merupakan golongan yang berisiko tinggi kerana pendedahan terhadap pestisid dan pengambilan makanan bergula boleh mempengaruhi paras kromium. Objektif kajian ini adalah untuk mengetahui status paras kromium dalam kalangan petani yang terdedah kepada pestisid dan baja kimia di Kelantan. Kajian ini adalah kajian keratan rentas yang dilakukan di Bachok dan Pasir Puteh, Kelantan. Responden adalah seramai 113 petani yang terdedah kepada pestisid atau baja kimia tidak kurang daripada satu tahun. Subjek ditemu bual menggunakan soal selidik pengetahuan, sikap dan amalan (KAP) yang telah divalidasi untuk informasi berkaitan data demografi k. Sampel kuku dan rambut telah dianalisia dengan menggunakan kaedah pencernaan asid dan Inductively Coupled Plasma Mass Spectroscopy (ICPMS) untuk mendapatkan paras kromium. Hasil kajian menunjukkan 81.4% adalah petani lelaki dan 18.6% adalah perempuan. Paras kromium kuku (125.82 ± 47.81 μg/L) dan rambut (39.63 ± 5.70 μg/L) petani adalah lebih rendah berbanding julat piawai kuku (6200 μg/L) dan rambut (100-2500 μg/L). Tiada perbezaan paras kromium yang signifi kan (p > 0.05) menurut jantina, umur, glukosa darah, tempoh pendedahan pestisid dan pemakanan. Petani yang merokok menunjukkan paras kromium yang lebih rendah (p < 0.05) berbanding petani yang tidak merokok. Kesimpulannya, paras unsur kromium petani di Bachok dan Pasir Puteh adalah rendah berbanding julat normal dan petani harus berhenti merokok kerana merokok akan merendahkan paras kromium.
    Matched MeSH terms: Spectrum Analysis
  15. In-situ measurement of temperature and alkali metal concentration in municipal solid waste incinerators using flame emission spectroscopy
    He X, Lou C, Qiao Y, Lim M
    Waste Manag, 2020 Feb 01;102:486-491.
    PMID: 31756685 DOI: 10.1016/j.wasman.2019.11.015
    In order to address slagging, fouling and high-temperature corrosion problems caused by alkali metals in Municipal Solid Waste (MSW), in-situ measurement of alkali metal in MSW incinerators is needed. The paper presents experimental measurements of temperatures and alkali metal concentrations in two MSW incinerators based on Flame Emission Spectroscopy (FES). Through the analysis of spontaneous emission spectra and a calibration procedure, the concentration of gas phase sodium (Na) and potassium (K), temperature and thermal radiation in the incinerator were in-situ measured by a portable spectral system simultaneously. Experimental results showed MSW composition has significant effect on the measured gaseous Na and K. Higher volatile content in MSW may enhance the alkali metal emission. Besides that, the released gaseous Na and K in the two incinerators are correlated with temperature in incinerators. The study provided a low cost and effective solution for in-situ measurement of temperature and alkali metal concentration in MSW incinerators.
    Matched MeSH terms: Spectrum Analysis
  16. High transparency iron doped indium oxide (in2—xfexo3, x = 0.0, 0.05,0.25, 0.35 and 0.45) films prepared by the sol-gel method
    Ibrahim N, Baqiah H, Abdullah M
    Sains Malaysiana, 2013;42:961-966.
    High quality indium oxide and iron doped indium oxide nanocrystalline films were prepared by the sol-gel method followed by a spin coating technique. The samples were characterized by an X-ray diffractometer, an atomic force microscopy and a UV-vis spectroscopy. All samples had good crystallinity with a preferred orientation in the (222) direction. The crystallite size increased from 12.1 nm for the pure sample to 16.1 nm for the sample with x=0.35 and then decreased to 12.1 nm for the sample with x=0.45. All samples contained nanometer grain sizes with a smooth surface. All films showed a high transmission of over 91% in the wavelength range of 200-800 nm.
    Matched MeSH terms: Spectrum Analysis
  17. Adsorbed CO at polycrystalline copper in phosphate buffered solution
    Jumat Salimon
    Sains Malaysiana, 2007;36:27-32.
    The adsorption of CO at polycrystalline copper surface was investigated spectroscopically. It was found that CO adsorbed as a linear adsorbed CO, Cu-COL and was a dominant species on copper surface at low CO concentration. A Cu-COL was electrochemically converted to a bridge bonded CO, Cu-COB at a high CO concentration condition. Increasing the CO surface coverage, qCO will increase the formation of adsorbed bridge bonded CO. A nitrogen gas purging treatment was used to examine the stability of an adsorbed CO through the evacuation process. The result showed that Cu-COB remained intact while Cu-COL was completely removed from the copper surface. It suggests that Cu-COL may involve in a weak bonding to a copper surface such as in a physisorbed interaction, while Cu-COB consists much stronger bonding such as a chemisorbed interaction. The N2 purging treatment also gave an additional prove that Cu-COB was partly converted to Cu(I)-CO at anodic potential regions.
    Matched MeSH terms: Spectrum Analysis
  18. Characterization and absorbing properties of oil palm empty fruit bunch filled poly (acrylic acid–co–acrylamide) superabsorbent polymer composites
    Nor Erma Shuhadah Abdul Razak, Shahrir Hashim, Abdul Razak Rahmat
    Sains Malaysiana, 2011;40:1179-1186.
    Oil palm empty fruit bunch graft poly (acrylic acid-co-acrylamide) superabsorbent composite (OPEFB-g-(PAA-co-PAM) SAPC) was synthesized by graft copolymerization of the acrylic acid (AA) and acrylamide (AM) comonomer onto OPEFB fibre using ammonium persulfate (APS) and N,N-methylene bisacarylamide (MBA) as an initiator and crosslinker, respectively. The absorbency in various chloride salt solutions indicated that the absorbency decreased with increasing ionic strength of the salt solutions. Moreover, the absorbency under load (AUL) of SAPC was investigated at various applied loading and results show that, AUL decreased with increasing applied loading. Infrared Spectroscopy (IR) and Thermogravimetric Analysis (TGA) were carried out to confirm the chemical structure and thermal properties of the synthesized superabsorbent, respectively.
    Matched MeSH terms: Spectrum Analysis
  19. Raman spectroscopy and X-ray photo-spectroscopy analysis of graphite media irradiated at low doses
    Bradley DA, Siti Rozaila Z, Khandaker MU, Almugren KS, Meevasana W, Abdul Sani SF
    Appl Radiat Isot, 2019 May;147:105-112.
    PMID: 30852298 DOI: 10.1016/j.apradiso.2019.02.016
    We explore the utility of controlled low-doses (0.2-100 Gy) of photon irradiation as initiators of structural alteration in carbon-rich materials. To-date our work on carbon has focused on β-, x- and γ-irradiations and the monitoring of radiotherapeutic doses (from a few Gy up to some tens of Gy) on the basis of the thermoluminescence (TL) signal, also via Raman and X-ray photo-spectroscopy (XPS), providing analysis of the dose dependence of single-walled carbon nanotubes (SWCNT). The work has been extended herein to investigate possibilities for analysis of structural alterations in graphite-rich mixtures, use being made of two grades of graphite-rich pencil lead, 8H and 2B, both being in the form produced for mechanical pencils (propelling or clutch pencils). 2B has the greater graphite content (approaching 98 wt %), 8H being a mixture of C, O, Al and Si (with respective weight percentages 39.2, 38.2, 9.8 and 12.8). Working on media pre-annealed at 400 °C, both have subsequently been irradiated to penetrating photon-mediated doses. Raman spectroscopy analysis has been carried out using a 532 nm laser Raman spectrometer, while for samples irradiated to doses from 1 to 40 Gy, XPS spectra were acquired using Al Kα sources (hv ∼1400 eV); carbon KLL Auger peaks were acquired using 50 eV Pass Energy. At these relatively low doses, alterations in order-disorder are clearly observed, defect generation and internal annealing competing as dominating effects across the dose range.
    Matched MeSH terms: Spectrum Analysis, Raman
  20. Synthesis of graphene flakes over recovered copper etched in ammonium persulfate solution
    Nizam MK, Sebastian D, Kairi MI, Khavarian M, Mohamed AR
    Sains Malaysiana, 2017;46:1039-1045.
    The synthesis of high quality graphene via economic way is highly desirable for practical applications. In this study, graphene flake was successfully synthesized on Cu/MgO catalyst derived from recovered Cu via etching in ammonium persulfate solution. Recovered Cu acted as efficient active metal in Cu/MgO catalyst with good crystal structure and composition according to XRD and XRF results. FESEM, EDX, HRTEM, Raman spectroscopy and SAED analysis were carried out on the synthesized graphene. The formation of single, bilayer and few layer of graphene from Cu/MgO catalyst derived from recovered Cu was feasible.
    Matched MeSH terms: Spectrum Analysis, Raman
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