Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2022/v76a02
Mzamo L. Shozi, Xolelwa Zulu, H. Friedrich
ABSTRACT A series of phosphorus and nitrogen-based ethylene oligomerization ligands of the type Ph2PN(X)PPh2 where X = i-propyl, n-butyl, ethylbenzene and cyclohexyl substituents are reported. These ligands were functionalized to enable tethering on amino-silica. The free ligands, amino-silica and the tethered ligands were characterized by BET, XRD, IR, TGA and NMR. The catalysts were tested for ethylene oligomerization using Cr(acac)3 (acac = acetylacetonate) as the precursor and MMAO (modified methylaluminoxane) as the activator. The activity and selectivity of these catalysts to 1-octene was monitored at 45 bar ethylene in the temperature range of45-100 °C. The activity of the supported catalysts was comparable to their homogeneous counterparts, surpassing them in some cases and selectivities to 1-octene in the C8 products were as high as 99 wt%. The steric effect of the substituent on the ligand as well as that of the support was found to influence the activity and product distribution. Keywords: 1-hexene, 1-octene, ethylene oligomerization, phosphine ligands, silica, supported catalysts
{"title":"Synthesis and characterization of amine-functionalized supported phosphine catalysts and their application in ethylene oligomerization","authors":"Mzamo L. Shozi, Xolelwa Zulu, H. Friedrich","doi":"10.17159/0379-4350/2022/v76a02","DOIUrl":"https://doi.org/10.17159/0379-4350/2022/v76a02","url":null,"abstract":"ABSTRACT A series of phosphorus and nitrogen-based ethylene oligomerization ligands of the type Ph2PN(X)PPh2 where X = i-propyl, n-butyl, ethylbenzene and cyclohexyl substituents are reported. These ligands were functionalized to enable tethering on amino-silica. The free ligands, amino-silica and the tethered ligands were characterized by BET, XRD, IR, TGA and NMR. The catalysts were tested for ethylene oligomerization using Cr(acac)3 (acac = acetylacetonate) as the precursor and MMAO (modified methylaluminoxane) as the activator. The activity and selectivity of these catalysts to 1-octene was monitored at 45 bar ethylene in the temperature range of45-100 °C. The activity of the supported catalysts was comparable to their homogeneous counterparts, surpassing them in some cases and selectivities to 1-octene in the C8 products were as high as 99 wt%. The steric effect of the substituent on the ligand as well as that of the support was found to influence the activity and product distribution. Keywords: 1-hexene, 1-octene, ethylene oligomerization, phosphine ligands, silica, supported catalysts","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2022/v76a12
S. Amin, S. Muhammad, J. Iqbal, S. Ullah, A. G. Al-Sehemi, H. Algarni, S. S. Alarfaji, K. Ayub
This study is carried out to find novel active drug candidates which can effectively bind to key residues of main protease (Mpro) of SARS-CoV-2. We performed molecular docking of fifty-seven (57) ligands from two classes: vanillylacetone and its derivatives and beta-hydroxy ketone derivatives against Mpro of SARS-CoV-2. We also docked three antiviral drugs as reference/benchmark drugs including remdesivir (RDV), chloroquine (CQ), and hydroxychloroquine (HCQ) against Mpro for comparison of inhibition tendencies of selected ligands. Binding energies of our reference drugs are as: CQ = -5.1 kcal mol-1 (with predicted inhibition constant (Ki pred) = 177 μmol), HCQ = -5.7 kcal mol-1 (Ki pred = 64.07 μmol) and RDV -6.3 kcal mol-1 (Ki pred = 13.95 μmol). We got remarkable results for our docked ligands as 79% of total ligands indicated binding energies better than CQ, 39 % better than both HCQ and CQ, and 19 % better than all reference drugs. More interestingly interaction analysis of eight best-docked ligands showed that they interacted with desired key residues of Mpro. We further selected the four best-docked ligands L1 = -6.6 kcal mol-1 (Ki pred =13.95 μmol), L6 = -7.0 kcal mol-1 (Ki pred = 7.08 μmol), L34 = -6.0 kcal mol-1 (Ki pred = 38.54 μmol), and L50 = -6.6 kcal mol-1 (Ki pred =13.95 umol) for further analysis by quantum chemical study, molecular dynamic (MD) simulations and ADMET analysis. We have also carried out MD-simulations of six more docked ligand L2, L14, L20, L36, L46 and L48 some of which were showing weak binding affinities and some average binding affinities to check their simulation behavior. Their RMSD, RMSF and binding free energy results were also quite satisfying. We believe the current investigation will evoke the scientific community and highlights the potential of selected compounds for potential use as antiviral compounds against Mpro of SARS-CoV-2.
本研究旨在寻找能有效结合SARS-CoV-2主要蛋白酶(Mpro)关键残基的新型候选活性药物。我们对来自两类的57个配体进行了分子对接:香草丙酮及其衍生物和β -羟基酮衍生物对抗SARS-CoV-2的Mpro。我们还将瑞德西韦(remdesivir, RDV)、氯喹(chloroquine, CQ)和羟氯喹(hydroxychloroquine, HCQ)三种抗病毒药物作为参比/基准对接，比较所选配体对Mpro的抑制倾向。参考药物的结合能分别为:CQ = -5.1 kcal mol-1(预测抑制常数Ki pred = 177 μmol)、HCQ = -5.7 kcal mol-1 (Ki pred = 64.07 μmol)和RDV -6.3 kcal mol-1 (Ki pred = 13.95 μmol)。我们得到了显著的结果，79%的配体的结合能优于CQ, 39%的配体结合能优于HCQ和CQ, 19%的配体结合能优于所有参考药物。更有趣的是，对八个最佳配体的相互作用分析表明，它们与Mpro所需的关键残基相互作用。我们进一步选择了L1 = -6.6 kcal mol-1 (Ki pred =13.95 μmol)、L6 = -7.0 kcal mol-1 (Ki pred = 7.08 μmol)、L34 = -6.0 kcal mol-1 (Ki pred = 38.54 μmol)和L50 = -6.6 kcal mol-1 (Ki pred =13.95 μmol)四个最佳配体进行量子化学研究、分子动力学模拟和ADMET分析。我们还对另外6种对接配体L2、L14、L20、L36、L46和L48进行了md模拟，其中一些配体的结合亲和力较弱，一些配体的结合亲和力一般，以检验它们的模拟行为。他们的RMSD、RMSF和结合自由能的结果也很令人满意。我们相信目前的研究将引起科学界的注意，并强调所选化合物作为抗病毒化合物用于对抗SARS-CoV-2的Mpro的潜力。
{"title":"Molecular docking, dynamics, and quantum chemical study of vanillylacetone and beta-hydroxy ketone derivatives against Mpro of SARS-CoV-2","authors":"S. Amin, S. Muhammad, J. Iqbal, S. Ullah, A. G. Al-Sehemi, H. Algarni, S. S. Alarfaji, K. Ayub","doi":"10.17159/0379-4350/2022/v76a12","DOIUrl":"https://doi.org/10.17159/0379-4350/2022/v76a12","url":null,"abstract":"This study is carried out to find novel active drug candidates which can effectively bind to key residues of main protease (Mpro) of SARS-CoV-2. We performed molecular docking of fifty-seven (57) ligands from two classes: vanillylacetone and its derivatives and beta-hydroxy ketone derivatives against Mpro of SARS-CoV-2. We also docked three antiviral drugs as reference/benchmark drugs including remdesivir (RDV), chloroquine (CQ), and hydroxychloroquine (HCQ) against Mpro for comparison of inhibition tendencies of selected ligands. Binding energies of our reference drugs are as: CQ = -5.1 kcal mol-1 (with predicted inhibition constant (Ki pred) = 177 μmol), HCQ = -5.7 kcal mol-1 (Ki pred = 64.07 μmol) and RDV -6.3 kcal mol-1 (Ki pred = 13.95 μmol). We got remarkable results for our docked ligands as 79% of total ligands indicated binding energies better than CQ, 39 % better than both HCQ and CQ, and 19 % better than all reference drugs. More interestingly interaction analysis of eight best-docked ligands showed that they interacted with desired key residues of Mpro. We further selected the four best-docked ligands L1 = -6.6 kcal mol-1 (Ki pred =13.95 μmol), L6 = -7.0 kcal mol-1 (Ki pred = 7.08 μmol), L34 = -6.0 kcal mol-1 (Ki pred = 38.54 μmol), and L50 = -6.6 kcal mol-1 (Ki pred =13.95 umol) for further analysis by quantum chemical study, molecular dynamic (MD) simulations and ADMET analysis. We have also carried out MD-simulations of six more docked ligand L2, L14, L20, L36, L46 and L48 some of which were showing weak binding affinities and some average binding affinities to check their simulation behavior. Their RMSD, RMSF and binding free energy results were also quite satisfying. We believe the current investigation will evoke the scientific community and highlights the potential of selected compounds for potential use as antiviral compounds against Mpro of SARS-CoV-2.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"31 15 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2022/v76a08
Frank Ssengooba, Thashree Marimuthu, E. Olivier, P. Demana, Y. Choonara
ABSTRACT Poor drug solubility is a major problem that hinders the discovery and development of new drugs. There is a need for rapid and inexpensive techniques for acquiring reliable drug solubility data. In this study, the suitability of laser nephelometry for the determination of solubility was investigated using ibuprofen, as a model drug of low solubility, and its 2-hydroxypropyl-p-cyclodextrin inclusion complex (ic). This investigation involved the preparation of ibuprofen-ic-cyclodextrin (1:1) using coprecipitation and characterisation. Thermal analysis and assessment of molecular vibrations confirmed the existence of the inclusion complex. The shake flask testing method was employed and carried out in acidic and alkaline media, and solubility data were verified against high-performance liquid chromatography (HPLC). Results obtained via nephelometry showed relative enhanced solubility of ibuprofen in both acidic (0.565 mg ml-1) and basic (7.5 mg ml-1) media, respectively, which was enabled via inclusion complex formation. Relative to nephelometry data, HPLC results showed a similar trend with increased solubility values in acidic (0.454 mg ml-1) and basic (201.73 mg ml-1) media, respectively. The application of laser nephelometry proved to be a quick and relatively cost-effective technique for solubility measurements of the parent drug and its carrier system. Keywords: cyclodextrin, ibuprofen, inclusion complex, laser nephelometry, solubility
{"title":"Comparison of laser nephelometric and HPLC techniques for efficient determination of solubility of ibuprofen and its 2-hydroxypropyl-p-cyclodextrin inclusion complex","authors":"Frank Ssengooba, Thashree Marimuthu, E. Olivier, P. Demana, Y. Choonara","doi":"10.17159/0379-4350/2022/v76a08","DOIUrl":"https://doi.org/10.17159/0379-4350/2022/v76a08","url":null,"abstract":"ABSTRACT Poor drug solubility is a major problem that hinders the discovery and development of new drugs. There is a need for rapid and inexpensive techniques for acquiring reliable drug solubility data. In this study, the suitability of laser nephelometry for the determination of solubility was investigated using ibuprofen, as a model drug of low solubility, and its 2-hydroxypropyl-p-cyclodextrin inclusion complex (ic). This investigation involved the preparation of ibuprofen-ic-cyclodextrin (1:1) using coprecipitation and characterisation. Thermal analysis and assessment of molecular vibrations confirmed the existence of the inclusion complex. The shake flask testing method was employed and carried out in acidic and alkaline media, and solubility data were verified against high-performance liquid chromatography (HPLC). Results obtained via nephelometry showed relative enhanced solubility of ibuprofen in both acidic (0.565 mg ml-1) and basic (7.5 mg ml-1) media, respectively, which was enabled via inclusion complex formation. Relative to nephelometry data, HPLC results showed a similar trend with increased solubility values in acidic (0.454 mg ml-1) and basic (201.73 mg ml-1) media, respectively. The application of laser nephelometry proved to be a quick and relatively cost-effective technique for solubility measurements of the parent drug and its carrier system. Keywords: cyclodextrin, ibuprofen, inclusion complex, laser nephelometry, solubility","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2021/v76a13
S. Gouws, M. Gouws
Green living walls can improve the aesthetic quality of a building and moderate the temperature within it. The purpose of this paper is to examine whether the green wall has any effect on the interior temperature of the building in the hot and cold months of the year. Temperatures on an outside wall as well as on research and control areas were monitored to capture temperature data for a one-year period that encompassed all seasons: sunny, cold and wet. The findings of this research contribute to the knowledge of the effects provided by green living walls in terms of cooling and heating, the influence on the proximity microclimatic conditions, and overall energy transfer. Heat flux of 20-100 W/m2 was found indicating an insulating effect that brings about cooling in the interior of the building. During summer months a cooling effect of 2-4 °C was observed, while the opposite effect was observed during winter in that the temperatures did not drop by much but provide a insulating effect of 2-3 °C higher than it was for the control area. Altogether, green living walls could be implemented to reduce and insulating interior living conditions and therefore reduce building energy demands.
{"title":"Thermally regulated green living wall","authors":"S. Gouws, M. Gouws","doi":"10.17159/0379-4350/2021/v76a13","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v76a13","url":null,"abstract":"Green living walls can improve the aesthetic quality of a building and moderate the temperature within it. The purpose of this paper is to examine whether the green wall has any effect on the interior temperature of the building in the hot and cold months of the year. Temperatures on an outside wall as well as on research and control areas were monitored to capture temperature data for a one-year period that encompassed all seasons: sunny, cold and wet. The findings of this research contribute to the knowledge of the effects provided by green living walls in terms of cooling and heating, the influence on the proximity microclimatic conditions, and overall energy transfer. Heat flux of 20-100 W/m2 was found indicating an insulating effect that brings about cooling in the interior of the building. During summer months a cooling effect of 2-4 °C was observed, while the opposite effect was observed during winter in that the temperatures did not drop by much but provide a insulating effect of 2-3 °C higher than it was for the control area. Altogether, green living walls could be implemented to reduce and insulating interior living conditions and therefore reduce building energy demands.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2022/v76a06
S. D. du Preez, A. Kozhukhova, D. Bessarabov
The implementation of catalytic hydrogen combustion (CHC) can mitigate the dependence on solid fuel combustion typically used in SubSaharan Africa as a means of heating. However, low-cost and readily available materials for catalyst fabrication are relatively unexplored. Considering the economic constraints regarding platinum group metals generally used for CHC, the cost of support materials and its functionalization as catalyst support has to be minimized. Typically, materials such as silicon carbide foam, extruded aluminium oxidebased ceramics, and titanium oxide mesh/sintered plates are used to withstand the high temperatures associated with CHC. In this paper, nanostructured anodized aluminium oxide (AAO) was synthesized as the support material via the anodization of high purity (>99%) aluminium (Al). The AAO layer intimately adhered to a metallic Al core acted as a thermal conduit to disperse heat throughout the catalyst. Platinum (Pt), considered as the reactive metal, was deposited to the AAO as nanoparticles with a diameter of approximately 19.3 nm. The CHC reaction proceeded spontaneously on the surface of the Pt/AAO catalyst. A combustion temperature of 408 ± 18 °C was maintained for 70 h at a 100 normal (N) mL min−1 hydrogen flow rate. The Pt-particles showed a relatively appreciable increase in particle size (from 19.3 nm to 25.0 nm), but the significance thereof was not evident during the 70 h CHC procedure.
实施催化氢燃烧(CHC)可以减轻对固体燃料燃烧的依赖，通常在撒哈拉以南非洲使用作为一种加热手段。然而，用于制造催化剂的低成本和容易获得的材料相对来说尚未开发。考虑到通常用于CHC的铂族金属的经济限制，必须最小化支撑材料及其作为催化剂载体的功能化成本。通常，诸如碳化硅泡沫、挤压氧化铝基陶瓷和氧化钛网/烧结板等材料用于承受与CHC相关的高温。本文采用高纯度(>99%)铝(Al)阳极氧化法制备了纳米结构的阳极氧化铝(AAO)作为载体材料。紧密粘附在金属铝芯上的AAO层充当热导管，将热量分散到整个催化剂中。作为活性金属的铂(Pt)以直径约19.3 nm的纳米颗粒沉积在AAO上。CHC反应在Pt/AAO催化剂表面自发进行。燃烧温度为408±18℃，氢气流量为100正常(N) mL min - 1，燃烧时间为70 h。pt颗粒的粒径明显增大(从19.3 nm增加到25.0 nm)，但在70 h CHC过程中，其显著性不明显。
{"title":"Catalytic hydrogen combustion using platinum supported on anodized aluminium oxide adhered to metallic aluminium","authors":"S. D. du Preez, A. Kozhukhova, D. Bessarabov","doi":"10.17159/0379-4350/2022/v76a06","DOIUrl":"https://doi.org/10.17159/0379-4350/2022/v76a06","url":null,"abstract":"The implementation of catalytic hydrogen combustion (CHC) can mitigate the dependence on solid fuel combustion typically used in SubSaharan Africa as a means of heating. However, low-cost and readily available materials for catalyst fabrication are relatively unexplored. Considering the economic constraints regarding platinum group metals generally used for CHC, the cost of support materials and its functionalization as catalyst support has to be minimized. Typically, materials such as silicon carbide foam, extruded aluminium oxidebased ceramics, and titanium oxide mesh/sintered plates are used to withstand the high temperatures associated with CHC. In this paper, nanostructured anodized aluminium oxide (AAO) was synthesized as the support material via the anodization of high purity (>99%) aluminium (Al). The AAO layer intimately adhered to a metallic Al core acted as a thermal conduit to disperse heat throughout the catalyst. Platinum (Pt), considered as the reactive metal, was deposited to the AAO as nanoparticles with a diameter of approximately 19.3 nm. The CHC reaction proceeded spontaneously on the surface of the Pt/AAO catalyst. A combustion temperature of 408 ± 18 °C was maintained for 70 h at a 100 normal (N) mL min−1 hydrogen flow rate. The Pt-particles showed a relatively appreciable increase in particle size (from 19.3 nm to 25.0 nm), but the significance thereof was not evident during the 70 h CHC procedure.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"9 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2021/v76a14
Ehab Norhan A Khalaf, Abdel-Latif, M. Ismail, H. Metwally, E. Abdel‐Latif
4-Aminobenzohydrazide (1) undergoes chloroacetylation twice, at the primary amine and hydrazide-NH2 functional groups. The conforming bis-chloroacetamide derivative 3 was reacted with different sulfur reagents (namely, 2-mercaptobenzothiazole, 6-amino-2-mercaptopyrimidin-4-ol, and 2-mercapto-4,6-dimethyl-nicotinonitrile) to give new bis-sulfide compounds 5, 7 and 9, respectively. The newly synthesised bis-chloroacetamide and corresponding sulfides were screened for anti-microbial and antioxidant potential. The sulfide derivative 7 exhibited the most potent activity against Staphylococcus aureus and Pseudomonas aeruginosa. It shows inhibition activities of 83.4% and 78.8%, respectively. Moreover, the sulfide derivative 7 showed the highest antioxidant activity with an inhibition ratio of 85.9%, which is close to L-ascorbic acid.
{"title":"Utilisation of bis-chloroacetamide derivative in the synthesis of new biologically active sulfide compounds","authors":"Ehab Norhan A Khalaf, Abdel-Latif, M. Ismail, H. Metwally, E. Abdel‐Latif","doi":"10.17159/0379-4350/2021/v76a14","DOIUrl":"https://doi.org/10.17159/0379-4350/2021/v76a14","url":null,"abstract":"4-Aminobenzohydrazide (1) undergoes chloroacetylation twice, at the primary amine and hydrazide-NH2 functional groups. The conforming bis-chloroacetamide derivative 3 was reacted with different sulfur reagents (namely, 2-mercaptobenzothiazole, 6-amino-2-mercaptopyrimidin-4-ol, and 2-mercapto-4,6-dimethyl-nicotinonitrile) to give new bis-sulfide compounds 5, 7 and 9, respectively. The newly synthesised bis-chloroacetamide and corresponding sulfides were screened for anti-microbial and antioxidant potential. The sulfide derivative 7 exhibited the most potent activity against Staphylococcus aureus and Pseudomonas aeruginosa. It shows inhibition activities of 83.4% and 78.8%, respectively. Moreover, the sulfide derivative 7 showed the highest antioxidant activity with an inhibition ratio of 85.9%, which is close to L-ascorbic acid.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2022/v76a03
B. Ma, L. Ren, G. Liu, J. Li, Y. Xiao, D. Li, Y. Gao, P. Kuang
Cyanogen chloride, as a systemic toxic agent, can cause death rapidly. In this paper, a non-dispersive infrared sensor was designed for the infrared absorption detection of cyanogen chloride at 800 cm−1. The roughness of the internal coating material was analyzed by experiments, and the gold-plated gas chamber was selected. The light path propagation of different cross-section gas chambers was simulated, and the circular section gas chamber was selected to increase the infrared detector signal. The effect of flow rate on voltage was studied. The standard curve between voltage and concentration was obtained under the optimal condition of 0.4 L min−1. The maximum response time was 19 s, and RSD was less than 2%. The interference experiment results showed that common gases entering the gas chamber do not cause interference. The non-dispersive infrared sensor for cyanogen chloride has good stability and detects cyanogen chloride in real-time.
氯化氰是一种全身毒性物质，可迅速导致死亡。本文设计了一种非色散红外传感器，用于800 cm−1波段的氯化氰红外吸收检测。通过实验分析了内涂层材料的粗糙度，并选择了镀金气室。模拟了不同截面毒气室的光路传播，选择圆形截面毒气室增加红外探测器信号。研究了流量对电压的影响。在0.4 L min−1的最佳条件下，得到了电压与浓度的标准曲线。最大反应时间为19 s, RSD < 2%。干扰实验结果表明，进入气室的普通气体不会产生干扰。该非色散氯氰红外传感器具有稳定性好、实时检测氯氰的特点。
{"title":"A non-dispersive infrared sensor for real-time detection of cyanogen chloride","authors":"B. Ma, L. Ren, G. Liu, J. Li, Y. Xiao, D. Li, Y. Gao, P. Kuang","doi":"10.17159/0379-4350/2022/v76a03","DOIUrl":"https://doi.org/10.17159/0379-4350/2022/v76a03","url":null,"abstract":"Cyanogen chloride, as a systemic toxic agent, can cause death rapidly. In this paper, a non-dispersive infrared sensor was designed for the infrared absorption detection of cyanogen chloride at 800 cm−1. The roughness of the internal coating material was analyzed by experiments, and the gold-plated gas chamber was selected. The light path propagation of different cross-section gas chambers was simulated, and the circular section gas chamber was selected to increase the infrared detector signal. The effect of flow rate on voltage was studied. The standard curve between voltage and concentration was obtained under the optimal condition of 0.4 L min−1. The maximum response time was 19 s, and RSD was less than 2%. The interference experiment results showed that common gases entering the gas chamber do not cause interference. The non-dispersive infrared sensor for cyanogen chloride has good stability and detects cyanogen chloride in real-time.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"54 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464424","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2022/v76a07
T. Mongwe, T. Ntuli, L. Sikeyi, N. Coville, M. Mamo, J. Serbena, M. Maubane-Nkadimeng
This study reports on the synthesis of carbon nano-onions (CNOs; ca. d ≤ 55 nm) and nitrogen-doped CNOs (N-CNOs) using a facile pyrolysis method and ex-situ doping of the CNOs. Elemental analysis of the N-CNOs revealed that their nitrogen content depended on the ammonia flow rate. Analysis of the N-CNOs revealed that they all exhibited structural defects. After the successful synthesis of CNOs and N-CNOs, polyvinylpyrrolidone (PVP):CNOs/N-CNOs:MnO2-nanorods (MONRs) composites were prepared and used as active sensing materials. In every case, the PVP polymer was used to stabilize the MONRs for acetone detection at 25 °C. The chemi-resistive gas sensors that showed the highest acetone sensitivity (pS = 2.0 × 10−4 ppm−1 ) was fabricated using a pristine CNOs (pCNOs) based composite. However, the N-CNOs based sensor (a1.5S) presented the lowest acetone limit of detection (LoD) at 1.2 ppm. The study implicated the effect of the nitrogen and oxygen content of the CNOs surfaces on the acetone detection. Thus, a higher sensitivity with lower LoD was observed at room temperature using the pCNOs based sensor, when compared to earlier literature reports.
{"title":"The use of ex-situ nitrogen-doped olive oil-derived carbon nano-onions for application in chemi-resistive gas sensors to detect acetone at room temperature","authors":"T. Mongwe, T. Ntuli, L. Sikeyi, N. Coville, M. Mamo, J. Serbena, M. Maubane-Nkadimeng","doi":"10.17159/0379-4350/2022/v76a07","DOIUrl":"https://doi.org/10.17159/0379-4350/2022/v76a07","url":null,"abstract":"This study reports on the synthesis of carbon nano-onions (CNOs; ca. d ≤ 55 nm) and nitrogen-doped CNOs (N-CNOs) using a facile pyrolysis method and ex-situ doping of the CNOs. Elemental analysis of the N-CNOs revealed that their nitrogen content depended on the ammonia flow rate. Analysis of the N-CNOs revealed that they all exhibited structural defects. After the successful synthesis of CNOs and N-CNOs, polyvinylpyrrolidone (PVP):CNOs/N-CNOs:MnO2-nanorods (MONRs) composites were prepared and used as active sensing materials. In every case, the PVP polymer was used to stabilize the MONRs for acetone detection at 25 °C. The chemi-resistive gas sensors that showed the highest acetone sensitivity (pS = 2.0 × 10−4 ppm−1 ) was fabricated using a pristine CNOs (pCNOs) based composite. However, the N-CNOs based sensor (a1.5S) presented the lowest acetone limit of detection (LoD) at 1.2 ppm. The study implicated the effect of the nitrogen and oxygen content of the CNOs surfaces on the acetone detection. Thus, a higher sensitivity with lower LoD was observed at room temperature using the pCNOs based sensor, when compared to earlier literature reports.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2022/v76a01
Lereko Mohafa, Makomosela Qhobela, M. George
ABSTRACT Traditional teaching strategies dominate science classrooms in Lesotho, resulting in poor academic performance at each level. Information and Communication Technology tools such as simulations offer potential benefits for improving science teaching. The purpose of this quasi-experimental study was to evaluate the effect of simulations on learners' performance and retention of stoichiometry concepts using Solomon's four-group design. Purposive sampling of two existing Form E (Grade 12) classes, with 81 learners, led to the creation of four groups. The study responds to the research question: How does using simulations as part of an intervention affect learners' academic performance in stoichiometry? Data were collected as learners' scores for pre-tests and post-tests, designed to assess their understanding of stoichiometry, and analysed through ANOVA and t-tests. After the intervention, the experimental group's mean score (M = 44.2, a = 18) was higher than that of control group (M = 32.6, a = 15.8), and the difference between the two mean scores was statistically significant, namely t(81) = 3.14, p = 0.002. The experimental group had a higher mean score for retention in post-test (M = 47.4, a =16.1) than the control group (M = 37.2, a = 13.7) which was statistically significant, namely t(81) = 3.10, p = 0.003. Therefore, it was concluded that simulations enhanced learners' performance and could improve the retention of stoichiometry concepts. This study recommends that simulations be used to supplement the teaching and learning of science, in particular chemistry. Keywords: cognitive theory of multimedia learning, high school learners' performance, interactive-simulations, stoichiometry
在莱索托，传统的教学策略主导着科学课堂，导致各级学生的学习成绩不佳。模拟等信息和通信技术工具为改善科学教学提供了潜在的好处。本拟实验研究的目的是利用所罗门四组设计来评估模拟对学习者化学计量概念的表现和记忆的影响。有目的的抽样现有的两个中E(12年级)班，81名学生，导致创建四个组。该研究回答了一个研究问题:如何使用模拟作为干预的一部分影响学习者在化学计量学方面的学习成绩?数据收集为学习者的前测和后测分数，旨在评估他们对化学计量学的理解，并通过方差分析和t检验进行分析。干预后，实验组平均得分(M = 44.2, a = 18)高于对照组(M = 32.6, a = 15.8)，且两组平均得分差异有统计学意义，即t(81) = 3.14, p = 0.002。实验组的后测记忆力平均分(M = 47.4, a =16.1)高于对照组(M = 37.2, a = 13.7)，差异有统计学意义，即t(81) = 3.10, p = 0.003。因此，我们得出结论，模拟可以提高学习者的表现，并可以改善化学计量概念的记忆。这项研究建议使用模拟来补充科学，特别是化学的教与学。关键词:多媒体学习认知理论，高中生学习表现，互动模拟，化学计量学
{"title":"Evaluating the influence of interactive simulations on learners' academic performance in stoichiometry","authors":"Lereko Mohafa, Makomosela Qhobela, M. George","doi":"10.17159/0379-4350/2022/v76a01","DOIUrl":"https://doi.org/10.17159/0379-4350/2022/v76a01","url":null,"abstract":"ABSTRACT Traditional teaching strategies dominate science classrooms in Lesotho, resulting in poor academic performance at each level. Information and Communication Technology tools such as simulations offer potential benefits for improving science teaching. The purpose of this quasi-experimental study was to evaluate the effect of simulations on learners' performance and retention of stoichiometry concepts using Solomon's four-group design. Purposive sampling of two existing Form E (Grade 12) classes, with 81 learners, led to the creation of four groups. The study responds to the research question: How does using simulations as part of an intervention affect learners' academic performance in stoichiometry? Data were collected as learners' scores for pre-tests and post-tests, designed to assess their understanding of stoichiometry, and analysed through ANOVA and t-tests. After the intervention, the experimental group's mean score (M = 44.2, a = 18) was higher than that of control group (M = 32.6, a = 15.8), and the difference between the two mean scores was statistically significant, namely t(81) = 3.14, p = 0.002. The experimental group had a higher mean score for retention in post-test (M = 47.4, a =16.1) than the control group (M = 37.2, a = 13.7) which was statistically significant, namely t(81) = 3.10, p = 0.003. Therefore, it was concluded that simulations enhanced learners' performance and could improve the retention of stoichiometry concepts. This study recommends that simulations be used to supplement the teaching and learning of science, in particular chemistry. Keywords: cognitive theory of multimedia learning, high school learners' performance, interactive-simulations, stoichiometry","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-01DOI: 10.17159/0379-4350/2022/v76a05
Lerato L. Mokoloko, R. Forbes, N. Coville
ABSTRACT Herein we report on the direct synthesis of solid hydrophobic carbon dots (CDs) and simultaneously carbon spheres (CSs), using a vertical chemical vapour deposition (CVD) reactor. The HRTEM data indicated that the CDs and CSs originated from different carbon building blocks indicated that the CDs and CSs originated from different carbon building blocks. The CDs were obtained by reacting acetylene (C2H2) and Ar mixtures at high flow rates (>500 sccm) and high temperatures (800-1000 °C). TEM studies indicated that the CDs produced were graphene-like quantum dots that increased in size from c. 3 nm to 8 nm as the Ar flow rate (constant C2H2 flow rate) was decreased, while small solid CSs (c. 100 nm) were also synthesised in the process. The CSs had a typical spherical layered structure with no graphitic core. A mechanism to rationalise the observation that the CDs and CSs grew simultaneously by different pathways with no formation of intermediate-sized particles is given. Keywords: carbon dots, chemical vapour deposition, nanostructure, spectroscopy
{"title":"The simultaneous synthesis of carbon dots and carbon spheres with tunable sizes using a vertical chemical vapour deposition method","authors":"Lerato L. Mokoloko, R. Forbes, N. Coville","doi":"10.17159/0379-4350/2022/v76a05","DOIUrl":"https://doi.org/10.17159/0379-4350/2022/v76a05","url":null,"abstract":"ABSTRACT Herein we report on the direct synthesis of solid hydrophobic carbon dots (CDs) and simultaneously carbon spheres (CSs), using a vertical chemical vapour deposition (CVD) reactor. The HRTEM data indicated that the CDs and CSs originated from different carbon building blocks indicated that the CDs and CSs originated from different carbon building blocks. The CDs were obtained by reacting acetylene (C2H2) and Ar mixtures at high flow rates (>500 sccm) and high temperatures (800-1000 °C). TEM studies indicated that the CDs produced were graphene-like quantum dots that increased in size from c. 3 nm to 8 nm as the Ar flow rate (constant C2H2 flow rate) was decreased, while small solid CSs (c. 100 nm) were also synthesised in the process. The CSs had a typical spherical layered structure with no graphitic core. A mechanism to rationalise the observation that the CDs and CSs grew simultaneously by different pathways with no formation of intermediate-sized particles is given. Keywords: carbon dots, chemical vapour deposition, nanostructure, spectroscopy","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67464461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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