Raman spectroscopy of dipyrrins: nonresonant, resonant and surface‐enhanced cross‐sections and enhancement factors

McLean, Tracey M.; Cleland, Deidre; Gordon, Keith C.; Telfer, Shane G.; Waterland, Mark R.

doi:10.1002/jrs.3093

Cited by 9 publications

(7 citation statements)

References 63 publications

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“…Resonance Raman spectroelectrochemistry measurements of PEDOT , N 3 -PEDOT , 1:2N 3 -PEDOT:PEDOT , and clicked M@tz-PEDOT or M@1:2tz-PEDOT:PEDOT films (M = Ni 2+ , Cu 2+ ) on ITO electrodes were carried out ex situ by applying a potential to the electrodes (in a two-compartment cell setup without a separating frit) followed by the measurement (ex situ) of the resonance Raman spectra of the electrodes. A 594 nm solid state laser (CrystaLaser, Reno, NV, USA) was used as an excitation with the collection of the Raman scattering through a 180° backscattering arrangement in a system previously described. , Collected scattering was dispersed through an Acton Isoplane 320 spectrograph (Princeton Instruments) with a 1200 grooves/mm grating, which dispersed the radiation in a horizontal plane on a PyLoN 400BR liquid-nitrogen-cooled CCD detector (Princeton Instruments). The spectrometer was calibrated using a 50:50 mixture of toluene and acetonitrile to be within 1 cm –1 .…”

Section: Experimental Methodsmentioning

confidence: 99%

Electroactive Metal Complexes Covalently Attached to Conductive PEDOT Films: A Spectroelectrochemical Study

Rodríguez‐Jiménez

Bennington

Akbarinejad

et al. 2020

ACS Appl. Mater. Interfaces

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The successful covalent attachment, via copper(I)-catalyzed azide alkyne cycloaddition (CuAAC), of alkyne-functionalized nickel(II) and copper(II) macrocyclic complexes onto azide (N3)-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) films on ITO-coated glass electrodes is reported. To investigate the surface attachment of the selected metal complexes, which are analogues of the cobalt-based complex previously reported to be a molecular catalyst for hydrogen evolution, first, three different PEDOT films were formed by electropolymerization of pure PEDOT or pure N3-PEDOT, and last, 1:2N3-PEDOT:PEDOT were formed by co-polymerizing a 1:4 mixture of N3-EDOT:EDOT monomers. The successful surface immobilization of the complexes on the latter two azide-functionalized films, by CuAAC, was confirmed by X-ray photoelectron spectroscopy (XPS) and electrochemistry as well as by UV–vis–NIR and resonance Raman spectroelectrochemistry. The ratio between the N3 groups, and hence, the number of surface-attached metal complexes after CuAAC functionalization, in pristine N3-PEDOT versus 1:2N3-PEDOT:PEDOT is expected to be 3:1 and seen to be 2.86:1 with a calculated surface coverage of 3.28 ± 1.04 and 1.15 ± 0.09 nmol/cm2, respectively. The conversion, to the metal complex attached films, was lower for the N3-PEDOT films (Ni 74%, Cu 76%) than for the copolymer 1:2N3-PEDOT:PEDOT films (Ni 83%, Cu 91%) due to the former being more sterically congested. The Raman and UV–vis–NIR results were simulated using density functional theory (DFT) and time-dependent DFT (TD-DFT), respectively, and showed good agreement with the experimental data. Importantly, the spectroelectrochemical behavior of both anchored metal complexes is analogous to that of the free metal complexes in solution. This proves that PEDOT films are promising conducting scaffolds for the covalent immobilization of metal complexes, as the existing electrochromic features of the complexes are preserved on immobilization, which is important for applications in electrocatalytic proton and carbon dioxide reduction, optoelectronics, and sensing.

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Section: Experimental Methodsmentioning

confidence: 99%

Electroactive Metal Complexes Covalently Attached to Conductive PEDOT Films: A Spectroelectrochemical Study

Rodríguez‐Jiménez

Bennington

Akbarinejad

et al. 2020

ACS Appl. Mater. Interfaces

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“…For quantitative analysis of the SERS activity or effect for these Au nanocrystals, enhancement factor (EF) was calculated in accordance with Formula (4) [ 40 , 41 , 42 ]:

where I RS and I SERS are the intensities of 4-ATP main peaks (1078 cm −1 and 1578 cm −1 ) without (Si substrate) and with (Au nanostructure) enhancement, respectively. N RS and N SERS are the numbers of different concentrations (50 μL 0.1M and 20 μL 10 −5 M) 4-ATP within φ1 μm laser spot areas on the films.…”

Section: Resultsmentioning

confidence: 99%

Kinetically-Controlled Growth of Chestnut-Like Au Nanocrystals with High-Density Tips and Their High SERS Performances on Organochlorine Pesticides

et al. 2018

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A modified seed growth route was developed to fabricate the Au nanocrystals with high-density tips based on kinetically-controlled growth via adjusting the adding rate of Au seeds into growth solution. The obtained Au nanostructures were chestnut-like in morphology and about 100 nm in size. They were built of the radial [111]-oriented nanoneedles and were 30–50 nm in length. There were about 120–150 tips in each nanocrystal. The formation of chestnut-like Au nanocrystals is ascribed to surfactant-induced preferential growth of seeds along direction [111]. Importantly, the chestnut-like Au configuration displayed powerful surface enhanced Raman scattering (SERS) performance (enhance factor > 107), owing to the high density of tips. Further, such film was used as a SERS substrate for the detection of lindane (γ-666) molecules (the typical organochlorine pesticide). The detection limit was about 10 ppb, and the relationship between SERS intensity I and concentration C of 666 accords with the double logarithm linear. This work presents a simple approach to Au nanocrystal with high-density tips, and provides a highly efficacious SERS-substrate for quantitative and trace recognition of toxic chlorinated pesticides.

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“…Raman instrumentation, parameters, data collection, and data analysis have been described in detail elsewhere. 5,25,26 Computational chemistry was performed using the Gaussian09 suite, 27 using an unrestricted B3LYP/6-31G(d) model and a C-PCM solvent model to obtain optimized geometry and frequencies, and the corresponding TD-UB3LYP method was used to determine transition dipoles and excited state energies.…”

Section: Experimental Computational and Theoretical Detailsmentioning

confidence: 99%

“…1,2 The core dipyrromethene structure provides π-π* transitions with very large molar absorption cross-section in the visible wavelength range which leads to excellent scattering cross-sections; derivatives with coordinated pyrrole rings, such as BODIPY™ have excellent emission quantum yields, 3,4 whilst the neutral uncoordinated dipyrrin has very strongly enhanced resonance Raman cross-sections. 5 Azadipyrromethene complexes have attracted interest due to low energy transitions generating strong absorption and emission in the near infrared, [6][7][8][9][10] and as potential n-type charge-carrier materials. 7,11 (Aza)dipyrrins exhibit rich coordination chemistry with a wide variety of transition metal species.…”

Section: Introductionmentioning

confidence: 99%

Molecular excitons in a copper azadipyrrin complex

et al. 2014

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Exciton coupling is investigated in a copper azadipyrrin complex, Cu(L-aza)2. Exciton coupling in Cu(L-aza)2 assuming a single π-π* state on the L-aza ligand fails to account for the electronic structure of Cu(L-aza)2, which displays two almost equal intensity transitions at 15 600 cm(-1) and 17 690 cm(-1). TD-UB3LYP/6-31G(d) calculations suggest multiple π-π* transitions for the L-aza ligands and simple vector addition of the transition dipoles predicts two nearly orthogonal co-planar excitonic transitions that correctly reproduce the absorption band profile. Empirical modelling of absolute resonance Raman intensities using wavepacket dynamics confirms Cu(L-aza)2 has two equal intensity orthogonal exciton transitions. The phenyl substituents at the α- and γ-positions of the pyrrole rings play a central role in determining the orientation of the transition dipoles. Consequently the π-π* transitions for the L-aza ligands are oriented towards the substituent groups and are not in the plane of the pyrrole rings. Mode displacements in the Franck-Condon (FC) region obtained from the wavepacket model suggest that pyrrole ring and phenyl modes control the exciton FC dynamics. Our results suggest that Cu(L-aza)2 is an ideal model for theoretical, computational and experimental investigations of molecular excitons in molecular systems.

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Raman spectroscopy of dipyrrins: nonresonant, resonant and surface‐enhanced cross‐sections and enhancement factors

Cited by 9 publications

References 63 publications

Electroactive Metal Complexes Covalently Attached to Conductive PEDOT Films: A Spectroelectrochemical Study

Electroactive Metal Complexes Covalently Attached to Conductive PEDOT Films: A Spectroelectrochemical Study

Kinetically-Controlled Growth of Chestnut-Like Au Nanocrystals with High-Density Tips and Their High SERS Performances on Organochlorine Pesticides

Molecular excitons in a copper azadipyrrin complex

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