Wavelength and coherence effects on the growth mechanism of silicon nanopillars and their use in the modification of spontaneous lifetime emission of BODIPY dye molecules

Silicon nanopillars are grown by an electrochemical anodization of p-type silicon wafers at low current densities in a hydrofluoric acid solution. CW, white light, and various UV pulsed lasers are employed as illumination sources in sample preparation to study wavelength and coherence effects on the growth mechanism of the nanopillars. Coherence is observed to be the foundation of regularity in obtaining conical shapes. The pillar size is found to be almost linearly proportional to the employed illumination wavelength during their growth. BODIPY dye molecules are chemically attached to these silicon nanopillars and the radiative decay rates are investigated by means of a time-resolved fluorescence experiment. The decay rate of the dye molecules embedded in the vicinity of various size pillar tips is significantly affected due to different apex angles of the conical nature. It is demonstrated that the pillar size and the separation between pillars can be adjusted if one uses a coherent light source with an appropriate wavelength during the course of fabrication process. Since change in the decay rate is due to tips of the pillars only, separation of a few micrometers between pillar tips allows one to directly monitor a dye, which is embedded to the tip of a single nanopillar, via a confocal microscopic method for the spontaneous lifetime measurements, without having needed to any extra efforts for an in situ imaging process. It is observed that as the pillar size gets smaller, the inhibition in the spontaneous lifetime of BODIPY is more pronounced. In addition, a more regular pillar structure yields nonvarying decay rates of the dye molecules throughout the silicon sample.     

Multipoint parallel excitation and CCD-based imaging system for high-throughput fluorescence detection of biochip micro-arrays

We report the development and the characterization of a multipoint parallel excitation and CCD-based imaging system for high-throughput fluorescence detection of biochip micro-arrays. A two-dimensional array of (19×19) points with uniform intensity distribution, generated by a holographic array generator, was used for parallel excitation of two-dimensional micro-arrays of fluorescence samples. A CCD-based imaging system was used for high-throughput parallel detection and quantitative analysis of the fluorescence output. Micro-array samples of cyanine (Cy5) dye dots on silicon wafers and on glass substrates with varying concentration were used to evaluate the performance of the system. Results of fluorescence intensity measurements with varying concentration of dye and with different image acquisition time are presented. We have demonstrated that this novel approach will, in general, outperform the conventional approach in the excitation efficiency, the signal-to-noise ratio, and the throughput. The limitations and the potential improvements of the present method are discussed.     

Fluorescence switch of dye-infiltrated SiO<Subscript>2</Subscript> inverse opal based on acid-base vapors or light

The acid-base vapors/light double responsive dye-infiltrated SiO₂ inverse opal photonic crystals (PCs) were fabricated by sacrificial template method and a subsequent infiltration of spiropyran derivative dye molecules. The fluorescence of ring-open dye molecules infiltrated in PCs can be switched on/off based on different fluorescence properties of spiropyran dye under stimuli of acid-base vapors or light, when PCs with suitable stopband were selected. The fluorescence switch behavior based on PCs has potential applications in data storage, color displays, chemical and biological sensors.     

用于靶丸装配的胶黏剂荧光性能及相容性研究

为充气靶丸的精密装配提供有效的胶斑定位检测方法,研究了具有荧光特性的环氧胶黏剂,通过环氧胶黏剂与香豆素和JS-064荧光染料的相容性及荧光性的研究,探索其适用于靶丸装配和检测的添加工艺。分别测定了入射波长和适用于工艺的激发波长,研究了荧光强度与香豆素浓度的关系以及固化剂对荧光强度的影响。并确定了无水乙醇减小表面张力的工艺方法。结果表明:香豆素的激发波长为274nm,入射波长为519nm;荧光染料的激发波长为435nm,适用于胶斑定位检测的激发波长为365nm;香豆素能很好地溶于固化剂176中,有淡蓝色荧光,而荧光染料均匀分散于胶黏体系,且荧光性能良好。     

Confocal microscopy of electrostatic properties of Si quantum dots and silica surfaces by charge-sensitive dye molecules

An aminonaphthylethenylpyridinium dye (ANEPPS) has been used to investigate the photoinduced charging of SiO₂ surfaces via fluorescence shifts. Confocal microscopy allows for a localization of the charge distributions of better than 250 nm. The surface becomes negatively charged upon photoexcitation. This effect is enhanced by silicon nanocrystals (quantum dots) of less than 20 nm in diameter. Experiments suggest that ANEPPS occupies the SiO₂ surface in an oriented way.     

Synthesis and Properties of a New Photostable Soluble Perylene Dye: N,N'-Di-(1-Dehydroabietyl) Perylene-3,4,9,10-Bis(Dicarboximide)

N,N'-Di-(-1-Dehydroabietyl) perylene-3,4,9,10-bis(dicarboximide) is prepared in 95% yield by the condensation of perylene 3,4,9,10-tetracarboxylic dianhydride with dehydroabietyl amine. Thermal and photostable bright red-orange dye is measured to have a fluorescence quantum yield of unity, Q_f=1, in chloroform solutions. Solubility of the dye is 1.8 g/L in chloroform. The diimide is an ideal reference probe for fluorescence quantum yield measurements in 500—650 nm region and also very interesting dye for chemiluminescent light devices.     

Observation of the electric hexadecapole moment of free Na atoms in a forward scattering experiment

We report the observation of an electric hexadecapole moment in the ground state of free sodium atoms. The Δm_F = 4 coherence, which corresponds to this moment, is created by the light field of a cw dye laser. The forward scattered light was used for detection, because of the higher sensitivity compared to lateral fluorescence.     

Rutacridone as a Fluorescent Dye for the Study of Pollen

Rutacridone, alkaloid from plant Ruta graveolens was used for the histochemical staining of Hippeastrum hybridum pollen. The rutacridone fluorescence (excited by UV light at 360–380 nm) has been studied with Karnaukhov-constructed microspectrofluorimeters. Nucleus and DNA were stained by this dye in cells and fluoresced by green light with maxima of 530 and 555 nm, respectively. Development of the pollen was analyzed with this dye.     

染料掺杂液晶可调谐光纤荧光光源的研究

本文提出了染料掺杂液晶填充空心光纤构造荧光可调谐光源.基于染料分子能级结构理论分析B4400荧光光谱依赖温度的变化特性,采用脉宽8 ns,波长为532 nm YAG倍频脉冲激光器抽运,向列相液晶作基体,实验分析染料B4400掺杂液晶填充空心光纤荧光光谱选择性荧光放大规律及温度调谐特性.结果表明:通过控制染料浓度可控制荧光输出功率水平;当温度升高时,中心波长发生红移,中心波长调谐范围为590—605 nm;荧光谱宽呈单调展宽,调制范围为228—236 nm;染料掺杂液晶填充空心光纤荧光光源可实现一定范围内的温度调谐.     

Design and development of a fiber-optic immunosensor utilizing near-infrared fluorophores

The design and application of a fluorescent fiber-optic immunosensor (FFOI) are reported. The FFOI is utilized for the detection of antibody/antigen binding within the near-infrared (NIR) spectral region. The technique is developed through the combined use of fiber-optic, semiconductor laser-excitation, fluorescence detection, NIR dye, and immunochemical techniques. The antibody is immobilized on the FFOI and utilized as a recognition component for trace amounts of specific antigen. The FFOI is constructed to utilize an antibody sandwich technique. The assay involves the immobilization of the capture antibody on the sensing tip of the FFOI followed by the exposure of the immobilized sensing tip to the antigen. The antigen-coated FFOI is then introduced to a second antibody previously labeled with the NIR dye. Typical measurements are performed in about 15 min. A semiconductor laser provides the excitation (780 nm) of the immune complex. The resulting emission is detected by a silicon photodiode detector (820 nm). The intensity of the resulting fluorescence is directly proportional to the concentration of the antigen. The sensitivity of the analysis reaches 10 ng/ml and the response time is 10–15 min.     

A laser-induced fluorescence biosensor by using ellipsoidal reflector

A new and compact fluorescence biosensor is constructed. The distinguished feature of this setup is the use of an ellipsoidal reflector as an optical collector of the fluorescence light. A traditional collecting lens with numerical aperture of 0.5 can only collect a few percent of the available signal, while the incorporation of the ellipsoidal reflector enables the apparatus to provide a signal increase of at least 66 times. A very good linear relationship between the concentration of fluorescent dye and the fluorescence intensity is achieved with correlation coefficient R=0.99979. The 3σ detection limit is 5 nM for microliter volume sample. Meanwhile, it is found that laser light scattering by dirts and scratches on the sample cell's windows and by turbidity in the sample solutions is the dominant limitation to increase the detection sensitivity. Approach to solve this problem is suggested.     

Spectroscopic and lasing characterisation of a dicarbazovinylene-MEH-benzene dye

The dye 1,4-bis(9-ethyl-3-carbazovinylene)-2-methoxy-5-(2′-ethyl-hexyloxy)-benzene (abbreviated 2CzV-MEH-B) dissolved in tetrahydrofuran (THF) and as neat film is characterised by optical absorption and emission spectroscopy. The absorption and stimulated emission cross-section spectra, the fluorescence quantum distributions, fluorescence quantum yields, degrees of fluorescence polarisation, and fluorescence lifetimes are determined. A lasing characterisation is carried out by pumping with single second harmonic pulses of a mode-locked ruby laser (wavelength 347.15 nm, pulse duration 35 ps). The excited-state absorption at the pump laser wavelength is determined by saturable absorption measurements. Laser oscillation of the dye in THF in a rectangular cell is achieved by transverse pumping using the uncoated cell windows for light feedback. From the emission behaviour around threshold the excited-state absorption cross-section spectrum in the laser active spectral region is extracted. The wave-guided travelling-wave lasing behaviour of the dye as neat film is studied by analysis of the amplification of the transverse pumped spontaneous emission. Surface emitting distributed-feedback lasing was achieved with a neat film on corrugated second-order periodic gratings.     

Fluorescence of a photosensitizer based on an indotricarbocyanine dye in photochemotherapy

We present the results for studies of the spectral luminescence properties of a symmetric indotricarbocyanine dye (PD1) in HeLa tumor cells and animal tissues in vivo during a photochemotherapy session and after the end of the session. We have established that when the dye is exposed to light in tumor tissues, changes occur in the position and half-width of the dye fluorescence spectra, while in a culture of HeLa cells its spectral characteristics are constant. Based on analysis of the effect of overlap between the absorption spectra of endogenous biomolecules and the fluorescence spectra of the dye plus comparison of the experimental data with numerical modeling results, we have concluded that the observed changes in the fluorescence spectra of PD1 in vivo are due to a change in the ratio of the different forms of hemoglobin in the tumor tissue. We have shown that the spectral characteristics of PD1, fluorescing in the near IR range, correlate with the depth of tumor tissue necrosis achieved on exposure to light. We have established that tumor tissue necrosis occurs down to a depth of 2 cm in the case of all strains studied: S-45, SM-1, and W-256, where as a result of exposure to light, we observe an increase in the half-width and a short-wavelength shift of the fluorescence spectrum of the dye PD1, and also the intensity of its fluorescence does not recover.     

Dynamics of fluorescence of solid solutions of quantum dots and the organic dye DODCI: Experiment and numerical simulation

The fluorescence of solid solutions of CdSe/ZnS quantum dots and the organic dye DODCI is investigated. It is shown that nonradiative transfer of electronic excitation energy to dye molecules, which with some probability lose their acceptor properties as a result of photoisomerization or photodegradation, is responsible for a significant increase in the fluorescence intensity of a donor. The degree of polarization of the donor fluorescence attains values exceeding 0.5, which is due to the difference in the fluorescence quantum yields of donors with different orientations of the oscillator with respect to the electric vector of an excitation light wave. A numerical simulation of the experimentally observed dependences is performed.     

多孔硅吸附染料分子的荧光增强效应

报道了利用多孔硅独特的表面特性,吸附染料分子后,使得染料的荧光得到很大的增强,并观察到了这种吸附过程中彼此间的能量转移过程。对染料的荧光增强机理及实验结果进行了讨论。     

The velocity distribution of sputtered Zr atoms for irradiation at normal and oblique angle of incidence

Laser-induced fluorescence by means of a cw dye laser has been used for investigating the velocity distribution of sputtered Zr atoms in the ground state. In order to evaluate the data the excitation probability of the atoms in the observation volume has been measured. The velocity distribution of Zr atoms for irradiation with Ar⁺-ions as well as light ions at normal and oblique angle (70°) of incidence is presented.     

应用于FAGE技术测量OH自由基的激光器波长修正方法研究

研究了一种应用于气体扩张激光诱导荧光(FAGE)技术测量OH自由基的染料激光器波长修正方法。该方法采用镍铝丝热解水汽产生稳定的高浓度OH自由基,利用重复频率为8500 Hz的染料激光器输出波长约282 nm激光作为光源.激发低压腔内热解产生的高浓度高稳定性OH自由基产生荧光,由普通光电倍增管和光电二极管分别探测激发荧光和出腔激光强度。通过延时信号发生器统一触发激光器和高速数据采集卡并结合LabVIEW软件处理得到单位激光强度的荧光积分强度数据。连续两次扫描激光波长,当第二次扫描的荧光积分强度达到第一次最大值的0.95倍时,停止波长扫描,此时的激光器波长位置即为激发线位置。本文首先扫描激光波长,研究了282 nm激发机制下的OH自由基激发谱;然后在Q_1 2激发线位置探究了气体湿度、氧气含量、进气量以及抽速对荧光积分强度和寿命的影响;并分析了镍铝丝热解水的反应机理,初步认为热解中OH自由基主要来源于氧原子与水的反应。在以上荧光积分强度和寿命影响因素的研究基础上,优化了系统参数,使荧光积分强度波动小于±1.9%。连续多次进行波长修正,修正偏差为0.1pm。该方法能够满足气体扩张激光诱导荧光(FAGE)技术定量精确测量大气OH自由基对波长的要求。     

Multiple switching behaviors of poly(N-isopropylacrylamide) hydrogel with spironaphthoxazine and D-π-A type dye

A multi-switchable poly(NIPAM-co-SPO-co-D-π-A dye) hydrogel with a photochromic spironaphthoxazine and an electron donor-π-conjugated-electron acceptor (D-π-A) type dye was prepared by typical radical copolymerization. The low critical solution temperature (LCST) behavior was investigated by UV–vis spectroscopy, which allows the measurement of the phase transition from 20 to 40 °C in aqueous solution. The fluorescence intensity of the poly(NIPAM-co-SPO-co-D-π-A dye) was temperature-dependent. Reversible modulation of fluorescence intensity was achieved using alternating irradiation with UV and visible light. Prepared polymer hydrogel also exhibited spectra change when not only used Cu²⁺ cation but also an acid unit.     

Photophysical Characterization of New 3-Amino and 3-Acetamido BODIPY Dyes with Solvent Sensitive Properties

The structural, electronic and photophysical properties of three new asymmetric, highly fluorescent difluoroborondipyrromethene (BODIPY) dyes, bearing an amino or an acetamido group at position 3 of the chromophoric core, have been studied in different apolar, polar and polar/protic solvents. The presence of the 3-amido group extents the delocalization of the π-system, leading to bathochromic shifts in the absorption and fluorescence bands, as predicted by quantum mechanic calculations. The 3-amino dye shows photophysical properties highly dependent on the solvent polarity and acidity, and is characterized by a hypsochromic shift of its absorption band, with regard to the corresponding acetylated dye, as well as a low fluorescence quantum yield in acid media with proton concentration lower than 4 × 10⁻⁴ M. In media with higher proton concentration, the BF₂ bridge group of the 3-amino dye is removed, yielding the corresponding non-fluorescent dipyrromethene precursor. These results suggest that the 3-amino dye could be used as a fluorescence probe for the study of the acidity of different environments.     

Dye Laser for Absorption Trace Analysis of Sodium

The advent of organic dye lasers made possible many experiments in physics, chemistry and biology. Most of these applications are based on the possibility to tune dye laser emission almost at any wavelength between 3400 Å and 12000 Å.This quality combined with high light power made feasible multiphotone absorption, selective absorption and fluorescence experiments. Recently a group of authors published the papers: “Enhancement of absorption spectra by dye laser quenching I and II”^1,2 which start a new field of applications of dye lasers. Namely if a weak absorber is placed inside the broad band laser cavity the absorption is enhanced and this results in the same absorption bands or lines observable in the spectrally resolved laser output. This effect can be used for detection of the traces of elements as a complementary method to the classical absorption spectroscopy but with much higher sensitivity. Same method could be also very useful for detection of transient species with a very short lifetimes.