PL2230 series

Diode Pumped High Energy Picosecond Nd:YAG Lasers
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  • DPSS high pulse energy mode-locked lasers
  • Up to 140 mJ
  • 20 – 80 ps pulses
  • 50 – 100 Hz pulse repetition rate
  • DPSS high pulse energy mode-locked lasers
  • Up to 140 mJ
  • 20 – 80 ps pulses
  • 50 – 100 Hz pulse repetition rate

Features & Applications

Features

  • Diode pumped power amplifier producing up to 40 mJ per pulse at 1064 nm
  • Beam profile improvement using advanced beam shaping system
  • Hermetically sealed DPSS master oscillator
  • Diode pumped regenerative amplifier
  • Air-cooled
  • <30 ps pulse duration
  • Excellent pulse duration stability
  • Up to 100 Hz repetition rate
  • Streak camera triggering pulse with <10 ps jitter
  • Excellent beam pointing stability
  • Thermo stabilized second, third or fourth harmonic generator options
  • PC control trough USB and with supplied LabView™ drivers
  • Remote control via keypad

Applications

  • Time resolved fluorescence (including streak camera measurements)
  • SFG/SHG spectroscopy
  • Nonlinear spectroscopy
  • Laser-induced breakdown spectroscopy
  • OPG pumping
  • Remote laser sensing
  • Satellite ranging
  • Other spectroscopic and nonlinear optics applications

Description

Innovative design

The heart of the system is a diode pumped solid state (DPSS) master oscillator placed in a sealed monolithic block, producing high repetition rate pulse trains (88 MHz) with a low single pulse energy of several nJ. Diode pumped amplifiers are used for amplification of the pulse to 30 mJ or up to 40 mJ output. The high‑gain regenerative amplifier has an amplification factor in the proximity of 10⁶. After the regenerative amplifier, the pulse is directed to a multipass power amplifier that is optimized for efficient stored energy extraction from the Nd:YAG rod, while maintaining a near Gaussian beam profile and low wavefront distortion. The output pulse energy can be adjusted in approximately 1% steps, while pulse‑to-pulse energy stability remains at less than 0.5% rms at 1064 nm.

Angle-tuned KD*P and KDP crystals mounted in thermostabilised ovens are used for second, third, and fourth harmonic generation. Harmonic separators ensure the high spectral purity of each harmonic guided to different output ports.

Built-in energy monitors continuously monitor output pulse energy. Data from the energy monitor can be seen on the remote keypad or on a PC monitor. The laser provides triggering pulses for the synchronisation of your equipment. The lead of the triggering pulse can be up to 500 ns and is user adjustable in ~0.25 ns steps from a personal computer. Up to 1000 μs lead of triggering pulse is available as a pretrigger feature. Precise pulse energy control, excellent short-term and long-term stability, and a 50 Hz repetition rate makes PL2230 series lasers an excellent choice for many demanding scientific applications.

Simple and convenient laser control

For customer convenience the laser can be operated from master device or personal computer through USB (VCP, ASCII commands), RS232 (ASCII commands) or LAN (REST API) interfaces or from remote control pad with backlit display that is easy to read even while wearing laser safety glasses.

Specifications

ModelPL2230-100PL2231-100PL2231-50PL2231A-50
MAIN SPECIFICATIONS 1)
Pulse energy 2)
    at 1064 nm3 mJ12 mJ30 mJ40 mJ
    at 532 nm 3)1.3 mJ5 mJ13 mJ18 mJ
    at 355 nm 4)0.9 mJ3.5 mJ9 mJ13 mJ
    at 266 nm 5)0.3 mJ1.2 mJ3 mJ5 mJ
    at 213 nm 6)inquire
Pulse energy stability (Std. Dev) 7)
    at 1064 nm< 0.2 %< 0.5 %
    at 532 nm< 0.4 %< 0.8 %
    at 355 nm< 0.5 %< 1.1 %
    at 266 nm< 0.5 %< 1.2 %
    at 213 nm< 1.5 %< 1.5 %
Pulse duration (FWHM) 8)29 ± 4 ps
Pulse duration stability 9)± 1 %
Power drift 10)± 2 %
Pulse repetition rate0 – 100 Hz 100 Hz50 Hz50 Hz
Polarizationvertical, >99 % at 1064 nm
Pre-pulse contrast> 200:1 (peak-to-peak with respect to residual pulses)
Beam profile 11)close to Gaussian in near and far fields
Beam divergence 12) <1.5 mrad <0.7 mrad
Beam propagation ratio M2<1.3<2.5
Beam pointing stability 13) ≤ 10 μrad StdDev≤ 20 μrad StdDev
Typical beam diameter 14) ~2 mm~4 mm~5 mm
Optical pulse jitter
    Internal triggering regime 15)<50 ps (StdDev) with respect to TRIG1 OUT pulse
    External triggering regime 16)~3 ns (StdDev) with respect to SYNC IN pulse
TRIG1 OUT pulse delay 17) -500 … 50 ns
Typical warm-up time5 min15 min
PHYSICAL CHARACTERISTICS
Laser head size (W × L × H)456×1031×249 ± 3 mm
Electrical cabinet size (W × L × H)12 V DC power adapter,
85×170×41 ± 3 mm
471×391×147 ± 3 mm
Umbilical length2.5 m
OPERATING REQUIREMENTS
Cooling 18)stand-alone chiller
Room temperature22±2 °C
Relative humidity20 – 80 % (non-condensing)
Power requirements110 – 240 V AC, 50/60 HzSingle phase, 110 – 240 V AC, 5 A, 50/60 Hz
Power consumption< 0.15 kVA< 1.0 kVA
  1. Due to continuous improvement, all specifications are subject to change without notice. Parameters marked typical are not specifications. They are indications of typical performance and will vary with each unit we manufacture. Unless stated otherwise, all specifications are measured at 1064 nm and for basic system without options. Specifications for models PL2231A and C are preliminary and should be confirmed against quotation and purchase order.
  2. Outputs are not simultaneous.
  3. For PL2230 series laser with –SH, -SH/TH, -SH/FH or -SH/TH/FH option or –SH/TH/FH/FiH module.
  4. For PL2230 series laser with –TH, -SH/TH or -SH/TH/FH option or –SH/TH/FH/FiH module.
  5. For PL2230 series laser with -SH/FH or -SH/TH/FH option or –SH/TH/FH/FiH module.
  6. For PL2230 series laser with –SH/TH/FH/FiH module.
  7. Averaged from pulses, emitted during 30 sec time interval.
  8. FWHM. Inquire for optional pulse durations in 20 – 90 ps range. Pulse energy specifications may differ from indicated here.
  9. Measured over 1 hour period when ambient temperature variation is less than ±1 °C.
  10. Measured over 8 hours period after 20 min warm-up when ambient temperature variation is less than ± 2 °C.
  11. Near field Gaussian fit is >80%.
  12. Average of X- and Y-plane full angle divergence values measured at the 1/e² level at 1064 nm.
  13. Beam pointing stability is evaluated from fluctuations of beam centroid position in the far field.
  14. Beam diameter is measured at 1064 nm at the 1/e² level.
  15. With respect to TRIG1 OUT pulse. <10 ps jitter is provided with PRETRIG standard feature.
  16. With respect to SYNC IN pulse.
  17. TRIG1 OUT lead or delay can be adjusted with 0.25 ns steps in specified range.
  18. Air cooled. Adequate room air conditioning should be provided.

Note: If laser is optimised for pumping parametrical generator, maximum output energy may be different than specified for stand alone application.

Note: Laser must be connected to the mains electricity all the time. If there will be no mains electricity for longer that 1 hour then laser (system) needs warm up for a few hours before switching on.

Custom products

Model 1)PL2231C-20 (inquire)
Pulse energy 2)
    at 1064 nm140 mJ
    at 532 nm 3)60 mJ
    at 355 nm 4)35 mJ
    at 266 nm 5)15 mJ
Pulse duration (FWHM) 6)80 ps ± 10 %
Pulse repetition rate20 Hz
  1. Due to continuous improvement, all specifications are subject to change without notice. Parameters marked typical are not specifications. They are indications of typical performance and will vary with each unit we manufacture. Unless stated otherwise, all specifications are measured at 1064 nm and for basic system without options. Specifications for model PL2231C are preliminary and should be confirmed against quotation and purchase order.
  2. Outputs are not simultaneous.
  3. For PL2230 series laser with –SH, -SH/TH, -SH/FH or -SH/TH/FH option or –SH/TH/FH/FiH module.
  4. For PL2230 series laser with –TH, -SH/TH or -SH/TH/FH option or –SH/TH/FH/FiH module.
  5. For PL2230 series laser with -SH/FH or -SH/TH/FH option or –SH/TH/FH/FiH module.
  6. FWHM. Inquire for optional pulse durations in 20 – 90 ps range. Pulse energy specifications may differ from indicated here.

Options

Option P20

Provides 20 ps ±10 % output pulse duration. Pulse energies are ~ 30 % lower in comparison to the 28 ps pulse duration version. See table below for pulse energy specifications:

ModelPL2231-50PL2231A-50
1064 nm23 mJ28 mJ
532 nm9 mJ13 mJ
355 nm6 mJ9 mJ
266 nm2 mJ4 mJ

Option P80

Provides 80 ps ±10 % output pulse duration. Pulse energy specifications are same as those of 28 ps lasers.

Option PLL

Allows locking the master oscillator pulse train repetition rate to an external RF generator, enabling precise external triggering with low jitter. Inquire for more information.

Performance & Drawings

Publications

Found total :
18 articles, 18 selected
Application selected :
All Applications
All Applications
Scientific Applications
Seeding and pumping
Laser Spectroscopy
SFG – sum frequency generation vibrational spectroscopy
Photoluminescence Spectroscopy
Pump-probe Spectroscopy
Time-resolved Spectroscopy
Biomedical – applications focusing on the biology of human health and disease

Structure Determination of Hen Egg-White Lysozyme Aggregates Adsorbed to Lipid/Water and Air/Water Interfaces

Related applications:  SFG Laser Spectroscopy

Authors:  S. Strazdaite, E. Navakauskas, J. Kirschner, T. Sneideris, G. Niaura

We use vibrational sum-frequency generation (VSFG) spectroscopy to study the structure of hen egg-white lysozyme (HEWL) aggregates adsorbed to DOPG/D2O and air/D2O interfaces. We find that aggregates with a parallel and antiparallel β-sheet structure together with smaller unordered aggregates and a denaturated protein are adsorbed to both interfaces. We demonstrate that to retrieve this information, fitting of the VSFG spectra is essential. The number of bands contributing to the VSFG spectrum might be misinterpreted, due to interference between peaks with opposite orientation and a nonresonant background. Our study identified hydrophobicity as the main driving force for adsorption to the air/D2O interface. Adsorption to the DOPG/D2O interface is also influenced by hydrophobic interaction; however, electrostatic interaction between the charged protein’s groups and the lipid’s headgroups has the most significant effect on the adsorption. We find that the intensity of the VSFG spectrum at the DOPG/D2O interface is strongly enhanced by varying the pH of the solution. We show that this change is not due to a change of lysozyme’s and its aggregates’ charge but due to dipole reorientation at the DOPG/D2O interface. This finding suggests that extra care must be taken when interpreting the VSFG spectrum of proteins adsorbed at the lipid/water interface.

Published: 2020.   Source: Langmuir 2020, 36, 17, 4766-4775

Near Infrared-Triggered Liposome Cages for Rapid, Localized Small Molecule Delivery

Related applications:  Biomedical

Authors:  J.E. Shin, M.O. Ogunyankin, J.A. Zasadzinski

Photolabile chelating cages or protecting groups need complex chemical syntheses and require UV, visible, or two-photon NIR light to trigger release. Different cages have different solubilities, reaction rates, and energies required for triggering. Here we show that liposomes containing calcium, adenosine triphosphate, or carboxyfluorescein are tethered to plasmon-resonant hollow gold nanoshells (HGN) tuned to absorb light from 650–950 nm. Picosecond pulses of near infrared (NIR) light provided by a two-photon microscope, or by a stand-alone laser during flow through microfluidic channels, trigger contents release with spatial and temporal control. NIR light adsorption heats the HGN, inducing vapor nanobubbles that rupture the liposome, releasing cargo within milliseconds. Any water-soluble molecule can be released at essentially the same rate from the liposome-HGN. By using liposomes of different composition, or HGN of different sizes or shapes with different nanobubble threshold fluences, or irradiating on or off resonance, two different cargoes can be released simultaneously, one before the other, or in a desired ratio. Calcium release from liposome-HGN can be spatially patterned to crosslink alginate gels and trap living cells. Liposome-HGN provide stable, biocompatible isolation of the bioactive compound from its surroundings with minimal interactions with the local environment.

Published: 2020.   Source: Scientific Reports volume 10, Article number: 1706 (2020)

Vibrational Relaxation Lifetime of a Physisorbed Molecule at a Metal Surface

Related applications:  SFG Laser Spectroscopy Pump-probe Spectroscopy

Authors:  S. Kumar, H. Jiang, M. Schwarzer, A. Kandratsenka, D. Schwarzer, A.M. Wodtke

Previous measurements of vibrational relaxation lifetimes for molecules adsorbed at metal surfaces yielded values of 1–3 ps; however, only chemisorbed molecules have been studied. We report the first measurements of the vibrational relaxation lifetime of a molecule physisorbed to a metal surface. For CO(v=1) adsorbed on Au(111) at 35 K the vibrational lifetime of the excited stretching mode is 49±3  ps. The long lifetime seen here is likely to be a general feature of physisorption, which involves weaker electronic coupling between the adsorbate and the solid due to bonding at larger distances.

Published: 2019.   Source: Phys. Rev. Lett. 123, 156101

High-Performance All-Organic DFB and DBR Waveguide Laser with Various Grating Height Fabricated by a Two-Photon Absorption DLW Method

Related applications:  Laser Spectroscopy Time-resolved Spectroscopy

Authors:  Naoto Tsutsumi, Keiichi Kaida, Kenji Kinashi, Wataru Sakai

Organic solid-state lasers (OSSLs) with distributed feedback (DFB) structures or distributed Bragg reflectors (DBRs) are promising for potential application in bio-sensing and hazardous materials detection. Here, the laser performances of the all-organic DFB waveguide lasers with various grating heights ranging from 0.4 to 4.7 μm were investigated. The grating structures used as the lasing cavity were fabricated using a two-photon absorption (TPA) direct laser writing (DLW) method with an SU-8 negative photoresist. The laser active layer consisted of a rhodamine 6G (R6G) laser dye and a cellulose acetate (CA) matrix. The R6G/CA solution was spin-coated onto the quartz substrate with the cavity (grating) structures to fabricate the DFB waveguide laser devices. The diffraction order of lasing ranged from m = 4 to 7. As the grating height was increased to 1.9 μm, the slope efficiency increased for all diffraction orders and the threshold decreases for each diffraction order. The dependence of the cavity (grating) length on the laser performances was investigated. The slope efficiency increased as the cavity length increased to 300 μm. The effect of the cavity (grating) position on the slope efficiency and the threshold position of the cavity (grating) was also studied. A maximum slope efficiency of 10.2% was achieved for the DFB waveguide laser device with a cavity (grating) length of 300 μm, a cavity position at 6 mm from the emission edge of the waveguide, and an aspect ratio ≈3 between the grating height of 1.74 μm and the grating width of 0.6 μm for the diffraction order m = 6 for lasing.

Published: 2019.   Source: Scientific Reports, vol. 9, art.: 10582 (2019)

A primary radiation standard based on quantum nonlinear optics

Related applications:  Seeding and pumping

Authors:  Samuel Lemieux, Enno Giese, Robert Fickler, Maria V. Chekhova, Robert W. Boyd

The black body remains the most prominent source of light for absolute radiometry. Its main alternative, synchrotron radiation, requires costly and large facilities. Quantum optics offers a new radiometric source: parametric down-conversion (PDC), a nonlinear optical process, in which pairwise photon correlations enable absolute calibration of photodetectors. Since the emission rate crucially depends on the brightness of the electromagnetic field, quantum-mechanical fluctuations of the vacuum can be seen as a seed of spontaneous PDC, and their amplitude is a natural radiometric standard. Thus, they allow for the calibration of the spectral radiance of light sources by measuring the ratio between seeded and unseeded PDC. Here, we directly use the frequency spectrum of the electromagnetic vacuum to trigger spontaneous PDC and employ the generated light to infer the spectral response of a spectrometer over a broad spectral range. Then, we deduce the absolute quantum efficiency from the spectral shape of PDC in the high-gain regime, without relying on a seed or reference detector. Our results compare well with the ones obtained with a reference lamp, demonstrating a promising primary radiation standard.

Published: 2019.   Source: Nature Physics, vol. 15, pp. 529–532 (2019)

Heavy Anionic Complex Creates a Unique Water Structure at a Soft Charged Interface

Related applications:  SFG Laser Spectroscopy

Authors:  W. Rock, B. Qiao, T. Zhou, A. E. Clark, A. Uysal

Ion hydration and interfacial water play crucial roles in numerous phenomena ranging from biological to industrial systems. Although biologically relevant (and mostly smaller) ions have been studied extensively in this context, very little experimental data exist about molecular-scale behavior of heavy ions and their complexes at interfaces, especially under technologically significant conditions. It has recently been shown that PtCl6 2− complexes adsorb at positively charged interfaces in a two-step process that cannot fit into well-known empirical trends, such as Hofmeister series. Here, a combined vibrational sum frequency generation and molecular dynamics study reveals that a unique interfacial water structure is connected to this peculiar adsorption behavior. A novel subensemble analysis of molecular dynamics simulation results shows that after adsorption PtCl6 2− complexes partially retain their first and second hydration spheres and that it is possible to identify three different types of water molecules around them on the basis of their orientational structures and hydrogen-bonding strengths. These results have important implications for relating interfacial water structure and hydration enthalpy to the general understanding of specific ion effects.

This in turn influences interpretation of heavy metal ion distribution across, and reactivity within, liquid interfaces.

Published: 2018.   Source: J. Phys. Chem. C 2018, 122, 29228−29236

Vibrational fingerprint of localized excitons in a two-dimensional metal-organic crystal

Related applications:  SFG Laser Spectroscopy

Authors:  M. Corva, A. Ferrari, M. Rinaldi, Z. Feng, M. Roiaz, C. Rameshan, G. Rupprechter, R. Costantini, M. Dell’Angela, G. Pastore, G. Comelli, N. Seriani, E. Vesselli

Long-lived excitons formed upon visible light absorption play an essential role in photovoltaics, photocatalysis, and even in high-density information storage. Here, we describe a self-assembled two-dimensional metal-organic crystal, composed of graphene-supported macrocycles, each hosting a single FeN4 center, where a single carbon monoxide molecule can adsorb. In this heme-like biomimetic model system, excitons are generated by visible laser light upon a spin transition associated with the layer 2D crystallinity, and are simultaneously detected via the carbon monoxide ligand stretching mode at room temperature and near-ambient pressure. The proposed mechanism is supported by the results of infrared and time-resolved pump-probe spectroscopies, and by ab initio theoretical methods, opening a path towards the handling of exciton dynamics on 2D biomimetic crystals.

Published: 2018.   Source: Nature Communications, vol. 9, art. 4703 (2018)

Ultra-sensitive mid-infrared emission spectrometer with sub-ns temporal resolution

Related applications:  Laser Spectroscopy Photoluminescence Spectroscopy

Authors:  L. Chen, D. Schwarzer, J. A. Lau, V. B. Verma, M. J. Stevens, F. Marsili, R. P. Mirin, S. Woo Nam, A. M. Wodtke

We evaluate the performance of a mid-infrared emission spectrometer operating at wavelengths between 1.5 and 6 μm based on an amorphous tungsten silicide (a-WSi) superconducting nanowire single-photon detector (SNSPD). We performed laser induced fluorescence spectroscopy of surface adsorbates with sub-monolayer sensitivity and sub-nanosecond temporal resolution. We discuss possible future improvements of the SNSPD-based infrared emission spectrometer and its potential applications in molecular science.

Published: 2018.   Source: Optics Express Vol. 26, Issue 12, pp. 14859-14868 (2018)

How nature covers its bases

Related applications:  Laser Spectroscopy Photoluminescence Spectroscopy

Authors:  S. Boldissar, M. S. de Vries

The response of DNA and RNA bases to ultraviolet (UV) radiation has been receiving increasing attention for a number of important reasons: (i) the selection of the building blocks of life on an early earth may have been mediated by UV photochemistry, (ii) radiative damage of DNA depends critically on its photochemical properties, and (iii) the processes involved are quite general and play a role in more biomolecules as well as in other compounds. A growing number of groups worldwide have been studying the photochemistry of nucleobases and their derivatives. Here we focus on gas phase studies, which (i) reveal intrinsic properties distinct from effects from the molecular environment, (ii) allow for the most detailed comparison with the highest levels of computational theory, and (iii) provide isomeric selectivity. From the work so far a picture is emerging of rapid decay pathways following UV excitation. The main understanding, which is now well established, is that canonical nucleobases, when absorbing UV radiation, tend to eliminate the resulting electronic excitation by internal conversion (IC) to the electronic ground state in picoseconds or less. The availability of this rapid “safe” de-excitation pathway turns out to depend exquisitely on molecular structure. The canonical DNA and RNA bases are generally short-lived in the excited state, and thus UV protected. Many closely related compounds are longer lived, and thus more prone to other, potentially harmful, photochemical processes. It is this structure dependence that suggests a mechanism for the chemical selection of the building blocks of life on an early earth. However, the picture is far from complete and many new questions now arise.

Published: 2018.   Source: Phys. Chem. Chem. Phys., 2018,20, 9701-9716

Excited-State Dynamics of Isocytosine: A Hybrid Case of Canonical Nucleobase Photodynamics

Related applications:  Laser Spectroscopy

Authors:  J. A. Berenbeim, S. Boldissar, F. M. Siouri, G. Gate, M. R. Haggmark, B. Aboulache, T. Cohen, M. S. de Vries

We present resonant two-photon ionization (R2PI) spectra of isocytosine (isoC) and pump–probe results on two of its tautomers. IsoC is one of a handful of alternative bases that have been proposed in scenarios of prebiotic chemistry. It is structurally similar to both cytosine (C) and guanine (G). We compare the excited-state dynamics with the Watson–Crick (WC) C and G tautomeric forms. These results suggest that the excited-state dynamics of WC form of G may primarily depend on the heterocyclic substructure of the pyrimidine moiety, which is chemically identical to isoC. For WC isoC we find a single excited-state decay with a rate of ∼1010 s–1, while the enol form has multiple decay rates, the fastest of which is 7 times slower than for WC isoC. The excited-state dynamics of isoC exhibits striking similarities with that of G, more so than with the photodynamics of C.

Published: 2017.   Source: J. Phys. Chem. Lett.20178205184-5189

Structure of the Fundamental Lipopeptide Surfactin at the Air/Water Interface Investigated by Sum Frequency Generation Spectroscopy

Related applications:  SFG Laser Spectroscopy

Authors:  S. A. Goussous, M. T. L. Casford, A. C. Murphy, G. P. C. Salmond, F. J. Leeper and P. B. Davies

The lipopeptide surfactin produced by certain strains of Bacillus subtilis is a powerful bio-surfactant possessing potentially useful antimicrobial properties. In order to better understand its surface behaviour, we have used surface sensitive Sum Frequency Generation (SFG) vibrational spectroscopy in the C-H and C=O stretching regions to determine its structure at the air/water interface. Using surfactin with the leucine groups of the peptide ring perdeuterated we have shown that the majority of the SFG signals arise from the 4 leucine residues. We find that surfactin forms a robust film, and that its structure is not affected by the number density at the interface or by pH variation of the sub-phase. The spectra show that the ring of the molecule lies in the plane of the surface rather than perpendicular to it, with the tail lying above this, also in the plane of the interface.

Published: 2017.   Source: J. Phys. Chem. B 2017, 121, 19, 5072-5077

A structural and temporal study of the surfactants behenyltrimethylammonium methosulfate and behenyltrimethylammonium chloride adsorbed at air/water and air/glass interfaces using sum frequency generation spectroscopy

Related applications:  SFG Laser Spectroscopy

Authors:  S. A. Goussous, M. T.L. Casford, S. A. Johnson, P. B. Davies

Molecular scale information about the structure of surfactants at interfaces underlies their application in consumer products. In this study the non-linear optical technique of Sum Frequency Generation (SFG) vibrational spectroscopy has been used to investigate the structure and temporal behaviour of two cationic surfactants used frequently in hair conditioners. SFG spectra of films of behenyltrimethylammonium methosulfate (BTMS) and behenyltrimethylammonium chloride (BTAC) were recorded at the air/water interface and on glass slides following Langmuir Blodgett (LB) deposition. The assignment of the BTMS and BTAC spectral features (resonances) to the C--H stretching modes of the surfactants was consolidated by comparison with the SFG spectrum of deuterated cetyltrimethylammonium bromide (d-CTAB) and by recording spectra on D2O as well as on water. The C--H resonances arise from the methylene and methyl groups of the tail and head-groups of the surfactants. A slow collapse mechanism was observed following film compression of both BTAC and BTMS. The change in molecular structure of the films undergoing this slow collapse was followed by recording sequential SFG spectra in the C--H region, and by monitoring the SFG intensity at specific wavenumbers over time. Additionally, LB deposition onto glass was used to capture the state of the film during the slow collapse, and these SFG spectra showed close similarity to the corresponding spectra on water. Complementary Atomic Force Microscopy (AFM) was used to elucidate the layering of the compressed and relaxed films deposited onto mica by LB deposition.

Published: 2017.   Source: Journal of Colloid and Interface Science 488 (2017) 365–372

Retrieval of complex χ(2) parts for quantitative analysis of sum-frequency generation intensity spectra

Related applications:  SFG Laser Spectroscopy

Authors:  M. J. Hofmann, P. Koelsch

Vibrational sum-frequency generation (SFG) spectroscopy has become an established technique for in situ surface analysis. While spectral recording procedures and hardware have been optimized, unique data analysis routines have yet to be established. The SFG intensity is related to probing geometries and properties of the system under investigation such as the absolute square of the second-order susceptibility |χ(2)|2 . A conventional SFG intensity measurement does not grant access to the complex parts of χ(2) unless further assumptions have been made. It is therefore difficult, sometimes impossible, to establish a unique fitting solution for SFG intensity spectra. Recently, interferometric phase-sensitive SFG or heterodyne detection methods have been introduced to measure real and imaginary parts of χ(2) experimentally. Here, we demonstrate that iterative phase-matching between complex spectra retrieved from maximum entropy method analysis and fitting of intensity SFG spectra (iMEMfit) leads to a unique solution for the complex parts of χ(2) and enables quantitative analysis of SFG intensity spectra. A comparison between complex parts retrieved by iMEMfit applied to intensity spectra and phase sensitive experimental data shows excellent agreement between the two methods.

Published: 2015.   Source: J Chem Phys. 2015 Oct 7; 143(13): 134112.

Quantitative Sum-Frequency Generation Vibrational Spectroscopy of Molecular Surfaces and Interfaces: Lineshape, Polarization, and Orientation

Related applications:  SFG Laser Spectroscopy

Authors:  H. Wang, L. Velarde, W. Gan, L. Fu

Sum-frequency generation vibrational spectroscopy (SFG-VS) can provide detailed information and understanding of the molecular composition, interactions, and orientational and conformational structure of surfaces and interfaces through quantitative measurement and analysis. In this review, we present the current status of and discuss important recent developments in the measurement of intrinsic SFG spectral lineshapes and formulations for polarization measurements and orientational analysis of SFG-VS spectra. The focus of this review is to present a coherent description of SFG-VS and discuss the main concepts and issues that can help advance this technique as a quantitative analytical research tool for revealing the chemistry and physics of complex molecular surfaces and interfaces.

Published: 2015.   Source: Annu. Rev. Phys. Chem. 2015. 66:189–216

Unified treatment and measurement of the spectral resolution and temporal effects in frequency-resolved sum-frequency generation vibrational spectroscopy (SFG-VS)

Related applications:  SFG Laser Spectroscopy

Authors:  L. Velarde, H. F. Wang

The lack of understanding of the temporal effects and the restricted ability to control experimental conditions in order to obtain intrinsic spectral lineshapes in surface sum-frequency generation vibrational spectroscopy (SFG-VS) have limited its applications in surface and interfacial studies. The emergence of high-resolution broadband sum-frequency generation vibrational spectroscopy (HR-BB-SFG-VS) with sub-wavenumber resolution [Velarde et al., J. Chem. Phys., 2011, 135, 241102] offers new opportunities for obtaining and understanding the spectral lineshapes and temporal effects in SFG-VS. Particularly, the high accuracy of the HR-BB-SFG-VS experimental lineshape provides detailed information on the complex coherent vibrational dynamics through direct spectral measurements. Here we present a unified formalism for the theoretical and experimental routes for obtaining an accurate lineshape of the SFG response. Then, we present a detailed analysis of a cholesterol monolayer at the air/water interface with higher and lower resolution SFG spectra along with their temporal response. With higher spectral resolution and accurate vibrational spectral lineshapes, it is shown that the parameters of the experimental SFG spectra can be used both to understand and to quantitatively reproduce the temporal effects in lower resolution SFG measurements. This perspective provides not only a unified picture but also a novel experimental approach to measuring and understanding the frequency-domain and time-domain SFG response of a complex molecular interface.

Published: 2013.   Source: Phys. Chem. Chem. Phys., 2013, 15, 19970-19984

Investigating buried polymer interfaces using sum frequency generation vibrational spectroscopy

Related applications:  SFG Laser Spectroscopy

Authors:  Z. Chen

This paper reviews recent progress in the studies of buried polymer interfaces using sum frequency generation (SFG) vibrational spectroscopy. Both buried solid/liquid and solid/solid interfaces involving polymeric materials are discussed. SFG studies of polymer/water interfaces show that different polymers exhibit varied surface restructuring behavior in water, indicating the importance of probing polymer/water interfaces in situ. SFG has also been applied to the investigation of interfaces between polymers and other liquids. It has been found that molecular interactions at such polymer/liquid interfaces dictate interfacial polymer structures. The molecular structures of silane molecules, which are widely used as adhesion promoters, have been investigated using SFG at buried polymer/silane and polymer/polymer interfaces, providing molecularlevel understanding of polymer adhesion promotion. The molecular structures of polymer/solid interfaces have been examined using SFG with several different experimental geometries. These results have provided molecularlevel information about polymer friction, adhesion, interfacial chemical reactions, interfacial electronic properties, and the structure of layerbylayer deposited polymers. Such research has demonstrated that SFG is a powerful tool to probe buried interfaces involving polymeric materials, which are difficult to study by conventional surface sensitive analytical techniques.

Published: 2010.   Source: Prog Polym Sci. 2010 Nov 1; 35(11): 1376–1402.

Probing the Orientation and Conformation of α-Helix and β-Strand Model Peptides on Self-Assembled Monolayers Using Sum Frequency Generation and NEXAFS Spectroscopy

Related applications:  SFG Laser Spectroscopy

Authors:  Tobias Weidner, Julia S. Apte, Lara J. Gamble, David G. Castner

The structure and orientation of amphiphilic α-helix and β-strand model peptide films on self-assembled monolayers (SAMs) have been studied with sum frequency generation (SFG) vibrational spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The α-helix peptide is a 14-mer, and the β-strand is a 15-mer of hydrophilic lysine and hydrophobic leucine residues with hydrophobic periodicities of 3.5 and 2, respectively. These periodicities result in the leucine side chains located on one side of the peptides and the lysine side chains on the other side. The SAMs were prepared from the assembly of either carboxylic acid- or methyl-terminated alkyl thiols onto gold surfaces. For SFG studies, the deuterated analog of the methyl SAM was used. SFG vibrational spectra in the C-H region of air-dried peptides films on both SAMs exhibit strong peaks near 2965, 2940, and 2875 cm-1 related to ordered leucine side chains. The orientation of the leucine side chains was determined from the phase of these features relative to the nonresonant gold background. The relative phase for both the R-helix and β-strand peptides showed that the leucine side chains were oriented away from the carboxylic acid SAM surface and oriented toward the methyl SAM surface. Amide I peaks observed near 1656 cm-1 for the R-helix peptide confirm that the secondary structure is preserved on both SAMs. Strong linear dichroism related to the amide π* orbital at 400.8 eV was observed in the nitrogen K-edge NEXAFS spectra for the adsorbed β-strand peptides, suggesting that the peptide backbones are oriented parallel to the SAM surface with the side chains pointing toward or away from the interface. For the α-helix the dichroism of the amide π* is significantly weaker, probably because of the broad distribution of amide bond orientations in the α-helix secondary structure.

Published: 2009.   Source: Langmuir 2010, 26(5), 3433–3440

Study of self-assembled triethoxysilane thin films made by casting neat reagents in ambient atmosphere

Related applications:  SFG Laser Spectroscopy

Authors:  Y. Yang, A. M. Bittner, S. Baldelli, K. Kern

We studied four trialkoxysilane thin films, fabricated via self-assembly by casting neat silane reagents onto hydrophilic SiOx/Si substrates in the ambient. This drop-casting method is simple, yet rarely studied for the production of silane self-assembled monolayers (SAMs). Various ex-situ techniques were utilized to systematically characterize the growth process: Ellipsometry measurements can monitor the evolution of film thickness with silanization time; water droplet contact angle measurements reveal the wettability; the change of surface morphology was followed by Atomic Force Microscopy; the chemical identity of the films was verified by Infrared–Visible Sum Frequency Generation spectroscopy. We show that the shorter carbon chain (propyl-) or branched (2-(diphenylphosphino)ethyl-) silane SAMs exhibit poor ordering. In contrast, longer carbon chain (octadecyl and decyl) silanes form relatively ordered monolayers. The growth of the latter two cases shows Langmuir-like kinetics and a transition process from lying-down to standing-up geometry with increasing coverage.

Published: 2007.   Source: Thin Solid Films, Vol. 516, Iss. 12, 2008, pp. 3948-3956

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