Synthesis of carbon nanotubes-mesostructured silica nanoparticles composites for adsorption of methylene blue

The mesostructured silica nanoparticles (MSN) have been widely developed for the removal of various pollutants due to their highly porous structure and other novel features. While carbon nanotubes (CNT) are attracting great interest owing to its large specific surface area, small size, hollow and layered structures. The integration of these outstanding properties by modification of MSN with singlewalled CNT (SWCNT) and multiwalled CNT (MWCNT) is quite new in this area of study and is expected to produce an adsorbent with higher adsorption capacity. In this study, three types of adsorbents were prepared by a simple one step method; MSN, series of SWCNT-MSN composites, and series of MWCNT-MSN composites. Their characteristics have been observed by XRD, N2 physisorption, FTIR, TEM, and FESEM, while their adsorption performance were evaluated on the adsorption of methylene blue (MB) at various pH, adsorbent dosage, initial MB concentration, and temperature. The results demonstrated that the adsorbents were prepared with mesoporous structures and produces relatively higher number of pores with larger diameters. The CNTs were found to improve the physicochemical properties of the MSN and led to an enhanced adsorptivity for MB. N2 physisorption measurements revealed the development of a bimodal pore structure in MWCNT-MSN composites that increased the pore size, pore volume and surface area. The best conditions for MSN, SWCNT-MSN and MWCNT-MSN composites achieved at pH 7 and 303 K using 0.05 g L-1 adsorbent and 100 mg L-1 MB. Fitting with linear Langmuir isotherm produce the maximum adsorption capacity of 500.1 mg g-1, 500.0 mg g-1, and 263.2 mg g-1 for MSNAP, SWCNT-MSN and MWCNT-MSN, respectively. The equilibrium data were evaluated using the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models, with the Freundlich model affording the best fit to the adsorption data for MSN and Langmuir model for both SWCNT-MSN and MWCNT-MSN. The adsorption kinetics for all MSN, SWCNT-MSN and MWCNT-MSN were best described by the pseudo-second order model. Thermodynamic study showed that the nature of MSNs and MWCNT-MSNs are exothermic, and endothermic for SWCNT-MSNs. This study is proven to produce a relatively new and potential mesostructured materials used as adsorbent for dye removal and water treatment

Multi-walled carbon nanotubes improve the physicochemical properties of mesostructured silica nanoparticles for efficient adsorption of methylene blue

Carbon nanotubes (CNTs) have attracted great attention in nanoscale science and technology due to their unique optical, electronic a nd mechanical properties 1 . Besides, mesostructured silica nanoparticles (MSN) have become effective adsorbents owe to its high surface area and pore size which is essential to adsorb wide range of organic pollutant 2-4 . Modification of CNT with MSN may enhance the dispersion properties and adsorption capacities from their singles. In this study, a series of carbon nanotubes–mesostructured silica nanoparticles (CNT–MSN) composites were prepared by a simple sol-gel method with 1, 3 and 5 wt.% loading of CNT. The composites then calcined to remove surfactants (Scheme 1). Their surface properties were characterized by XRD, N 2 physisorption, TEM and FTIR, while the adsorption performance of the CNT–MSN composites were evaluated on the adsorption of methylene blue (MB) under varying pH (2–11), adsorbent dosage (0.05–0.5 g L - 1 ), initial MB concentration (5–100 mg L -1 ) and temperature (303-323 K). The increasing CNT loading into MSN were found to improve the physicochemical properties of the material and led to an enhanced adsorptivity for MB. N 2 physisorption measurements revealed the developmen t of a bimodal pore structure that increased the pore size, pore volume and surface area. The best conditions were achieved at pH 8, 0.05 g L -1 CNT–MSN dosage, 100 mg L -1 MB concentration and 303 K. The maximum adsorption capacity re ached for 5 wt.% CNT- MSN was 524 mg g -1 . The equilibrium data were evaluated using the Langmuir and Freundlich isotherm models, with the Langmuir model affording the best fit to the adsorption data. The adsorption kinetics was best described by the pseudo-first order model. Thermodynamic studies showed that the adsorption process was spontaneous, exothermic and occur through physisorption mechanism. Therefore, CNT-MSN is believed to be a promising adsorbent for dye removal as well as removal of wide range wastewater

Synthesis of mesoporous silica nanoparticles by variation of microwave power for the ibuprofen drug delivery

Mesoporous silica nanoparticles (MSN), which combine both unique properties of nanomaterials and mesostructured substances, have arouse special attention in biomedical research field due to its great advantages in many aspects such as well biocompatible, unique properties of tunable pore size and structure, large surface areas and pore volumes, controllable morphology and modifiable surfaces1-2. The traditional synthesis method of mesoporous materials is the hydrothermal route, which uses a certain amount of surfactants, as well as acid or alkali to compose a mixed aqueous preparation. Although finely ordered mesoporous materials are obtained, the process is time and energy consuming3. It is known that microwave (MW) heating promotes nucleation and can reduce the synthesis time and particle size significantly in comparison with the conventional convection heating method3. For the synthesis of periodic mesoporous organosilica, it was reported that the synthesis time was reduced from 72 h to 36 h when the self-assembly process was performed under MW irradiation. The resulting materials also exhibited a high surface area, large pore volume and large pore diameters4. Within this context, the microwave was utilized to synthesize the MSN under 100 W, 300 W and 450 W heating powers. Ammonia was chosen as the catalyst and ethylene glycol as the co-solvent because of their polarity, which is higher than that of NaOH and methanol or ethanol which are commonly used to synthesize mesoporous silica. All MSNs was tested for adsorption and release of an anti-inflammatory and anti-cancer drug, ibuprofen. The characterization revealed that the MSN prepared under 450 W (MSN450) produced the most crystallized and prominent mesoporous structure compared to lower power applied (Figure 1). MSN450 exhibited the highest ibuprofen adsorption, followed by MSN300 and MSN100, confirming that more crystallized MSN demonstrated higher adsorptivity toward ibuprofen. For the release study, MSN450 showed the slowest release rate of ibuprofen, followed by MSN300 and MSN100. All MSNs was found to exhibit good activity for the ibuprofen adsorption and release

Recent progress on CVD growth of graphene from a liquid carbon precursor

Graphene has become a remarkable highlight of advanced material research because of its far superior properties compared to other materials. Chemical vapor deposition (CVD) has emerged as an essential method for scalable production and large area graphene for various applications. Various carbon precursors have been reported for graphene production as they can dramatically impact the graphene growth yield. In the early years of graphene CVD growth, hydrocarbon gases such as methane and acetylene have become favorable carbon precursors because of their stability at elevated temperature and controllable growth. However, hydrocarbon gases are known as explosives and toxic, therefore require a growth system with a high degree of safety and handling precautions. With the limitations mentioned above, liquid carbon source may change the graphene growth landscape as it is relatively inexpensive, nonexplosive compared to the conventional gaseous precursor. This article aims to review a detailed synthesis of large-area graphene using liquid carbon precursors via the CVD technique. Challenges and future perspectives are highlights

Structural rearrangement of mesostructured silica nanoparticles incorporated with ZnO catalyst and its photoactivity: effect of alkaline aqueous electrolyte concentration

ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the introduction of Zn ions into the framework of MSN via a simple electrochemical system in the presence of various concentrations of NH4OH aqueous solution. The physicochemical properties of the catalysts were studied by XRD, 29Si MAS NMR, nitrogen adsorption-desorption, FE-SEM, TEM, FTIR, and photoluminescence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simply generated abundant silanol groups on the surface of the catalysts as a consequence of desilication to form the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by the creation of oxygen vacancies and formation of Si-O-Zn during the electrolysis, as well as formation of new Si-O-Si bonds during calcination seemed to be the main factors that enhanced the catalytic performance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH4OH (ZM-1.0) was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rate of 3.87 × 10-1 h-1 than unsupported ZnO (1.13 × 10-1 h-1) that prepared under the same conditions in the absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generated from the three main sources; reduced O2 at the conduction band, decomposed water at the valence band and irradiated H2O2 in the solution, are key factors that influenced the reaction. It is also noted that the recycled ZM-1.0 catalyst maintained its activity up to five runs without serious catalyst deactivation

Hubungan Antara Kerja Rumah Dengan Pencapaian Akademik Dalam Kalangan Pelajar Dari Kelas Premier Di Dua Buah Sekolah Menengah

Kerja rumah telah menjadi komponen penting dalam sistem persekolahan di Malaysia. Kerja rumah memainkan peranan yang penting untuk membantu pelajar supaya lebih memahami pelajaran yang diajarkan di dalam kelas. Kerja rumah juga berperanan untuk menyumbangkan pencapaian yang tinggi terhadap sesuatu mata pelajaran. Kajian ini bertujuan untuk mengkaji hubungan antara kerja rumah dengan pencapaian mata pelajaran Matematik, Bahasa Inggeris dan Sejarah dalam kalangan pelajar tingkatan dua dari kelas premier di Sekolah Menengah Kebangsaan Taman Mutiara Rini dan Sekolah Menengah Kebangsaan Sri Skudai, Johor Bahru. Kajian ini menumpukan tiga faktor yang berkaitan dengan kerja rumah, iaitu peruntukan masa, jenis-jenis kerja rumah, dan cara pengelolaan guru terhadap kerja rumah. Seramai 106 orang pelajar telah dipilih sebagai sampel kajian: dua kelas tingkatan dua premier dari SMK Sri Skudai dan satu kelas tingkatan dua premier dari SMK Taman Mutiara Rini. Alat kajian yang digunakan ialah borang soal selidik. Borang ini terdiri daripada dua bahagian. Bahagian A mengandungi soalan yang berkaitan dengan demografi pelajar, pencapaian mata pelajaran dan faktor peruntukan masa. Manakala Bahagian B pula terdiri daripada 30 soalan berkaitan dengan faktor jenis kerja rumah dan faktor cara pengelolaan guru terhadap kerja rumah pelajar. Nilai kebolehpercayaan alat kajian ini ialah ? = 0.929. Keputusan peperiksaan akhir tahun dijadikan sebagai ukuran pencapaian pelajar dalam setiap mata pelajaran yang dikaji. Analisis deskriptif (kekerapan dan peratusan) dan inferensi (korelasi Pearson) digunakan dalam tatacara menganalisis data. Secara keseluruhannya, tahap pencapaian pelajar dalam setiap mata pelajaran berada pada tahap tinggi (60–79%). Hasil kajian ini menunjukkan bahawa terdapat hubungan signifikan tetapi sederhana antara faktor cara pengelolaan guru semasa dan selepas pemberian kerja rumah dengan pencapaian bagi mata pelajaran Matematik

Hubungan antara kerja rumah dengan pencapaian akademik dalam kalangan pelajar dari kelas premier di dua buah sekolah menengah

Homework has become an important component in schooling system in Malaysia. Besides this, homework is also an essential tool contributing towards higher achievement. This research is aimed to study the relationship between homework with students’ achievement in the subjects of Mathematics, English, and History among the form two premier students at Sekolah Menengah Kebangsaan Taman Mutiara Rini and Sekolah Menengah Kebangsaan Sri Skudai, Johor Bahru. In this research, the researcher focused on three factors, which include time spent, types of homework, and teacher supervision. The samples in this study were selected from two form two premier classes at SMK Sri Skudai and class at SMK Taman Mutiara Rini. Questionnaire was chosen by the researcher as the instrument to investigate the outcome of this study. This questionnaire consists of 2 sections. Section A includes the demographic items, students’ achievement, and time management. Section B includes 30 questions on the types of homework and teachers’ supervision on homework. The reliability of this instrument is ? = 0.929. The students’ result in end-year examination was used as students’ achievement in this study. In analyzing the data, researcher used two types of analysis: descriptive and inference statistic (Pearson correlation). Overall, the majority of students tend to have high achievement (60 – 79 %). The findings of this study showed significant correlation at medium level was found in two aspects: (1) teacher’s supervision during homework was assigned in Mathematics homework; and (2) teacher’s supervision after homework was assigned in Mathematics homework

WO3 monolayer loaded on zro2: property-activity relationship in n-butane isomerization evidenced by hydrogen adsorption and ir studies

The property-activity relationship of WO 3 supported on ZrO 2 (WZ) was evaluated in n-butane isomerization for a series of catalysts with WO 3 loading ranging from 5 to 20 wt% on ZrO 2. The catalysts were prepared by incipient-wetness impregnation of Zr(OH) 4 with an aqueous solution of (NH 4) 6[H 2W 12O 40·nH 2O], followed by drying and calcination at 1093 K. The introduction of WO 3 continuously increased the tetragonal phase of ZrO 2, WO 3 surface density and coverage. The specific surface area and total pore volume passed through a maximum of WO 3 loading at 13 wt%; this loading corresponds to 5.9 WO 3/nm 2 and is near the theoretical monolayer-dispersed limit of WO 3 on ZrO 2. The IR results indicate that the presence of WO 3 eroded the absorbance bands at 3738 and 3650 cm -1 corresponding to bibridged and tribridged hydroxyl groups up to near the monolayer-dispersed limit of WO 3. A new broad and weak band appeared, centered at 2930 cm -1, indicating the presence of bulk crystalline WO 3 for WO 3 coverage exceeding the theoretical monolayer-dispersion limit. In addition to the band at 2930 cm -1, two WO stretching bands were observed at about 1021 and 1014 cm -1 for all WZ catalysts, confirming the existence of WO connected to coordinative unsaturated (cus) Zr 4+ through O and to the other W through O, respectively. Pyridine adsorbed IR and NH 3-TPD revealed that the presence of WO 3 modified the nature and concentration of acidic sites. The highest acidity was observed with 13 wt% loading WO 3. The decrease in the intensity of peaks due to increasing WO 3 loading was much higher on Lewis acid sites than on Bronsted acid sites. Hydrogen adsorption isotherms and the IR results for hydrogen adsorption on preadsorbed pyridine were used to evaluate the formation of active protonic acid sites from molecular hydrogen. The catalyst with 13 wt% WO 3 loading showed the maximum hydrogen uptake capacity and formation of protonic acid sites. These results show a direct correlation with the activity of WZ in n-butane isomerization at 573 K in which 13 wt% WO 3 loading on ZrO 2 yielded the highest amount of isobutane. It is suggested that the presence of strong Lewis acid sites on monolayer-dispersed WO 3 facilitates the formation of protonic acid sites from hydrogen in the gas phase which act as active sites in n-butane isomerization. The presence of permanent Bronsted acid sites could not be directly associated with activity. In fact, no isomerization activity was observed in the absence of hydroge

IR study of active sites for n-heptane isomerization over MoO 3-ZrO2

The property of acidic sites on MoO3-ZrO2 was studied for n-heptane isomerization. A 2,6-lutidine IR study showed that the introduction of MoO3 on ZrO2 partially eliminated the absorbance band at 1605 cm-1 ascribed to Lewis acid sites corresponding to the presence of the monoclinic phase of ZrO2 and developed several Brönsted and Lewis acid sites with different acidic strengths. MoO3-ZrO2 possesses a large number of relatively weak Lewis and Brönsted acid sites as well as strong acid sites. The active protonic acid sites in n-heptane isomerization were formed from molecular hydrogen through a spillover mechanism with the involvement of doublet bands at 1595 and 1580 cm-1 ascribed to the Lewis acid sites corresponding to the presence of the tetragonal phase of ZrO2. No catalytic activity of MoO3-ZrO2 for n-heptane isomerization was observed in the absence of the doublet bands at 1595 and 1580 cm-1 and hydrogen in the gas phase