Obaid Alqahtani

In recent decades, researchers have developed innovative compositions and methods to fabricate geopolymers and enhance their properties for diverse multifunctional applications. Geopolymer foams are regarded as promising functional materials across numerous disciplines; however, they face challenges such as brittleness and limited mechanical strength. This investigation aims to produce a geopolymer foam composite by incorporating three-dimensional (3D) Luffa Cylindrical Fibers (LCF) into a metakaolin-wollastonite geopolymer matrix. The composites were synthesized using an alkaline activator, mineral powders (wollastonite and metakaolin), a foaming agent (aluminum powder), and a foam stabilizer (olive oil). Their mechanical characteristics and capacity for Cu and As ion adsorption were examined, with structural analyses supplemented by scanning electron microscopy (SEM) and optical microscopy. Reinforcing with LCF markedly improved mechanical performance: flexural strength increased from 0.27 MPa to 0.60 MPa, while compressive strength rose from 0.04 MPa to 0.34 MPa. In addition to the amorphous structure, two new crystalline phases were detected: analcime and anorthite in the GLF matrix. The geopolymer foam composite (GLF) exhibited adsorption capacities of 4.6 mg/g for Cu, 5.18 mg/g for As, and 5.09 mg/g for methylene blue (MB) dye. The equilibrium adsorption capacity (qe) for Cu ions varies with the GLF mass, with smaller GLF masses yielding higher qe. Specifically, qe increases from 2.1 mg/g to 12 mg/g as the GLF mass decreases from 2 g to 0.25 g. Visual assessments reveal enhanced dye adsorption following LCF incorporation. Its high efficacy in removing Cu ions and metal-uptake capacity underscores its potential for practical water-treatment applications, offering sustainable solutions for environmental management.

Local molecular orientation and conformation within nanostructures is central to their behavior in devices, emergent quantum states, and biological processes. X-ray microscopy and scattering at the carbon absorption edge is uniquely sensitive to these phenomena, through transition dipole moments encoded with photon energy and polarization. However, quantitative analysis is precluded due to the lack of accurate optical models with bond and orientation specificity. We generate such a model through an unsupervised machine learning algorithm that clusters density functional theory calculations into principle electronic transitions, quantitatively refined with angle-resolved absorbance measurements. The resulting optical tensor reproduces data from samples with domains of different orientation and crystalline packing. This refinement method connects spectral features to chemical moieties and resolves measurement-inaccessible dipole moments, establishing a new paradigm for label-free orientation analyses of bonds within molecular nanostructures.

Over the past few decades, researchers have focused on developing new compositions and preparation techniques for geopolymers, as multifunctional products, to optimize their characteristics for use in multiple applications. Therefore, this paper investigates metakaolin geopolymer foam and introduces new geopolymer foams based on hybrid metakaolin and wollastonite mineral precursors for water purification. The geopolymer foams were prepared using an alkaline activator, mineral-based powders (wollastonite and metakaolin), a foaming agent (aluminum powder), and a foam stabilizer (olive oil). In addition to mechanical tests and assessments of the adsorption capacity of heavy metal ions, the geopolymer foams were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The geopolymer foams exhibited unique pore structures, containing four classes of pore networks with diameters around 1000 µm, 25 µm, 3 µm, and a well-arranged mesopore network of 50 nm. The utilization of wollastonite (CaSiO₃) alongside metakaolin as a hybrid precursor led to fundamental changes in the composition of the geopolymer binders: a new crystal phase, Ca₅(SiO₄)₂(OH)₂, was formed, and the Si-Al-Na crystal phase disappeared, which led to an increase in the amorphous phase from 87% to 92%. The adsorption rate of heavy metal ions, namely Cr, Co, Cu, Zn, Pd, and As, increased upon introducing wollastonite as a precursor, with absorption rates ranging from 11% to 68%. The findings also revealed that wollastonite significantly increased the geopolymers foams’ compressive strength and elastic modulus from 30 KPa to 67 KPa and from 31 MPa to 126 MPa, respectively.

Suppressed face-on stacking and crystallinity in ZR1:Y6 reduce charge dissociation, leading to more field-dependent charge generation compared to PM7:Y6, despite similar energy offsets in both blends.

Low‐offset organic solar cell systems have attracted great interest since nonfullerene acceptors came into the picture. While numerous studies have focused on the charge generation process in these low‐offset systems, only a few studies have focused on the details of each loss channel in the charge generation process and their impact on the overall device performance. Here, several nonfullerene acceptors are blended with the same polymer donor to form a series of low‐offset organic solar cell systems where significant variation in device performance is observed. Through detailed analyses of loss pathways, it is found that: i) the donor:acceptor interfaces of PM6:Y6 and PM6:TPT10 are close to the optimum energetic condition, ii) energetics at the donor:acceptor interface are the most important factor to the overall device performance, iii) exciton dissociation yield can be field‐dependent owing to the sufficiently small energetic offset at the donor:acceptor interface, and iv) the change in substituents in the terminal group of Y‐series acceptors in this work mainly affects energetics at the donor:acceptor interface instead of the interface density in the active layer. In general, this work presents a path toward more efficient organic solar cells.

Although solvent additives are used to optimize device performance in many novel non‐fullerene acceptor (NFA) organic solar cells (OSCs), the effect of processing additives on OSC structures and functionalities can be difficult to predict. Here, two polymer‐NFA OSCs with highly sensitive device performance and morphology to the most prevalent solvent additive chloronaphthalene (CN) are presented. Devices with 1% CN additive are found to nearly double device efficiencies to 10%. However, additive concentrations even slightly above optimum significantly hinder device performance due to formation of undesirable morphologies. A comprehensive analysis of device nanostructure shows that CN is critical to increasing crystallinity and optimizing phase separation up to the optimal concentration for suppressing charge recombination and maximizing performance. Here, domain purity and crystallinity are highly correlated with photocurrent and fill factors. However, this effect is in competition with uncontrolled crystallization of NFAs that occur at CN concentrations slightly above optimal. This study highlights how slight variations of solvent additives can impart detrimental effects to morphology and device performance of NFA OSCs. Therefore, successful scale‐up processing of NFA‐based OSCs will require extreme formulation control, a tuned NFA structure that resists runaway crystallization, or alternative methods such as additive‐free fabrication.