The interaction of simple and ternary Cu(II) complexes of 1,10-phenanthrolines with DNA has been studied extensively because of their various interesting and important functions such as DNA cleavage activity, cytotoxicity towards cancer cells, and DNA based asymmetric catalysis. Such functions are closely related to the DNA binding modes of the complexes such as intercalation, groove binding, and electrostatic surface binding. A variety of spectroscopic methods have been used to study the DNA binding mode of the Cu(II) complexes. Of all these methods, DNA-fiber electron paramagnetic resonance (EPR) spectroscopy affords unique information on the DNA binding structures of the complexes. In this review we summarize the results of our DNA-fiber EPR studies on the DNA binding structure of the complexes and discuss them together with the data accumulated by using other measurements.
Visible light driven C-doped mesoporous TiO2 (C-MTiO2) nanorods have been successfully synthesized through green, low cost, and facile approach by sol-gel bio-templating method using regenerated cellulose membrane (RCM) as nanoreactor. In this study, RCM was also responsible to provide in-situ carbon sources for resultant C-MTiO2 nanorods in acidified sol at low temperatures. The composition, crystallinity, surface area, morphological structure, and optical properties of C-MTiO2 nanorods, respectively, had been characterized using FTIR, XRD, N2 adsorption/desorption, TEM, UV-vis-NIR, and XPS spectroscopy. The results suggested that the growth of C-MTiO2 nanorods was promoted by the strong interaction between the hydroxyl groups of RCMs and titanium ion. Optical and XPS analysis confirmed that carbon presence in TiO2 nanorods were responsible for band-gap narrowing, which improved the visible light absorption capability. Photocatalytic activity measurements exhibited the capability of C-MTiO2 nanorods in degradation of methyl orange in aqueous solution, with 96.6% degradation percentage under visible light irradiation.
A highly active and stable nano structured Pt/Mg1-xNixO catalysts was developed by a simple co-precipitation method. The obtained Pt/Mg1-xNixO catalyst exhibited cubic structure nanocatalyst with a size of 50-80 nm and realized CH4 and CO2 conversions as high as 98% at 900°C with excellent stability in the dry reforming of methane. The characterization of catalyst was performed using various kinds of analytical techniques including XRD, BET, XRF, TPR-H2, TGA, TEM, FESEM, FT-IR, and XPS analyses. Characterization of spent catalyst further confirms that Pt/Mg1-xNixO catalyst has high coke-resistance for dry reforming. Thus, the catalyst demonstrated in this study, offers a promising catalyst for resolving the dilemma between dispersion and reducibility of supported metal, as well as activity and stability during high temperature reactions.
Steam and air gasification with 5 wt% Ni/Al2O3 eggshell (Ni-EG) and homo (Ni-H) catalysts were performed for the first time to produce biohydrogen from food waste. The steam gasification produced comparably higher gas yield than air gasification. In non-catalytic experiments, steam gasification generated a higher volume percent of H2, whereas more CO, CO2, CH4, and C2-C4 were produced in air gasification. Ni-EG demonstrated higher potential to obtain H2-rich gases with a low C2-C4 content compared to that obtained by Ni-H, particularly in steam gasification at 800 °C, which produced gaseous products with 59.48 vol% H2. The long-term activity of both catalysts in steam gasification was evaluated, and Ni-EG exhibited higher stability than Ni-H. The ideal distribution of Ni species on the outer region of γ-Al2O3 pellets in Ni-EG resulted in higher activity, stability, and selectivity than Ni-H in both steam and air gasification.
Within a small, interconnected reaction network, orthogonal recognition processes drive the assembly and replication of a [2]rotaxane. Rotaxane formation is governed by a central, hydrogen-bonding-mediated binding equilibrium between a macrocycle and a linear component, which associate to give a reactive pseudorotaxane. Both the pseudorotaxane and the linear component undergo irreversible, recognition-mediated 1,3-dipolar cycloaddition reactions with a stoppering maleimide group, forming rotaxane and thread, respectively. As a result of these orthogonal recognition-mediated processes, the rotaxane and thread can act as auto-catalytic templates for their own formation and also operate as cross-catalytic templates for each other. However, the interplay between the recognition and reaction processes in this reaction network results in the formation of undesirable pseudorotaxane complexes, causing thread formation to exceed rotaxane formation in the current experimental system. Nevertheless, in the absence of competitive macrocycle-binding sites, realization of a replicating network favoring formation of rotaxane is possible.
A γ-NA5 catalyst in the form of pellet was first to be reported and was pioneering in gasification to accelerate the production of syngas through biomass (palm empty fruit brunch) conversion. The synthesised γ-NA5 pellet possesses a high surface area of 212.32 m2 g-1, which renders more active sites for hydrocarbon cracking, subsequently leading to high H2 production (0.0716 m3 kg-1). Additionally, the pellet exhibits remarkable reversibility and reusability with 91% H2 production efficiency being retained after five consecutive gasification cycles. Distinctively, the feature of the synthesised γ-NA5 pellet from the conventional powder-like catalyst is that it eases the separation of the used catalyst from the biomass ash, and subsequently facilitates regeneration solely by calcination process. The loading of 20 wt.% optimised amount of catalyst itself has successfully shorten the completion of gasification process up to 135 min, which is highly feasible for a large scale industrial usage after considering the cost of the catalyst, facile preparation method, and catalyst's effectiveness towards gasification.
The K2NiF6 catalytic effect on the NaAlH4 dehydrogenation properties was studied in this work. The desorption temperature was studied using temperature-programmed desorption and exhibited a lower onset hydrogen release after doped with different wt % of K2NiF6 (5, 10, 15 and 20 wt %). It was found that the NaAlH4 doped with 5 wt % K2NiF6 showed the optimal value that can reduce the onset desorption temperature of about 160 °C compared to 190 °C for the milled NaAlH4. The NaAlH4 + 5 wt % K2NiF6 sample showed faster desorption kinetics where 1.5 wt % of hydrogen was released in 30 min at 150 °C. In contrast, the milled NaAlH4 only released about 0.2 wt % within the same time and temperature. From the Kissinger analysis, the apparent activation energy was 114.7 kJ/mol for the milled NaAlH4 and 89.9 kJ/mol for the NaAlH4-doped 5 wt % K2NiF6, indicating that the addition of K2NiF6 reduced the activation energy for hydrogen desorption of NaAlH4. It is deduced that the new phases of AlNi, NaF, and KH that were formed in situ during the dehydrogenation process are the key factors for the improvement of dehydrogenation properties of NaAlH4.
This study investigated the catalytic co-pyrolysis of sugarcane bagasse (SCB) and waste high-density polyethylene (HDPE) over faujasite-type zeolite derived from electric arc furnace slag (FAU-EAFS) in a fixed-bed reactor. The effects of reaction temperature, catalyst-to-feedstock ratio, and HDPE-to-SCB ratio on product fractional yields and chemical compositions were discussed. The co-pyrolysis of SCB and HDPE over FAU-EAFS increased the liquid yield and enhanced the quality of bio-oil. The maximum bio-oil (68.56 wt%) and hydrocarbon yield (74.55%) with minimum yield of oxygenated compounds (acid = 0.57% and ester = 0.67%) were achieved under the optimum experimental conditions of catalyst-to-feedstock ratio of 1:6, HDPE-to-SCB ratio of 40:60, and temperature of 500 °C. The oil produced by catalytic co-pyrolysis had higher calorific value than the oil produced by the pyrolysis of SCB alone.
The combination of exceptional functionalities offered by 3D graphene-based macrostructures (GBMs) has attracted tremendous interest. 2D graphene nanosheets have a high chemical stability, high surface area and customizable porosity, which was extensively researched for a variety of applications including CO2 adsorption, water treatment, batteries, sensors, catalysis, etc. Recently, 3D GBMs have been successfully achieved through few approaches, including direct and non-direct self-assembly methods. In this review, the possible routes used to prepare both 2D graphene and interconnected 3D GBMs are described and analyzed regarding the involved chemistry of each 2D/3D graphene system. Improvement of the accessible surface of 3D GBMs where the interface exchanges are occurring is of great importance. A better control of the chemical mechanisms involved in the self-assembly mechanism itself at the nanometer scale is certainly the key for a future research breakthrough regarding 3D GBMs.
Indoles are amongst the most important class of heteroaromatics in organic chemistry, being commonly found in biologically active natural products and therapeutically useful compounds. The synthesis of indoles is therefore important and several methods for their synthesis that make use of silver(I) catalysts and reagents have been developed in recent years. This Focus Review contains, to the best of our knowledge, a comprehensive coverage of silver-mediated indole forming reactions since the first reaction of this type was reported in 2004.
Non-edible bio-oil derived from lignocellulosic biomass could be used as environmentally friendly lubricant-ester base stock for maritime and road-type transportations. However, the use of crude bio-oil with highly oxygenated compounds required further upgrading to yield ester that mimicked the characteristics of Group V base oil (polyolesters). In this study, bio-oil based polyolesters was produced via esterification using green biopolymer alginate acid catalyst (Al-Alg). The bio-oil compounds used were acetic acid (AcA), propionic acid (PrA) and levulinic acid (LA), while polyols such as neopentyl glycol (NPG), trimethylolpropane (TMP) and pentaerythritol (PE) were used. Optimization studies revealed that NPG-PrA ester gave the best ester purity of 100%, with 95% of diester selectivity under optimum conditions of 15 wt% Al-Alg, 8 h, 6:1 PrA:NPG and 140 °C. The produced polyolesters showed potential lube characteristics with viscosity index of 76, kinematic viscosity of 2.3 mm2 s-1 at 40 °C and oxidative induction time of 15 min at 100 °C. Furthermore, a reusability study of the Al-Alg catalyst indicated high NPG-PrA diester selectivity (above 90%) for 8 consecutive cycles. The physico-chemical properties of spent Al-Alg catalyst were also discussed.
Carbon monoxide (CO) is the most harmful pollutant in the air, causing environmental issues and adversely affecting humans and the vegetation and then raises global warming indirectly. CO oxidation is one of the most effective methods of reducing CO by converting it into carbon dioxide (CO2) using a suitable catalytic system, due to its simplicity and great value for pollution control. The CO oxidation reaction has been widely studied in various applications, including proton-exchange membrane fuel cell technology and catalytic converters. CO oxidation has also been of great academic interest over the last few decades as a model reaction. Many review studies have been produced on catalysts development for CO oxidation, emphasizing noble metal catalysts, the configuration of catalysts, process parameter influence, and the deactivation of catalysts. Nevertheless, there is still some gap in a state of the art knowledge devoted exclusively to synergistic interactions between catalytic activity and physicochemical properties. In an effort to fill this gap, this analysis updates and clarifies innovations for various latest developed catalytic CO oxidation systems with contemporary evaluation and the synergistic relationship between oxygen vacancies, strong metal-support interaction, particle size, metal dispersion, chemical composition acidity/basicity, reducibility, porosity, and surface area. This review study is useful for environmentalists, scientists, and experts working on mitigating the harmful effects of CO on both academic and commercial levels in the research and development sectors.
We report the use of a new precursor as active agents to promote the growth of carbon nanotubes (CNT) in methane ambient using a simple thermal chemical vapour deposition method. The agents consist of ammonia and methanol mixed at different ratios and was found to enhance the growth of CNTs. The optimum methanol to ammonia ratio was found to be 8 to 5, whereby longer and denser CNTs were produced compared to other ratios. The result was found otherwise when the experiment was done solely in methane ambient. In addition, CNT growth on substrates coated with double layer Ni catalyst was improved in terms of quality and density compared to a single coated substrates. This finding is supported by Raman spectrometry analysis.
The utilization of carbon dioxide for the production of valuable chemicals via catalysts is one of the efficient ways to mitigate the greenhouse gases in the atmosphere. It is known that the carbon dioxide conversion and product yields are still low even if the reaction is operated at high pressure and temperature. The carbon dioxide utilization and conversion provides many challenges in exploring new concepts and opportunities for development of unique catalysts for the purpose of activating the carbon dioxide molecules. In this paper, the role of carbon-based nanocatalysts in the hydrogenation of carbon dioxide and direct synthesis of dimethyl carbonate from carbon dioxide and methanol are reviewed. The current catalytic results obtained with different carbon-based nanocatalysts systems are presented and how these materials contribute to the carbon dioxide conversion is explained. In addition, different strategies and preparation methods of nanometallic catalysts on various carbon supports are described to optimize the dispersion of metal nanoparticles and catalytic activity.
Finding a proper transition structure for the peptide bond formation process can lead to a better understanding of the role of the ribosome in catalyzing this reaction. A potential energy surface scan was performed on the ester bond dissociation of the P-site aminoacyl-tRNA and the peptide bond formation of P-site and A-site amino acids. The full fragment of initiator tRNAi met attached to both cognate (met) and non-cognate (ala) amino acids as the P-site substrate and the methionine as the A-site amino acid was used in this study. Due to the large size of tRNA, ONIOM calculations were used to reduce the computational cost. This study illustrated that the rate of peptide bond formation was reduced for misacylated tRNA without the presence of ribosomal bases. This demonstrated that there were indeed specific structural interactions involving the amino acid side chain within the tRNAi met.
In this study, we have employed a photocatalytic method to restore the liquid effluent from a palm oil mill in Malaysia. Specifically, the performance of both TiO2 and ZnO was compared for the photocatalytic polishing of palm oil mill effluent (POME). The ZnO photocatalyst has irregular shape, bigger in particle size but smaller BET specific surface area (9.71 m2/g) compared to the spherical TiO2 photocatalysts (11.34 m2/g). Both scavenging study and post-reaction FTIR analysis suggest that the degradation of organic pollutant in the TiO2 system has occurred in the bulk solution. In contrast, it is necessary for organic pollutant to adsorb onto the surface of ZnO photocatalyst, before the degradation took place. In addition, the reactivity of both photocatalysts differed in terms of mechanisms, photocatalyst loading and also the density of photocatalysts. From the stability test, TiO2 was found to offer higher stability, as no significant deterioration in activity was observed after three consecutive cycles. On the other hand, ZnO lost around 30% of its activity after the 1st-cycle of photoreaction. The pH studies showed that acidic environment did not improve the photocatalytic degradation of the POME, whilst in the basic environment, the reaction media became cloudy. In addition, longevity study also showed that the TiO2 was a better photocatalyst compared to the ZnO (74.12%), with more than 80.0% organic removal after 22 h of UV irradiation.
Organically (octyl amine, OA) surface modified electrocatalyst (OA-Pt/CB) was studied for its oxygen reduction reaction (ORR) activity via dc methods and its charge and mass transfer properties were studied via electrochemical impedance spectroscopy (EIS). Comparison with a commercial catalyst (TEC10V30E) with similar Pt content was also carried out. In EIS, both the catalysts showed a single time-constant with an emerging high-frequency semicircle of very small diameter which was fitted using suitable equivalent circuits. The organically modified catalyst showed lower charge-transfer resistance and hence, low polarization resistance in high potential region as compared to the commercial catalyst. The dominance of kinetic processes was observed at 0.925-1.000 V, whereas domination of diffusion based processes was observed at lower potential region for the organic catalyst. No effect due to the presence of carbon was observed in the EIS spectra. Using the hydrodynamic method, higher current penetration depth was obtained for the organically modified catalyst at 1600 rpm. Exchange current density and Tafel slopes for both the electrocatalysts were calculated from the polarization resistance obtained from EIS which was in correlation with the results obtained from dc methods.
Many studies have been done on various species of insects to investigate their potential use in industries. This is because insects have high protein content which could be further manipulated. Due to its eating habit, Zophobas morio larvae, also known as super mealworm has been shown to have high amylase activity. In this study, amylase from super mealworm has been immobilized via Cross-Linked Enzyme Aggregates (CLEA) technique and its kinetic performance, evaluated. CLEA is one of the best immobilization method with respect to enzyme stability and reusability. Kinetic performance of both free and CLEA-amylase were evaluated based on the Michaelis-Menten model. Results obtained based on Hanes-Woolf, LineweaverBurk, Eadie-Hofstee and Hyperbolic Regression plots showed that the kinetic parameters, Vmax and KM, changed upon immobilization. For CLEA-amylase, Hanes-Woolf plot showed the bestfitted model based on R2 with Vmax= 1.068 mM/min and KM= 0.182 mM, however, LineweaverBurk plot was used to obtain the kinetic parameters for free amylase, with Vmax and KM of 17.230 mM/min and 2.470 mM, respectively. Thus it is observed that upon immobilization, Vmax for amylase dropped appreciably, however, much lower substrate concentration is needed to saturate the enzymatic sites to reach its maximum catalytic efficiency. The result from this study might open the new path in discovering the potential use of insects in industrial applications, for example, making use of the recovered enzymes in the detergent industry.
Silicon dioxide (SiO2) has been extensively studied due to their unique properties that make it desirable for many applications ranging from electronic, catalysis, pigment as well as sensors. Multitude of methods and processes are established with the ability to manipulate and control the key properties that can cater for specific applications. Stober method is a very simple and easy for up-scale production of SiO2. This paper presents the experimental study on the effect of synthesis parameter on the morphology of SiO2 synthesized via Stober method. Three parameters were investigated such as concentration of catalyst, concentration of precursor and percentage of water content. The obtained samples were characterized using scanning electron microscopy (SEM) analysis. The findings showed that the size of particles produced is dependent on the synthesis parameter. In this study, particles size ranging from 50 nm to >100 nm are easily produced. The sphere size of SiO2 can be increased by increasing the concentration of ammonia hydroxide catalyst, the concentration of TEOS, as well as the percentage of water content.
The simulation of the catalytic converter system is quite needed in order to characterize the catalyst and also
optimizing the monolithic design for the gas emission in the catalytic converter and other related mechanism. The
objective of this study is to obtain quantitative description of the gas emission in the catalytic converter system of
natural powered automobile exhaust gas using ANSYS Software. This work will present a finite element calculation
to predict and evaluate the mass transfer, energy balance and velocity of gas emission in the catalytic converter. The
expected result for this research is to evaluate data of the gas emission obtained from the software to be compared with
the manual experiment in order to verify the effectiveness of modified catalytic converter.