Light In Near-infrared Region Research Articles

Internal profile measurement of GaAs microstructures based on near-infrared light phase-stepping interferometry

Internal profile nondestructive measurement of MEMS microstructures based on semiconductor materials is urgently demanded with the dramatic development of MEMS industry. A new attempt was made to extend the interferometric method and the thickness-profile measurement theory of transparent thin film layers from the visible light region (400–800 nm) to near-infrared light region (900–1700 nm). The measurement system based on Linnik interferometer using a near-infrared halogen light source with 1127 nm center wavelength was established for internal profile measurement. The measurement method for internal profile of GaAs microstructures was realized. From a comparison of reflection interferometry and transmission interferometry, it can be concluded that the latter measurement results were consistent with those of the former and internal profile was determined within an error range of 8%.

Development of functional gold nanorods for bioimaging and photothermal therapy

Gold nanorods have strong surface plasmon band at near-infrared light region, and are used as a photothermal converter. Since the near-infrared light penetrates into tissues deeply, it has been expected as a contrast agent for near infrared light bioimaging, a photosensitizer for photothermal therapy, and functional device for drug delivery system responding to near-infrared light irradiation. In this study, the surface plasmon bands of intravenously injected gold nanorods were monitored in the mouse abdomen using a spectrophotometer equipped with an integrating sphere, then we determined pharmacokinetics parameters of the gold nanorods after intravenous injection. Next, the PEG-modified gold nanorods were directly injected into subcutaneous tumors in mice, then, near-infrared pulsed laser light was irradiated the tumors. Significant tumor damage and suppression of the tumor growth was observed. We constructed targeted delivery system of the gold nanorods by modifying with a thermo-responsive polymer and a peptide responding to a protease activity. These modified gold nanorods are expected as functional nanodevices for photothermal therapy and drug delivery system.

Enhanced near-infrared electrochromism in triphenylamine-based aramids bearing phenothiazine redox centers

A series of organosoluble polyamides based on N-phenothiazinylphenyl redox units showing anodically electrochromic characteristics both in the near-infrared (NIR) and visible light regions were prepared from the phosphorylation polyamidation reactions of a newly synthesized diamine monomer, 4,4′-diamino-4′′-N-phenothiazinyltriphenylamine, with various dicarboxylic acids. These polymers were readily soluble in many polar solvents and showed useful levels of thermal stability associated with relatively high glass-transition temperatures (Tg) (255–277 °C) and high char yields (higher than 67% at 800 °C in nitrogen). In addition, the polymer films showed reversible electrochemical oxidation with enhanced NIR contrast, high coloration efficiency (CE), low switching time, and anodic green/purple electrochromic behaviors.

Detection and evaluation of initial cartilage pathology in man: A comparison between MRT, arthroscopy and near-infrared spectroscopy (NIR) in their relation to initial knee pain

Background and aims: MRI and arthroscopy are important methods in the evaluation of cartilage pathology. But frequently initial changes of cartilage in combination with chronic knee pain cannot be detected by employing these two methods. Better diagnostic tools for the detection of the early stages of osteoarthritis (OA) are required. The objective of this study was to show that near-infrared spectroscopy (NIRS) can be incorporated into routine arthroscopy to improve detection and assessment of the initial cartilage pathology. Furthermore correlations between findings in MRI, arthroscopy and NIRS in patients with initial symptoms of OA have studied. Methods: Patients ( n = 21, 12 women, 9 men, age: 15–59 years, mean 34.19 years) with knee pain lasting for at least half a year without any trauma of the knee in their history were interviewed (body weight, smoking behaviour) and clinically evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS). Also serum parameters (cholesterol, lipids) were analysed, conventional X-rays in three directions (evaluated according to Kellgren and Lawrence) and MRI (evaluation of cartilage damage according to the ICRS-score) were performed preoperatively in all patients. During subsequent arthroscopy cartilage damage was evaluated according to the ICRS-score. In addition the spectral reflection of cartilage was investigated in all knees using a special micro-glass-fiber probe in the near-infrared light region (spectral range between 1150 and 1475 nm). To characterize relations between the investigated parameters the Spearman's rank correlation coefficient was used. Inter-observer variance was calculated employing the Cohens–Kappa-test. Results: MRI demonstrated a strong inter-observer variance with no significant correlations to other parameters. The same was observed for arthroscopic findings. Only NIRS showed significant correlations with three out of five KOOS subscores. Within the general parameters only smoking behaviour showed a significant correlation with two of the KOOS-scores. NIRS therefore seemed to be a sensitive diagnostic tool in detection of initial pathology in human cartilage. The additional necessary time for the spectroscopic investigation as part of the routine arthroscopy ranged between 3 and 7 min (mean: 4 min 18 s). Conclusion: Particularly for early-stage cartilage lesions (ICRS 0/I) MRI and arthroscopy have rather low predictive value. The inter-observer variance is very high (Cohens–Kappa < 0.4). Correlations found between NIRS and KOOS suggest that NIRS potentially can be used for detection of initial cartilage pathology and may be helpful in the evaluation of the benefit of different medical or surgical interventions at early-stage of articular cartilage damage.

Facile Synthesis of Cu2O Nanocrystals with Systematic Shape Evolution from Cubic to Octahedral Structures

We report a facile method for the synthesis of cuprous oxide nanocrystals with systematic shape evolution. Monodisperse truncated cubic, cuboctahedral, truncated octahedral, and octahedral nanocrystals can be synthesized directly in an aqueous solution of CuCl2, sodium dodecyl sulfate (SDS) surfactant, hydroxylamine (NH2OH·HCl) reductant, and NaOH by simply varying the volume of hydroxylamine added to the reaction mixture. SDS surfactant was found to be necessary for a precise control of the nanocrystal morphology. Adjustment of the volume of NaOH added provides a means to vary the particle size. In the case of octahedral nanocrystals, particles with sizes of 160−460 nm can be prepared. By examining the intermediate products formed, which resemble the final nanocrystal structures, a growth mechanism is proposed. Optical characterization of these Cu2O nanocrystals showed band gap absorption at 470−490 nm and strong light scattering bands extending from the visible to the near-infrared light region. All four samples displayed activity toward photodegradation of rhodamine B molecules, but truncated octahedral and octahedral nanocrystals exhibited a higher extent of the photodecomposition reaction, suggesting the {111} faces of Cu2O nanostructures are catalytically more active than the {100} faces. These nanocrystals should allow the examination of their various properties as a function of the particle shape.

Luminescence and photovoltaic cells of benzoselenadiazole-containing polyfluorenes

In this work, light-emitting and photovoltaic properties of new low band-gap copolymers (PFO-DBSe) based on 9,9-dioctylfluorene and 4,7-di-2-thienyl-2,1,3-benzoselenadiazole (DBSe) were investigated. The peak positions of photoluminescence and electroluminescence (EL) of the copolymers reach 758 and 727 nm, respectively, and locate in near-infrared light region. At a current of ∼5 mA, EL emission with peak position of 701 nm and a maximum external quantum efficiency of 1.62% was achieved from EL device with poly(9,9-dioctylfluorene) and the copolymer with DBSe content of 5% as the blend-type emitter, by utilizing of a configuration of ITO/PEDOT/PVK/emitter/CsF/Al. This is a high efficiency for deep red EL emission. The copolymer with DBSe content of 35% possesses good solar light spectral coverage according to its absorption spectrum, and a bulk-heterojunction photovoltaic cell with the copolymer as the electron donor and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as the electron acceptor displayed an energy conversion efficiency of 0.91% under an AM1.5 solar simulator at 100 mW/cm 2.

Optical Absorption and Electron Spin Resonance Studies of Nonlinear Optical Crystal Li3VO4 Grown by the Floating-Zone Method

The optically nonlinear Li3VO4 crystal grown by the floating-zone (FZ) method has been characterized by optical absorption and electron spin resonance (ESR) spectroscopy. The as-grown single crystals grown in gaseous argon exhibit a broad absorption extending from the uv to near-infrared light regions and an absorption band at about 3 eV. Postoxidation reduces the whole optical absorption and reveals an additional 1.9 eV band. ESR detects several signals associated with transition-metal ions in as-grown and reduced crystals, i.e., Fe3+, Mn2+ and Cr3+ ions. The Mn2+ and Cr3+ signals are absent in well-oxidized crystals, while the Fe3+ signal shows no significant change. The reduced crystals have three absorption bands associated with transition-metal impurities and oxygen vacancies. The diffuse reflectance spectra of transition-metal-doped Li3VO4 polycrystals were also measured to examine the effect of the presence of Fe3+, Mn2+ and Cr3+. The origin of the optical absorption in as-grown, oxidized and reduced Li3VO4 are discussed in terms of unexpectedly doped iron-group transition-metals and oxygen vacancies. The 3 eV and 1.9 eV absorption bands and the broad band extending from the uv to near-infrared regions are suppressed in the well-oxidized crystals subjected to repeated zone refining, indicating that multiple zone refining and complete oxidation are important in obtaining optical-quality Li3VO4 single crystals.

62. Imaging of a thermionic emitter in an emission microscope: N N Sedov, Izv Akad Nauk SSSR Ser Fiz, 35 (3), 1971, 641–643 ( in Russian).

This chapter discusses the multialkali effects and polycrystalline properties of multialkali antimonide photocathodes. The concept of multialkali effects is aligned with the fact that photocathodes of high sensitivity may be obtained if antimony is combined with more than one alkali metal. Because of the background of its real applications, the characteristics of the multialkali photocathode, especially its integral sensitivity and spectral response in the red and near-infrared light regions, have been improved successively in the recent past. It is believed that this photocathode still has large potential. One of the significant problems in this regard is the influence of the polycrystalline grain sizes and grain boundaries on photoemission. Usually a semiconductor model was used for the multialkali photocathode, but it is really a monocrystal model. This model cannot be used to discuss its spectral response, quantum yield, or integral sensitivity. In addition to the influence of the composition and surface structure of the photocathode, the grain sizes and grain boundaries also have obvious influence on photoemissive properties. The physical basis for the multialkali effect and the influence of the grain sizes and grain boundaries on photoemission are discussed in this chapter.