Current Nanoscience - Volume 19, Issue 2, 2023

Graphitic carbon nitride (g-C3N4) is an extraordinary semiconductor photocatalyst (PC), which transforms solar energy into chemical energy for the photodisintegration of several noxious organic contaminants into non-toxic derivatives. Polymeric g-C3N4 is a metal-free PC with high chemical stability, eco-friendly composition, and suitable energy band potential that absorb a significant portion of the solar spectrum. Despite its outstanding characteristics, g-C3N4 has some limitations, including low visible light absorption, low surface area, and rapid recoupling of charge carriers. These limitations over-shaded its proficient efficiency as a PC. The current g-C3N4 related research focuses on developing g-C3N4 nanocomposites (NCs) with high-surface-area, broad lightabsorbing, and reduced recombination via physicochemical modifications. This review highlights the latest developments in the synthesis and application of pristine g-C3N4 and its NCs with inorganic constituent and nanomaterials. A critical analysis of the strategies to enhance g-C3N4’s photocatalytic efficiency via excited charge separation and visible light absorption is also presented. Furthermore, the photocatalytic degradation of organic pollutants (OPs), including dyes, phenol, antibiotics, and pharmaceutical drugs, is summarized herewith.

Renewable-energy sources have been explored recently by scientists to fulfill the global energy demand. According to the International Energy Agency (IEA), by 2040, wind and solar power will be the star performers for energy conservation. The annual potential energy received from the sun ranges from 1,575 to 49,800 exajoules (EJ). However, this energy is not being utilized to its potential. Recently, researchers have proven that nanofluids can be used as a working fluid replacing the conventional working fluid for solar collectors and other heat exchange operations. The selection of the nanofluid is not only based on the size and shape of nanoparticles but the pH value and stability of nanofluids are also important parameters. This review paper is mainly focused on the recent trends in nanofluids applications for the capture, conservation, and utilization of solar energy. The present paper reviews the detailed analysis of various forces affecting the nanofluid system and also highlights the important aspects to reduce the frictional energy losses, exergy destruction, entropy generation, effect of the flow properties, and thermo-physical properties of the nanofluids, and other reasons for wastage of the exergy. This study also compares the performance of the direct absorption solar panel, flat plate solar panel, parabolic solar collector, photovoltaic thermal solar collector, linear Fresnel solar collector, solar dish, and evacuated type solar collector. Among these solar collectors, direct absorption solar collectors, flat plate solar collectors, photovoltaic solar collectors, and evacuated type solar collectors are more commonly used solar collectors; thus, the exergy and energy analyses of these collectors are important for their design and application. Stability issues and agglomeration problems are still some major concerns involved in the application of nanofluids. However, the use of nanofluid increases the performance of the solar collector compared to the base fluid as a working fluid. This paper also highlights the recent trends in the application of nanofluids in solar collectors.

Background: Green synthesis of nanomaterials has gained interest over the years as it has many benefits compared to conventional methods. Green methods are non-toxic and economic due to the use of aqueous extracts as reducing agents. Yerba mate is a widely used herb in South America, showing an available and economical alternative to conventional methods. Methods: Different copper and zinc nanostructures were obtained using yerba mate extract (Ilex paraguariensis) as a reducing and capping agent. Furthermore, adjusting NaCl concentration and temperature, it was possible to successfully tune and examine the morphology of the resulting nanostructures by Scanning Electron Microscopy (SEM). Phenolic oxidation was evaluated by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FT-IR) to assess the role of yerba mate extract in the reaction. Moreover, antimicrobial activity versus Pseudomonas aeruginosa was assayed, and antioxidant activity was performed by the DPPH method. Results and Conclusion: The present study reveals a powerful method to obtain zinc and copper nanostructures, showing a logarithmic reduction of Pseudomonas aeruginosa of 2.14 and 5.92 CFU/mL at 96 hours respectively and scavenger activity of 42% and 22%, respectively. These properties highlight the potential of the nanomaterials for applications in catalysis, textile, biomedical and agricultural fields.

Background: MWCNTs tend to form agglomerates in nonpolar polymers due to their small size and large surface area. A promising approach to facilitate their dispersion within the polymeric matrix is based on employing a compatibilizer agent. Objective: The current study aimed to investigate the effect of a compatibilizer agent based on maleic anhydride grafted HDPE (PE-g-MAH) on the electrical and morphological properties of highdensity polyethylene/multi-wall carbon nanotubes nanocomposites (HDPE/MWCNT/PE-g-MAH) prepared by solution mixing and hot compaction two-step approach. Methods: A two-step approach based on solvent mixing and hot compaction was used to prepare nanocomposites of HDPE/MWCNT/PE-g-MAH with different MWCNTs and PE-g-MAH contents. The electrical, morphological, and HDPE crystalline structure properties of the nanocomposites were characterized by impedance spectroscopy, high-resolution field emission scanning electron microscopy, and X-ray diffraction, respectively. Results: The results confirm the positive role of the PE-g-MAH compatibilizer in enhancing the dispersion of the MWCNTs and, in turn, the formation of more conductive pathways at low MWCNTs content in the nanocomposites. Adding 2 wt% of the compatibilizer to the nanocomposite of 1 wt% MWCNTs increases the electrical conductivity by more than three orders of magnitude. Increasing the MWCNTs concentration by more than 1 wt% leads to a limited enhancement in conductivity of the nanocomposite prepared using 2 wt% of PE-g-MAH compatibilizer. Meanwhile, the morphological characterization revealed that the limited increase in conductivity of nanocomposites with only 1 wt% compatibilizer is related to a substantial increase in the HDPE crystallinity (from 14.8 to 43.9%) induced by the enhanced nucleating effect of the dispersed MWCNTs. The excess HDPE crystalline regions suppress the formation of effective MWCNTs conducting pathways due to their confinement into smaller inter-crystallite regions in the nanocomposite. Conclusion: Therefore, a balanced role of the compatibilizer between the dispersion of the MWCNTs and the nucleation of more HDPE crystallites has to be achieved by carefully selecting the compatibilizer type and concentration.

Objective: Dry deposition velocity towards a surface is commonly investigated by modelling. However, there is still a lack of understanding about the nature of the concentration boundary layer (CBL). Methods: We aimed at acquiring an in-depth description of the particle concentration profile within the CBL by investigating the layer height and the concentration profile. The particle concentration, as a solution to the particle flux equation, is obtained and modeled numerically by performing the left Riemann sum using MATLAB software. The friction velocity u* and the particle diameter Dp are the major parameters taken into consideration when characterizing the concentration boundary layer above a surface. The particle concentration profile depends on the friction velocity; the concentration gradient starts from zero at the surface and reaches its maximum in the middle of the layer and then reaches zero again at the top of the boundary layer. Results: The concentration profile is slightly altered with a sudden increase in the concentration gradient at the surface when considering large particles or when the friction velocity has extreme values. Conclusion: The boundary layer height (y+ cbl) varied with the particle diameter, and a proper value is 100 to ensure accurate calculations for the dry deposition velocity (diameter 0.01 – 100 μm) above a smooth surface. From a numerical point of view, the numerical setup of the calculation required y+ divisions to be more than 1000 for all particle diameters included in the investigation. In addition, y+ max = 10⁴ is important for ultrafine particles (diameter smaller than 0.1 μm). Nevertheless, y+ maxdoes not need to be investigated beyond 100 when the friction velocity is below 10 cm/s.

Background & Aims: Nanobacteria are unconventional agents that are 100-fold smaller than common bacteria. It has been hypothesized that nanobacteria are responsible for kidney stone formation. This systematic review was designed to address this question related to the role of nanobacteria in the development of nephrolithiasis. Methods: Keywords related to nanobacteria and nephrolithiasis on MeSH were identified and searched in PubMed, Scopus, Google Scholar, and Web of Science until Oct 2021. The full text of identified papers was obtained and assessed based on exclusion and inclusion criteria. The reviews is based on articles that have focused on the role of nanobacteria in nephrolithiasis. Result: A total of 17 studies were identified based on the inclusion criteria; however, nine studies qualified for this systematic review. The findings of the 9 articles indicated the role of nanobacteria in nephrolithiasis. After assessing the quality of the study, 7 papers were included in this systematic study. Conclusion: Regarding the limitation of the short number of evidence to recognize how nanobacteria cause kidney stones, nevertheless it is obvious that high concentrations of nanobacteria are directly related to initiating crystal nucleation in the kidney and lead to nephrolithiasis; some variables like physiochemical factors, gender and so on could certainly affect crystallization in kidneys. Also, therapeutic decisions for these issues are limited to antibiotics. Our findings, by focusing on the impact of nanobacteria on kidneys, bring a new overview to the study of the factors related to them.

Background: A promising strategy is to apply biodegradable and biocompatibility lignin micro/nanoparticles (LMPs/LNPs) as carriers or coating materials for biological active agent delivery in agriculture medicine and pharmaceuticals. Controlled release systems (CRSs) based on LMPs/LNPs are suitable systems to target specific tissues, cells, or plant roots by taking advantage of the unique properties of LMPs/LNPs. Methods: This review discusses changes in the properties of LNPs caused by different parameters in the synthesis method, such as the type of biologically active agent, loading/release method, modification method, encapsulation efficiency, and release rate of the CRSs based on LMPs/LNPs. Results: Research shows that during the LMPs/LNPs synthesis, nanospheres with a porous surface, nanocapsules, or hollow nanospheres with excellent stability and chemical properties are produced, which causes high loading capacity and reduced release rates of active agents. Moreover, the advantages and technical challenges of lignin application as a micro/ nanocarrier were investigated. Conclusion: Finally, several suggestions for the future trend of research and development were recommended.

Background: A metal oxide semiconductor field effect transistor (MOSFET) is widely used to make integrated circuits (ICs). MOSFET devices are reaching the practical limitations for further scaling in the nanoscale regime. It motivates the researchers to explore and develop new ways to advance the electronics industry. Quantum-dot cellular automata (QCA) is a potential way to replace the MOSFET devices in the nanoscale regime. QCA nanotechnology not only solves the issue of scalability but also degrades the leakage current. It has numerous benefits, such as a highly dense design, fast speed, and energy efficiency compared to complementary metal-oxide-semiconductor (CMOS) technology. Objective: An extensive study of QCA nanotechnology is needed to quickly understand the field. Optimizing the QCA designs is the mandatory requirement to minimize the occupied cell area, latency and quantum cost. The preliminary knowledge of QCA nanotechnology boosts the idea of generating different logic functions. This review paper presents the methodology for making the fundamental logic gates using QCA nanotechnology. XOR gate is commonly used to implement popular circuits such as adders, subtractors, comparators, code converters, reversible gates etc. The various available QCA-based 2-input XOR gate designs are discussed and compared for the different performance metrics. Methods: Columbic interaction causes logical operations, and data is transferred from one cell to another cell using cell-to-cell interaction. A specific arrangement of QCA cells produces a specific logic. QCA Designer tool using a Bi-stable simulation engine is used to design different digital circuits. Results: This review paper deals with the design of the 2-input XOR gate. The considered performance metrics for the comparison purpose are cell count, occupied area, clock cycle, and quantum cost. Existing works on 2-input XOR gates show that a minimum of 8 QCA cells are needed for a 2-input XOR gate using QCA nanotechnology. A single clock cycle-based 2-input XOR gate requires at least 9 QCA cells. The quantum cost can be minimized by reducing the number of QCA cells and clock cycles. Conclusion: This review paper helps the circuit designers to select the appropriate 2-input XOR gate for the design of complex circuits. Circuit designers can use the fundamental concepts detailed in the paper to implement any Boolean function and optimize it for the existing designs. A researcher had developed a 2-input XOR gate using only 8 QCA cells with 0.50 clock cycles. Therefore, designers can start from here to further optimize the 2-input XOR gate with a single clock cycle.

Hydrogels are an integrated three-dimensional network of water-absorbing hydrophilic polymers that can support tissue regeneration and release medication under controlled conditions. Hydrogel-based structures physically resemble the extracellular matrix besides being effective for biomedical applications and tissue engineering. Hydrogels must provide relevant biological signals to control the cell behavior to become an ideal bioactive scaffold for tissue regeneration. Incorporating virus nanoparticles (VNP) that can release essential peptides into the hydrogels is a promising option to formulate a bioactive scaffold that can facilitate cell proliferation, adhesion, migration, and differentiation. Over the recent period, virologists have discovered many viruses that lead to a great understanding of the diversity of viruses in nature. Viruses affecting the plants are called plant viruses, and they have a wide variety of shapes and sizes, yet each species produces monodisperse nucleoprotein particles. Plant viruses are not capable of infecting or reproducing in humans. Therefore, VNPs are engineered from plant viruses whose genetically programmed structures can be manipulated at the gene level, bioconjugated, or encapsulated. Plant VNPs can act as clinical diagnostic agents, immunomodulators, medicines, nanoreactors, and biosensors by displaying protein molecules or epitopes, constructing inorganic hybrid materials, or carrying molecular charges. The present review focuses on the plant virusmediated nanoparticles encapsulated in bioactive hydrogels to provide an ideal platform for tissue engineering.

Background: As a new type of coating material, graphene has an important application prospect in creating hydrophobicity on the material surface. It can be seen that research on the wettability of graphene has a very actual significance in its application. Graphene membrane can change the wettability of the aluminum surface effectively. It can be combined with the traditional method to tune the wettability of the metal surface. Adding the microstructure is a very common method for changing the wettability. Therefore, the results have guided significance for the practical application of graphene in controlling the wettability of aluminum substrate with microstructure. Methods: This paper uses molecular dynamics to simulate graphene’s adsorption and wetting behavior on the aluminum substrate with microstructure and to calculate energy changes in the two processes. Results: The adsorption state of graphene is related to the aspect ratio of the microstructure. When the aspect ratios of the microstructure become larger, the graphene can be completely absorbed by the substrate, causing larger binding free energy and higher adhesion spontaneity of graphene. The wetting contact angles of the substrate with graphene are significantly higher than those of the aluminum substrate without graphene. Conclusion: The aspect ratio can influence the free energy and the binding energy, causing different states in graphene. The large aspect ratio will increase the absolute value of the free energy and release more binding energy, causing a more stable state. The graphene may prevent the deformation of the hydrogen bond and cause worse wettability. The results have been of great significance for the practical application of graphene in controlling the wettability of aluminum substrate with microstructure.

Background: Zinc oxide (ZnO) is a transparent oxide material with a theoretical bandgap of 3.4 eV, which finds potential applications, including transistors, varistors, solar cells, and other solar applications. The properties of ZnO can be manipulated by controlling its morphology. Methods: The orientation and well-defined nanostructures can be obtained by controlling the growth rates of various ZnO facets by utilizing appropriate capping agents. Here, we report the electrodeposition of ZnO nanostructured thin films in the presence of various capping agents to obtain different ZnO morphologies. The electrodeposition of ZnO nanostructures was carried out on an indium doped tin oxide (ITO) with a glass substrate by using a zinc nitrate (Zn (NO3)2) bath at 70 °C and an applied potential of -1.0 V. To this zinc nitrate bath, capping agents like ammonium fluoride (NH4F) or ethylenediamine (EDA) were added to obtain different ZnO morphologies. These various ZnO morphologies were characterized by scanning electron microscopy. Results: The composition of the nanostructures was analyzed by X-ray diffraction. The photoelectrochemical (PEC) properties of these ZnO nanostructures were measured using a PEC cell. Conclusion: The PEC properties were influenced by different ZnO morphologies.

Aims: Photocatalysis has become a crucial area in the field of energy generation. Background: The conversion of solar energy into chemical or thermal energy for various energyrelated applications has taken precedence over many traditional research areas. Objective: The urgency to become independent of non-renewable energy resources is paramount due to issues of global warming. Methods: To that end, researchers are exploring various material systems, geometries, and material combinations to obtain ideal photocatalysts for efficient solar conversion. Here, the nanostructures were fabricated via electrodeposition. Results and Discussion: The morphology was controlled by varying the concentration of chemical additive, namely dimethyl sulfoxide, during the deposition process. The morphology-controlled cerium oxide nanostructures were thoroughly characterized and tested for their photoelectrochemical performances. Conclusion: Our present investigation contributes to this area of research by studying the influence of morphology on the photoelectrochemical activity of cerium oxide nanostructures.

Introduction: Titanium Dioxide (TiO2) has gained a lot of focus in today’s world owing to its wide usage in several industries. The hazardous effects of TiO2 and its nanoparticles are also slowly revealing. The need for a proper cure of these toxic effects is of utmost importance. Due to its few side effects, medicinal plants can be an efficient source of remedy but are least considered compared to synthetic medicines. Cinnamomum cassia and Azadirachta indica are the most common of such medicinal plants used extensively in Pakistan and India. In this study, we carried out experiments to know the toxic effects of TiO2 nanoparticles in kidneys using a murine model and observed the ameliorating effects of Cinnamomum cassia and Azadirachta indica on the toxicity of TiO2 nanoparticles. Methods: Rats were given a subcutaneous injection of TiO2 nanoparticles at the dose of 150mg/kg body weight for 28 days along with oral administration of Cinnamomum cassia and Azadirachta indica alone and in combination. Results and Discussion: Both Cinnamomum cassia and Azadirachta indica at doses of 100 or 150mg/kg reduced the toxic effects of TiO2 nanoparticles evident from reduced alterations in kidney histopathology and also decreased DNA damage. Conclusion: It was concluded that Cinnamomum cassia and Azadirachta indica showed remedial or healing effects against nephrotoxicity in rats exposed to TiO2 sublethal doses.