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This first-principles study investigates the interactions between amino acids and various types of montmorillonite clay surfaces, including a pristine surface, a surface with an oxygen vacancy, a surface with a silicon vacancy, and an Fe-doped surface. Our results show that all clay surfaces exhibit negative binding energies, indicating that the interaction between clay and amino acids is thermodynamically favorable. Among them, the surface with a Si vacancy displays the most negative binding energy, corresponding to the strongest interaction. We also examine the reactions between two alanine molecules to form a dipeptide molecule through the elimination of a water molecule in the absence of clay surfaces. The transition state search suggests that a proton transfer plays a critical role in the peptide bond formation based on structural and energetic features observed along the reaction path. Circular dichroism spectra computed for reactant, intermediate, and product states show distinct chiral signatures. Wave packet dynamics calculations indicate that quantum tunneling might be the mechanism underlying the reduced activation energy at low temperatures. These findings offer insight into the physicochemical processes at clay–amino acid interfaces and support the design of clay-based materials with applications in biotechnology and prebiotic chemistry. 

The efficiency of silicon solar cells is affected by the light absorption and recombination losses of photoexcited charge carries. One possible way to improve the efficiency is through the deposition of transition metal nanoparticles on Si surfaces. Here, we first carry out density functional theory (DFT) calculations to obtain electronic structures for Agn (n = 1–7) monolayered clusters adsorbed on Si(111)/H surfaces. Results are presented in the form of the density of states, band gaps, and light absorption, which allow for the investigation of the interaction of Ag clusters with Si. Different behaviors can be expected depending on the size of the deposited Ag clusters. Overall, the deposition of Ag clusters leads to smaller band gaps, red-shifts, and large increases in light absorption compared to the pristine Si slab. We then study the relaxation dynamics of electron–hole pairs for slabs based on nonadiabatic couplings using the reduced density matrix approach within the Redfield formalism. Nonradiative relaxation rates are noticeably different for various structures and transitions. One observes higher relaxation rates for surfaces with adsorbates than for the pristine Si surface due to charge transfer events involving Ag orbitals. We also compute emission spectra from excited-state relaxation dynamics. The band gap emission is dark for the pristine Si due to the indirect nature of its band gap. The addition of larger Ag clusters breaks the symmetry of Si slabs, enabling indirect gap transitions. These slabs thus exhibit bright band gap emission. The introduction of adsorbates is advantageous for applications in photovoltaics and photocatalysis. 

Semiconducting conjugated polymers (CPs) are pivotal in advancing organic electronics, offering tunable properties for solar cells and field-effect transistors. Here, we carry out first-principle calculations to study individual cis-polyacetylene (cis-PA) oligomers and their ensembles. The ground electronic structures are obtained using density functional theory (DFT), and excited state dynamics are explored by computing nonadiabatic couplings (NACs) between electronic and nuclear degrees of freedom. We compute the nonradiative relaxation of charge carriers and photoluminescence (PL) using the Redfield theory. Our findings show that electrons relax faster than holes. The ensemble of oligomers shows faster relaxation compared to the single oligomer. The calculated PL spectra show features from both interband and intraband transitions. The ensemble shows broader line widths, redshift of transition energies, and lower intensities compared to the single oligomer. This comparative study suggests that the dispersion forces and orbital hybridizations between chains are the leading contributors to the variation in PL. It provides insights into the fundamental behaviors of CPs and the molecular-level understanding for the design of more efficient optoelectronic devices. 

Organic color centers (OCCs), generated by the covalent functionalization of single-walled carbon nanotubes, have been exploited for chemical sensing, bioimaging, and quantum technologies. However, monovalent OCCs can assume at least 6 different bonding configurations on the sp2 carbon lattice of a chiral nanotube, resulting in heterogeneous OCC photoluminescence emissions. Herein, we show that a heat-activated [2 + 2] cycloaddition reaction enables the synthesis of divalent OCCs with a reduced number of atomic bonding configurations. The chemistry occurs by simply mixing enophile molecules (e.g., methylmaleimide, maleic anhydride, and 4-cyclopentene-1,3-dione) with an ethylene glycol suspension of SWCNTs at elevated temperature (70–140 °C). Unlike monovalent OCC chemistries, we observe just three OCC emission peaks that can be assigned to the three possible bonding configurations of the divalent OCCs based on density functional theory calculations. Notably, these OCC photoluminescence peaks can be controlled by temperature to decrease the emission heterogeneity even further. This divalent chemistry provides a scalable way to synthesize OCCs with tightly controlled emissions for emerging applications. 

Inorganic mixed-halogen perovskites exhibit excellent photovoltaic properties and stability; yet, their photoelectric conversion efficiency is limited by inherent surface defects. In this work, we study the impact of defects on properties of CsPbI2Br slabs using first-principles calculations, focusing on specific defects such as I vacancy (VI), I interposition (Ii), and I substitution by Pb (PbI). Our findings reveal that these defects affect the geometric and optoelectronic properties as well as dynamics of charge carriers of slabs. We employ two theoretical frameworks (surface hopping and Redfield theory) of nonadiabatic molecular dynamics simulations to comprehensively study relaxation processes and obtain consistent results. The presence of VI reduces carrier lifetimes, while the influence of PbI on carrier lifetimes is negligible. In contrast, Ii defects lead to prolonged carrier lifetimes. These insights provide valuable guidance for the rational design of perovskite photovoltaic devices, aiming to enhance their efficiency and stability. 

The development of reusable polymeric materials inspires an attempt to combine renewable biomass with upcycling to form a biorenewable closed system. It has been reported that 2,5-furandicarboxylic acid (FDCA) can be recovered for recycling when incorporated as monomers into photodegradable polymeric systems. Here, we develop a procedure to better understand the photodegradation reactions combining density functional theory (DFT) based time-dependent excited-state molecular dynamics (TDESMD) studies with machine learning-based quantitative structure–activity relationships (QSAR) methodology. This procedure allows for the unveiling of hidden structural features between active orbitals that affect the rate of photodegradation and is coined InfoTDESMD. Findings show that electrotopological features are influential factors affecting the rate of photodegradation in differing environments. Additionally, statistical validations and knowledge-based analysis of descriptors are conducted to further understand the structural features’ influence on the rate of photodegradation of polymeric materials.