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  1. Fulltext Detection of formaldehyde in water: a shape-effect on the plasmonic sensing properties of the gold nanoparticles
    Nengsih S, Umar AA, Salleh MM, Oyama M
    Sensors (Basel), 2012;12(8):10309-25.
    PMID: 23112601 DOI: 10.3390/s120810309
    The effect of morphology on the plasmonic sensing of the presence of formaldehyde in water by gold nanostructures has been investigated. The gold nanostructures with two different morphologies, namely spherical and rod, were prepared using a seed-mediated method. In typical results, it was found that the plasmonic properties of gold nanostructures were very sensitive to the presence of formaldehyde in their surrounding medium by showing the change in both the plasmonic peaks position and the intensity. Spherical nanoparticles (GNS), for example, indicated an increase in the sensitivity when the size was increased from 25 to 35 nm and dramatically decreased when the size was further increased. An m value, the ratio between plasmonic peak shift and refractive index change, as high as 36.5 nm/RIU (refractive index unit) was obtained so far. An expanded sensing mode to FD was obtained when gold nanostructures with nanorods morphology (GNR) were used because of the presence of two plasmonic modes for response probing. However, in the present study, effective plasmonic peak shift was not observed due to the intense plasmonic coupling of closely packed nanorod structures on the surface. Nevertheless, the present results at least provide a potential strategy for response enhancement via shape-effects. High performance plasmonic sensors could be obtained if controlled arrays of nanorods can be prepared on the surface.
  2. Fulltext Gold nanonetwork film on the ITO surface exhibiting one-dimensional optical properties
    Umar AA, Iwantono I, Abdullah A, Salleh MM, Oyama M
    Nanoscale Res Lett, 2012;7(1):252.
    PMID: 22587640 DOI: 10.1186/1556-276X-7-252
    A network of gold nanostructures exhibiting one-dimensional gold nanostructure properties may become a prospective novel structure for optical, electrical and catalytic applications benefited by its unusual characteristics resulting from the collective properties of individual nanostructures in the network. In this paper, we demonstrate a facile method for the formation of high-density gold nanonetwork film on the substrate surface composed of quasi-1D nanoparticles (typically fusiform) with length ca. 10 nm - via reduction of gold ions in the presence of nanoseeds attached surface, binary surfactants of cetyltrimethylammonium bromide and hexamethyleneteramine and Ag+ ions. The length of the nanonetworks can be up to ca. 100 nm, which corresponds to the aspect ratio of ca. 10. The quasi-1D gold nanostructures as well as the nanonetworks were found to be sensitive to the binary surfactants system and the Ag+ ions as they can only be formed if all the chemicals are available in the reaction. The nanonetworks exhibit unique 1D optical properties with the presence of transverse and longitudinal surface plasmon resonance absorption. Owing to their peculiar structures that are composed of small quasi-1D nanoparticles, the nanonetworks may produce unusual optical and catalytic properties, which are potentially used in surface-enhanced Raman scattering, catalysis and optical and non-linear optical applications.
  3. Fulltext Thermal Annealing Effect on Structural, Morphological, and Sensor Performance of PANI-Ag-Fe Based Electrochemical E. coli Sensor for Environmental Monitoring
    Mohammad Naim N, Abdullah H, Umar AA, Abdul Hamid A, Shaari S
    ScientificWorldJournal, 2015;2015:696521.
    PMID: 26078996 DOI: 10.1155/2015/696521
    PANI-Ag-Fe nanocomposite thin films based electrochemical E. coli sensor was developed with thermal annealing. PANI-Ag-Fe nanocomposite thin films were prepared by oxidative polymerization of aniline and the reduction process of Ag-Fe bimetallic compound with the presence of nitric acid and PVA. The films were deposited on glass substrate using spin-coating technique before they were annealed at 300 °C. The films were characterized using XRD, UV-Vis spectroscopy, and FESEM to study the structural and morphological properties. The electrochemical sensor performance was conducted using I-V measurement electrochemical impedance spectroscopy (EIS). The sensitivity upon the presence of E. coli was measured in clean water and E. coli solution. From XRD analysis, the crystallite sizes were found to become larger for the samples after annealing. UV-Vis absorption bands for samples before and after annealing show maximum absorbance peaks at around 422 nm-424 nm and 426 nm-464 nm, respectively. FESEM images show the diameter size for nanospherical Ag-Fe alloy particles increases after annealing. The sensor performance of PANI-Ag-Fe nanocomposite thin films upon E. coli cells in liquid medium indicates the sensitivity increases after annealing.
  4. Formation of high-density crystalline-shape gold nanoparticles on indium tin oxide surfaces: effects of alcohothermal seeding
    Umar AA, Salleh MM, Majlis BY, Oyama M
    J Nanosci Nanotechnol, 2011 Jun;11(6):4974-80.
    PMID: 21770130
    We found that the gold nanoparticles with high-density and crystalline-shape, such as nanocubes, nanobricks, pentahedral nanorods, etc., can be realized on the surface by using a seed-mediated growth method with a unique seeding process, namely alcohothermal. By using a conventional growth solution that contains HAuCl4, cetyltrimethylammonium bromide, NaOH and ascorbic acid, gold nanoparticles with crystalline-morphology (gold nanocrystals) of yield up to ca. 95%, can be prepared. An alcohothermal seeding was carried out by a thermal reduction of gold ions from an alcoholic solution of gold salt on the surface through an annealing process at a moderate temperature, namely 250 degrees C. It is believed that the unique initial characteristic (presumably the structures) of the gold nanoseeds particles as the result of peculiar nanoseeds formation process, prepared using this approach, instead of a simple thermal restructuring of the as prepared nanoseeds as confirmed by the results of annealing treatment on the nanoseed prepared using the normal and in-situ reduction seeding, was as the driving factor for the projected growth of crystalline-shape gold nanoparticles on the surface. The crystalline-shape gold nanoparticles modified-surface should find a potential application in catalysis, sensors and SERS.
  5. Iridium-palladium binary alloy as a counter electrode in dye-sensitized solar cells
    Aziz NAS, Rahman MYA, Umar AA, Mawarnis ER
    Dalton Trans, 2023 Nov 24.
    PMID: 37999726 DOI: 10.1039/d3dt03375a
    This study is concerned with the iridium-palladium (Ir-Pd) binary alloy as a counter electrode (CE) for DSSC. The CE was prepared using the liquid phase deposition (LPD) technique. The influence of the concentration of hydrogen hexachloroiridate(IV) hydrate (H2Cl6Ir·H2O) on the properties and the performance of the device was investigated. The source of iridium was H2Cl6Ir·H2O. XRD analysis confirmed that the dominant phase of Ir-Pd existed in the sample. The grain size of Ir-Pd increased with the increase in the concentration of H2Cl6Ir·H2O until an optimum concentration of 0.7 mM was reached. The % wt of Ir was found to increase with the concentration of H2Cl6Ir·H2O. The device utilizing Ir-Pd CE with 0.7 mM H2Cl6Ir·H2O demonstrated the highest power conversion efficiency (PCE) of 5.84%, beating that of the device with Pt CE having a PCE of 5.04%. This is because the device possesses the lowest charge transfer resistance (Rct), highest recombination resistance (Rcr), and longest carrier lifetime (τ), and the device possesses the highest reduction current (Jpc) and incident-photon conversion efficiency (IPCE). The PCE was significantly affected by Ir content in the binary alloy of Ir-Pd. According to the PCE result, Ir-Pd CE was found as a suitable substitution for Pt as CE for the device.
  6. ZnO nanocubes with (101) basal plane photocatalyst prepared via a low-frequency ultrasonic assisted hydrolysis process
    Tan ST, Umar AA, Balouch A, Yahaya M, Yap CC, Salleh MM, et al.
    Ultrason Sonochem, 2014 Mar;21(2):754-60.
    PMID: 24184009 DOI: 10.1016/j.ultsonch.2013.10.009
    The crystallographic plane of the ZnO nanocrystals photocatalyst is considered as a key parameter for an effective photocatalysis, photoelectrochemical reaction and photosensitivity. In this paper, we report a simple method for the synthesis of a new (101) high-energy plane bounded ZnO nanocubes photocatalyst directly on the FTO surface, using a seed-mediated ultrasonic assisted hydrolysis process. In the typical procedure, high-density nanocubes and quasi-nanocubes can be grown on the substrate surface from a solution containing equimolar (0.04 M) zinc nitrate hydrate and hexamine. ZnO nanocubes, with average edge-length of ca. 50 nm, can be obtained on the surface in as quickly as 10 min. The heterogeneous photocatalytic property of the sample has been examined in the photodegradation of methyl orange (MO) by UV light irradiation. It was found that the ZnO nanocubes exhibit excellent catalytic and photocatalytic properties and demonstrate the photodegradation efficiency as high as 5.7 percent/μg mW. This is 200 times higher than those reported results using a relatively low-powered polychromatic UV light source (4 mW). The mechanism of ZnO nanocube formation using the present approach is discussed. The new-synthesized ZnO nanocubes with a unique (101) basal plane also find potential application in photoelectrochemical devices and sensing.
  7. Fulltext Modified microwave method for the synthesis of visible light-responsive TiO2/MWCNTs nanocatalysts
    Alosfur FK, Jumali MH, Radiman S, Ridha NJ, Yarmo MA, Umar AA
    Nanoscale Res Lett, 2013;8(1):346.
    PMID: 23919496 DOI: 10.1186/1556-276X-8-346
    Recently, TiO2/multi-walled carbon nanotube (MWCNT) hybrid nanocatalysts have been a subject of high interest due to their excellent structures, large surface areas and peculiar optical properties, which enhance their photocatalytic performance. In this work, a modified microwave technique was used to rapidly synthesise a TiO2/MWCNT nanocatalyst with a large surface area. X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller measurements were used to characterise the structure, morphology and the surface area of the sample. The photocatalytic activity of the hybrid nanocatalysts was evaluated through a comparison of the degradation of methylene blue dye under irradiation with ultraviolet and visible light. The results showed that the TiO2/MWCNT hybrid nanocatalysts degraded 34.9% of the methylene blue (MB) under irradiation with ultraviolet light, whereas 96.3% of the MB was degraded under irradiation with visible light.
  8. Selective heterogeneous catalytic hydrogenation of ketone (C═O) to alcohol (OH) by magnetite nanoparticles following Langmuir-Hinshelwood kinetic approach
    Shah MT, Balouch A, Rajar K, Sirajuddin, Brohi IA, Umar AA
    ACS Appl Mater Interfaces, 2015 Apr 1;7(12):6480-9.
    PMID: 25785883 DOI: 10.1021/am507778a
    Magnetite nanoparticles were successfully synthesized and effectively employed as heterogeneous catalyst for hydrogenation of ketone moiety to alcohol moiety by NaBH4 under the microwave radiation process. The improvement was achieved in percent recovery of isopropyl alcohol by varying and optimizing reaction time, power of microwave radiations and amount of catalyst. The catalytic study revealed that acetone would be converted into isopropyl alcohol (IPA) with 99.5% yield in short period of reaction time, using 10 μg of magnetite NPs (Fe3O4). It was observed that the catalytic hydrogenation reaction, followed second-order of reaction and the Langmuir-Hinshelwood kinetic mechanism, which elucidated that both reactants get adsorb onto the surface of silica coated magnetite nanocatalyst to react. Consequently, the rate-determining step was the surface reaction of acetone and sodium borohydride. The current study revealed an environment friendly conversion of acetone to IPA on the basis of its fast, efficient, and highly economical method of utilization of microwave irradiation process and easy catalyst recovery.
  9. Microwave assisted hydrothermal method for porous zinc oxide nanostructured-films
    Ridha NJ, Umar AA, Alosfur F, Jumali MH, Salleh MM
    J Nanosci Nanotechnol, 2013 Apr;13(4):2667-74.
    PMID: 23763142
    Porous ZnO nanostructures have become the subject of research interest--due to their special structures with high surface to volume ratio that may produce peculiar properties for use in optoelectronics, sensing and catalysis applications. A microwave-assisted hydrothermal method has been used for effecting the formation of porous nanostructure of metaloxide materials, such as CoO and SnO2, in solution. Here, by adopting the unique performance of a microwave-assisted-hydrothermal method, we realized the formation of highly porous ZnO nanostructures directly on the substrate surface, instead of in solution. The effects of the ambient reaction conditions and the microwave power on the structural growth of the ZnO nanostructures were studied in detail. Two different ambient reaction conditions, namely refluxed and isolated in autoclave systems, were used in this work. Porous ZnO (PZO) nanostructures with networked-nanoflakes morphology is the typical result for this approach. It was found that the morphology of the ZnO nanostructures was strongly depended on the ambient conditions of the reaction; the isolated-autoclave system may produce reasonably high porous ZnO that is constituted by vertically oriented grainy-flakes structures, whereas the refluxed system produced solid vertically-oriented flake structures. The microwave power did not influence the structural growth of the ZnO. It was also found that both the ambient reaction conditions and the microwave power used influenced the crystallographic orientation of the PZO. For instance, PZO with dominant (002) Bragg plane could be obtained by using refluxed system, whereas PZO with dominant (101) plane could be realized if using isolated system. For the case of microwave power, the crystallographic orientation of PZO prepared using both systems changed from dominant (002) to (101) planes if the power was increased. The mechanism for the formation of porous ZnO nanostructures using the present approach is proposed. The ZnO nanostructures prepared using the present method should find an extensive use in currently existing application due to its property of reasonably high porosity.
  10. Fulltext Urea and creatinine detection on nano-laminated gold thin film using Kretschmann-based surface plasmon resonance biosensor
    Menon PS, Said FA, Mei GS, Berhanuddin DD, Umar AA, Shaari S, et al.
    PLoS One, 2018;13(7):e0201228.
    PMID: 30052647 DOI: 10.1371/journal.pone.0201228
    This work investigates the surface plasmon resonance (SPR) response of 50-nm thick nano-laminated gold film using Kretschmann-based biosensing for detection of urea and creatinine in solution of various concentrations (non-enzymatic samples). Comparison was made with the presence of urease and creatininase enzymes in the urea and creatinine solutions (enzymatic samples), respectively. Angular interrogation technique was applied using optical wavelengths of 670 nm and 785 nm. The biosensor detects the presence of urea and creatinine at concentrations ranging from 50-800 mM for urea samples and 10-200 mM for creatinine samples. The purpose of studying the enzymatic sample was mainly to enhance the sensitivity of the sensor towards urea and creatinine in the samples. Upon exposure to 670 nm optical wavelength, the sensitivity of 1.4°/M was detected in non-enzymatic urea samples and 4°/M in non-enzymatic creatinine samples. On the other hand, sensor sensitivity as high as 16.2°/M in urea-urease samples and 10°/M in creatinine-creatininase samples was detected. The enhanced sensitivity possibly attributed to the increase in refractive index of analyte sensing layer due to urea-urease and creatinine-creatininase coupling activity. This work has successfully proved the design and demonstrated a proof-of-concept experiment using a low-cost and easy fabrication of Kretschmann based nano-laminated gold film SPR biosensor for detection of urea and creatinine using urease and creatininase enzymes.
  11. Fulltext Phases evolution and photocatalytic activity of Cu2O films electrodeposited from a non-pH-adjusted solution
    Budi S, Takahashi M, Sutrisno MG, Adi WA, Fairuza Z, Kurniawan B, et al.
    R Soc Open Sci, 2023 Jun;10(6):230247.
    PMID: 37351492 DOI: 10.1098/rsos.230247
    A pure-phase Cu2O film photocatalyst was successfully prepared by the electrodeposition technique from a non-pH-adjusted solution. To investigate the phase evolution and photocatalytic activity of the film, the electrodeposition was conducted at different deposition temperatures. Photocatalytic activity of the films was evaluated from methylene blue (MB) dye degradation. The Cu2O phase initially appeared at room temperature and its fraction was found to increase with increasing the deposition temperature, while the impurity phase was successfully diminished. A pure Cu2O film with a narrow optical bandgap energy of 1.96 eV was obtained at 75°C. The multi-faceted crystals were found to form at 45°C and became a truncated octahedral structure that possessed {111} and {100} facets as deposition temperature further increased. A preferred orientation growth of {110} facet, which is known to possess a relatively high surface energy, was produced at 75°C. The performance of MB photodegradation enhanced gradually by increasing the deposition temperature. The increase of photocatalytic activity could be attributed to the rise of photoelectrochemical response and the decrease of resistance charge transfer because of narrowing bandgap energy, increasing Cu2O fraction, and growing a relatively high catalytic activity facet which had escalated redox reaction that decomposed MB at the photocatalyst-solution interface.
  12. Fabrication of Pt-Pd@ITO grown heterogeneous nanocatalyst as efficient remediator for toxic methyl parathion in aqueous media
    Mahar AM, Balouch A, Talpur FN, Abdullah, Panah P, Kumar R, et al.
    Environ Sci Pollut Res Int, 2020 Mar;27(9):9970-9978.
    PMID: 31933082 DOI: 10.1007/s11356-019-07548-y
    In this study, nano-sized ITO supported Pt-Pd bimetallic catalyst was synthesized for the degradation of methyl parathion pesticide, a common extremely toxic contaminant in aqueous solution. On the characterization with different techniques, a beautiful scenario of honeycomb architecture composed of ultra-small nanoneedles or fine hairs was found. Average size of nanocatalyst also confirmed which was in the range of 3-5 nm. High percent degradation (94%) was obtained in 30 s using 1.5 × 10- 1 mg of synthesized nanocatalyst, 0.5 mM NaBH4, and 110 W microwave radiations power. Recyclability of nanocatalyst was efficient till 4th cycle observed during study of reusability. The supported Pt-Pd bimetallic nanocatalyst on ITO displayed many advantages over conventional methods for degradation of methyl parathion pesticide, such as high percent degradation, short reaction time, small amount of nanocatalyst, and multitime reusability. Graphical abstract Schematic illustration of reaction for degradation of methyl parathion.
  13. Role of the IL8 rs4073 polymorphism in central nervous system toxicity in patients receiving multidrug-resistant tuberculosis treatment
    Badamasi IM, Muhammad M, Umar AA, Madugu UM, Gadanya MA, Aliyu IA, et al.
    J Bras Pneumol, 2024;50(1):e20230338.
    PMID: 38359298 DOI: 10.36416/1806-3756/e20230338
    OBJECTIVE: To determine the role of the IL8 rs4073 polymorphism in predicting the risk of central nervous system (CNS) toxicity in patients receiving standard pharmacological treatment for multidrug-resistant tuberculosis (MDR-TB).

    METHODS: A cohort of 85 consenting MDR-TB patients receiving treatment with second-line antituberculosis drugs had their blood samples amplified for the IL8 (rs4073) gene and genotyped. All patients were clinically screened for evidence of treatment toxicity and categorized accordingly. Crude and adjusted associations were assessed.

    RESULTS: The chief complaints fell into the following categories: CNS toxicity; gastrointestinal toxicity; skin toxicity; and eye and ear toxicities. Symptoms of gastrointestinal toxicity were reported by 59% of the patients, and symptoms of CNS toxicity were reported by 42.7%. With regard to the genotypes of IL8 (rs4073), the following were identified: AA, in 64 of the study participants; AT, in 7; and TT, in 11. A significant association was found between the dominant model of inheritance and CNS toxicity for the crude model (p = 0.024; OR = 3.57; 95% CI, 1.18-10.76) and the adjusted model (p = 0.031; OR = 3.92; 95% CI, 1.13-13.58). The AT+TT genotype of IL8 (rs4073) showed a 3.92 times increased risk of CNS toxicity when compared with the AA genotype.

    CONCLUSIONS: The AT+TT genotype has a tendency to be associated with an increased risk of adverse clinical features during MDR-TB treatment.

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