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Learners’ opportunities to learn algebra content in Grade 9
Get PDFJournal article published in African Perspectives of Research in Teaching & Learning Journal (APORTAL) Vol 7 (2) (2023)The aim of this research was to examine the extent to which algebra content was taught to Grade 9 mathematics learners in four schools within a specific education district in Gauteng province, South Africa. This qualitative case study was conducted within the framework of interpretive qualitative research. Document analysis was employed as the method of data collection. The findings of the study indicate that the coverage of algebra content in the participating schools did not align with the prescribed curriculum. Consequently, it can be inferred that the learners did not have adequate opportunities to learn the algebra content. It is recommended that teachers adhere to the curriculum guidelines when delivering instructio
Resistance to online learning in Zimbabwean secondary schools : the content and seasons
Get PDFJournal article published in African Perspectives of Research in Teaching & Learning Journal (APORTAL) Vol 7 (2) (2023)This study examined the content and reasons for the resistance to the implementation of
online learning in secondary education in Zimbabwe in light of the lessons and experiences from the COVID-19 pandemic. The study employed a systematic literature review as its methodology that relied exclusively on secondary data. The Overcoming Resistance to Change (ORC) model was exploited as a desirable model for the review, findings, and recommendations. The study found that online learning as a pedagogical innovation is and has been resisted by stakeholders such as teachers, parents, and learners due to factors like poor communication, unpreparedness, education, and training. Other factors like isolation, costs, fear, vested interests, ingrained habits, and workload also compounded and increased the magnitude of resistance. The study recommended the need to overcome resistance to the implementation of online learning by proposing strategies such as education and communication, participation, negotiation, resource provision, and positive soft powe
The impact of the fourth industrial revolution on the performance of small and micro enterprises : a case of Mankweng Township, Polokwane Local Municipality, South Africa
Get PDFThesis (M.Dev. (Planning and Management)) -- University of Limpopo, 2023The Small and Micro Enterprises (SMEs) are mostly viewed as the catalysts of
development in both developed and developing countries. Their significant contribution
to socio-economic development has captured the attention of governments across the
world. Hence, most governments rely on SMEs to uplift and spearhead their local
economy. They also assist the governments to meet or at least fulfil some of the national
imperatives. The SMEs in South Africa are mostly located in townships and largely in rural
areas and are very accessible to the people on the ground. However, SMEs have
currently met the unprecedented growth of technology which is the Fourth Industrial
Revolution (4IR). The growth of the 4IR influences SMEs to change their traditional way
of conducting business operations to be compatible with the changing technology.
Meanwhile, the 4IR refers to the usage of the Artificial Intelligence (AI), the Internet of
Things (IoT), digitalization, robotics, Cyber-Physical Systems (CPS), and nanotechnology
amongst others. This study discusses both variables in length to answer the research
questions. Therefore, this study investigated the impact of the 4IR on the performance of
SMEs. The study used judgemental sampling to sample the owners of SMEs to solicit
their perceptions on the subject under investigation and as such, open-closed-ended
questionnaires were administered to them. It sampled 50 SMEs around Mankweng
Township which was sufficient to draw relevant conclusions. The study used a thematic
analysis to analyse qualitative data and adopted Statistical Package for Social Science
(SPSS) and Microsoft excel to analyse quantitative data collected from the participants.
This study reveals that SMEs are underperforming with a decline in customers and loss
of sales as a result of poor financial resources and poor state of technology. The study
recommends that stakeholders such as individuals, the private sector and the government
come on board and actively provide more concerted efforts and resources to aid SME
Ion imprinted polymer/metal-organic framework composites as efficient adsorbents for selective recognition and separation of selected platinum group metals from wastewater
Get PDFThesis (Ph.D. (Chemistry)) -- University of Limpopo, 2023Platinum group metal (PGMs) are the most extracted non-renewable mineral resources in South African due to their high demand for various applications. During mineral processing some of these valuable metals are lost into the generated toxic which is excessively released into the environment. Adsorption technology offers advantages of ease operation, high effectiveness and opportunity to incorporate other techniques such as ion-imprinting method. Metal-organic frameworks have been explored as adsorbent due to their interesting properties such tuneable surface functionality and ability to host guest molecules. In this work, metal organic framework, MIL-101(Cr), (MIL= Matérial Institut Lavoisier) prepared from polyethylene-terephlalate waste was initially functionalised with ethylenediamine (ED) to form MIL-101(Cr)/ED for the adsorption of palladium (Pd) ions from aqueous solution. The successful incorporation of ED was confirmed by Fourier transform infrared spectroscopy with N-H vibrations at 3300 -3000 cm-1. The MIL-101(Cr)/ED achieved a maximum adsorption capacity (qm) of 454.2 mg/g for the uptake of Pd(II) ions in a pH =3.0 and 0.03 g of the adsorbent dose. MIL-101(Cr)/ED adsorbent was selective and fast towards the adsorption of Pd(II) ions. However, the regeneration and reusability of the adsorbent was still a challenge. The MIL-101(Cr)/ED was further grafting with glutaraldehyde (GA) to enhance the regeneration and reusability. This functionalisation was noted by the appearance 1554 and 1052 cm-1 for N-H bend and C-N stretch in the MIL-101(Cr)/ED-GA due to the amide bond formation. The efficiency of MIL-101(Cr)/ED-GA was tested for Pd(II) and platinum (Pt(IV)) ions. The data showed a good fit to the Langmuir isotherm and pseudo-second order (PSO) kinetic models. The estimated qm values were 414.4 for Pt(IV) and 308.3 mg/g for Pd(II) ions. The adsorption rate of the MIL-101(Cr)/ED-GA adsorbent was very rapid towards Pd(II) ions intake than Pt(IV) ions and resulted in higher selectivity of Pd(II) ions over Pt(IV) ions. Adsorption-desorption cycles for the reusability of MIL-101(Cr)/ED-GA in removing both metal ions were stable for two successive cycles and started to decrease in the third cycle. The reusability of MIL-101(Cr)/ED-GA showed a significant drop in removal efficiency (%R) towards Pd(II) ions from 84% in the first cycle to 73% in the fourth and fifth cycle. The regeneration and reusability of the MIL-101(Cr)/ED-GA was improved by ion-imprinting Pd(II) ions on a glycylglycine (glygly) functional monomer and formed an ion specific IPMIL-101(Cr) composite. The optimum adsorption conditions for the uptake of Pd(II) ions were achieved at 0.03 g of the IP-MIL-101(Cr) adsorbent and pH=2.0. This suggested electrostatic interaction between the protonated nitrogen (N) groups on the adsorbent surface and the Pd(II) ions complexes. The Langmuir isotherm was the well fitted model and estimated the qm of 195.3 mg/g for the adsorption of Pd(II) ions IPMIL-101(Cr) composite which was higher than 177.7 mg/g of the its non-imprinted counterpart (NIMIL-101(Cr). Kinetics data further confirmed the improved rapid adsorption rate of Pd(II) by the IPMIL-101(Cr) which obeyed the PSO kinetic model. The ion specific IPMIL-101(Cr) adsorbent was re-generable for five consecutive cycle without loss in the removal efficiency and adsorption capacity.
The Pt(IV) ion imprinted IIGlyMIL-101(Cr) composite, which was prepared using the same glygly functional monomer showed enhanced performance in the adsorption of targeted Pt(IV) ions from aqueous solution. In an initial solution pH of 3.0, 0.02 g of the IIGlyMIL-101(Cr) adsorbent was able to recover 85% of the Pt(IV) ions at 25 oC. The qm value were obtained from the Langmuir isotherm model to be 531.3 mg/g for the IIGlyMIL-101(Cr) adsorbent in the intake of Pt(IV) ions, which was higher than 296.4 mg/g of the non-imprinted counterpart (NIGlyMIL-101(Cr)) composite. Kinetics data revealed fast adsorption of Pt(IV) ions by IIGlyMIL-101(Cr) which equilibrated within 30 minutes and fitted well with PSO kinetic model. The selectivity towards Pt(IV) ions intake by the IIGlyMIL-101(Cr) composite was also improved with an efficiency of 80% in comparison to the non-imprinted adsorbent which was 50% in the presence of various anions. Moreover, the IIGlyMIL-101(Cr) composite was able to maintained 88% removal efficiency after five subsequent cycles, suggesting improved stability of the adsorption active sites. The results observed in this study proved the efficiency of ion-imprinted MOF composites and their potential application in the recovery of PGMs form industrial wastewater should be considered.NRF Thuthuka Research Gran
Atomistic simulation studies of Li2MnO3 nanoarchitectures
Get PDFThesis (Ph.D. (Physics)) -- University of Limpopo, 2023High-energy lithium-ion batteries (LIBs) are in high demand for the establishment of
electric vehicles and hybrid vehicles in the automotive sector. Considering that the
cathode is the limiting factor, it is of significant importance to discover cathode materials
with a large number of lithiums, as this has a positive effect on the voltage, capacity and
potential difference required for the advancement of the next-generation LIBs. Lithium
manganite (Li2MnO3), owing to its huge capacity (458 mAh.g-1), nontoxicity and
affordability has been considered an active cathode material for high-capacity LIBs.
However, its capacity degradation and phase transformation during the cycling process
are the main limiting factors to its commercialisation. The mechanisms behind these
degradations are not yet fully understood to enable a complete diagnosis of the drawback.
Sodium-ion doping at the Li-sites of Li2MnO3 can, however, mitigate structural
transformation during the charge/discharge process by prohibiting the migration of
manganese ions from the transition metal (TM) layers to lithium layers.
In this work, the simulated amorphisation and recrystallisation (A+R) technique was
employed during the high-temperature synthesis of Li2MnO3 nano-architectures i.e.
nanosphere, nanoporous and the bulk material consisting of a large number of atoms
(32148). Nanostructuring, due to the advantage in particle size reduction, has been
considered, owing to the large surface exposure and shortened diffusion path. Thus
facilitating effective activation of the Li2MnO3 electrode material. The nano-architectures
were investigated between the temperature range of 1500 K and 1900 K as guided by
the melting point, which was found to be around 1845 K, from the total energy graph.
Recrystallisation of the Li2MnO3 models was confirmed by the radial distribution functions
(RDFs) which depicted multiple sharp peaks due to the long-range ordering of atoms and
strong bonds. Structural validation through the x-ray diffraction plots (XRD) compared
very well with experimental work in literature, displaying broadening, splitting and partial
shifting of peaks resulting from the mixing of Li and Mn layers. However, the nanosphere
depicted broader peaks compared to both the nanoporous and bulk systems. The
microstructural features that evolved during the recrystallisation of all the models
contained cation mixing and vacancies resulting in structures constituting mixed layers Li-ion kinetics for the nanosphere model was found to be higher (approximately 1.54
nm2s-1) than in the nanoporous and bulk systems which were below 0.3 nm2s-1.
The Li2MnO3 nanosphere model was then used to dope sodium ions into the Li-sites.
Accordingly, a series of Li2-xNaxMnO3 (0≤x≤2) nanosphere models of different lithium and
sodium content were generated via the amorphisation and recrystallisation strategy. The
results thereof showed structural collapse upon amorphisation for systems containing a
large dosage of Na-ions. However, systems with 25% Na content and below, were
successfully amorphised and recrystallised at 1700 K, while retaining their structural
morphology, with the Li1.75Na0.25MnO3 system resulting in a polycrystalline structure. The
microstructural analysis also revealed the mixing of layers and improved structural
arrangement for the Li1.95Na0.05MnO3 system, which showed a large portion of a wellordered
Li2MnO3 phase. Li-ion mobility for the Na-incorporated systems was found to be
higher compared to the undoped systems with the system containing the lowest Na-ions
(Li1.975Na0.025MnO3) diffusing better. This proves that incorporating sodium ions into the
Li2MnO3 lattice aid in improving the ionic movement. XRD analysis revealed peaks with
a broad character. The Peaks belonging to 2Θ~38 slightly shift to the right as a result of
the enlarged Li-layers which are occupied by Na ions. The enlargement of the Li-layers
facilitates Li-ion kinetics. Again, superlattice peaks were observed for the Li1.95Na0.05MnO3
at lower angles due to the ordering of Li/Mn ions in the transitional metal layers.
Charging was achieved by simultaneously removing Li+ and O- ions from the outer
surfaces of the Li2MnO3 and Li2-xNaxMnO3 nanoarchitectures. All the Li/O deficient
systems crystallised into multi-grained crystals with grain boundaries increasing with a
decrease in Li/O content for the undoped systems. For the Na-incorporated systems, the
Li1.95Na0.05MnO3 revealed minimal grain boundaries as Li/O was varied, with the
Li1.70Na0.05MnO2.75 and Li1.45Na0.05MnO2.50 concentrations showing no formation of grain
boundaries. Characterisation of the XRD for the charged systems also resulted in broad
peaks, accompanied by the growth of peaks 2Θ~18-25⁰ peak and the 2Θ~29⁰ associated
with the spinel phase. Contrarily, the nanoporous system (Li1.25MnO2.25) depicts the
narrowing and decreasing of diffraction peaks at 2Θ~18-25 and 2Θ~29⁰. The Li2-
xNaxMnO3 systems also depict the narrowing and decreasing of the peak at approximately 2Θ~38⁰. In addition, the complex internal microstructures of the Li/O deficient models (Li2-
xMnO3-x) revealed structures governed by defects. These defects contribute to the
evolution of distorted LiMn2O4, Li2MnO3 and LiMnO2 polymorphs. The spontaneous
migration of manganese into the lithium layers triggers the transformation from layered to
spinel-type configurations. The charging of the Li1.95Na0.05MnO3 system resulted in
improved structural stability, with structures revealing a high concentration of the layered
Li2MnO3 structure. Again, the diffusion has been improved by doping sodium into the
lithium sites of the Li2MnO3 nanosphere upon charging. Our results accentuate the
process or mechanism behind the charging of the Li2MnO3 and Li2-xNaxMnO3 constituting
complex structures. This study will help guide the optimisation of high-capacity cathodes
for advanced LIB technologies.National Research Foundation (NRF
Challenges experienced by grade 11 learners in Xitsonga home language essay writing in Mafarana Circuit, Limpopo Province, South Africa
Get PDFThesis (M.Ed. (Language Education)) -- University of Limpopo, 2023The study investigated the Challenges experienced by Grade 11 Learners in Xitsonga Home Language Essay Writing in Mafarana Circuit, Limpopo Province, South Africa. The focus of the study was to explore challenges that learners experience when writing argumentative essays, with significant focus on meaningful sentence construction, correct spelling, grammar, and punctuations, as these are important components of writing. This study applied qualitative methodology and used a case study design to generate data. Semi-structured interviews, classroom observations and documents (text) analysis was used in collecting data used to gain different perspectives regarding different factors that affect learners’ essay writing skills in Xitsonga. The collected data was analyzed using thematic data analysis to develop the necessary writing process when writing argumentative essays. The results revealed that learners from both selected schools faced challenges of not being able to form sound sentences in Xitsonga argumentative essays. Their background and lack of knowledge regarding writing argumentative essays were found to be the main factors influencing their writing skills. The findings also revealed that learners experience challenges regarding essay structure, words choice in sentences, sentence formation, punctuation, word order within sentences and good writing. Furthermore, the results of this study indicated that teachers when teaching these learners essay-writing skills follow not all process-writing steps. Therefore, the study recommends that teachers create conducive learning environment in which learners will learn to follow steps when writing argumentative essays. It is also recommended that teachers should use sociocultural writing strategies to advocate knowledge that is experimentally and socially based, wherein learners can reflect and share their experiences of writing
Exploring Grade 10 learner's spatial skills of computing sides and angles figures using trigonometric ratios
Get PDFThesis (M.Ed. (Mathematics Education)) -- University of Limpopo, 2023In Grade 10, learners are facing challenges to compute sides and angles using
trigonometric ratios. This is a result of accessing inappropriate and fragmented
trigonometric concepts which complicates their computational procedures. The purpose
of this study was to explore Grade 10 learners’ spatial skills when computing sides and
angles in figures using trigonometric ratios. This was achieved by adhering to the
elements of an exploratory case study. The qualitative study was underpinned by the
three principles of semantic tenets, conceptual structures, system representation and
sense. Grade 10 learners were purposively sampled to explore their spatial skills
exhibited whilst computing sides and angles using the three basic ratios. Data were
collected in three phases from 22 purposively sampled Grade 10 learners using three
mathematical tasks and semi-structured interviews. The two sets of data were analysed
thematically. In summary, the textual data from the three mathematical tasks were read
critically and the audio data was transcribed. Both sets of data were categorised using
axial coding and four themes emerged. The major findings revealed that learners who
leave blank spaces have spatial skills that can be expressed verbally. This was shown as
learners exhibited appropriate spatial skills during semi-structured interviews. Moreover,
learners utilised improper properties of a right-angled triangle during computations of
sides and angles using trigonometric ratios. On the other hand, some learners struggled
to relate concepts used within the given questions. This resulted from a lack of
prerequisite trigonometric concepts to comprehend what the question requires. Based on
the findings of the study, the recommendation is that the learning of trigonometry should
be based on developing spatial skills that permit the exploitation of relevant properties
during the computations of sides and angles using ratios. This should be followed by
inclusive formative assessment and verbal assessment to accommodate learners
struggling to achieve in written assessment
Exploring English language challenges faced by Grade 12 learner : the case of two secondary schools in Sekhukhune, Limpopo Province, South Africa
Get PDFThesis (M.A. (English Studies)) -- University of Limpopo, 2023This study explored the English language challenges faced by grade 12 pupils at the selected high schools in Limpopo province, South Africa. Therefore, in order to contribute to the literature regarding English language learning and teaching with specific reference to grade 12 pupils who do not speak English as L1, data was collected using in depth interviews and observations of classroom teaching and learning where students attended English lessons. Field notes were also used as supplementary information. Due to the nature of the study, the in-depth interviews were held with pupils and English teachers to gather data about their English language challenges as viewed by them and to evaluate if they are satisfied with their English language competency. Data from in-depth interviews and observations were analysed qualitatively.
The overall findings of the research revealed that grade 12 pupils English language competency is limited and needs to be improved in order to aid their academic performance and also to be able to communicate clearly without any linguistic hindrances with their teachers. Grade 12 like any other students who study through English language, need to have a good and adequate English language to be able to access content of some of their subjects. In addition to English language competency, grade 12 are at the apex of their basic education journey and need to improve their English language competency as a prerequisite to their higher education journey. Most (if not all) the universities in SA and around the world use English as a Language of teaching and Learning (LoLT)
Synthesis of imidazopyridazine and pyrazolopyrimidine derivatives as potential inhibitors of Plasmodium kinases P14K and PKG
Get PDFThesis (M. Sc. (Chemistry)) -- University of Limpopo, 2023Malaria is a disease that is caused by various Plasmodium species, with Plasmodium falciparum and vivax being the most prevalent. The disease is usually mostly severe in pregnant women and children under the age of five. The 2020 World Malaria Report from WHO estimated 241 million new malaria cases and 627000 malaria deaths globally. In comparison to 2019, there has been an increase of approximately 14 million new cases and 69000 deaths. Approximately 47000 of these additional deaths were caused by interruptions in malaria diagnosis, prevention, and treatment during the COVID-19 pandemic. Emergence of resistance towards previously effective anti-malarial drugs, has resulted in an urgent need for the development of new drugs with new modes of action.
A series of imidazopyridazine and pyrazolopyrimidine derivatives have been reported to be potent against sensitive (NF54) strain of the human malaria parasite Plasmodium falciparum. In this study we focused on synthesizing a new library of imidazopyridazine and pyrazolopyrimidine derivatives, with substituents at 3- & 6- positions and 3- & 5- positions respectively. The compounds were successfully synthesized and characterized by NMR and HRMS. The imidazopyridazine derivatives percentage yields ranged from 38% to 70%, whereas the percentage yields for the pyrazolopyrimidine derivatives ranged from 41% to 75%. All the imidazopyridazine compounds were evaluated for their in vitro antiplasmodial activities against NF54 strain and inhibitory activity against Plasmodium falciparum cGMP-dependent protein kinase (PfPKG) and Plasmodium vivax phosphatidylinositoil 4-kinase type III beta (PvPI4Kβ). The pyrazolopyrimidine compounds were only evaluated for their in vitro antiplasmodial activity against the NF54 strain.
Imidazopyridazine compounds 20B, 20D, 20E, 20F, 20M and 20O demonstrated in vitro antiplasmodial activity of below 6 M against NF54 strain, which was used as a cutoff to determine good activity versus moderate activity. Imidazopyridazine compounds 20A, 20C, 20G, 20H, 20I, 20J, 20K, 20L and 20N demonstrated a moderate activity of greater than 6 M against NF54 strain. Imidazopyridazine compounds 20H, 20K, 20L and 20N demonstrated good activity against both PfPKG and PvPI4Kβ with IC50 values ranging from 0.96 M to 5.04 M and 0.006 M to 0.071 M, respectively. Imidazopyridazine
compounds 20A, 20B, 20C, 20D, 20E, 20F, 20G, 20I, 20J, 20M and 20O demonstrated moderate activity of greater than 10 M against PfPKG and good activity against PvPI4Kβ with IC50 values ranging from 0.006 M to 0.643 M.
From the pyrazolopyrimidine scaffold, compounds 39A (0.013
M) and 39E (0.009
M) demonstrated the highest activities against the NF54 strain. The reduction of the pyrazolopyrimidine scaffold did not improve the potency, as it was seen with compounds 39A (0.013 M) reduced to 40A (0.197 M), compound 39B (0.190 M) reduced to 40B (1.056 M) and compound 39C (1.504 M) reduced to 40C (2.113 M). 3-(Methylsulfonyl) phenyl was a better substituent to have on the left-hand side of the pyrazolopyrimidine core scaffold than 4-(methylsulfonyl) phenyl substituent. Pyrazolopyrimidine compounds demonstrated very good in vitro antiplasmodial activity against the sensitive (NF54) strain as compared to the imidazopyridazine compounds. Therefore, pyrazolopyrimidine is a better scaffold to explore to eradicate malaria. Compounds 38A, 38A, 39B, 39D and 39E have a selectivity index of more than 100, therefore they will be progressed further for solubility, chemical stability, microsomal stability (m,r,h) and in vitro PfK1, Dd2 assaysNational Institute of Health (NIH
Enhenced gas sensing perfomance induced by CuO-ZnO heterostructure towards NO2 gas
No full textThesis (M.Sc. (Physics)) -- University of Limpopo. 2023The selective detection of gaseous benzene, toluene, ethylbenzene, and xylene
(BTEX) is challenging due to their similar molecular structures. In addition, BTEX
vapours are extremely hazardous and carcinogenic. Thus, in the current study, n-type
ZnO and p-type CuO nanostructures were synthesized utilizing various bases by a
simple hydrothermal method. Among the tested sensors, the ZnO-NaOH-based
sensor displayed a temperature dual-mode selectivity toward benzene with responses
(Ra/Rg) of 2.5 and 24 at 5 and 100 ppm, respectively at 75 C, and Ra/Rg 142 toward
xylene vapour at 100 ppm at an operating temperature of 150 C. While the CuO
based sensors showed a poor response, sensitivity, and selectivity towards tested
analytes. Moreover, the ZnO-NaOH based sensor revealed enormous sensitivity of
1.21 ppm-1 and a low limit of detection (LoD) of 0.018 ppm (i.e., 18 ppb) toward xylene.
The ultra-sensitivity, selectivity, and low LoD of ZnO-NaOH-based sensor toward
benzene and xylene are associated with the improved VO observed in the in-situ
photoluminescence and electron paramagnetic resonance studies, as well as the x
ray photoelectron spectroscopy analyses. The ZnO-NaOH-based sensor, which was
stored for roughly 18 months (547 days), demonstrated reliable repeatability and long
time operation stability for 22 hours of exposure to xylene. The superior sensitivity,
stability, and selectivity indicate openly that the strategy of using various bases is a
striking method for fabricating a temperature dual-mode selectivity for the detection of
benzene and xylene vapours.
Xylene is not just considered detrimental to the environment; it is also hazardous to
humans. Herein we report on xylene vapour detection using CuO-ZnO
heterostructures containing various concentrations (0.1-1.0 wt. %) of ZnO, prepared
via hydrothermal synthesis. X-ray diffraction, scanning, and transmission electron
microscopy, as well as x-ray photoelectron spectroscopy, validated the formation of
the CuO-ZnO heterostructure. Gas detection, sensitivity, selectivity and stability tests
of nine different gases, namely benzene, toluene, ethylbenzene, xylene, ethanol,
methane, SO2, NO2, and CO2 at various operational temperatures were subsequently
investigated. It was found that a CuO-ZnO heterostructure with 1.0 wt. % ZnO showed
excellent selectivity towards 100 ppm of xylene at 100 C. The sensor further
demonstrated an insignificant cross-sensitivity (Sxylene/Stoluene= 2.7) and (Sxylene/Sbenzene
= 8.5) towards toluene and benzene vapour. Additionally, the ultra-low limit of
detection of 9.5 ppb and sensitivity of 0.063 ppm-1 were observed towards xylene
vapour, which indicated that the CuO-ZnO (1.0 wt. %) heterostructure-based sensor
can produce sub-ppb-level xylene concentration. The sensor disclosed excellent long
term stability in dry air and 40% relative humidity.
Finally, at room temperature, the CuO-ZnO (0.5 wt. %) based sensor disclosed a
superior selectivity towards NO2. Additionally, concerning other gases, the sensors
showed poor responses at room temperature. While at higher temperatures, the
sensors showed better selectivity towards xylene. Thus, these findings showed that
while the sensors could detect xylene at high temperatures, nonetheless, the room
temperature sensitivity of the CuO-ZnO (0.5 wt. %) based sensor towards NO2
denoted that the sensor could be used for low power consumption. The superior gas
sensing characteristics could be ascribed to the creation of p-n heterojunction, the
robust chemical affinity, and the catalytic performance of p-type CuO on xylene and
NO2 gases