Spectromicroscopy and internal photoemission spectroscopy of semiconductor interfaces

For decades, techniques based on synchrotron light sources have played a central role in solid interface research. This role has been recently enhanced by two factors: the commissioning of the third generation of sources, characterized by unprecedented levels of brightness, and the first utilization cases of another class of photon sources related to synchrotron facilities, the free electron lasers (FEL's). This review will first present some relevant examples of how the new facilities are changing the scene of interface research, most notably in the domain of spectromicroscopy. We will specifically illustrate how the crucial problem of the lateral fluctuations of interface properties is being attacked with both synchrotron-light and FEL techniques. Then, we will argue that the present applications are only marginally exploiting the amazing capabilities of the new sources. The main case to illustrate this point is coherence-sharpened x-ray imaging, a very promising and spectacular technique developed for medical radiology, which could find extremely interesting applications in interface research.     

Practical applications of radiation chemistry

The physical, chemical, and biological effects of ionizing radiation on matter are the basis of many practical applications. The number of such applications is growing, and sources of gamma radiation and X-rays are now being operated in harsh, demanding environments. They play an important role in the economic development of many countries. The text was submitted by the author in English.     

X-ray and neutron imaging with colloids

A series of technical advances are helping to revolutionise the possibilities for X-ray and neutron imaging in colloidal science. These include the development of new imaging modalities with high coherence X-rays such as diffractive imaging, ptychography, and femtosecond holography; and Talbot phase contrast tomography with conventional laboratory based low coherence X-ray sources e.g. standard rotating anodes. A crucial insight is that the available phase contrast with synthetic organic and biological colloids can be two orders of magnitude stronger than the absorption contrast with X-rays, providing large improvements in the signal to noise ratio in the resultant images. Furthermore new developments with the sources of X-rays and neutrons are helping to increase the possibilities for this research as the available coherence, flux and collimation are improved e.g. third generation high brilliance synchrotrons, free electron lasers, high flux pulsed neutron sources and table-top X-ray lasers are being developed. Highlights of the application of these techniques and sources to colloids include: the measurement of the internal strains inside individual crystalline colloidal nanoparticles, the imaging of nanoparticles embedded in opaque solid composite materials, images of defects in the growth of colloidal crystals, and the morphology of nanofoams, intact human chromosomes, protein nanocrystals, viruses, bacteria, and blood cells. The resolution of the reconstructed images can be achieved at the 10–50 nm length scale, without the need for the invasive sample preparation techniques required for transmission electron microscopy e.g. microtoming of specimens is not required. Furthermore fluorescent staining is also not required, as with super-resolution microscopies at visible optical wavelengths (e.g. STED, PALM and STORM), and thick opaque samples can be investigated, although some fragile organic and biological materials require freezing to reduce beam damage with X-rays. Neutron imaging has also benefited from the development of analogous Talbot phase contrast techniques to those possible with low coherence X-rays and a number of useful applications in non-invasive imaging at the 100 μm length scale have been demonstrated e.g. the internal structure of live plants, the inner workings of fuel cells and the three-dimensional domain structure of magnetic materials.     

X射线成像技术在能源材料研究中的应用

随着人类对可持续能源的需求不断增长,先进的表征方法在能源材料研究等领域变得越来越重要。借助X射线成像技术,我们可以从二维和三维角度实时获取能源材料的形貌、结构和应力变化信息。此外,借助高穿透性X射线和高亮度同步辐射源,设计原位实验,可以获取充放电过程中样品的定性和定量变化信息。本文综述了基于同步加速器的X射线成像技术及其相关应用,讨论了包括X射线投影成像、透射式X射线显微成像、扫描透射X射线显微成像、X射线荧光显微成像以及相干衍射成像等几种主要的X射线成像技术在能源材料研究领域的应用,展望了未来X射线成像的应用前景及发展方向。     

X-ray imaging during plasma-source ion implantation

Plasma source ion implantation (PSII) is a technique for modifying stafaces that places the object to he modified directly into a plasma and then negatively pulse biases the object so as to implant positive ions. If the voltage is high enough, X-rays can he generated by electrons that are also accelerated by the pulse. This work describes techniques for imaging and characterizing the X-rays A pinhole camera was used to image the X-rays being emitted as electrons collided with surfaces in the chamber. The images show that X-rays are generated at the chamber walls and near the target. The time dependence of these X-rays during each pulse was examined using a PIN diode X-ray detector. Then, using another X-ray sensor and pulseheight analyzer, the spectra of the emitted X-rays was determined. The object is to relate the X-ray intensity and spectrum to the temporal and spatial values of the implantation dose so that it may he used as a process monitor and a control sensor.     

Higher-order processes in X-ray photoionization of atoms

There are several fourth-generation X-ray light source projects now underway around the world and it is anticipated that by the end of the decade, one or more of these X-ray free-electron lasers will be operational. In this contribution, we describe recent measurements and future plans to study both multielectron and multiphoton atomic photoionization. Although such higher-order processes are rare with present third-generation sources, they will be commonplace in experimental work with the new sources. The topics we discuss here are double K-shell ionization and two-photon X-ray photoionization.     

元素成像技术在安检领域的研究进展

元素成像作为一种快速、直观的无损检测技术,在核工业、航空航天、新能源、地质、考古、先进制造等多个领域得到广泛应用。其中的X射线凭借较强的穿透物体的能力,太赫兹和毫米波凭借对人体无接触、低损害的特点,在安检领域得到了广泛应用。本文对这三种成像技术的数据集和近几年的图像处理技术进行了总结和归纳,为该领域的进一步深入应用提供了有力的技术支撑。     

X-Ray-Induced Drug Release for Cancer Therapy

Drug delivery systems (DDSs) are designed to deliver therapeutic agents to specific target sites while minimizing systemic toxicity. Recent developments in drug-loaded DDSs have demonstrated promising characteristics and paved new pathways for cancer treatment. Light, a prevalent external stimulus, is widely utilized to trigger drug release. However, conventional light sources primarily concentrate on the ultraviolet (UV) and visible light regions, which suffer from limited biological tissue penetration. This limitation hinders applications for deep-tissue tumor drug release. Given their deep tissue penetration and well-established application technology, X-rays have recently received attention for the pursuit of controlled drug release. With precise spatiotemporal and dosage controllability, X-rays stand as an ideal stimulus for achieving controlled drug release in deep-tissue cancer therapy. This article explores the recent advancements in using X-rays for stimulus-triggered drug release in DDSs and delves into their action mechanisms.     

Time‐Resolved Synchrotron Radiation Excited Optical Luminescence: Light‐Emission Properties of Silicon‐Based Nanostructures

The recent advances in the study of light emission from matter induced by synchrotron radiation: X‐ray excited optical luminescence (XEOL) in the energy domain and time‐resolved X‐ray excited optical luminescence (TRXEOL) are described. The development of these element (absorption edge) selective, synchrotron X‐ray photons in, optical photons out techniques with time gating coincide with advances in third‐generation, insertion device based, synchrotron light sources. Electron bunches circulating in a storage ring emit very bright, widely energy tunable, short light pulses (<100 ps), which are used as the excitation source for investigation of light‐emitting materials. Luminescence from silicon nanostructures (porous silicon, silicon nanowires, and Si–CdSe heterostructures) is used to illustrate the applicability of these techniques and their great potential in future applications.     

Optimizing UV laser focus profiles for improved MALDI performance

Matrix assisted laser desorption/ionization (MALDI) applications, such as proteomics, genomics, clinical profiling and MALDI imaging, have created a growing demand for faster instrumentation. Since the commonly used nitrogen lasers have throughput and life span limitations, diode-pumped solid-state lasers are an alternative. Unfortunately this type of laser shows clear performance limitations in MALDI in terms of sensitivity, resolution and ease of use, for applications such as thin-layer sample preparations, acceptance of various matrices (e.g. DHB for glycopeptides) and MALDI imaging. While it is obvious that the MALDI process has some dependence on the characteristics of the laser used, it is unclear which features are the most critical in determining laser performance for MALDI. In this paper we show, for the first time, that a spatially structured laser beam profile in lieu of a Gaussian profile is of striking importance. This result enabled us to design diode-pumped Nd : YAG lasers that on various critical applications perform as well for MALDI as the nitrogen lasers and in some respects even better. The modulation of the beam profile appears to be a new parameter for optimizing the MALDI process. In addition, the results trigger new questions directing us to a better understanding of the MALDI process.     

A perspective on novel sources of ultrashort electron and X-ray pulses

Recently, much attention has been devoted to the development of new pulsed sources of radiation for investigating matter with atomic scale temporal and spatial resolution. While much has been achieved thanks to modern ultrafast laser technology, the ultimate coherent light source, the X-ray free electron laser (X-FEL), promises to deliver the highest X-ray photon flux in the shortest pulses at energies unreachable by conventional solid-state lasers. In parallel, other approaches that utilize electrons in table-top setups as a probe have been developed demonstrating the potential for a valid complement to X-ray based techniques. Here, we consider yet another possible avenue in which the technology of electron diffraction and imaging is pushed further; we estimate the interest and performances of a femtosecond high energy electron microscope and propose a hybrid experiment with relativistic electrons as a probe and fs X-ray pulses as a pump taking advantage of both technologies.     

Diagnostic prospects and preclinical development of optical technologies using gold nanostructure contrast agents to boost endogenous tissue contrast

Numerous developments in optical biomedical imaging research utilizing gold nanostructures as contrast agents have advanced beyond basic research towards demonstrating potential as diagnostic tools; some of which are translating into clinical applications. Recent advances in optics, lasers and detection instrumentation along with the extensive, yet developing, knowledge-base in tailoring the optical properties of gold nanostructures has significantly improved the prospect of near-infrared (NIR) optical detection technologies. Of particular interest are optical coherence tomography (OCT), photoacoustic imaging (PAI), multispectral optoacoustic tomography (MSOT), Raman spectroscopy (RS) and surface enhanced spatially offset Raman spectroscopy (SESORS), due to their respective advancements. Here we discuss recent technological developments, as well as provide a prediction of their potential to impact on clinical diagnostics. A brief summary of each techniques'' capability to distinguish abnormal (disease sites) from normal tissues, using endogenous signals alone is presented. We then elaborate on the use of exogenous gold nanostructures as contrast agents providing enhanced performance in the above-mentioned techniques. Finally, we consider the potential of these approaches to further catalyse advances in pre-clinical and clinical optical diagnostic technologies.

Optical biomedical imaging research utilising gold nanostructures as contrast agents has advanced beyond basic science, demonstrating potential in various optical diagnostic tools; some of which are currently translating into clinical applications.     

Photoresponsive molecular tools for emerging applications of light in medicine

Light-based therapeutic and imaging modalities, which emerge in clinical applications, rely on molecular tools, such as photocleavable protecting groups and photoswitches that respond to photonic stimulus and translate it into a biological effect. However, optimisation of their key parameters (activation wavelength, band separation, fatigue resistance and half-life) is necessary to enable application in the medical field. In this perspective, we describe the applications scenarios that can be envisioned in clinical practice and then we use those scenarios to explain the necessary properties that the photoresponsive tools used to control biological function should possess, highlighted by examples from medical imaging, drug delivery and photopharmacology. We then present how the (photo)chemical parameters are currently being optimized and an outlook is given on pharmacological aspects (toxicity, solubility, and stability) of light-responsive molecules. With these interdisciplinary insights, we aim to inspire the future directions for the development of photocontrolled tools that will empower clinical applications of light.

This perspective article explores the current state of light-controlled molecular tools for medical therapy and imaging and offers an outlook on clinical application scenarios and optimisation strategies.     

INSTRUMENTATION FOR FLUORESCENCE MICROSCOPY WITH PICOSECOND TIME RESOLUTION

Abstract— Time-resolved fluorescence microscopy using excitation by actively mode-locked dye lasers and analysis by time-correlated single photon counting is shown to be an effective way of obtaining a high degree of spatial and temporal resolution. The imaging capabilities of the microscope make for optimal instrument response functions even with inexpensive photomultiplier tubes. Thus far limited (by the laser source) to long wavelength visible excitation, the excellent light collection and imaging, coupled with the sensitivity of single photon counting make it highly probable that the much weaker U-V second harmonics of the visible dyes will be useable. Certainly the potential of using the third harmonic line (355 nm) of a mode-locked c.w. Nd: YAG laser, or fundamental lines from mode-locked c.w. ion lasers as excitation sources will enhance the technique. Nevertheless, with visible-absorbing dyes only it is possible to excite such fluorochromes as chlorophylls, porphyrins, xanthenes (rose bengal, erythrosin B), phycobiliproteins, thionine dyes, ethidium bromide, and so on. Furthermore, this technique can be straightforwardly extended for polarized light measurements thereby allowing determinations of rotational diffusion of fluorochromes in cells and organelles. The extension to variable temperature situations is easy to conceive. In addition to its use for examination of cellular and sub-cellular entities, the equipment described can be profitably employed wherever spatial resolution may provide extra information, such as studies of powders and the structures of surfaces and interfaces.     

Laser and synchrotron-based sources for excited state intramolecular dynamics studies

Energy ranges and time scales for excitation and relaxation of intramolecular processes are discussed and compared with the operational characteristics of laser and synchrotron radiation sources. The basic physics of synchrotron radiation and undulator emission is presented. It is shown how undulators can be used to generate short wavelength harmonics. Free electron lasers of the Compton and Raman scattering types and the associated electron beam sources are described. The properties and applications of free electron lasers are reviewed.     

Polymers for microlithographic applications: new directions and challenges

Advances in the fabrication technologies associated with electronic devices have placed increasing demands on microlithography, the technology used to generate today's integrated circuits. Within the next few years, a new form of lithography will be required that routinely produces features of less than 0.1 μm. As the exposing wavelength of light decreases to facilitate higher resolution imaging, the opacity of traditional materials precludes their use; and major research efforts to develop alternate materials are underway. As a current example, lithography tools utilizing 193 nm light are now being introduced into the manufacturing environment. Through understanding of materials structure and its relationship to device process requirements and performance, a new class of cyclo‐olefin based polymers was designed for these applications. In particular, alicyclic monomers such as norbornene are readily copolymerized with maleic anhydride and substituted acrylates to afford a wide range of alternative matrices that exhibit transparency at the exposing wavelength and aqueous base solubility. Materials properties must be carefully tailored to maximize lithographic performance with minimal sacrifice of other performance attributes. Further reduction in exposing wavelength to 157 nm introduces new challenges in polymer materials design. Efforts to address those challenges will be discussed.     

Chemiluminescence as a PDT light source for microbial control

The photodynamic therapy (PDT) is a combination of using a photosensitizer agent, light and oxygen that can cause oxidative cellular damage. This technique is applied in several cases, including for microbial control. The most extensively studied light sources for this purpose are lasers and LED-based systems. Few studies treat alternative light sources based PDT. Sources which present flexibility, portability and economic advantages are of great interest. In this study, we evaluated the in vitro feasibility for the use of chemiluminescence as a PDT light source to induce Staphylococcus aureus reduction. The Photogem? concentration varied from 0 to 75 μg/ml and the illumination time varied from 60 min to 240 min.The long exposure time was necessary due to the low irradiance achieved with chemiluminescence reaction at μW/cm2 level. The results demonstrated an effective microbial reduction of around 98% for the highest photosensitizer concentration and light dose. These data suggest the potential use of chemiluminescence as a light source for PDT microbial control, with advantages in terms of flexibility, when compared with conventional sources.     

Plasma-cavity ringdown spectroscopy for analytical measurement: Progress and prospectives

Plasma-cavity ringdown spectroscopy is a powerful absorption technique for analytical measurement. It combines the inherent advantages of high sensitivity, absolute measurement, and relative insensitivity to light source intensity fluctuations of the cavity ringdown technique with use of plasma as an atomization/ionization source. In this review, we briefly describe the background and principles of plasma-cavity ringdown spectroscopy(CRDS) technology, the instrumental components, and various applications. The significant developments of the plasma sources, lasers, and cavity optics are illustrated. Analytical applications of plasma-CRDS for elemental detection and isotopic measurement in atomic spectrometry are outlined in this review. Plasma-CRDS is shown to have a promising future for various analytical applications, while some further efforts are still needed in fields such as cavity design, plasma source design, instrumental improvement and integration, as well as potential applications in radical and molecular measurements.     

Photothermal Conversion of Hydrogel-Based Biomaterial

Traditional energy from fossil fuels like petroleum and coal is limited and contributes to global environmental pollution and climate change. Developing sustainable and eco-friendly energy is crucial for addressing significant challenges such as climate change, energy dilemma and achieving the long-term development of human society. Biomass hydrogels, which are easily synthesized and modified, have diverse sources and can be designed for different applications. They are being extensively researched for their applications in artificial intelligence, flexible sensing, biomedicine, and food packaging. The article summarizes recent advances in the preparation and applications of biomass-based photothermal conversion hydrogels, discussing the light source, photothermal agents, matrix, and preparation methods in detail. It also explores the use of these hydrogels in seawater desalination, photothermal therapy, antibacterial agents, and light-activated materials, offering new ideas for developing sustainable, efficient, and advanced photothermal conversion biomass hydrogel materials. The article concludes with suggestions for future research, highlighting the challenges and prospects in this field and paving the way for developing of long-lasting, efficient energy materials.