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1.
Appl Opt ; 56(23): 6663-6667, 2017 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-29047959

RESUMO

The purpose of this study is to extend the spectral range of a differential method of infrared micro-spectroscopy in order to allow the accurate detection of nanoparticles of interest for biomedical applications. Among these, metal-organic framework (MOF) nanoparticles have attracted increasing interest due to their capacity to incorporate high drug payloads, biodegradability, and possibility of tailoring their surfaces by grafting specific ligands. However, MOF particle detection in biological media without grafting or incorporating fluorescent molecules is challenging. We took advantage here of the presence of the specific absorption bands of nanoscale MOFs in far infrared in order to individually discriminate them. Here we show that single MOF nanoparticles can be imaged with a spatial resolution of a few tens of nanometers.

2.
Opt Lett ; 38(24): 5319-22, 2013 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-24322247

RESUMO

We have extended the spectral range of a differential method of infrared microspectroscopy in order to operate in the terahertz spectral region. We show on samples of graphite embedded in a matrix of polymers that the spatial resolution is practically independent of the wavelength and is at least λ/100. This method aims at performing "chemical mapping" of various objects since it is sensitive only to the imaginary part of the index of refraction.

3.
Opt Lett ; 33(14): 1611-3, 2008 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-18628814

RESUMO

We have performed IR spectromicroscopy of cells immersed in liquid water, with a lateral resolution better than 100 nm. Here, we use the motion of an atomic force microscope tip, probing the local transient deformation induced by an IR pulsed laser tuned at a sample absorbing wavelength. By Fourier analysis of the vibration of the cantilever tip, we can discriminate frequencies that are characteristic of the object, thus eliminating the influence of the water absorption. This opens the door of chemical imaging of living species in vivo, with spatial resolution of the order of the size of cell components.


Assuntos
Microscopia/instrumentação , Microespectrofotometria/instrumentação , Espectrofotometria Infravermelho/instrumentação , Espectrofotometria Infravermelho/métodos , Absorção , Candida/fisiologia , Candida/ultraestrutura , Desenho de Equipamento , Análise de Fourier , Glicogênio/química , Lasers , Microscopia/métodos , Microscopia de Força Atômica , Microespectrofotometria/métodos , Distribuição Normal , Óptica e Fotônica , Espectroscopia de Infravermelho com Transformada de Fourier , Água/química
4.
Ultramicroscopy ; 108(7): 635-41, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-18037564

RESUMO

We show that an infrared spectromicroscopy method based on a photo-thermal effect, is able to localize single viruses as well when they are isolated and when they are located inside the bacteria they have infected. In this latter case, although the topography performed by an AFM cannot image the viruses, the AFMIR is able to do so. In addition, we are able to determine different stages of the bacteria infection.


Assuntos
Bactérias/virologia , Bacteriófagos/isolamento & purificação , Microespectrofotometria , Espectrofotometria Infravermelho , Bactérias/ultraestrutura , Bacteriófagos/crescimento & desenvolvimento
5.
Ultramicroscopy ; 107(12): 1194-200, 2007 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17382474

RESUMO

In this paper, we analyze in detail a new method of infrared micro-spectroscopy, which aims at performing "chemical mapping" of various objects with sub-wavelength lateral resolution by using the infrared vibrational signature characterizing different molecular species. Its principle consists in an atomic force microscope tip, probing the local transient deformation induced by an infrared pulsed laser tuned at a sample absorbing wavelength. The cantilever oscillates at resonant frequencies, which amplitudes can be correlated with local absorption. We show that the system acts as an amplifier of extremely small motions induced by optical absorption and that different frequencies provide different informations, leading to a full description of the sample deformation. We estimate also the influence of the light confinement in the sample and exemplify the accuracy of the method by mapping Escherichia coli bacteria at different cantilever frequencies.


Assuntos
Escherichia coli/química , Microespectrofotometria/métodos , Espectrofotometria Infravermelho/métodos
6.
Opt Lett ; 30(18): 2388-90, 2005 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-16196328

RESUMO

We describe a new method of infrared microspectroscopy. It is intended for performing chemical mapping of various objects with subwavelength lateral resolution by using the infrared vibrational signature characterizing different molecular species. We use the photothermal expansion effect, detected by an atomic force microscope tip, probing the local transient deformation induced by an infrared pulsed laser tuned at a sample absorbing wavelength. We show that this new tool opens the way for measuring and identifying spectroscopic contrasts not accessible by far-field or near-field optical methods and with a subwavelength lateral resolution.


Assuntos
Escherichia coli/química , Escherichia coli/ultraestrutura , Aumento da Imagem/métodos , Microscopia de Força Atômica/métodos , Espectrofotometria Infravermelho/métodos , Termografia/métodos , Aumento da Imagem/instrumentação , Microscopia de Força Atômica/instrumentação , Espectrofotometria Infravermelho/instrumentação , Termografia/instrumentação , Transdutores
7.
Phys Rev Lett ; 88(17): 177402, 2002 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-12005783

RESUMO

We have investigated the polaron dynamics in n-doped InAs/GaAs self-assembled quantum dots by pump-probe midinfrared spectroscopy. A long T1 polaron decay time is measured at both low temperature and room temperature, with values around 70 and 37 ps, respectively. The decay time decreases for energies closer to the optical phonon energy. The relaxation is explained by the strong coupling for the electron-phonon interaction and by the finite lifetime of the optical phonons. We show that, even for a large detuning of 19 meV from the LO photon energy in GaAs, the carrier relaxation remains phonon assisted.

8.
Arq Neuropsiquiatr ; 58(3B): 947-51, 2000 Sep.
Artigo em Português | MEDLINE | ID: mdl-11018839

RESUMO

Despite the lipomas are the tumors that more commonly occur in the corpus callosum (CC), its incidence in the population is not common. We report on a 5-year old boy, with history of retardation in the psychomotor development and disturbs in the gait, secondary to generalized hypotony. Magnetic resonance imaging showed a curvilinear lipoma of the CC related to its hypertrophy. In the literature patients with CC lipoma usually have agenesis or hypotrophy of the CC, but in the reported case we have seen, by the first time, a hypertrophy of the CC. We made embryologic, genetic, clinical, radiographic and therapeutic considerations about the patients that have CC lipoma comparing to findings in the case we report.


Assuntos
Neoplasias Encefálicas/complicações , Corpo Caloso/patologia , Lipoma/complicações , Pré-Escolar , Humanos , Hipertrofia/complicações , Imageamento por Ressonância Magnética , Masculino
9.
J Synchrotron Radiat ; 5(Pt 3): 293-8, 1998 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-15263494

RESUMO

Considerable progress in the investigation of the electronic and vibrational properties of atoms, molecules, materials, surfaces and interfaces has been achieved by combining different photon sources of complementary characteristics. In this paper some experimental results obtained recently at LURE by using two synchronized sources, such as the IR free-electron laser (FEL) CLIO, the VUV storage ring FEL, synchrotron radiation and table lasers, are presented. Using CLIO synchronized with a YAG laser allows the investigation of the vibrational properties of adsorbed species by the non-linear optical technique of visible-IR sum (difference) frequency generation, as shown for the adsorption of hydrogen on platinum in the electrochemical environment. The second result reported here relates to the study of the intersubband stimulated emission in GaAs/GaAlAs quantum wells by pump-probe experiments using the two-colour configuration of CLIO. The combination of a mode-locked Ar(+) laser and synchrotron radiation has been used for investigations in a pump-probe arrangement of the ionization of Xe atoms via the resonant state Xe* 5p(5)5d [3/2](1). The final example is a time-resolved core-level spectroscopy study of photoexcited Si(111) 2 x 1 surfaces by using a combination of the naturally synchronized UV storage ring laser and synchrotron radiation.

12.
Phys Rev Lett ; 72(15): 2387-2390, 1994 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-10055867
13.
Phys Rev Lett ; 71(16): 2587-2590, 1993 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-10054719
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