Photon Absorption Research Articles

Study on photochemistry and component transport coupling processes of azobenzene molecular solar thermal system

Molecular solar thermal (MOST) system is a new technology to collect, transform and store solar energy. The mechanism of photochemical reaction and component transport of molecular photoswitches in the reactor is still unclear. In this paper, a simulated theoretical framework for energy conversion rate and energy storage efficiency of solar energy collection and conversion devices based on a molecular solar thermal system was presented. The mathematical model of the photochemical reaction studied was based on an azobenzene derivative, which acted as a molecular photoswitch that can store energy by the switch of molecular structures. The microscopic parameters of reactants were obtained by quantum mechanics calculation and applied to the macroscopic energy conversion analysis of reaction processes. The theoretical framework can predict the conversion and energy storage efficiency of photoisomerization reactions, and can be used for component transport analysis, energy conversion analysis and reaction rate contribution analysis in reactors. We focused on the influence of macroscopic factors, including the flow velocity, inlet reactants concentration and reactor size on the photoisomerization energy storage process. The results of the theoretical analysis were in good agreement with those of existing laboratory equipment. The relative error of the conversion rate is only 0.71% in the photostable state, and the maximum relative error of the conversion rate is 10.99% in the whole process. In addition, in the photochemical reaction, we introduced the concept of absorbance field for the absorbance attenuation caused by the absorption of photons in the medium, so that the local material conversion, absorbance and energy conversion of this type of photochemical reaction can be more clearly understood. This simulated theoretical framework allows the study of molecules in a macroscopic setting, thereby establishing a link between practical engineering and basic chemistry, and providing guidance for the design of molecular solar thermal systems in the future.

Enhanced nonlinear absorption and photoluminescence properties of Zn, Fe, Cu, V and Ni doped MoO3 transition metal oxide thin films

Abstract In this study, the effect of the dopant element on the linear, nonlinear absorption and optical limiting properties of ultrasonically sprayed MoO3 thin films is presented. The linear optical results showed an increase with the density of the defect states in the bandgap with doping, in conjunction with a decrease in bandgap energy and an increase in Urbach energy. Broad photoluminescence emissions are detected in the range of 350 and 600 nm, decreasing in intensity by doping. To reveal the defect states effects’ on the nonlinear absorption (NA) behavior, OA Z-scan data were analyzed with two theoretical models considering only two photon absorption (2PA) (model 1), and one photon absorption (OPA), 2PA and free carrier absorption (model 2). The NA behavior is observed and found to get enhanced by increasing input intensity and doping atoms due to generation of new oxygen vacancies and formation of further defect states. The NA coefficient values of the thin films in model 2 are 100 times higher than that of 2PA coefficient values in model 1. This result revealed the strong effect of defect states on the NA behavior. Among the investigated dopant atoms, Cu resulted in enhanced NA due to the higher density of defect states. While the genuine 2PA is the dominant NA mechanism for V and Fe doped MoO3 thin films, OPA and 2PA are the dominant NA mechanisms for the Ni, Zn and Cu doped MoO3 thin films due to their higher concentration of defect states. Cu-doped MoO3 thin film has a lower optical limiting threshold of 0.026 mJ/cm2 due to its enhanced NA behavior. Considering the results obtained, this study opens the door to the potential of doped MoO3 thin films to be used as optical limiters in the visible wavelength region.

Current Remedy in Ultrathin Crystalline Si Solar Cell by Cu2SnS3 Thin Film toward High Efficiency

An ultrathin 15 μm wafer‐based c‐Si solar cell is designed and simulated, wherein the current remedy is done by Cu2SnS3 (CTS) thin film. The ZnSe and AlSb are incorporated as window and back surface field (BSF) layers, respectively, in this model. The ultrathin Si‐based n‐ZnSe/p‐Si exhibits the short‐circuit current density of 30.66 mA cm−2 with an efficiency of 18.80%. The inclusion of p+‐CTS thin film as a second absorber layer has enhanced this current to 42.14 mA cm−2. By absorbing sunlight up to 1200 nm, the CTS layer is able to successfully overcome the constraint of thinner Si wafers on longer‐wavelength photon absorption leading to current augmentation. The addition of p++‐AlSb as the BSF layer also boosts the open‐circuit voltage by 300 mV. The rise in VOC is a result of the larger built‐in potential in ZnSe/Si, Si/CTS, and CTS/AlSb interfaces. With enriched current and voltage, the final proposed n‐ZnSe/p‐Si/p+‐CTS/p++‐AlSb heterostructure theoretically records an efficiency of 35.48% in ultrathin Si solar cells. The current compensation obtained using CTS thin film in this work can give optimism about the future of ultrathin Si solar cells.

Quasiparticle Poisoning of Superconducting Qubits from Resonant Absorption of Pair-Breaking Photons.

The ideal superconductor provides a pristine environment for the delicate states of a quantum computer: because there is an energy gap to excitations, there are no spurious modes with which the qubits can interact, causing irreversible decay of the quantum state. As a practical matter, however, there exists a high density of excitations out of the superconducting ground state even at ultralow temperature; these are known as quasiparticles. Observed quasiparticle densities are of order 1 μm^{-3}, tens of orders of magnitude greater than the equilibrium density expected from theory. Nonequilibrium quasiparticles extract energy from the qubit mode and can induce dephasing. Here we show that a dominant mechanism for quasiparticle poisoning is direct absorption of high-energy photons at the qubit junction. We use a Josephson junction-based photon source to controllably dose qubit circuits with millimeter-wave radiation, and we use an interferometric quantum gate sequence to reconstruct the charge parity of the qubit. We find that the structure of the qubit itself acts as a resonant antenna for millimeter-wave radiation, providing an efficient path for photons to generate quasiparticles. A deep understanding of this physics will pave the way to realization of next-generation superconducting qubits that are robust against quasiparticle poisoning.

Elettra 2.0: The Vacuum System Design for a New Generation Storage Ring

Next-generation synchrotron facilities currently under development and construction are promising and delivering great advances in terms of machine design and research physics. At the same time, they are pushing the limits of technological solutions for various subsystems: to achieve the desired ultra-low electron beam emittance required in the next generation machines, the magnetic lattice has to adopt a compact design with reduced magnet apertures and other constraints like high heat load from synchrotron radiation, dynamic pressure inside vacuum chambers and chamber wall impedance are presenting unique challenges for the vacuum and engineering teams. At Elettra-Sincrotrone Trieste (Italy), the Elettra 2.0 project aims to develop a new-generation storage ring. Taking into consideration the above-mentioned constraints, we decided to adopt a new design of a vacuum chamber, while utilizing novel pumping solutions to overcome hugely reduced conductance compared to the current machine. Large sputter ion pumps (SIP) will be in the majority replaced by distributed non-evaporable getter (NEG) coatings and small NEG cartridges and SIP pumps. For the synchrotron radiation handling, due to the tight space constraints imposed by the compact lattice, the photon absorption will be managed jointly with discrete and distributed solutions: photon absorbers have been carefully studied for combining compact form and high power density loads, while key sections of the new storage ring will be water-cooled. Throughout the whole development phase, we were using Monte-Carlo simulation codes like SynRad and MolFlow+ as effective tools supporting the design of new vacuum chambers and photon absorbers. The current state of development for the Elettra 2.0 vacuum system, the challenges we faced and the solutions we adopted are presented here.

Time-resolved vibrational spectroscopic study of molecular nanoaggregate photocatalysts.

The controlled aggregation of organic chromophores into supramolecular structures offers a way to control and tune photocatalytic activity. However, the underlying mechanisms of charge transfer and accumulation are still unclear. Time-resolved vibrational spectroscopy is a powerful structural probe for studying photogenerated intermediates. Here, we employ time-resolved infrared (TRIR) spectroscopy to study CNP (2,6-bis(4-cyanophenyl)-4-(9-phenyl-9H-carbazol-3-yl)pyridine-3,5-dicarbonitrile) and its supramolecular aggregates. We show that excitation of the charge transfer (CT) band of semi-crystalline nanofibers (CNP-f) gives rise to long-lived delocalised polarons, which form within the instrument response timescale. By contrast the CNP nanospheres (CNP-s) give rise to a shorter lived polaron that appears to have a greater degree of localization. CNP-f and CNP-s are known to show markedly different levels of photocatalytic activity for hydrogen and hydrogen peroxide formation which are rationalised owing to these differences in photodynamics immediately following photon absorption.

Use of photosensitive molecules in the crosslinking of biopolymers: applications and considerations in biomaterials development.

The development of diverse types of biomaterials has significantly contributed to bringing new biomedical strategies to treat clinical conditions. Applications of these biomaterials can range from mechanical support and protection of injured tissues to joint replacement, tissue implants, and drug delivery systems. Among the strategies commonly used to prepare biomaterials, the use of electromagnetic radiation to initiate crosslinking stands out. The predominance of photo-induced polymerization methods relies on a fast, efficient, and straightforward process that can be easily adjusted to clinical needs. This strategy consists of irradiating the components that form the material with photons in the near ultraviolet-visible wavelength range (i.e., ∼310 to 750 nm) in the presence of a photoactive molecule. Upon photon absorption, photosensitive molecules can generate excited species that initiate photopolymerization through different reaction mechanisms. However, this process could promote undesired side reactions depending on the target zone or treatment type (e.g., oxidative stress and modification of biomolecules such as proteins and lipids). This review explores the basic concepts behind the photopolymerization process of ex situ and in situ biomaterials. Particular emphasis was put on the photosensitization initiated by the most employed photosensitizers and the photoreactions that they mediate in aqueous media. Finally, the undesired oxidation reactions at the bio-interface and potential solutions are presented.

Charge transfer excitons and directional fluorescence of in-plane lateral MoSe2-WSe2 heterostructures.

In this article, the linear and nonlinear optical properties of in-plane lateral MoSe2-WSe2 heterostructures are theoretically investigated. The polarization-dependent strongest optical absorption in one-photon absorption occurs in charge transfer excited states, where electrons transfer from WSe2 to MoSe2. This phenomenon is supported by the LUMO (lowest unoccupied molecular orbital) and HUMO (highest occupied molecular orbital) imaging obtained through scanning tunneling microscopy. The charge difference density and transition density matrix are used to interpret the electronic transitions, and these interpretations rely on the concept of transition density. The optical properties of two-photon absorption in its nonlinear optical process are significantly different from the excitation in one-photon absorption, where the strongest optical absorption is contributed from direct transition from the ground state to the final state without going through an intermediate excited state, due to the very large difference of permanent dipole moments between the excited and ground states. Our results also reveal directional fluorescence and physical mechanism of in-plane lateral MoSe2-WSe2 heterostructures. Our work can provide insights into the physical mechanism of the optical properties of in-plane lateral MoSe2-WSe2 heterostructures.

Multimodal optoacoustic imaging: methods and contrast materials.

Optoacoustic (OA) imaging offers powerful capabilities for interrogating biological tissues with rich optical absorption contrast while maintaining high spatial resolution for deep tissue observations. The spectrally distinct absorption of visible and near-infrared photons by endogenous tissue chromophores facilitates extraction of diverse anatomic, functional, molecular, and metabolic information from living tissues across various scales, from organelles and cells to whole organs and organisms. The primarily blood-related contrast and limited penetration depth of OA imaging have fostered the development of multimodal approaches to fully exploit the unique advantages and complementarity of the method. We review the recent hybridization efforts, including multimodal combinations of OA with ultrasound, fluorescence, optical coherence tomography, Raman scattering microscopy and magnetic resonance imaging as well as ionizing methods, such as X-ray computed tomography, single-photon-emission computed tomography and positron emission tomography. Considering that most molecules absorb light across a broad range of the electromagnetic spectrum, the OA interrogations can be extended to a large number of exogenously administered small molecules, particulate agents, and genetically encoded labels. This unique property further makes contrast moieties used in other imaging modalities amenable for OA sensing.

DFT insights on the Be1-xCrxS alloys for optoelectronic and magnetic devices

In this work, the electro-optical and magnetic characteristics of Be1-xCrxS (x= 6.25%, 12.5% and 25%) are brought into investigation by employing full potential linearized augmented plane wave (FP-LAPW) scheme designed within density functional theory (DFT). The stability of the Be1-xCrxS alloy is justified by the negative values of formation energy. The band structures and density of states are examined by using GGA functional. Be1-xCrxS compound demonstrates the half-metallic (HM) ferromagnetic behavior for all doping concentrations; spin-up channel reveals the metallic character and other spin version displays the semiconductor (SC) behavior. The values of total magnetic moment (µB) are recorded as 4.0 8.0 and 16.0 µB for corresponding 6.25%, 12.5% and 25%, which mainly arises owing to Cr-3d state. Moreover, optical features including dielectric function ε(ꞷ), reflectivity, refraction, and absorption are explored within range of 0-10 eV. The maximum absorption of incident photons was found in ultraviolet (UV) span which implies their importance for optoelectronic applications. Results reveal that the studied alloy has potential applications in magnetic and optoelectronic gadgets.

Omic Evaluation of Nanomaterial-Based Photodynamic Therapy of Cancer.

Photodynamic therapy (PDT), a noninvasive cancer treatment, relies on three components: light source, oxygen, and photosensitizer (PS). When PS is excited by a specific wavelength of light in the presence of oxygen, it leads to the generation of reactive oxygen species (ROS), which results in targeted destruction of cancer cells. The success of PDT mainly depends on the properties of the chosen PS, emphasizing selectivity, high absorbance, drug conjugation, controlled biodistribution, and low toxicity. Nanomaterials not only play an important role in photochemical activity by maximizing the absorption of photons from the light source but can also adjust the pharmacokinetics and tumor selectivity of photoactive molecules. Therefore, they can be used as a PS on their own and conjugated with other PS molecules. When combined with selectivity, high targeting capacity, and finally, light of the appropriate wavelength, the scenario results in localized ROS formation and cell death. However, the signaling pathways of PDT-induced cell death may differ depending on the cell type or nanomaterial properties. For this reason, omics analyses are needed to clarify the mechanisms underlying photodynamic reactions. Proteomics, crucial in molecular sciences, sheds light on cancer mechanisms, identifying biomarkers and therapeutic targets. Examining nanoparticle-based PDT in cancer cell lines in vitro, this chapter aims to molecularly evaluate efficacy, utilizing proteomic analysis to understand the underlying mechanisms.

Ultrafast, Single-Event Ptychographic Imaging of Transient Electron Dynamics

Dynamic phenomena occurring on the ultrafast time scales are inherently difficult to image. While pump–probe techniques have been used for decades, probing nonrepeatable phenomena precludes this form of imaging. Additionally, many ultrafast phenomena, such as electron dynamics, exhibit low amplitude contrast in the optical wavelength range and thus require quantitative phase imaging. To better understand the underlying physics involved in a plethora of ultrafast phenomena, advanced imaging techniques must be developed to observe single events at an ultrafast time scale. Here, we present, to the best of our knowledge, the first ptychographic imaging system capable of observing ultrafast dynamics from a single event. We demonstrate ultrafast dynamic imaging by observing the conduction band electron population from a 2-photon absorption event in ZnSe pumped by a single femtosecond pulse. We verify experimental observations by comparing them to numeric solutions of a nonlinear envelope equation. Our imaging method represents a major step forward in ultrafast imaging, bringing the capabilities of ptychography to the ultrafast regime.

Light harvesting FIT DNA hybridization probes for brightness-enhanced RNA detection.

Fluorogenic hybridization probes are essential tools in modern molecular biology techniques. They allow detection of specific nucleic acid molecules without the need to separate target-bound from unbound probes. To enable detection of targets at low concentration, fluorogenic probes should have high brightness. Here, we report the development of RNA hybridization probes (RNA FIT probes) that use smart quenching and a light harvesting principle to enhance the brightness of fluorescence signaling. The signaling mechanism is based on FRET between brightly emitting donor dyes and a fluorescent base surrogate, such as quinoline blue (QB) or thiazole orange (TO). In the single-stranded state, QB/TO nucleotides fluoresce weakly and quench the fluorescence of the donor dyes. Upon target recognition, QB/TO stack with adjacent base pairs, resulting in enhanced fluorescence quantum yields. The donor dyes are blue-shifted by only 5-20 nm relative to the QB/TO nucleotides, allowing simultaneous excitation of both dye groups with efficient energy transfer. The combined photon absorption results in exceptionally bright FIT probes. This feature facilitated the detection of RNA target in undiluted cell lysates. The present study examines the utilization of probes to detect mRNA targets in live T cells using flow cytometry.

A first-principles prediction of the structural, electronic, transport and photocatalytic properties of GaGeX3 (X = S, Se, Te) monolayers.

The discovery of new 2D materials with superior properties motivates scientists to make breakthroughs in various applications. In this study, using calculations based on density functional theory (DFT), we have comprehensively investigated the geometrical characteristics and stability of GaGeX3 monolayers (X = S, Se, or Te), determining their electronic and transport properties, and some essential optical and photocatalytic properties. AIMD simulations show that these materials are highly structurally and thermodynamically stable. Notably, the GaGeSe3 monolayer is a semiconductor with a band gap of 1.9 eV and has a high photon absorption coefficient of up to 1.1 × 105 cm-1 in the visible region. The calculated solar-to-hydrogen conversion efficiency of the GaGeSe3 monolayer is 11.33%, which is relatively high compared to some published 2D materials. Furthermore, the electronic conductivity of the GaGeSe3 monolayer is 790.65 cm2 V-1 s-1. Our findings suggest that the GaGeSe3 monolayer is a new promising catalyst for the solar water-splitting reaction to give hydrogen and a potential new 2D material for electrical devices with high electron mobility.

Label-Free Non-Contact Vascular Imaging using Photon Absorption Remote Sensing.

Functional vascular imaging is a critical method for early detection and prevention of disease. Established non-contact vascular imaging techniques capture predominantly structural information. In this study, a novel non-contact label-free in vivo Photon Absorption Remote Sensing (PARS) microscope is developed for structural and functional vascular imaging. The presented in vivo PARS microscope captures the endogenous absorption of green (532nm) light to form a complete picture of vasculature and surrounding tissues. Imaging system repeatability is enhanced through robust transient absorption signal extraction, and state-of-the-art real-time alignment methods. Detailed imaging of vascular structure is demonstrated through in vivo microscopy of two established animal models: mouse ear and chicken embryo. Preliminary functional contrast is realized through video rate imaging of red blood cell dynamics in the capillary networks of chicken embryos. The presented in vivo PARS microscope successfully captures detailed structural and functional vascular contrast. This innovative non-contact label-free imaging technique holds promise as a tool for preventative medical care, as functional change often precedes structural change.

Nanomaterials-Based Multiple Quantum Wells for High Photovoltaic Conversion Solar Cells

Using metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) and pulse Laser deposition (PLD) techniques on GaN, Silicon, Silicon Carbide and sapphire substrates, high efficiency InGaN/GaN solar cells are reported with a particular emphasis on the work and achievements made with multi-junction tandem and Nanomaterials (Quantum well (QW), Multiple Quantum Wells (MQW), and Quantum Dots (QD)). An effective method for increasing photon absorption in ultrathin cells made for the best possible photovoltaic response is the InGaN/GaN QW system. To maximize light absorption, the quantum well and barrier thicknesses and number of wells in the MQW active region must be adjusted.

A label-free and immobilization-free approach for constructing photoelectrochemical nucleic acid sensors utilizing DNA-silver nanoparticle affinity interactions.

Efficient and affordable nucleic acid detection methods play a pivotal role in various applications. Herein, we developed an immobilization-free and label-free strategy to construct a photoelectrochemical nucleic acid biosensing platform based on interactions between silver nanoparticles and DNA. First, CRISPR-Cas12a exhibited a trans-cleavage effect on adenine nucleotide sequences upon recognizing the target DNA. The resulting adenine nucleotide sequences of varying lengths then engaged in interactions with silver nanoparticles, leading to a solution characterized by distinct light transmittance. Subsequently, the solution was positioned between the light source and the photoelectrode, strategically impacting the photon absorption step within the photoelectrochemical process. Consequently, the detection of nucleic acid was accomplished through the analysis of the resultant photocurrent signal. The developed platform exhibits a detection limit of 0.06 nM (S/N = 3) with commendable selectivity. The innovative use of adenine nucleotide sequences as cost-effective probes interacting with silver nanoparticles eliminates the need for complex interfacial immobilization processes, significantly simplifying the fabrication of DNA sensors. The outcomes of our research present a promising pathway for advancing the development of economically feasible miniature DNA sensors.

Manipulating photon absorption and trap energy supply for multimode dynamic anti-counterfeiting

Manipulating photon absorption and trap energy supply ensures the adjustable luminescence intensity of colored sample, and ultimately achieve dynamic anti-counterfeiting modes dependent on wavelength, time and space.

Fabrication of zinc oxide nanorods for photocatalytic degradation of docosane, a petroleum pollutant, under solar light simulator.

The use of advanced oxidation processes (AOP) in photocatalysis is critical for treating hazardous chemical compounds in oil-produced water (OPW). ZnO NRs are one of the most important modern and safe photocatalysts and have been easily prepared by a microwave-assisted hydrothermal method and grown on glass substrates. Hexagonal-shaped ZnO NRs and a bandgap energy (Eg) of up to 3.2 eV were characterized using SEM, XRD, UV-Vis, and PL devices, respectively. The effectiveness of photocatalytic degradation on the organic docosane solution was evaluated using a solar light simulator. On the surface area of the ZnO NRs, high photon absorption causes e-/h+ pairs to be excited between the VB and CB, producing free radicals that immediately react with organic contaminants and transform them into harmless chemicals. The photocatalytic degradation efficiency of the compound docosane analysed using GC-MS/MS reached 68.5% at 5 hours of irradiation. A mechanism for the photocatalytic degradation of docosane was proposed at pH ∼ 6.5, and a reduction of 60.5% of the total organic carbon (TOC) was achieved. Thus, the photocatalytic treatment of organic compounds contained in OPW has great potential and serves an important environmental purpose.

Nickel nanoparticle-decorated twinned crystal CdxZn1−xS for enhanced photocatalytic hydrogen production

In photocatalysis, maximizing light absorption and utilizing light-stimulated electrons is of paramount importance. In this study, Ni-decorated CdxZn1−xS twinned crystals were synthesized via solvothermal method with Ni loadings ranging from 0.5 to 5 wt%. The Ni nanoparticles introduced the Surface Plasmon Resonance (SPR) effect, broadening photon absorption and extending the photo-response into the visible light range. Notably, 1 wt % Ni-decorated Cd0.5Zn0.5S exhibited remarkable H2 evolution rate of 1497 μmol(h.gcat)−1. This enhancement is attributed to the SPR effect, which enhances light absorption and photogenerated electron generation, as well as efficient electron transfer facilitated by Ni's lower Fermi level. These findings emphasize the crucial role of optimal Ni loading and the SPR effect in enhancing photocatalytic efficiency.