Fabrication and characterisation of nanostructured zinc oxide thin films incorporated with nanorod arrays-based solar cells / Mohd Firdaus Malek

In this research, several types of solar cells have been successfully fabricated using zinc oxide-based nanoparticles (ZnO NPs) and ZnO-based nanorod arrays (ZnO NRAs). Both of ZnO NPs and ZnO NRAs were synthesised via novel dual sonication sol-gel immersion process. In this work, ZnO NRAs were grown on a seed layer by ultrasonic-assisted immersion technique while the seed layer, which consists of ZnO NPs were deposited by ultrasonic-assisted sol-gel dip-coating technique. The main points for this thesis are not only to successfully realise the controllable growth of ZnO NPs and ZnO NRAs but also investigate the structural, optical and electrical properties in detail by means of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope, energy dispersive X-ray spectroscopy, ultraviolet-visible-infrared spectrophotometry and two-probe current-voltage measurement system. There are several processing parameters such as dopant concentration, annealing temperature, growth time and various types of dopants which can be controlled were being optimised. The optimised growth parameters were applied to fabricate several solar cell devices which were dye sensitised solar cells (DSSCs), hybrid solar cells (HSCs), perovskite solar cells (PSCs) and inverted organic solar cells (IOSCs)

Enhancing the performance of self-powered ultraviolet photosensor using rapid aqueous chemical-grown aluminum-doped titanium oxide nanorod arrays as electron transport layer

Aluminum (Al)-doped titanium dioxide nanorod arrays (ATNs) were grown on fluorine-doped tin oxide-coated glass at different Al atomic concentrations ranging from 1 at.% to 5 at.% in a Schott bottle through single-step aqueous chemical growth for self-powered photoelectrochemical cell-type ultraviolet (UV) photosensor applications. X-ray diffraction patterns showed that the grown ATNs exhibited a crystalline rutile structure. The ATNs showed smaller crystallite size and average nanorod diameter and length compared with the undoped sample. The photocurrent measured from the fabricated UV photosensors improved to some extent with increasing Al-dopant concentration. Samples with 2 at.% Al showed the maximum photocurrent of 108.87 μA/cm2 at 0 V bias under UV irradiation (365 nm, 750 μW/cm2). The results show that high-performance UV photosensors can be fabricated and enhanced using ATNs easily prepared in a glass container

Career satisfaction of Malaysian dentists with expanded roles at a specialist clinic

Objectives:Public dentists interested in postgraduate studies were required to complete clinical attachments at the Malaysian Ministry of Health (MOH) Dental Specialist Clinic (DSC). This cross-sectional quantitative study aimed to explore career satisfaction (CS) and barriers perceived by Malaysian dentists at Malaysia's MOH DSC. Methods: A total of 208 dentists from DSC nationwide completed an online questionnaire in June 2022. Demographic data and information on dentists’ expanded roles were retrieved. Responses on dentists’ satisfaction and perceived barriers were collected using a 5-point ordinal scale. Mann–Whitney U and Kruskal–Wallis tests were used to compare the mean rank differences for CS. Factors influencing CS were analysed using multiple logistic regression (MLR) (P < .05). Results: The mean age of the respondents was 32.68 ± 2.48 years. Almost half (49.0%) of the respondents were attached to a non–hospital-based clinic. The majority (72.0%) of them were permanently attached to the DSC. About half of the dentists (51.0%) strongly agreed that they received no financial incentives for their expanded role at the MOH DSC. Dentists attached at a non–hospital-based clinic (P = .046), working with more than 15 years of experience (P = .013), and having 12 to 18 months’ duration of attachment (P = .014) were more satisfied. MLR analysis revealed that non-Malay respondents (odds ratio [OR], 1.54; P = .035) and those who applied for scholarships more than 3 times (OR, 1.85; P = .050) were more satisfied. In contrast, more than 19 months at the DSC decreased CS (OR, 0.44; P = .029). Conclusions: Despite having a similar organisational structure, DSC dentists had different satisfaction levels. Dentists’ ethnicity, duration of attachment, and frequency of applying for scholarships influenced their CS. Future career advancement plans in the MOH should consider these important influencing factors to ensure the delivery of quality health care from their personnel

Career satisfaction and barriers perceived among Malaysian dentists with expanded roles at specialist clinic

Public dentists interested in postgraduate studies were required to complete clinical attachments at the Ministry of Health (MOH) Dental Specialist Clinic (DSC). This cross-sectional quantitative study aimed to explore career satisfaction and barriers perceived by Malaysian dentists at MOH Malaysia's DSC. A total of 208 dentists from DSC nationwide completed an online questionnaire in June 2022. Demographic data and information on dentists' expanded roles were retrieved. Responses on dentists' satisfaction and barrier perceived were collected using a 5-point ordinal scale. The Mann-Whitney U and Kruskal Wallis Test were used to compare the mean rank differences for career satisfaction. Factors influencing career satisfaction were analysed using Multiple Logistic Regression (MLR) (p<0.05). The mean age of the respondents was 32.68 ± 2.48. Almost half (49%) of the respondents were attached to a non-hospital-based clinic. The majority (72%) of them were permanently attached to the DSC. Most dentists (50.96%) strongly agree they received no financial incentives for their expanded role at the MOH DSC. Dentists attached at a non-hospital-based clinic (p=0.046), working with more than 15 years of experience (p=0.013) and having 12 to 18 months duration of attachment (p=0.014), were more satisfied. MLR analysis revealed that non-Malay (OR=1.54; p=0.035) and those who applied for scholarships more than three times (OR=1.85; p=0.050) were more satisfied. In contrast, over 19 months at DSC decreased career satisfaction (OR=0.44; p=0.029). Despite a similar organisational structure, DSC dentists had different satisfaction levels. Dentists' ethnicity, duration of attachment, and frequency of applying for scholarships influenced their career satisfaction. Future career advancement plans in the MOH should consider these important influencing factors to ensure the delivery of quality healthcare from their personnel

Career expectations and satisfaction among Malaysian dentists with expanded roles at government dental specialist clinic

Introduction: Public dentists in Malaysia undergoing attachment at the Ministry of Health (MOH) Dental Specialist Clinic (DSC) hold enhanced skills that enable them to treat cases of intermediate complexity. Public dentists interested in pursuing post-graduate studies for career advancement were required to complete a period of clinical attachment at selected MOH DSCs. Objectives: This cross-sectional study aimed to explore dentists' expanded roles, career expectations and satisfactions at the MOH DSC. Methods: A total of 208 dentists from DSC nationwide completed an online questionnaire in June 2022. Demographic data and information on dentists' expanded roles were retrieved. Responses on dentists' career expectations and satisfaction were collected using a 5-point ordinal scale. Associations between sociodemographic and other variables were determined using the chi-square, independent t-test and ANOVA (p<0.05). Results: The mean age of the respondents was 32.68 ± 2.48. Almost half (49%) of the respondents were attached to a non-hospital-based clinic. 71% of the dentist was permanently attached at the DSC, while 21% were attached temporarily at the DSC. Permanently-attached dentists had significantly higher career expectations mean scores of 24.5 ± 5 compared to partially-attached dentists (27.2 ± 7) (p = 0.004). Dentists attached at a non-hospital-based clinic (p=0.046), working with more than 15 years of experience (p=0.013) and 12-18 months of attachment (p=0.014), had higher career satisfaction. Multiple logistics regression analysis revealed that non-Malay (OR=1.54; p=0.035) and those who applied for scholarships more than three times (OR=1.85; p=0.050) had a higher satisfaction level. In contrast, the duration of attachment at DSC of more than 19 months contributed to a lower career satisfaction level (OR=0.44; p=0.029). Conclusions: Dentists at DSC, MOH demonstrated diverse career expectations and satisfaction levels despite working under a similar organizational structure. Dentists' ethnicity, duration of attachment, workplace and frequency of applying for scholarships influenced their career expectations and satisfaction

Heterogeneous SnO2/ZnO nanoparticulate film: Facile synthesis and humidity sensing capability

Highly sensitive and extremely thin tin oxide/zinc oxide (SnO2/ZnO) heterojunction films were prepared via a two-step solution-based method for humidity-sensing application. The average diameters of the ZnO and SnO2 nanoparticles were 26 and 6 nm, respectively. The deposition of SnO2 for 3 min reduced film resistance from 6.74 MΩ to 0.40 MΩ. Remarkably, the humidity-sensing performance of the heterojunction sensors was critically dependent on deposition time, and sensors subjected to 3 min deposition exhibited the highest sensitivity (90.56) to humidity, which was significantly higher than that of bare ZnO. This study indicates that the use of SnO2/ZnO heterojunction has a great potential in humidity sensing applications

Microbiological analysis of drinking water from water vending machines

Commercial water vending machines are gaining popularity nowadays among the general public, probably due to the ease of obtaining clean drinking water. However, improper maintenance of the machines can lead to bacterial contamination. Hence, this study aimed to investigate and determine the microbiological characteristics of drinking water from Water Vending Machines (WVM) by isolating and characterizing culturable bacteria in the water and nozzle swab samples. The samples were obtained from WVM at eight different locations around Johor Bahru, Johor, Malaysia. Several unique bacterial isolates were found, from both Gram-positive and Gram-negative groups. Polymerase chain reaction amplification and 16S rRNA sequence analysis suggested that these isolates are from Pseudomonas, Bacillus, and Stenotrophomonas genera. In situ water quality tests which include pH, conductivity, and total dissolved solids were also conducted. Two samples from the inlet source have pH and conductivity values slightly above the reference values stipulated in drinking water regulations. The findings presented here suggest the importance of regular service maintenance of the WVM to ensure that the water samples meet the standard stipulated by the authority

Low-temperature-dependent growth of titanium dioxide nanorod arrays in an improved aqueous chemical growth method for photoelectrochemical ultraviolet sensing

The growth of titanium dioxide nanorod arrays (TNAs) in aqueous solutions containing titanium butoxide and hydrochloric acid can be controlled by regulating the temperature from 115 to 150 °C as an adjustable physical parameter. The transparent colloidal solution of titanates is clouded on the basic growth of TNAs when heated at a certain temperature using an improved aqueous chemical growth method in a clamped Schott bottle. The structural, optical and electrical properties of grown TNAs films were thoroughly investigated and discussed. The distinct and high-intensity peaks observed in the X-ray diffraction pattern and Raman spectra of the grown TNAs show the rutile phase with high crystal quality. The crystallite size, diameter size, and thickness of TNAs decrease with decreasing growth temperature. The prepared TNAs were used to detect 365 nm ultraviolet (UV) photon energy (750 µW/cm2) in a photoelectrochemical cell structure with a maximum photocurrent of 26.31 µA and minimum photocurrent of 3.48 µA recorded for TNAs grown at 150 °C and 115 °C, respectively. The size, structural properties, charge transfer resistance, and electron lifetime play a key role in determining the UV sensing characteristics of the TNAs. Results show that TNAs are very promising in fabricating a UV sensor with a high response at 0 V bias even at a low growth temperature of 115 °C

The Future Electrical Multiplexing Technique for High Speed Optical Fibre

Advancement in transmission technology based on fiber optic such as multiplexing technique is an attractive research area for future development of high capacity and high speed optical communication system. Typical electrical based multiplexing such as electrical time division multiplexing (ETDM) and duty cycle division multiplexing (DCDM) have difficulty to fulfil the requirements of modern fiber optic communication with practical solution. Multi slot amplitude coding (MSAC) is the latest multiplexing technique that has been proposed as an alternative to ETDM and DCDM. The results show that the spectral width is reduced by around 25%, not less than 55% improvement of chromatic dispersion (CD) tolerance, 0.6 dB better receiver sensitivity, and 1.5 dB better optical signal to noise ratio (OSNR) compared to DCDM for 30 Gbit/s transmission capacity. The spectral width for 3 × 10 Gbit/s, 4 × 10 Gbit/s and 5 × 10 Gbit/s MSAC is 60 GHz, which indicates improvement of spectral efficiency. This advantage is not possible to be achieved through ETDM technique. In addition, 10 GHz clock signal can be extracted from the MSAC signal which is important for recovery circuit at receiver since it is similar to symbol rate

Coupling heterostructure of thickness-controlled nickel oxidenanosheets layer and titanium dioxide nanorod arrays via immersionroute for self-powered solid-state ultraviolet photosensor applications

A coupling heterostructure consisting of nickel oxide nanosheets (NNS) and titanium dioxide nanorod arrays (TNAs) was fabricated for self-powered solid-state ultraviolet (UV) photosensor applications. By controlling the thickness of the NNS layer by via varying the growth time from 1 to 5 h at a deposition temperature of 90 °C, the coupling NNS/TNAs heterojunction films were formed and their structural, optical, electrical and UV photoresponse properties were investigated. The photocurrent measured from the fabricated self-powered UV photosensor was improved by increasing the thickness of NNS from 140 to 170 nm under UV irradiation (365 nm, 750 µWcm−2) at 0 V bias. A maximum photocurrent density of 0.510 µA∙cm−2 was achieved for a sample with a NNS thickness of 170 nm and prepared with a 3 h NNS growth time. Our results showed that the fabricated NNS/TNAs heterojunction has potential applications for self-powered UV photosensors