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This article presents a detailed analysis of parameters that affect the optical performance of parabolic trough solar collector (PTSC) and proposes a suitable method to optimize the relevant ones. A mathematical model is drafted and simulated for known geometry and parameters of industrial solar technology (IST) PTSC. The model was evaluated for three different configurations of IST PTSC involving distinct components. A comparison between the experimental results and model estimations indicates a maximum root-mean-square error (RMSE) of 0.7997, confirming the reliability of the proposed model. The influence of variations in absorber diameter (Dao), length (lrc), width (wrc), and focal length of PTSC (frc), along with direct normal incidence (In), dirt factors (ξdm, ξdhc), and angle of incidence (θ) on the optical performance of PTSC has been investigated. It was established that variation in mentioned parameters exhibits both positive and negative impacts on optical performance. After careful analysis, lrc, wrc, frc, Dao, and θ were chosen for optimization as it was perceived that by varying these in a reasonable range, an optimal set of parameters could be obtained that maximize the absorbed solar irradiation for a given PTSC. Genetic algorithm (GA), particle swarm optimization (PSO), and African vultures optimization algorithm (AVOA) are utilized to estimate the optimal values of parameters. Significant improvement in absorbed solar irradiation (∼16%) is registered with optimized parameters, suggesting that benefits can be obtained if a study is performed prior to producing PTSC modules for an application.

Fly ash (FA) particles were surface modified with cetyltrimethylammonium bromide (Ctab) and hybridized with graphene oxide (GO) and carboxymethyl cellulose (CMC) separately to increase interfacial adhesion with the polypropylene (PP) matrix. For a 5 wt.% CMC-hybridized FA, and Ctab-treated FA-filled PP composite, the highest increase in tensile (13% and 7%) and flexural (30% and 25%) strength was observed compared to pristine PP. The functionalization on FA surface was confirmed by ATR-IR analysis. Morphological study using FE-SEM showed that FA particles were successfully carried on to CMC and GO surfaces. An increment in melting temperature by ~ 3 °C was obtained. Improved thermal stability of the composites was confirmed from TGA analysis. The molecular dynamics (MD) simulations were carried out for all the three modification and it predicted highest interfacial interaction in case of Ctab-FA-reinforced PP composite.

The electrically conductive and optically transparent flexible nanocomposites made of polymers and multi-walled carbon nanotube (MWCNT) have the potential to be used as a transparent substrate for optoelectronic applications. In this investigation, we have fabricated a series of nanocomposites of MWCNT, used as conductive filler, with a copolymer of methyl methacrylate and acrylonitrile as a matrix, and solution blending method was used to achieve suitable dispersions. The MWCNT content varied sequentially in these nanocomposite thin films. A detailed study about the dispersion of MWCNTs in the matrix was done by attenuated total reflectance-infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The surface roughness is continuously increasing with an increase in the amount of conductive filler in the polymer matrix. However, it never exceeds 10 nm, which is very small compared to the MWCNT length, and also confirmed nearly complete embedding of conducting filler in the insulating matrix. The diffusion coefficient of nanocomposite was investigated for O2 and H2O with Molecular Dynamics simulations and found to decrease with increasing load percentage of MWCNT. The thin film’s optical transmittance and electrical conductivity are characterized thoroughly. An optimized formulation of nanocomposite with 0.25% MWCNT has shown enhanced conductivity of 10–2 S/cm (semiconductive range) with ~ 94% optical transparency at 550 nm.

This study explores the hybridizing effect of mechano-chemical activated fly-ash (FA) in sisal fiber reinforced polymer composites. Activation and resistance against agglomeration of FA has been achieved by modifying it with 2, 4, and 6 wt.% of the cetyltrimethylammonium bromide (C‑tab). FA activation with C-tab and particle size reduction to nano-level (2) than that of neat PP and composite reinforced with only 30 wt.% of sisal fiber. This increase in tensile and flexural strength was 30.54% and 48% higher than neat PP. Maximum notched impact strength of 0.80 kJ/m2 have been reported by hybrid composite containing FA treated with 2 wt.% of the C-tab. Micromechanical modelling using a combination of rule of mixture and inverse rule of mixture separately with Halpin-Tsai predicted a value close to the experimental Young’s modulus. DSC studies showed an increment in the composite's crystallinity upon fiber addition. Morphological analysis of the hybrid composite revealed good wettability of reinforcing fiber and FA within the matrix, whereas TGA showed an improved thermal stability of the composites.

Organic–inorganic hybrid perovskite materials have recently attracted extensive interest to develop next-generation high efficiency optoelectronic devices. However, in many of these devices, perovskite thin films are the key source of photogenerated electron and hole pairs. Therefore, a strategy for the preparation of high-quality perovskite thin films with a fewer number of traps at surfaces and grain boundaries is highly desired. In this work, sulfur-doped graphene quantum dots (S-GQDs) were synthesized and incorporated in the CH3NH3PbBr3 perovskite precursor to prepare S-GQDs incorporated perovskite thin films. The as-prepared thin films were systematically characterized using X-ray diffractometer, field emission scanning electron microscope, UV–Vis and fluorescence spectrophotometer to investigate the effect of different amounts of S-GQDs on their morphology, optical absorbance and electron transfer properties. The experimental findings revealed that multiple surface functional groups, quantum confinement and desirable electronic conductivity in S-GQDs help passivate the perovskite surface by reducing the surface and grain boundary traps. Interestingly, the incorporation of S-GQDs increased the light absorption of CH3NH3PbBr3 along with faster electron transfer across their interfaces. Hence, this strategy of S-GQDs incorporation presents a versatile and novel way to prepare highly efficient perovskite thin films for developing next-generation solar cells, light emitting diodes and other optoelectronic devices.

Over the last few years, due to its exceptional two-dimensional (2D) structure, graphene has played a key role in developing conductive transparent devices and acquired significant attention from scientists to get placed as a boon material in the energy industry. Graphene-based materials have played several roles, including interfacial buffer layers, electron/hole transport material, and transparent electrodes in photovoltaic devices. Apart from charge extraction and electron transportation, graphene protects the photovoltaic devices from atmospheric degradation through its 2D network and offers long-term air or environmental stability. This chapter focuses on the recent advancements in graphene and its nanocomposites-based solar cell devices, including dye-sensitized solar cells (DSSCs), organic solar cells (OSCs), and perovskite solar cells (PSCs). We further discuss the impact of incorporating graphene based materials on the power conversion efficiency for each type of solar cell. The last section of this chapter highlights the potential challenges and future research scope of graphene-based nanocomposites for solar cell applications.

Multifunctional cotton fabric was prepared through a two-step layer-by-layer spray coating method, where the first layer of the coating comprising chitosan and ammonium phytate provided fire retardancy, and the second one with PDMS-ZnO composite imparted hydrophobicity to the fabric. A molecular dynamics (MD) simulation study was carried out to calculate interfacial adhesion of different components of the coating, based on which the sequencing of the coating layers was determined and used to prepare coated samples. The coated fabric demonstrated a significant improvement in fire retardancy through an increase in LOI from 18 % in control to 30 %, a reduction in char length from 30 cm to 7 cm, and a decrease in peak and total heat release rate values by 75 % and 33 %, respectively. The hydrophobicity of coated fabric was tested via water drop test where coated sample maintained a contact angle of 148° for up to 120 s, while the control sample showed 0°.

In this study, an effective surface functionalization of carbon fiber (CF) and its subsequent coating with functionalized carbon nanotubes (CNTs) were carried out to obtain improved interfacial shear strength (IFSS) which was validated by single fiber fragmentation test (SFFT). Functional groups, -COOH, -OH, and -NH2, were separately grafted on the CF surface using different chemical routes. Additionally, ultrasonic assisted electrophoretic deposition (EPD) technique was used to coat -COOH, -OH, and -NH2 functionalized CNTs on the sized and surface functionalized CFs. Attenuated total reflection-infrared spectroscopy (ATRIR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM) images confirmed the successful surface functionalization and coating on CF. Neat PP and a blend of PP and maleic anhydride-grafted-styrene ethylene butylene styrene (MA-g-SEBS) were used as two different base polymer matrixes in preparing a total of 26 different SFFT samples. Silane functionalized CF coated with amine functionalized CNTs using ultrasonic assisted EPD process showed IFSS of ~ 29 MPa which was an impressive ~ 758% higher than pristine CF and highest among all the surface modified CFs. Interestingly, this translated into useful increase of ~ 13% in single fiber tensile strength of functionalized and treated CF over and above that of as received CF.

This study focused on developing fly-ash and sisal fiber reinforced hybrid polypropylene (PP) composites. The hybridized composite containing 15 wt.% each of sisal fiber and fly-ash shows highest impact strength of 1.42 kJ/m2, demonstrating an improvement by ~ 125 % and ~ 25 % respectively in comparison to neat PP and composite reinforced with only sisal fiber. Highest and lowest tensile strengths of 37.09 MPa and 24.69 MPa were recorded by composite containing 30 wt.% each of sisal fiber and fly ash with PP and impact modified PP respectively. Flexural strength recorded a greatest value of 44.09 MPa for 30 wt.% reinforced sisal fiber with PP against a lowest estimate of 30.86 MPa for 30 wt.% reinforced fly ash with impact modified PP. The FTIR results confirmed the esterification reaction among sisal fibers and maleic anhydride groups. DMA showed an apparent positive shift in the glass transition temperatures of hybrid composites upon the addition of fly ash. Composite reinforced with 30 wt.% sisal fiber and fly ash exhibited a storage modulus of 13,155 MPa and 8,795 MPa at −80 oC, respectively. Thermal degradation stability of all the hybrid composites improved significantly. The lowest water uptake properties have been demonstrated from the composite with highest fly ash content (15 %).

This work is strategically premeditated to study the potential of a herbal medicinal product as a natural bioactive ingredient to generate nanocellulose-based antibacterial architectures. In situ fibrillation of purified cellulose was done in cinnamon extract (ciE) to obtain microfibrillated cellulose (MFC). To this MFC suspension, carboxylated cellulose nanocrystals (cCNCs) were homogeneously mixed and the viscous gel thus obtained was freeze-dried to obtain lightweight and flexible composite aerogel architectures impregnated with ciE, namely, ciMFC/cCNCs. At an optimal concentration of 0.3 wt % cCNCs (i.e., for ciMFC/cCNCs_0.3), an improvement of around 106% in compressive strength and 175% increment in modulus were achieved as compared to pristine MFC architecture. The efficient loading and interaction of ciE components, specifically cinnamaldehyde, with MFC and cCNCs resulted in developing competent antibacterial surfaces with dense and uniform microstructures. Excellent and long-term antimicrobial activity of the optimized architectures (ciMFC/cCNCs_0.3) was confirmed through various antibacterial assays like the zone inhibition method, bacterial growth observation at OD600, minimum inhibitory concentration (MIC, here 1 mg/mL), minimum bactericidal concentration (MBC, here 3-5 mg/mL), and Live/Dead BacLight viability tests. The changes in the bacterial morphology with a disrupted membrane were further confirmed through various imaging techniques like confocal laser scanning microscopy, FESEM, AFM, and 3D digital microscopy. The dry composite architecture showed the persuasive capability of suppressing the growth of airborne bacteria, which in combination with antibacterial efficiency in the wet state is considered as an imperative aspect for a material to act as the novel biomaterial. Furthermore, these architectures demonstrated excellent antibacterial performance under real "in use" contamination prone conditions. Hence, this work provides avenues for the application of crude natural extracts in developing novel forms of advanced functional biomaterials that can be used for assorted biological/healthcare applications such as wound care and antimicrobial filtering units.

Ion migration in hybrid halide perovskites is ubiquitous in all conditions. However, the ionic conductivity can be manipulated by changing the material composition, operating temperature, light illumination, and applied bias as well as the nature of the interfaces of the devices. There have been various reports on electron ion coupling in hybrid perovskite semiconductors which gives rise to anomalous charge transport behavior in these devices under an applied bias. In this investigation, we have synthesized a mixture of 2D/3D perovskites by incorporating sulphur-doped graphene quantum dots (SGQDs) and demonstrated that the optical and electrical properties of the hybrid system can be tuned by controlling the ion conductivity through the active layer. It has been observed that the recombination resistance in undoped CH3NH3PbBr3 perovskites follows an anomalous behavior while the doped CH3NH3PbBr3 perovskite shows a monotonic increase with increasing applied bias due to reduced ionic conductivity. SGQDs at the grain boundaries of 2D/3D perovskites prohibit ion migration through the active layer, and therefore the electronic-ionic coupling is reduced. This results in increased recombination resistance with increasing applied bias.

Being a novel and interesting zero-dimensional material of the carbon family, graphene quantum dots (GQDs) have been studied extensively in the last few years due to their exceptional and desirable optical, chemical, physical, electrical and biological characteristics. Such unique size-dependent properties exhibited by them are a reflection of combined structural characteristics of small graphene sheets, furnished with quantum confinement and edge effects, and help them to demonstrate versatile applications in biomedical and optoelectronic domains. In this review, we summarize various top-down and bottom-up synthetic procedures to prepare GQDs with ease. Following this, several strategies adopted by researchers such as heteroatom doping, functionalization and controlling the reaction parameters to regulate their structure and chemical behavior are also discussed. A concise summary of several recent advances in the areas of biomedical (bio-sensing, bio-imaging, drug delivery, anti-bacterial activity and photo-thermal/dynamic therapy) and optoelectronic (light emitting diodes and solar cells) applications of GQDs has also been presented. Finally, a brief discussion on existing challenges and future prospective of this exciting material has also been included.

Since the day of their origin, the graphene quantum dots (GQDs) have been considered a predominant material for biosensing applications in view of their unique and exciting electronic, physicochemical and optical properties. By combining the quantum-confinement and edge effects of carbon dots with the graphene structure, GQDs have emerged as a wonder material. These photoluminescent QDs possess remarkable biocompatibility, high current density, fast electron mobility, high water solubility, good photochemical stability, and low cytotoxicity, thereby prevailing in the field of sensing. Moreover, the high electron-transfer and easy biomolecule-immobilization capabilities of GQDs make them suitable for developing efficient (bio)analytical sensors. In this direction, the review is proposed to enlighten the scope of GQDs in a variety of optical and electrochemical chemosensors as well as biosensors. Recent advancements pertaining to their synthesis methods, unique properties, and their regulation through heteroatom-doping and surface-functionalization strategies are discussed, along with the current challenges and future prospects.

The development of an analytical probe to monitor highly mutagenic picric acid (PA) carries enormous significance for the environment and for health. A novel, simple and rapid fluorescence analytical assay using sulfur-doped graphene quantum dots (SGQDs) was designed for the highly sensitive and selective detection of PA. SGQDs were synthesized via simple pyrolysis of 3-mercaptopropionic acid and citric acid and characterized using advanced analytical techniques. Fluorescence intensity (FI) of SGQDs was markedly quenched by addition of PA, attributed to the inner filter effect and dominating static quenching mechanism between the two, in addition to a significant colour change. The calibration curve of the proposed assay exhibited a favourable linearity between quenched FI and PA concentration over the 0.1-100 μΜ range with a lowest detection limit of 0.093 μΜ and a correlation coefficient of 0.9967. The analytical assay was investigated for detection of trace amounts of PA in pond and rain water samples and showed great potential for practical applications with both acceptable recovery (98.0-100.8%) and relative standard deviation (1.24-4.67%). Analytical performance of the assay in terms of its detection limit, linearity range, and recovery exhibited reasonable superiority over previously reported methods, thereby holding enormous promise as a simple, sensitive, and selective method for detection of PA.

The importance of surface roughness on wettability is vital in developing novel techniques and materials for fabrication of self-cleaning coatings. In this study, the effect of varying roughness of a surface on its wettability was explored through changing the interspacing (ai) and particle diameter (D) of ZnO agglomerated particles in poly(vinylacetate)-graft-poly(dimethylsiloxane) based coatings by constructing and simulating different atomistic and mesoscopic models. The surface roughness has been characterized in terms of roughness factor (Rq = D/ai). Compared to the base matrix, a maximum enhancement in fluid phobicity was observed to be 33% and 172% against water and oil for Rq = 0.9. The surface energy increased moderately (∼21%) and interaction energy against an Al substrate significantly (∼1251%) by a 15 wt% filler incorporation. The investigation reveals that both ai and filler concentration (thereby Rq) control imbibition of water/oil molecules by surface grooves to ensure limited wettability and useful self-cleaning ability. Specifically, optimal surface roughness is achieved at a critical Rq = 0.9 when the ZnO filler interspacing is neither too low for it to act as a continuous surface itself nor too high to allow easy penetration of fluid inside surface grooves.

Quantitative detection of cancer biomarkers with higher accuracy and sensitivity provides an effective platform for screening, monitoring, early diagnosis, and disease surveillance. The present work demonstrates the fabrication and application of fluorescent turn-on biosensor for ultrasensitive detection of small cell lung cancer biomarker utilizing biofunctionalized graphene quantum dots as the energy donor and gold nanoparticles (AuNPs) as the energy acceptor. One-pot and the bottom-up hydrothermal route have been employed for the synthesis of