Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/21—Polarisation-affecting properties

Definitions

• the present invention relates to a method and a device for determining the spatial configuration of molecules in particles or macromolecules.
• This method and this device are particularly suitable for determining the shape of nanometric metal particles.
• the present invention provides a method and a device for characterizing the spatial configuration of molecules or macromolecules and in particular the shape of nanometric metal particles from their non-linear optical response to a high peak power excitation peak established by a laser for example.
• the method of the invention is notably based on the exploitation of measurements of the intensity of Hyper-Rayleigh scattering, or HRS intensity (for Hyper-Rayleigh Scattering in English) in order to extract from these intensities information on the spatial configuration different assemblies of molecules and in particular the shape of nanometric metal particles.
• HRS intensity for Hyper-Rayleigh Scattering in English
• the object of the present invention is to provide a method that makes it possible to determine and characterize at a given moment the geometry and the spatial conformation of the molecules within an arrangement of molecules, in particular to characterize the shape of a metallic particle. nanoscale.
• the particle (s) or macro-molecules placed in solution are excited by means of at least two polarized excitation light beams.
• the photons of light diffused by at least one excited particle or macro-molecule present in the solution are detected in non-linear optics;
• G which is a constant, ⁇ , F two tensors and ⁇ *, F * their conjugated complex tensors
• the method of the present invention has the advantage of allowing the direct determination of the shape of the particles and the spatial configuration of molecules within aggregates or macromolecules from the measurement of the HRS intensity transmitted by these particles or macromolecules placed in solution, without further treatment or transformation of the tested samples.
• the method works regardless of the nature of the solution in which the samples are placed, as long as it is transparent to the wavelengths of the light beams used.
• the method of the present invention provides a good statistical representativity, as well as a very high sensitivity to defects (being considered as defects deviations from the organizations or forms having an inversion center) of the tested samples, in particular in comparison with a reading by electron microscopy in particular.
• the implementation of the method of the invention is finally very simple, and it can be easily automated and compacted to make it exploitable on an industrial level.
• the detection of photons of light diffused by at least one particle or macro-molecule excited in solution is carried out in a direction forming an angle ⁇ with the direction of incidence of a first light beam of excitation and forming an angle ⁇ with the direction of incidence of the second excitation light beam in the solution containing the particles or macro-molecules studied, ⁇ being different from ⁇ and greater than zero.
• the excitation of the particles or macro-molecules in solution is carried out by at least two polarized light beams of coherent light, such as for example two polarized laser beams, and preferably two excitation beams whose incidence directions. relative to the solution containing the samples are perpendicular to each other.
• the two excitation light beams are emitted by at least one coherent light source of the laser type, in particular a nanosecond or femtosecond type laser.
• the polarization of each excitation light beam is rotated according to at least three distinct polarization angles during each phase of illumination and excitation of the particles or macro-waves. molecules in solution.
• the detection direction of the photons of light diffused by the particles or macro-molecules studied is chosen to coincide with the direction of incidence of at least one of the two excitation light beams. the solution containing the particles or macromolecules.
• Another object of the invention also resides in the provision of a particular device adapted for implementing the method of the invention.
• This device comprises: means for producing at least two coherent light beams,
• the cell or cell capable of containing at least one particle or macro-molecule placed in solution, the cell or cell being made of a material transparent to the two beams of coherent light in order to allow excitation, by these two beams, at least one particle or macro-molecule in solution placed in the cell or cell,
• the means for producing the two coherent light beams comprise at least one coherent light source and means for dividing a single beam emitted by this source into two light beams distinct;
• the means for orienting the light beams in two distinct bearing directions with respect to the cell or cell comprise reflecting mirrors and / or semi-reflecting mirrors;
• the cell or cell consists of a material transparent to the wavelengths ⁇ and ⁇ / 2 of the at least two excitation beams;
• the coherent light source is a source of the nanosecond or femtosecond laser type.
• FIG. 1 represents a polar coordinate Hyper-Rayleigh (HRS) intensity scattering diagram on which the Cartesian coordinates decomposition of the HRS intensities values according to 3 different polarization angles to obtain the parameter values is schematically represented.
• HRS Hyper-Rayleigh
• a, b, c useful for calculating parameters r i and ⁇ 2 according to the method of the invention
• FIG. 3 represents an exemplary device for implementing the method of the invention
• FIG. 4 represents a representative diagram of the directions of the excitation beams according to the method of the invention.
• the present invention provides a method for determining and characterizing the spatial configuration of molecules within a molecular array or the shape of nanometric metal particles.
• This method is based on an optical method comprising in a simplified manner:
• the method of the invention consists in exciting said particles or macro-molecules placed in solution using two El beams, E 2 pulsed and polarized lasers of different incidence and to collect and detect second harmonic light photons generated by the interaction of each excitation beam El, E2 with the particles in solution. From the detection of these photons of second harmonic light, the method of the invention proposes to draw a polarization-resolved Hyper Rayleigh scattering intensity (HRS) diagram as represented for example in FIG. non-linear optics emitted by particles or macro-molecules placed in solution under the excitation of each beam E1, E2.
• HRS Hyper Rayleigh scattering intensity
• the device of the invention firstly comprises means for producing at least two coherent light beams E1, E2 formed in the embodiment shown by a laser source 1 and a splitter plate 5.
• the laser source 1 is in particular preferably a source of the nanosecond or femtosecond laser type. This source 1 emits a laser beam 2 whose wavelength ⁇ is located in the near infra-red, and preferably between 800 and 1100 nm.
• the laser beam 2 encounters the separating plate 5 placed on the optical transmission axis of the source 1 so as to divide the laser beam 2 into two identical excitation beams E1 and E2.
• a filter 3 to perfectly monochromatic the incident beams and polarization means formed for example by a half-wave plate 4.
• These polarization means provide a determined polarization of the laser beam 2 before its division at the splitter plate 5, this polarization can be continuously modified in order to rotate the polarization of the beams E1 and E2 during at least three distinct angles during the illumination phases of the tested samples whose spatial configuration is to be determined or the form according to the method of the invention.
• the two excitation beams E1, E2 are respectively guided by reflecting or semi-reflecting mirrors 7 towards a cell or cell 8 capable of containing at least one particle or macromolecule placed in solution.
• This tank or cell 8 is advantageously constituted by a material transparent to the two excitation laser beams E1, E2 at their wavelength ⁇ and at their half-wavelength ⁇ / 2 to allow excitation, by these two beams, at least one particle or macro-molecule in solution placed in the tank 8.
• This aqueous or organic solution must not influence the nonlinear optical response of the particles or macro-molecules placed therein at the excitation of the beams E1, E2. If necessary, its contribution may be subtracted by a measurement performed in the absence of particles or macromolecules.
• the mirrors 7 are preferably suitably positioned to orient the two excitation beams E1, E2 to the vessel 8 in two non-collinear directions of incidence II, 12, and preferably perpendicular to each other.
• the two bundles E1, E2 penetrate the tank 8 and the solution contained therein and meet at least one particle or macro-molecule bathed in said solution and whose geometric configuration is to be known.
• This particle or macro-molecule is then subjected to the very high luminous power of the beams E1, E2 and then emits photons, or in all rigor at least one so-called photon of second harmonic generation, whose wavelength is equal to half of the fundamental wavelength ⁇ of the beams E1, E2.
• the method of the present invention proposes it in a new and inventive way to achieve an excitation of the particles tested in two directions of incidence II, preferably 12 but not necessarily perpendicular, using two laser beams El, E2 excitation and polarized preferably linearly and which is further rotated polarization during each phase of illumination and excitation of the particles or macro-molecules in solution.
• This Illumination is preferably performed according to only three distinct linear polarization angles. It should be noted here, however, that a higher number of polarization angles improves the results.
• This series of measurements of the intensity as a function of the polarization angle makes it possible to draw a diagram as represented in FIG. 1, the adjustment of which by a simple mathematical function makes it possible to obtain coefficients a, b, c which will be presented subsequently.
• the device also comprises an optical chopper 6 which enables alternately pass each of the excitation beams E1, E2 towards the test vessel 8 containing the particles tested in solution.
• This optical chopper 6 thus makes it possible to limit any disturbance due to possible interferences between the two beams E1, E2 at the level of the particles in the tank 8 if the two beams E1, E2 were simultaneously projected towards the tank. It is thus possible to detect only the nonlinear response signals of the tested particles corresponding exactly to each of the two light excitations, for a better exploitation of the results.
• the device of the invention comprises means for detecting light scattered photons by second harmonic generation (SHG) by at least one particle or macro -molecule in solution present in the tank 8 and excited by the beams E1, E2.
• SHG second harmonic generation
• These detecting means comprise in the first place an analyzer 9 composed of a collection lens of the scattered light coming out of the tank 8, a half-wave plate ⁇ / 2 to select the wavelength corresponding to the second harmonic light. and a polarizer cube, this device in series making it possible to take account of the biases of the spectrometer network with respect to a particular polarization selected.
• the detection means and in particular the analyzer 9, are placed in such a way that the detection is carried out in a direction D forming an angle ⁇ with the direction of incidence II of a first excitation light beam and forming an angle ⁇ with the direction of incidence 12 of the second excitation light beam in the solution containing the particles or macro-molecules studied, ⁇ being different from ⁇ and greater than zero, as shown in FIG. 4.
• the detection direction D coincides with the direction of incidence II, 12 of one of the excitation beams E1, E2, for example in the direction 12 in the embodiment shown in FIG.
• the detecting means comprise, placed in series, a spectrometer 10, a photomultiplier 11 and a photon counter 12.
• the photomultiplier 11 may also be replaced by a CCD camera or an avalanche photodiode, for example.
• the photon counter 12 becomes superfluous and can be removed from the assembly, but a data processing routine must be added to extract the intensity measured at ⁇ / 2.
• This detection means 9, 10, 11, 12 advantageously make it possible to select and then to detect the light diffused in non-linear optics in order to analyze the non-linear response of the particles placed in solution in the tank 8 and to establish from this response a electrical signal image of this response to a computer station 13.
• This computer station 13 constitutes means for calculating the intensity of Hyper-Rayleigh scattering (HRS intensity) of the photons detected by the detection means as a function of each excitation beam El, E2 and their polarization and calculation for each beam of the parameters ⁇ E1 and ⁇ E 2 representative of the molecular organization within the macromolecules or the shape of the particles placed in the tank 8.
• HRS intensity Hyper-Rayleigh scattering
• C q G ⁇ Ak ⁇ ci 2 ([rL, ZXYY + TL, YXYY] [ ⁇ * L, ZXYY + T * L, YXYY]) the indices d and q respectively indicating a dipole and quadrupole component of the intensity values HRS a, b, c for each excitation beam (E1, E2), and with, in these relations: G which is a constant, ⁇ , two tensors and ⁇ *, r * their conjugated complex tensors,
• [Ak) 2 the square differential of the wave vectors 2k of the fundamental and K the wave vector of the harmonic, and has the size of the particle or macroparticle.
• the method of the invention can particularly find an application in fields such as the characterization of optoelectronic and optical components, then biosensors and biochips.

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• General Health & Medical Sciences (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
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• Biochemistry (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Length Measuring Devices By Optical Means (AREA)

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• 2008
  • 2008-04-04 FR FR0852286A patent/FR2929708B1/fr not_active Expired - Fee Related
• 2009
  • 2009-03-30 EP EP09731191A patent/EP2257787A2/de not_active Withdrawn
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