Archives

  • 2018-07
  • 2018-10
  • 2018-11
  • 2019-04
  • 2019-05
  • 2019-06
  • 2019-07
  • 2019-08
  • 2019-09
  • 2019-10
  • 2019-11
  • 2019-12
  • 2020-01
  • 2020-02
  • 2020-03
  • 2020-04
  • 2020-05
  • 2020-06
  • 2020-07
  • 2020-08
  • 2020-09
  • 2020-10
  • 2020-11
  • 2020-12
  • 2021-01
  • 2021-02
  • 2021-03
  • 2021-04
  • 2021-05
  • 2021-06
  • The working modes of the spectrometer were tested experiment

    2018-10-24

    The working modes of the spectrometer were tested experimentally with the use of a thermoemitter as a sample. All the abilities of the new spectrometer cannot, of course, be proved while recording thermoemission spectra, because the last do not possess sharp singularities of about 10meV in width. Nevertheless, emission peaks were recorded just in the calculated modes, and the physical phenomena taking place on the emitter surface were demonstrated to be reflected in the form of the recorded spectra. Three working modes of the spectrometer have been revealed which are meant for strongly different levels of recorded signals. The minimal emission current at which spectra recording is possible is evaluated to be about 0.1nA.
    Introduction Ensembles of nano- and/or micro-particles can be considered as three-dimensional disperse systems (3DDS) with particles as a disperse phase in the dispersive medium [1]. Multiparametric analysis of optical data for 3DDS can provide further progress in detailed characterization of 3DDS with particles of different nature (biological, mineral, metallic, organic, inorganic and their mixtures). This analysis includes the following:
    Materials and methods Our studies [9–22] have been focused on different 3DDS with nano- and/or micro-particles (with diameter less than 10µm) and their mixtures: proteins and nucleic acids; proteins and polymers; liposomes and viruses; liposomes carrying various substances (X-ray Bestatin agents, metallic particles, enzymes, viruses, antibiotics, etc.); liquid crystals with surfactants; mixtures of Coli bacillus with kaolin; mixtures of anthracene with cyclodextrin [16–18]; samples of natural and water-supply waters; air sediments in water, etc. In this paper, the application of the ND vector approach is shown through examples of 3DDS mixtures such as:
    In our previous articles [18–22], we described the main optical methods used in our studies for 3DDS characterization: spectroturbidimetry, refractometry, fluorescence, absorbency, integral light scattering, differential static and dynamic light scattering, measurements of light scattering matrix elements. The measurements of dispersions were made under the same conditions. The uncertainty was about 5–10%. Optical particle characterization in the range of nanometers up to about ten micrometers requires sophisticated data inversion techniques. The inverse problem can be formulated as a solution of the linear first-kind Fredholm integral equation of the finite domain (1) [4], where the measured (experimental) optical characteristic S(x) is related to f(a) that is the unknown particle size distribution [4]: where a is the radius of an individual particle; amin, amax are the limiting radii of particle size distribution, s(x, a) is the kernel of the equation known from experiment or from the theory of light scattering for the individual particle with radius a. In Eq. (1), x can be a scattering angle Ө or a wavelength λ, or a frequency ν. At =0 and =∞Eq. (1) converts into the linear first-kind Fredholm integral equation of infinite domain [4]:
    The examples of the kernel s(x, a) and S(x) in Eq. (2) are presented in Table 1 (based on the discussion in Ref. [4]). In addition to Notes to Table 1, it is necessary to remark that the complex refractive index of the particle substance is entered as a parameter in all kernels [4]. For homogeneous spherical particles, the kernel s(x,a) can be calculated according to Mie theory [1–4]. In our previous papers, we discussed the 3DDS problem of polydispersity and polymodality [21] and the possibility of measuring polarization [22] for 3DDS characterization. For polymodal polydisperse 3DDS, the regularization technique is often used for solving the inverse light scattering problem [1–8]. The information-statistical methodology [23,24] also can be used for characterization of complex 3DDS.
    Results and discussion Experience suggests that the set of optical parameters of the so-called “second class” [15] (obtained by processing the measured values and independent on the concentration of particles) is unique for each 3DDS [15]. In other words, each 3DDS can be characterized by an N-dimensional vector in an N-dimensional space of the “second-class” optical parameters (ND-vector) [15]. In our previous paper [18], mixtures of anthracene with cyclodextrin were characterized by four-dimensional (4D) vectors. It was supposed in Ref. [18] that the position of mixture ND-vector on the line connecting the separate component ND-vector points could be the justification that there is no interaction between particles in the mixture.