Roslan Md Nor
I am a physicist at the University of Malaya with interests in nanocarbon and oxide materials, plasma technology and materials characterization.
Address: Department of Physics, Faculty of Science Building, University of Malaya, 50603 Kuala Lumpur, MALAYSIA
Address: Department of Physics, Faculty of Science Building, University of Malaya, 50603 Kuala Lumpur, MALAYSIA
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Papers by Roslan Md Nor
(CNT) was studied using oxygen–hydrogen (O2–H2)
gas mixture direct current (DC) glow discharge plasma
technique for cathode/CNT-anode separation of 0.10 ±
0.01 cm. O2 and H2 were fixed at flowrate of 10.0 ml/min in
order to obtain gas mixture ratio of 1:1. During the (O2–H2)
gas mixture DC glow discharge, current–voltage (I–V)
characteristic of gaseous species studied for various settings
of gas pressures 1, 2, 3 and 4 mbar. The voltage at gap
between cathode/CNT and anode, a breakdown voltage, was
identified as ‘‘functionalization voltage’’ (Vfunc). Vfunc was
noticed responsible for functionalization of functional
groups on sidewall of CNT. The Vfunc were recorded as 796,
707, 594, and 663 V for gas pressures of 1, 2, 3 and 4 mbar,
respectively. The co-relation between Vfunc and gas pressure
was identified as linear relationship. But a voltage obtained
due to the CNT/Cathode fall shows exponential relationship
with the gas pressures. The possibility of [O] [H] functionalization
was proved using Fourier transmission infra-red
(FTIR) spectroscopy. Hydroxyl (–OH), carboxyl (–COOH),
and carbonyl (–C=O) functional groups were identical as
identified in the FTIR spectra. The field emission scanning
electron microscope images show significant changes in the
morphology of CNT which proves that the DC gas discharge
plasma is a possible technique for [O] [H] functionalization
on the sidewall of CNT.
off the coast of peninsular Malaysia. The media include seafood, sea water and sediment. The samples were collected some
weeks prior to the devastating 2011 To¯hoku earthquake and associated tsunami, the occurrence of which precipitated the
Fukushima incident. All samples showed the presence of naturally occurring 226Ra, 228Ra and primordial 40K, all at typically
prevailing levels. The concentrations of natural radioactivity in molluscs were found to be greater than that of other marine
life studied herein, the total activity ranging from 337 to 393 Bq kg21 dry weight. The total activity in sea water ranged from
15 to 88 Bq l21. Sediment samples obtained at deep sea locations more than 20 km offshore further revealed the presence of
137Cs. The activity of 137Cs varied from ND to 0.5 Bq kg21 dry weight, the activity increasing with offshore distance and
depth. The activity concentrations presented herein should be considered useful in assessing the impact of any future
radiological contamination to the marine environment.
carbon nanotube (SWCNT) poly-ethylene oxide (PEO) composite as a passive saturable absorber (SA). The
composite with an SWCNT concentration of 18wt% is prepared by mixing the SWCNT homogeneous solution
with a diluted PEO polymer solution. A droplet of the polymer composite is applied on the fiber ferrule end,
which is then mated to another clean ferrule connector to construct an SA. The SA is then integrated into the
laser system to self-start stable mode locking at 1557nm without employing a polarization controller. The EDFL
generates a stable soliton pulse train with a duration of 0.81 ps, repetition rate of 44MHz and average output
power of 92.4 𝜇W at a 980nm pump power of 26.8mW. The soliton laser starts to lase at a pump power threshold
of 14.6mW.
using a single-walled carbon nanotube–polyethylene oxide (SWCNT–PEO) saturable absorber
(SA). The SA is fabricated by cutting off a small part of the developed SWCNT–PEO film and
sandwiching it in between two FC/PC (fiber connector/physical contact) fiber connectors.
Multi-wavelength combs with ten lasing lines and spacing of 0.158 nm are obtained by the use
of 2 km long dispersion compensating fiber as the Brillouin gain medium and a four-port
circulator to isolate and circulate the odd-order Stokes signals. Q-switched pulse trains with a
repetition rate of 105.2 kHz and a pulse width of 0:996 s are obtained in the proposed
MWBEFL at a 1480 nm pump power of 120 mW and a Brillouin pump power of 5.4 dBm.
of single-and multi-walled VACNTs was synthesized at a fixed temperature of 750 oC in a thermal chemical vapour deposition furnace. Field emission scanning electron microscopy, micro-Raman spectroscopy and thermogravimetric analyses showed that the produced VACNTswereofexcellent
quality,comparabletothoseobtainedusingconventionalcarbonsources,withapurityof88.2%andtube
diameters rangingfrom18to78nm.Basedonourstudy,wastechickenfatisapromisingcarbonsource
for thesynthesisofhigh-qualityandhigh-purityVACNTs.
power plant fuelled predominantly by bituminous coal. The concentrations of 226Ra, 232Th and 40K in
onsite bottom-ashwerefoundtobe139Bq/kg,108Bq/kgand291Bq/kg,respectively,thelevelsforthese
radiolnuclides insoildecreasingwithdistancefromthepowerplant.Attheplantperimeterthe
respectiveradionuclideconcentrationswere87Bq/kg,74Bq/kgand297Bq/kg.Inanearbytown,the
corresponding concentrationswere104Bq/kg,52Bq/kgand358Bq/kg,suggestiveofuseofTENORM
affected soils.Themeanradiumequivalentactivities(Raeq) insoilandashsampleinthetownwere
205 Bq/kgand316Bq/kg,respectively.TheKaparplantash/slagappearstocontainahigherlevelof
TENORM thantheworldaverage.Thedegreeofcontaminationismuchhigherinsidethetownwhere
slag hasbeenmixedwithtopsoilaslandfill orassimpledomesticwaste.Fortheprevailinglevelsof
exposureandaworstcasesenario,thepredictedcommittedeffectivedoseduetoingestionand
inhalation forintakedurationsof1-and30yearswouldbe4.2 μSv and220 μSv,respectively.
produced usingdifferentconcentrationofzincacetatewhichwasusedasthezincsource.FESEMimagingshowedtheformationof
nanoparticles inthesizerangeof50–200nm.XRDanalysisrevealedwurtzitehexagonalZnOwithpreferentialorientationat(100)
reflection plane.TheroomtemperaturePLspectroscopyshowedlittlevariationforsamplesdepositedwithdifferentzincacetate
concentration. Peakdueto Vo
þ, Vo, holetrappedat Vo
nn, Oi and hydroxylgroupswereobservedwithslightvariationinpeakposition.
The synthesisofzincoxidenanoparticlesusingthecitrusextractswerefoundtobecomparabletothoseobtainedfromconventional
reduction methodsusinghexamethylenetetramineorcetyltrimethylammoniumbromideandcanbeanexcellentalternativeforthe
synthesis ofZnOnanoparticlesusingbiomaterials.
75% H2. Characterization of formations used FESEM, XRD and EDX. The nanophosphors consisted of
particles of sizes in the range 85–150nm, thethermoluminescence(TL)- based radiation detection
medium giving rise to a single peaked glow curve of maximum yield at a temperature of 250 oC at a
heating rate of 5 oC/s. The TL response increased linearly with radiation dose, ZnS doped to 2 mol of Mn
being found the most sensitive. Regarding chemical vapour deposited(CVD )carbon, inappreciable TL was
found for the resultant ball-like amorphous carbon films, graphite, and the silicon substrate,whereas
CVD diamond films showedapromisingdegreeoflinearitywithdose.ForboththeZnSanddiamond
samples, TLsignalfadingwasappreciable,beingsome40%perdayforZnSand450% perdayforCVD
films evenunderstorageinthedarkatroomtemperature,makingitapparentthatthereisneedtoadjust
parameterssuchasthesizeofnanoparticles.
carbo-thermal evaporation of graphite at 1200˚C. The obtained β-SiC nanowires were aligned with
diameters ranged between 40 to 500 nm. The majority of crystal planes were β-SiC (111) with other
less intensity of (200), (220) and (311). The silicon substrate location inside the furnace found to be
critical in the formation of the β-SiC nanowires. Also, FTIR absorption peaks for β-SiC nanowires
found at higher frequency side of 1110 cm-1 which is pointed to Si–O asymmetric stretching mode.
carbon nanotubes (SWCNTs) embedded in a poly-ethylene oxide (PEO) thin film as a passive saturable absorber.
The film is fabricated by using a prepared homogeneous SWCNT solution, which is mixed with a diluted PEO
solution and cast onto a glass Petri dish to form, by evaporation, a thin film. The 50 𝜇m-thick film is sandwiched
between two fiber connectors to construct a saturable absorber, which is then integrated in an EDFL cavity to
generate self-started stable soliton pulses operating at 1560.8 nm. The soliton pulse starts to lase at a pump
power threshold of 12.3mW with a repetition rate of 11.21 MHz, a pulse width of 1.02 ps, an average output
power of 0.65mW and a pulse energy of 57.98 pJ.
investigated.Zinc nitrate solutions and C. aurantifolia fruit extracts mixtures were heated at 90oC at pH
of 5,7and9.Solid reaction products were annealed in air at 300 oC yielding nanorods with diameters of
about 100nm for all samples. XRD analysis showed pure hexagonal wurtzite ZnO structure.Room
temperature visible photoluminescence spectroscopy revealed emissions which were attributed to the
common defects states associated with ZnO. Nanorods growth in acidic solution was found to be inhibited compared to nanorods from neutral and alkaline solutions. This was due to preferential erosion of ZnO(0001)face in acidic solution and the enhanced growth in neutral and alkaline solutions which
favored the formation of Zn (OH)2 which is an intermediate molecule in the reaction to form ZnO.
evaporation of brass (CuZn) which contain in-situ three stages in obtaining un-doped and Mn-doped zinc oxide
(ZnO) nanostructures (NSs). The structure and morphology were characterized by energy dispersive analysis
X-ray (EDAX), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The role of
Ar as feed gas and interaction between methanol and brass have been predicted based on work reported
elsewhere. Photoluminescence (PL) properties of un-doped and Mn-doped ZnO showed significant changes
in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen
interstitials (Oi), zinc vacancy (VZn), singly charged zinc vacancy (V−
Zn), oxygen vacancy (Vo), singly charged
oxygen vacancy (V+
o ) and oxygen antisite defects (OZn) in the grown NS. The Mn-doped ZnO NSs have exhibited
shifted PL peaks compared to the un-doped ZnO.
due to the presence of radioactivity in soil and agricultural crops. Tapioca and sweet potato, both root
crops, are popular foodstuffs for a significant fraction of the Malaysian population, and result in intake of
radionuclides. For the natural field conditions experienced in production of these foodstuffs, TFs and the
annual effective dose were evaluated for the natural radionuclides 226Ra, 232Th, 40K, and for the
anthropogenic radionuclide 88Y, the latter being a component of fallout. An experimental tapioca field
was developed for study of the time dependence of plant uptake. For soil samples from all study locations
other than the experimental field, it has been shown that these contain the artificial radionuclide
88Y, although the uptake of 88Y has only been observed in the roots of the plant Manihot esculenta
(from which tapioca is derived) grown in mining soil. The estimated TFs for 226Ra and 232Th for tapioca
and sweet potato are very much higher than that reported by the IAEA. For all study areas, the annual
effective dose from ingestion of tapioca and sweet potato are estimated to be lower than the world
average (290 mSv y1).
materials. One of the requirements of this technique is a model to forecast conductivity in preliminary experiments. The aim
of this paper is to examine the prediction of conductivity by neuro-fuzzy inference with basic experimental factors such as
temperature, frequency, thickness of the film and weight percentage of salt. In order to provide the optimal sets of fuzzy
logic rule bases, the grid partition fuzzy inference method was applied. The validation of the model was tested by four
random data sets. To evaluate the validity of the model, eleven statistical features were examined. Statistical analysis of the
results clearly shows that modeling with an adaptive neuro-fuzzy is powerful enough for the prediction of conductivity.
nanostructures for measurement of different concentrations of uric acid in de-ionized water
and changes in relative humidity (RH). The sensor operates based on intensity modulation
technique. The tapered POF were fabricated by etching method using acetone, sand paper and
de-ionized water to achieve a waist diameter of 0.45 mm and tapering length of 10 mm. The
tapered fiber were then coated with ZnO nanostructures using sol-gel immersion method on
ZnO seeded and non-seeded fiber. As the concentration of the uric acid was varied from 0
ppm to 500 ppm, the output voltage of the sensor using tapered POF with seeded ZnO
nanostructures increased linearly with a higher sensitivity of 0.0025 mV/ppm compared to
0.0009 mV/ppm for unseeded tapered POF coated with ZnO. Both samples showed almost
similar linearity of the response cuves of about 98.2%. The tapered POF with ZnO
nanostructures interact with uric acid due to strong electrostatic interaction resulting in the
increase in response with the increasing concentration. In addition, the seeded ZnO nanostructure could significantly enhance the transmission of the sensor that is immersed in
solutions of higher concentration. On the other hand, for both samples, the change in the
intensity of the transmitted light of the tapered POF coated with ZnO nanostructures
decreases linearly with relative humidity. The tapered POF with grown (seeded) ZnO
provides better sensitivity at 0.0258mV/% with a slope linearity of 95.48%. The ZnO
nanostructures that are exposed to an environment of humidity causes rapid surface
adsorption of water molecules and changes in optical properties. The tapered POF coated
with ZnO nanostructures using the seeding technique causes an increase in both effective RI
of surrounding medium and absorption coefficient of the ZnO nanostructures surfaces and
leads to larger leakage of light. Results show that tapered POF with seeded ZnO
nanostructures enable to increase the sensitivity of fiber for uric acid detection as well as
relative humidity. The proposed sensors provide numerous advantages such as simplicity of
design, low cost of production, higher mechanical strength and easier to handle compared to
silica fiber optic.
carbon nanotubes (SWCNTs) embedded in polyethylene oxide (PEO) thin film as a passive saturable absorber (SA). The
film with a thickness of 50 μm was fabricated using a prepared homogeneous SWCNT solution with 0.1% loading percentage,
which was mixed with a diluted PEO solution and casted onto a glass Petri dish to form a thin film by evaporation
technique. The film is sandwiched between two fiber connectors to construct a SA, which is then integrated in an
EDFL cavity to generate a self-started stable soliton pulses operating at 1558 nm. The soliton pulse starts to lase at pump
power threshold of 17.6mW with a repetition rate of 50 MHz, pulse width of 0.67 ps, average output power of 0.158
mW, pulse energy of 3.16 pJ, and peak power of 4.43W.