Aflatoxins’ Clean-Up in Food Samples by Graphene Oxide–Polyvinyl Poly Pyrrolidone—Hollow Fiber Solid-Phase Microextraction

Aflatoxins in the rice production chain: A review on prevalence, detection, and decontamination strategies

Rice (Oryza sativa L.) is one of the most consumed cereals that along with several important nutritional constituents typically provide more than 21% of the caloric requirements of human beings. Aflatoxins (AFs) are toxic secondary metabolites of several Aspergillus species that are prevalent in cereals, including rice. This review provides a comprehensive overview on production factors, prevalence, regulations, detection methods, and decontamination strategies for AFs in the rice production chain. The prevalence of AFs in rice is more prominent in African and Asian than in European countries. Developed nations have more stringent regulations for AFs in rice than in the developing world. The contamination level of AFs in the rice varied at different stages of rice production chain and is affected by production practices, environmental conditions comprising temperature, humidity, moisture, and water activity as well as milling operations such as de-husking, parboiling, and polishing. A range of methods including chromatographic techniques, immunochemical methods, and spectrophotometric methods have been developed, and used for monitoring AFs in rice. Chromatographic methods are the most used methods of AFs detection followed by immunochemical techniques. AFs decontamination strategies adopted worldwide involve various physical, chemical, and biological strategies, and even using plant materials. In conclusion, adopting good agricultural practices, implementing efficient AFs detection methods, and developing innovative aflatoxin decontamination strategies are imperative to ensure the safety and quality of rice for consumers.

Optimization and synthesis of a novel sorbent composite based on magnetic chitosan-amine-functionalized bimetallic MOF for the simultaneous dispersive solid-phase microextraction of four aflatoxins in real water, herbal distillate, and food samples

Aflatoxins (AFs), an important category of pollutants, are formed in many foods and adversely affect human health. Therefore, their determination is critical to ensuring human food health. An efficient dispersive solid-phase microextraction technique was developed as a simple and straightforward sample preparation technique for determination of four aflatoxins using a high-performance liquid chromatography (HPLC) fluorescence detector. A novel efficient, green sorbent for extracting AFs was synthesized based on hydrothermal and chemical strategies. The amounts of three sorbent components were optimized using a mixture design (simplex lattice design), including 14 experiments. The optimal amount of amino-bimetallic Fe/Ni-MIL-53 nanospheres, chitosan, and magnetic Fe3O4 nanoparticles as sorbent components was 0.87, 0.67, and 0.47 g, respectively. Also, various factors affecting the process of AF determination were studied and optimized in two successive experimental designs, including the definitive screening design and the Box-Behnken design. Under optimal conditions, the linear ranges for measuring aflatoxin B1, aflatoxin B2, aflatoxin G1, and aflatoxin G2 were 0.05-82.6, 0.07-86.4, 0.08-85.7, and 0.07-89.5 ng mL-1, respectively. The relative standard deviations under inter-day and intra-day conditions for measuring AFs at three analyte concentrations were determined in triplicate analysis and were in the ranges of 3.7-4.6% and 4.9-6.1% for water sample analysis, respectively. The qualitative detection limits for determining AFs were between 0.01 and 0.05 ng mL-1. The pre-concentration factor of the method for measuring AFs ranged from 739.7 to 802.1. The proposed method was used for determining AFs in several real samples, including herbal distillate, black tea, corn, and real water samples. The relative recovery and standard deviation were 87.8-97.8% and 4.10-6.82%, respectively.

Development and Characterization of Carbon-Based Adsorbents Derived from Agricultural Wastes and Their Effectiveness in Adsorption of Heavy Metals in Waste Water

The current work focuses on peanut shells and agricultural wastes richly in many nations subjected to pyrolysis treatment at various temperatures in the range of 500–800°C to determine the feasible physiochemical characteristics of the biochar. The biochars with the high surface area were employed to adsorb Pb²⁺ (lead) ions, the heaviest pollutants in the water bodies. The raw material, biochar, and pyrolyzed biochar were characterized by SEM, FTIR, partial and elemental analysis, and BET tests. The adsorption characteristics of the biochar, pre- and postpyrolysis treatment, were studied with the assistance of batch adsorption tests under varying test conditions. Adsorbing conditions were determined by evaluating the effects of adsorbing parameters like initial concentration of the lead in water, pH of the adsorbent, contact time, and mixing speed on the effective adsorption of Pb²⁺ ions from water. Langmuir, Freundlich, and Themkin isotherm expressions were employed to study the experimental results. The adsorption kinetics study showed that the synthesized biochars were chemically stable enough to adsorb the Pb ions onto the surface.

Investigation of Mechanical and Thermal Properties on Novel Wheat Straw and PAN Fibre Hybrid Green Composites

Grewia optiva wheat straw waste fibre and PAN fibre are combined in this study to create new composite materials. The novel specimens were created in the hydraulic hind moulding machine with varying percentages of mass of wheat straw fibres, PAN fibre (2–8%) in an equivalent ratio with other materials, and Kevlar fibre-based composites (2–4%). Natural fibre-reinforced clothing is getting increasingly fashionable these days; thus, this research is important. In several papers, natural fibre has been stated to have the potential to replace synthetic fibres. Natural fibre reinforcing has also proven to be quite effective as composites. It is currently used in a range of fields, including medical fields, aerospace, and the automobile industry, among others. Synthetic fibres are used. The usage of synthetic fibres such as asbestos and Kevlar has already been linked to mesothelioma, a kind of lung cancer. Many people have died as a result of Kevlar and asbestos. As a result, an effort to replace these materials is ongoing. Fabricated material’s mechanical, chemical, physical, tribological, and thermal properties were evaluated.

Effect of Mechanical Properties on Fibre Addition of Flax and Graphene-Based Bionanocomposites

Natural fibre-based polymer nanocomposites have played an essential role in many industry domains for four to five years because of their strong mechanical and physical qualities. The primary goal of this research is to establish the mechanical and morphological properties of nanocomposite materials in natural environments. Flax fibre was employed as a reinforcement, nanographene powder was used as a filler, and epoxy resin was used as a matrix material to achieve the goals above, keeping the following restrictions in mind: (i) fibre length (15, 30 and 45 mm), (ii) fibre content (10, 15 and 20 mm), and (iii) wt.% of nanofiller (2.5, 5 and 7.5 wt.%). The composite materials were laminated using the compression moulding process per the Taguchi L9 design. The mechanical characteristics of the material, such as flexural, tensile, and impact properties, were examined according to ASTM standards. The mechanical characteristics of combinations A2, B2, and C2 are the best when compared to other combinations. The graphene-based nanocomposites revealed that 2.5 wt.% graphene contributes 33.08% of mechanical properties, the 5 wt.% graphene contributes 36.4%, and the 7.5 wt.% graphene contributes 30.53%. Including 5 wt.% graphene content provides the highest mean values of mechanical strength like 36.59 MPa tensile, 40.25 MPa flexural, and 31.68 kg/m2 of impact. Scanning electron microscopy (SEM) images of the cracked specimens were used better to understand the failure process of composites during mechanical testing.

Development of Novel Bio-mulberry-Reinforced Polyacrylonitrile (PAN) Fibre Organic Brake Friction Composite Materials

Natural fibre reinforcement is used in important sectors such as medical, aerospace, automobile, and many other fields. Many articles have reported that natural fibre has the potential to replace synthetic fibres. Natural fibre reinforcement has given good results as a brake friction material. It has already been proven that asbestos causes lung cancer and mesothelioma in brakes. Many people died from the effects of asbestos. According to the World Health Organization's trending brake report, this material leads to serious health issues. This work is going on for the replacement of these materials. Mulberry fibre is a unique material, and PAN fibre is combined with mulberry fibre and used as a brake reinforcement material to replace Kevlar fibre. The brake pads were fabricated with the various wt% of mulberry fibres and PAN fibre [3-12%] with an equal ratio and aramid fibre [3-6%] in the hydraulic hind brake moulding machine. The mechanical, chemical, physical, tribological, and thermal properties were evaluated. MF-2 [6 wt%] mulberry-PAN-fibre-based brake pad composites have shown better results for ultimate shear strength and proof stress, tensile strength, compressive strength, and impact energy.

Surface State Treatment of Carbon Dots Using Sulphur Dioxide Isotherm

Low toxicity carbon dots are combating the disadvantages of quantum dots. The carbon dots find their applications in many fields due to their versatile nature. Four different types of carbon dots are present, according to the way of manufacturing and application the type is chosen. The water-soluble characteristics of carbon dots help them be involved in biomedicine applications. The optical properties of the carbon dots find applications as drug delivery, biosensors, LED, etc. The properties like fluorescence, photoluminescence, and phosphorescence are found in the carbon dots. The carbon dots occupy the tiny spot that exhibits different optical properties on excitation. The carbon dots excitation is mainly due to surface states. The characterization of surface states is very complex. The surface states contain the core structure of carbon and oxygen functional groups on the surfaces. The anions and cations formed from functional groups on excitation will recombine themselves. The functional groups are usually carboxyl and hydroxyl groups. The Π-collaborative network of the electronic structure contains many quantization levels which help the carbon dots to produce different wavelengths adapting to different applications. Due to the interference of the structure of the carbon dots, the entire property will vary. Doping of heteroatom methods is employed to enhance the fluorescence, and photoluminescence property carried out. They used N, S, P, and B heteroatoms singly and in combination to doping carbon dots. Here, the paper proposes the sulphur dioxide adsorption technique to enhance the optical properties of the carbon dots. The proposed method shows 8.5% efficiency in relative fluorescence intensity and 8% efficiency in terms of photoluminescence intensity.

Synthesis and Characterization of TiO2-Water Nanofluids

Nanofluids made of TiO2 and multiwalled carbon nanotubes are the focus of our study. Using TiO2 and water as the basic fluids, nanofluids were created in 100 : 0, 75 : 25, and 50 : 50 proportions. Carbon nanotubes (CNTs) were disseminated into these base fluids of three types at 0.125, 0.25, and 0.5 percentages. Over the course of two months, the change of zeta potential is monitored to assess the stability of the dispersion. XRD analysis and SEM and TEM analysis are carried out for TiO2 nanofluids. Nanoparticles were analyzed using EDAX analysis to identify their composition. SEM examination was used to investigate the morphology for TiO2 nanoparticles. Particles of TiO2 produced in this manner seemed to have an average diameter of 27 nm. Nanofluids have a poor stability, which is the most important aspect of employing them, although most studies did not focus on this. When it comes to nanofluids, this study is unique in that it provides an in-depth look of surface modification approaches that have been employed by researchers to address these issues, as well as an evaluation of their stability over two months. Solubility is improved by acid treatment of CNTs, which results in functional groups on the surface of CNTs.

Reduction of 1 / f Noise in Single-Walled Carbon Nanotubes (SWCNTs) Using Gas Adsorption Technique

Single-walled carbon nanotube (SWCNT) plays a major role in electromagnetic absorption and shielding. Their applications as semiconductors make a breakthrough in communication by miniaturizing the communication devices. The main drawback of the SWCNT is found to $1/f$ noise. Because of this limitation, high attenuation at the low-frequency band cannot be achieved, limiting its application in terms of selectivity. The spectral density study shows that the noise’s amplitude is directly proportional to the temperature and inversely proportional to the number of carriers in the nanotube. The SWCNT is mainly synthesized using hydrocarbons which contains carbonaceous impurities. On the removal of impurities, more surface oxygen functional groups are formed. On the other hand, the diameter of the carbon nanotube is very small, increasing the resistance of carrier flow. In this research work, gas adsorption was used in SWCNT by treating the carbon nanotube using nitric acid. Isotherms determine porous size. The adsorbate-adsorbent interaction on carbon nanotube reduces the microporosity in the surface by treating with nitric acid. Therefore, the density of the surface increases and the CNT bundle separation will be reduced, increasing the carbon nanotube’s resistivity. This increase in resistivity reduces the excess carrier flow; therefore, the temperature will reduce the $1/f$ noise. The proposed system is cost-effective and has shown 11% improvement by reducing the noise amplitude by increasing carbon nanotube resistance. This proposed method has less complexity compared with existing models.

Adsorption of SO2 on ZnO Nanowires Using Activated Carbon by Langmuir Adsorption Isotherm

Sulphur dioxide (SO2) is one of the contaminants present in the environment. They are the by-product of combustion, industrial pollution, generation of electricity, etc. After some reactions in the atmosphere, SO2 changes its form and produces acid rain. The presence of SO2 needs to be detected to combat its effect. Many nanosensors are designed to detect the presence of SO2 in the environment. Zinc oxide (ZnO) nanowire sensor is one of those sensors used for SO2 detection. The size, structure, cost-effectiveness, and unique properties made it a choice for sensing purposes. Activated carbon is another compound that has porous substances that helps the adsorbate to settle down on the large surface area of its adsorbent surfaces. Combining the nature of ZnO nanowire and activated carbon, the adsorption of SO2 can be increased. This paper proposes a novel technique involving the activated carbon in the ZnO nanowire sensor to increase its SO2 adsorption capacity and rate. The Langmuir adsorption isotherm is used to find the adsorption efficiency between the solid adsorbent and gaseous adsorbate. MATLAB simulation was carried out for the proposed work in which it is seen that the novel method shows 33.34% efficiency in terms of SO2 adsorption capacity. The response of the proposed sensor shows 23% efficiency over time. The analysis shows that the usage of the activated carbon increases the adsorbent site for SO2 adsorbate to adsorb on the surfaces. According to the adsorption quantity, SO2 level has been obtained in the environment.