Nanoscience & Nanotechnology-Asia - Volume 12, Issue 2, 2022

Graphitic carbon nitride (g-C3N4) is an important photocatalytic material that is receiving a lot of research attention globally due to its favourable thermal and chemical stability as well as electronic band structure. However, the photocatalytic performance of the bulk g-C3N4 is limited by fast recombination of electron-hole pair and poor visible light-harvesting ability. Thus, different strategies, such as heterostructuring, nanotuning, doping, etc., have been adopted to overcome the aforementioned challenges to enhance the photocatalytic performance of g-C3N4. In recent times, various nanostructured g-C3N4 photocatalytic materials with various tuned morphologies have been designed and fabricated in literature for different photocatalytic activities. This mini-review summarized the progress development of nanostructured g-C3N4 photocatalysts with various tuned morphologies for solar fuel generation. This article briefly highlights the research status of various g-C3N4 with tuned morphologies and enhanced solar fuel generation abilities. Finally, a conclusion and future research were also suggested, opening up new areas on g- C3N4 photocatalysis.

Polymer-based nanofibril finds its application in various fields including tissue engineering, environmental monitoring, food packaging, and micro/nanoelectromechanical systems. These nanofibrils are subjected to chemical treatment and constant stress, which may cause permanent deformation to the fibrils when it is used. Therefore, the synthesis of well-defined nanofibrils and characterization techniques are key elements in identifying desired chemical and physical properties for suitable applications. Many methods have been developed to prepare individual nanofibrils, including electrospinning, phase separation, template synthesis, and self-assembly. Among all, self-assembly offers simple, efficient, and lowcost strategies that produce high-ordered nanofibrils using noncovalent interactions including hydrogen bonding, electrostatic interactions, π-π interactions, and hydrophobic interactions. The first part of the review provides detailed molecular interactions and simulations that can be controlled to achieve the formation of well-defined individual nanofibrils. The second part of the review describes the various existing tools to characterize the chemical and physical properties of single nanofibrils including atomic force microscopy. In the final part of the review, recently developed novel nanotools that measure the mechanical properties of nanofibrils are described. By bridging the gap between molecular interactions and resulting nanoscale fibirls, physical and chemical properties may lead to the construction of novel nanomaterials in the area of nanoscience and nanotechnology.

Layered silicates (nanoclay) are new types of nanomaterials derived from clay minerals with a wide range of applications in different fields such as catalysts, soil industry, etc. Nanoclays are wide ranges of naturally occurring inorganic minerals with different derivatives. Montmorillonite is a wellknown nanoclay consisting of a 2:1 layered structure with two-silica tetrahedron sandwiching an alumina octahedron. In nature, nanoclays can be found in both crystalline (phyllosilicates) and non-crystalline (imogolite) forms. Nanoclays incorporated into polymer matrices have demonstrated a significant capability to improve the tensile and barrier properties of soil. Nanoclays play a vital role in enhancing soil quality due to their high surface area and porous structure. On the other hand, due to the positive charge of sand grains and the chemical compositions of clay particles, the negatively charged clay particles help create a good condition to improve soil properties. According to the best of our knowledge, there is no review paper to study the role of nanoclays on soil samples. This review paper describes the role of nanoclay compounds in the improved properties of soil samples and introduces different types of modified nanoclay used in soil samples. Reported results showed that nanoclays with complex structures are useful nanomaterials for improving the quality of soil samples.

Background: Broth microdilution is the only available microscale endpoint technique used to evaluate the antimicrobial potency of nanostructures. In the case of unstable nanostructures or at high concentrations of nanostructures, this technique is not applicable due to aggregation and sedimentation issues. Most nanostructures can absorb visible light, and this optical feature can interfere with the OD600 measurement that is commonly employed for the evaluation of microbial cells growth. The demand for high-tech plate readers is another limitation of the broth microdilution procedure. Agar microdilution can be a promising novel procedure to overcome all these technical difficulties. Objective: In the current experiment, the agar microdilution procedure was developed and introduced to be employed for the evaluation of antimicrobial potency of colloidally unstable nanostructures even at extremely high concentrations. Methods: Thymus daenensis herbal nanoparticles (HrbNPs) were fabricated through a top-down approach and were tested against Methicillin-Resistant Staphylococcus Aureus (MRSA). Also, the particles were fortified with povidone-iodine and peracetic acid as potent antimicrobial compounds to achieve the enhanced antimicrobial activity. Results: Viscose molten agar media prevented the particles from sedimentation during 96-well plate preparation. By agar solidification, the nanoparticles were immobilized in the media, and no aggregation or sedimentation could occur. After incubation, the bacterial growth was recognizable in the well as a thin creamy layer. The MIC of HrbNPs against MRSA was found to be 20 mg/ml. Fortification with povidone- iodine had no impact on the antimicrobial potency of HrbNPs. However, fortification of HrbNPs with peracetic acid resulted in a four-fold increase in the antimicrobial potency of nanoparticles, and MIC was reduced to 5 mg/mL. Conclusion: Results indicated that agar microdilution can be a promising procedure for the antimicrobial susceptibility test of nanostructures at extremely high concentrations. Also, colloidally unstable nanostructures can be tested via this procedure without any concern for possible aggregation and sedimentation. On the other hand, it was found that fortification with antimicrobial compounds can be an effective approach to increasing the antimicrobial potency of HrbNPs against superbugs.

Background: This study investigates an unsteady, two-dimensional, incompressible viscous boundary layer flow of an electrically conducting nanofluid past parallel plates. The plates are permeable to allow both suction and injection to take place. It is assumed that viscosity, thermal conductivity and mass diffusivity of the nanofluid vary with temperature. The novelty of this study is in consideration of the combined effects of chemical reaction, permeability, externally applied magnetic field, and momentum diffusivity on the flow varibles. The magnetic field force is significant because it provides information regarding the boundary layer characteristics. Methods: The highly nonlinear partial differential equations are solved numerically using the newly developed Bivariate Spectral Quasilinearization Method (BSQLM) along with varying thermal and concentration boundary conditions. The BSQLM method is an innovative technique that is more reliable and robust as it demands fewer grid points and has a global approach to solving PDEs. Results: An analysis and comparison of results with existing literature are reported. Excellent agreement has been found between our results and those previously published. Among the findings, we show, inter alia, a significant increase in the profiles for fluid velocity, temperature and concentration with an increase in the chemical reaction, applied magnetic field, and thermal radiation. The BSQLM converges fast and is computationally efficient when applied to boundary layer problems that are defined on a large computational domain. Conclusion: A numerical study on nanofluid flow between parallel porous plates has been carried out, and here are the key findings: 1. Heat flux is directly related to thermal radiation, the applied magnetic field, permeability, and the chemical reaction involved. 2. Mass flux increases with increased chemical reaction, permeability, and the magnetic parameters. 3. The nanofluid concentration is directly related to the Prandtl and magnetic numbers and inversely related to the Reynolds number and chemical reaction. 4. The skin-friction coefficient reduces with higher values of magnetic field and permeability parameters and increases with an increment in thermal radiation and chemical reaction. 5. The BSQLM has a high convergence rate with high accuracy.

Objective: This study aimed to design and statistically optimize the potential of intranasallydelivered chitosan-wrapped linagliptin nanosuspension as an alternative approach for brain targeting for enhancing cognitive behaviour, increasing its solubility/permeability characteristics, and reducing the side effects. Methods: Linagliptin nanosuspensions were prepared by the nanoprecipitation method. We investigated the effects of independent variables, i.e., linagliptin concentration (D) and chitosan concentration (P), on the dependent factors like % drug loading (R1), % entrapment efficiency (R2), and % drug release (R3) via a central composite design. Furthermore, the optimized formulation was evaluated for surface morphology/ size, ex-vivo permeation study, in-vitro release study, and stability study. Results: The optimized formulation was further evaluated by different evaluation parameters such as FESEM and TEM study of the optimized formulation (LS 1) showed spherical morphology. Mean particle size (250.7 nm), charge (-16.3 mV), % entrapment efficiency (95.8 ± 1.45 %), and % drug loading (35.78 ± 0.19 %) were determined. Saturation solubility (0.987 mg/ml), in vitro dissolution rate (89.65 ± 0.82 %), and ex vivo permeation (82.23 ± 1.25 %) of LS 1 were higher than pure linagliptin. Conclusion: Response surface methodology was applied successfully to obtain LS 1 as an optimized formulation with enhanced solubility and dissolution characteristics at minimized dose, alleviating side effects and with improvised cognitive effects. Thus, an efficient intranasal delivery platform of linagliptin based on nanosuspension was designed for bypassing the BBB and delivering therapeutics directly to the brain. This can be a futuristic approach for enhancing cognitive effects by linagliptin nanosuspension via the intranasal route.

Background: Green synthesis of nanoparticles has emerged as an interesting and expanding research area due to environmental friendliness, non-toxicity, cleanliness, and cost-effectiveness. Moreover, it can be performed at room pressure and temperature. Blumea lacera is described as a valuable medicinal plant in many vital systems of medicines. The study explored the eco-friendly green synthesis of MnO2 NPs using Blumea lacera leaf extract. Methods: Reduction of potassium permanganate (KMnO4) using Blumea lacera leaf extract was carried out at room temperature. The crude extract of Blumea lacera was added to metal ion reagents of specific volume and specific concentration at ambient temperature and stirred continuously using a magnetic stirrer. The aqueous leaf extract reduced and stabilized the KMnO4 into MnO2 NPs. The MnO2 NPs obtained from the solution were purified and separated by repeated centrifugation using Remi cooling centrifuge model C-24. Results: The biosynthesized MnO2 NPs characterized by UV-Vis spectroscopy showed an absorption peak at 400 nm. The XRD studies revealed the spherical shape of MnO2 NPs with an average particle diameter of 20 nm. FT-IR analysis confirmed the presence of functional groups -OH, C=O, C=C, and CH triggering the synthesis of MnO2 NPs. Vibrational mode at around 606.62 and 438.81 cm⁻¹ supports the occurrence of the O-Mn-O bond. Conclusion: The synthesized MnO2 NPs were found to be good antibacterial and antifungal agents against bacterial strains Staphylococcus aureus, B. subtilis, Pseudomonas aeruginosa, E. coli, and fungal strains C. albicans, Aspergillus niger, and Sclerotium rolfsii.

A vast number of methods have been applied to water-insoluble pharmaceuticals to improve their solubility. Nanoparticle production of pharmaceuticals is considered as one of the high-speed ways to improve solubility. Objective: Supercritical CO2 was applied to extract Zingiber officinale Roscoe rhizome pharmaceutical. Then, a modified RESS (Rapid Expansion of Supercritical Solution) method, called ESS (Expansion of Supercritical Solution), was exerted to obtain NPs (nanoparticles) of the extracted pharmaceuticals. Methods: Initially, applying high pressure in supercritical CO2 contributed to the extract dissolution such that supercritical CO2 was saturated with the sample. Then, by decreasing the pressure, an expansion occurred in the saturated medium. This expansion reduced the power of supercritical CO2 solvent and induced the sample nanoparticle nucleation in the needle valve. Results: LC-MS (Liquid Chromatography-Mass Spectrometry) and EDX (Energy Dispersive X-ray Spectroscopy) result provided solid evidence for the presence of anti-cancer pharmaceutical, [6]-Gingerol, in the extract. The medium size of the nanoparticles in FESEM (Field Emission Scanning Electron Microscopy) analysis was 36 nm. The most satisfactory parameters for a 2 mg mL^-1 feeding solution were the initial pressure of 350 atm, secondary pressure of 160 atm, equilibrating time of 10 min, precipitating time of 20 min, and temperature of 48 °C. Conclusion: Unlike rapid expansion of supercritical solution methodology, in this technique, the initial and secondary pressures were permanently above the critical pressure to provide a gentle expansion, which contributes to the production of uniform and small particles. The obtained uniform NPs had a narrow size distribution. Consequently, ESS technique can be considered as an efficient technique for improving the solubility of hydrophobic pharmaceuticals, such as [6]-gingerol.