Pump-probe Transient Absorption Spectroscopy Research Articles

Insights into Excitonic Dynamics of Terpolymer-Based High-Efficiency Nonfullerene Polymer Solar Cells: Enhancing the Yield of Charge Separation States.

Ternary copolymerization strategy is considered an effective method to achieve high-performance photovoltaic conjugated polymers. Herein, a donor-acceptor1-donor-acceptor2-type random copolymer, named PBDTNS-TZ-BDD (T1), containing one electron-rich unit alkylthionaphthyl-flanked benzo[1,2-b/4,5-b'] di-thiophene (BDTNS) as D and two electron-deficient moieties benzo[1,2-c/4,5-c']dithiophene-4,8-dione (BDD) and fluorinated benzotriazole as A, was synthesized to investigate the excitonic dynamic effect. Also, the D-A-type alternating copolymer PBDTNS-BDD (P1) was also prepared for a clear comparison. Although the UV-Vis spectra and energy levels of P1 and T1 are similar, the power conversion efficiencies (PCEs) of the related devices are 11.50% (T1/ITIC) and 8.89% (P1/ITIC), respectively. The reason for this is systematically investigated and analyzed by theoretical calculation, photoluminescence, and pump-probe transient absorption spectroscopy. The density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculation results show that the terpolymer T1 with a lower exciton binding energy and a longer lifetime of spontaneous luminescence can synergistically increase the number of excitons reaching the donor/acceptor interface. The results of the pump-probe transient absorption spectroscopy show that the yield of charge separation of T1/ITIC is higher than that of the P1/ITIC blend film, and improved PCE could be achieved via copolymerization strategies. Moreover, the fabrication of the T1-based device is also simple without any additive or postprocessing. Therefore, it provides a promising and innovative method to design high-performance terpolymer materials.

Ultrafast stimulated emission microscopy of single nanocrystals.

Single-molecule detection is a powerful method used to distinguish different species and follow time trajectories within the ensemble average. However, such detection capability requires efficient emitters and is prone to photobleaching, and the slow, nanosecond spontaneous emission process only reports on the lowest excited state. We demonstrate direct detection of stimulated emission from individual colloidal nanocrystals at room temperature while simultaneously recording the depleted spontaneous emission, enabling us to trace the carrier population through the entire photocycle. By capturing the femtosecond evolution of the stimulated emission signal, together with the nanosecond fluorescence, we can disentangle the ultrafast charge trajectories in the excited state and determine the populations that experience stimulated emission, spontaneous emission, and excited-state absorption processes.

Dynamics of photo-excited carriers in CsPbBr<sub>3</sub> perovskite

Perovskite materials have outstanding photoelectric properties and can be used in optoelectronic devices. The dynamics of photo-excited carriers in the perovskite can determine the photoelectric properties of these optoelectronic devices. In this paper, the dynamics of photo-excited carriers in CsPbBr₃ quantum dots is studied via pump-probe transient absorption spectroscopy, and the transient absorption spectrum is analyzed by singular value decomposition and global fitting. The results show the red-shift and blue-shift of the band edge can be attributed to the exciton-exciton interaction and Burstein-Moss effect, respectively. The results also reveal the dynamics and corresponding preexponential factors spectra of photo-excited carriers. The relaxation time of hot carriers is 0.4 ps, decay times in the order of ten picoseconds and hundred picoseconds can be attributed to the lifetime of both double excitons and charged excitons, while the decay time on the order of nanoseconds can be attributed to the radiative recombination of excitons.

Exploring Differences in Excited-State Properties of Styryl-BODIPY Chromophores upon Change from α- to β-Substitution

Abstract We present a femtosecond pump-probe UV-Vis broadband transient absorption spectroscopy study of two styryl-substituted BODIPY chromophores with different position of the substituent. The α-substituted isomer shows typical BODIPY-type spectral features, such as sharp absorption and emission bands, a small Stokes shift and an excited-state lifetime in the 4 ns range, which only weakly depends on the solvent. In contrast, β-styryl-BODIPY features much broader steady-state absorption and emission spectra and a larger Stokes shift, particularly in polar solvents. Transient absorption spectroscopy including a complete global kinetic analysis reports a substantial decrease in S1 lifetime to 300 ps for polar solvents upon change from α- to β-substitution. In the case of the α-isomer, TD-DFT calculations identify a typical “cyanine-type” electron rearrangement upon S0 → S1 excitation accompanied by a slight reduction in dipole moment. In contrast, the same transition in the β-isomer shows strong intramolecular charge transfer (ICT) character involving a substantial increase in dipole moment. Assuming a simple energy-gap-law argument, the accelerated nonradiative decay of the β-isomer in polar solvents may be linked to the decrease of the S1(ICT)-S0 energy difference. BODIPY dyes with a conjugated substituent in β-position therefore suffer a substantial loss in fluorescence brightness in polar environments compared with their α-substituted counterparts. This might limit their applicability in fluorescence imaging.

Photoinduced Intercomponent Processes in Selectively Addressable Bichromophoric Dyads Made of Linearly Arranged Ru(II) Terpyridine and Expanded Pyridinium Components.

Three new linearly arranged bichromophoric systems 1-3 have been prepared, and their photophysical properties have been studied, taking also advantage of femtosecond pump-probe transient absorption spectroscopy. The three compounds contain the same chromophores, that is a Ru(II)-terpy-like species and a fused expanded bipyridinium (FEBP) unit, separated by three different, variously methylated biphenylene-type bridges. The chromophores have been selected to be selectively addressable, and excitation involving the Ru-based or the FEBP-based dyes results in different excited-state decays. Upon Ru-based excitation at 570 nm, oxidative photoinduced electron transfer (OPET) takes place in 1-3 from the 3MLCT state; however, the charge-separated species does not accumulate, indicating that the charge recombination rate constant exceeds the OPET rate constant. Upon excitation of the organic dye at 400 nm, the FEBP-based 1π-π* level is prepared, which undergoes a series of intercomponent decay events, including (i) electron-exchange energy transfer leading to the MLCT manifold (SS-EnT), which successively decays according to 570 nm excitation, and (ii) reductive photoinduced electron transfer (RPET), leading to the preparation of the charge-separated (CS) state. Reductive PET, involving the FEBP-based singlet state, is much faster than oxidative PET, involving the MLCT triplet state, essentially because of driving force reasons. The rate constant of CR is intermediate between the rate constants of OPET and RPET, and this makes 1-3 capable to selectively read the 400 nm excitation as an active input to prepare the CS state, whereas excitation at wavelengths longer than 480 nm is inefficient to accumulate the CS state. Moreover, intriguing differences between the rate constants of the various processes in 1-3 have been analyzed and interpreted according to the superexchange theory for electron transfer. This allowed us to uncover the role of the electron-transfer and hole-transfer superexchange pathways in promoting the various intercomponent photoinduced decay processes occurring in 1-3.

Reverse Photodynamics of the Noncanonical Red/Green NpR3784 Cyanobacteriochrome from Nostoc punctiforme.

In the companion paper (10.1021/acs.biochem.8b01274), we examined the forward Pr photodynamics of NpR3784 (UniProtKB B2J457 ), a representative member of a noncanonical red/green (R/G) cyanobacteriochrome (CBCR) subfamily. Here the reverse Pg → Pr photodynamics of NpR3784 was studied by broadband transient absorption pump-probe spectroscopy. Primary (100 fs to 10 ns) and secondary (10 ns to 1 ms) photodynamics were characterized over nine decades of time, which also were complemented with temperature-jump cryokinetics measurements. In contrast with canonical R/G CBCRs, the NpR3784 reverse photoconversion yielded two spectrally distinct primary photoproducts, Lumi-Go and Lumi-Gr, which decay on different time scales. The two primary photoproducts of NpR3784 equilibrate on the 40 ns time scale and subsequently propagate as a single intermediate population into Pr. Such heterogeneity could arise from differences in the direction of D-ring rotation, in chromophore protonation or hydrogen bonding, or in the mobility of protein residues or of solvent water nearby the chromophore or some combination therein. We conclude that the atypical photodynamics of NpR3784 reflects chromophore-protein interactions that differ from those present in the canonical R/G CBCR family.

Forward Photodynamics of the Noncanonical Red/Green NpR3784 Cyanobacteriochrome from Nostoc punctiforme.

Cyanobacteriochromes (CBCRs) make up a diverse family of cyanobacterial photoreceptors distantly related to the phytochrome photoreceptors of land plants. At least two lineages of CBCRs have reacquired red-absorbing dark states similar to the phytochrome Pr resting state but are coupled to green-absorbing light-adapted states rather than the canonical far-red-absorbing light-adapted state. One such lineage includes the canonical red/green (R/G) CBCRs that includes AnPixJg2 (UniProtKB Q8YXY7 ) and NpR6012g4 (UniProtKB B2IU14 ) that have been extensively characterized. Here we examine the forward Pr photodynamics of NpR3784 (UniProtKB B2J457 ), a representative member of the second R/G CBCR subfamily. Using broadband transient absorption pump-probe spectroscopy, we characterize both primary (100 fs to 10 ns) and secondary (10 ns to 1 ms) forward (Pr → Pg) photodynamics and compare the results to temperature-jump cryokinetics measurements. Our studies show that primary isomerization dynamics occur on an ∼10 ps timescale, yet remarkably, the red-shifted primary Lumi-Rf photoproduct found in all photoactive canonical R/G CBCRs examined to date is extremely short-lived in NpR3784. These results demonstrate that differences in reaction pathways reflect the evolutionary history of R/G CBCRs despite the convergent evolution of their photocycle end products.

Pyrimidyl-substituted anthracene fluorophores: Syntheses, absorption spectra, and photophysical properties

Twelve new polycyclic aromatic chromophores whose structures recall 9,10-substituted anthracene have been prepared and their absorption spectra, and luminescence properties (both in ethanol and dichloromethane solution at room temperature and in MeOH/EtOH (4:1 v/v) rigid matrix at 77 K) have been analyzed as well as pump-probe transient absorption spectroscopy and computational studies have been performed. The compounds have variously decorated pyrimidyl groups as substituents of the anthracene framework. The compounds are conveniently grouped in two series: 1–4 and 11, in which the pyrimidine nitrogen atoms are on the external side with respect to the anthracene framework (Ext-type compounds), and 5–10, where the pyrimidine nitrogen atoms are pointing towards the anthracene platform (Int-type compounds). Compound 12 contains both a pyrimidine substituent with “inner” nitrogen atoms (“Int”) and a pyrimidine with “outer” nitrogen atoms (“Ext”). All the new species are quite efficient luminophores (spectral range of emission maxima: 400–450 nm at 77 K; 415–520 nm at room temperature; emission lifetimes: 0.25–8.7 ns range; emission quantum yields ranging between 0.08 to 0.99, with a single exception), with their photophysical properties depending on the connection scheme of the pyrimidyl groups to the anthryl platform (i.e., Int-type vs Ext-type compounds). Luminescence originating from locally excited π−π* anthracene-based singlet states, delocalized states largely involving the pyrimidyl moieties, and charge transfer states has been identified. For the Int-type series, the initially-prepared excited state can deactivate via interconversion to a saddle-shaped conformation, opening the way to fast nonradiative decays.

Electron Transfer of the Metal/Semiconductor System in Photocatalysis

Probing into the relationship between charge carrier dynamics and photocatalytic reactions is central to the understanding and therefore the design of photocatalysts. We have studied the charge carrier lifetime of Pt/C3N4 and compared it to that of C3N4 alone using femtosecond pump–probe transient absorption spectroscopy in the 500–900 nm signal range. Parallel photocatalytic reactions were also conducted to link the extracted lifetime to the corresponding rates of hydrogen production from water. The presence of Pt (with a mean particle size of ca. 2.5 nm) on C3N4 decreased the lifetime of excited electrons in the conduction band (CB). This has occurred in pure water as well as in the presence of the organic sacrificial agent used. These results suggest that Pt particles on this n-type semiconductor act as electron trap centers (either by pumping away CB electrons or by creating trap centers at the interface). The corresponding increase in reaction rates can be linked to this electron transfer.

Bias-induced modulation of ultrafast carrier dynamics in metallic single-walled carbon nanotubes

The gate bias dependence of excited-state relaxation dynamics in metallic single-walled carbon nanotubes (MCNTs) was investigated using pump-probe transient absorption spectroscopy coupled with electrochemical doping through an ionic liquid. The transient transmittance decayed exponentially with the pump-probe delay time, whose value could be tuned via the Fermi-level modulation of Dirac electrons under a bias voltage. The obtained relaxation time was the shortest when the Fermi level was at the Dirac point of the MCNTs, and exhibited a U-shaped dependence on the bias voltage. Because optical dipole transitions between the Dirac bands are forbidden in MCNTs, the observed dynamics were attributed to carrier relaxation from the ${E}_{11}$ band to the Dirac band. Using a model that considers the suppression of electron-electron scattering (impact ionization) due to Pauli blocking, we could qualitatively explain the obtained bias dependence of the relaxation time.

Reactivity of prehydrated electrons toward nucleobases and nucleotides in aqueous solution.

DNA damage induced via dissociative attachment by low-energy electrons (0 to 20 eV) is well studied in both gas and condensed phases. However, the reactivity of ultrashort-lived prehydrated electrons ([Formula: see text]) with DNA components in a biologically relevant environment has not been fully explored to date. The electron transfer processes of [Formula: see text] to the DNA nucleobases G, A, C, and T and to nucleosides/nucleotides were investigated by using 7-ps electron pulse radiolysis coupled with pump-probe transient absorption spectroscopy in aqueous solutions. In contrast to previous results, obtained by using femtosecond laser pump-probe spectroscopy, we show that G and A cannot scavenge [Formula: see text] at concentrations of ≤50 mM. Observation of a substantial decrease of the initial yield of hydrated electrons ([Formula: see text]) and formation of nucleobase/nucleotide anion radicals at increasing nucleobase/nucleotide concentrations present direct evidence for the earliest step in reductive DNA damage by ionizing radiation. Our results show that [Formula: see text] is more reactive with pyrimidine than purine nucleobases/nucleotides with a reactivity order of T > C > A > G. In addition, analyses of transient signals show that the signal due to formation of the resulting anion radical directly correlates with the loss of the initial [Formula: see text] signal. Therefore, our results do not agree with the previously proposed dissociation of transient negative ions in nucleobase/nucleotide solutions within the timescale of these experiments. Moreover, in a molecularly crowded medium (for example, in the presence of 6 M phosphate), the scavenging efficiency of [Formula: see text] by G is significantly enhanced. This finding implies that reductive DNA damage by ionizing radiation depends on the microenvironment around [Formula: see text].

Physical mechanism on exciton-plasmon coupling revealed by femtosecond pump-probe transient absorption spectroscopy

The unclear mechanism of exciton-plasmon coupling interaction in monolayer MoS2-Ag nanoparticles hybrid, as a longstanding target in molecular nanotechnology and catalysis, is systemically investigated with transmission spectra and femtosecond pump-probe transient absorption spectroscopy in this paper. The properties of exciton in monolayer MoS2 are strongly enhanced due to the local surface plasmon resonance (LSPR) induced by Ag nanoparticles, and manifested by obvious changes in transmission spectra. Furthermore, we discuss the dynamic processes of exciton-plasmon coupling interaction with the femtosecond transient absorption spectroscopy, which indicates that there are three lifetimes, Auger scattering, electron-electron interaction and electron-phonon interaction, and illustrate the reason of the enlarged lifetime in hybrid system. Meanwhile, the intensity of A excitonic state in femtosecond transient absorption spectroscopy is significantly enhanced by LSPR, instead of excitonic state B. In conclusion, our study can promote the deeper understanding and illustrate the unique merits of the exciton-plasmon coupling interaction in the monolayer MoS2-Ag nanoparticles hybrid system.

Temperature dependence of the hydrated electron's excited-state relaxation. I. Simulation predictions of resonance Raman and pump-probe transient absorption spectra of cavity and non-cavity models.

We use one-electron non-adiabatic mixed quantum/classical simulations to explore the temperature dependence of both the ground-state structure and the excited-state relaxation dynamics of the hydrated electron. We compare the results for both the traditional cavity picture and a more recent non-cavity model of the hydrated electron and make definite predictions for distinguishing between the different possible structural models in future experiments. We find that the traditional cavity model shows no temperature-dependent change in structure at constant density, leading to a predicted resonance Raman spectrum that is essentially temperature-independent. In contrast, the non-cavity model predicts a blue-shift in the hydrated electron's resonance Raman O-H stretch with increasing temperature. The lack of a temperature-dependent ground-state structural change of the cavity model also leads to a prediction of little change with temperature of both the excited-state lifetime and hot ground-state cooling time of the hydrated electron following photoexcitation. This is in sharp contrast to the predictions of the non-cavity model, where both the excited-state lifetime and hot ground-state cooling time are expected to decrease significantly with increasing temperature. These simulation-based predictions should be directly testable by the results of future time-resolved photoelectron spectroscopy experiments. Finally, the temperature-dependent differences in predicted excited-state lifetime and hot ground-state cooling time of the two models also lead to different predicted pump-probe transient absorption spectroscopy of the hydrated electron as a function of temperature. We perform such experiments and describe them in Paper II [E. P. Farr et al., J. Chem. Phys. 147, 074504 (2017)], and find changes in the excited-state lifetime and hot ground-state cooling time with temperature that match well with the predictions of the non-cavity model. In particular, the experiments reveal stimulated emission from the excited state with an amplitude and lifetime that decreases with increasing temperature, a result in contrast to the lack of stimulated emission predicted by the cavity model but in good agreement with the non-cavity model. Overall, until ab initio calculations describing the non-adiabatic excited-state dynamics of an excess electron with hundreds of water molecules at a variety of temperatures become computationally feasible, the simulations presented here provide a definitive route for connecting the predictions of cavity and non-cavity models of the hydrated electron with future experiments.

Mechanism of Triplet Energy Transfer in Photosynthetic Bacterial Reaction Centers.

In purple bacterial reaction centers, triplet excitation energy transfer occurs from the primary donor P, a bacteriochlorophyll dimer, to a neighboring carotenoid to prevent photodamage from the generation of reactive oxygen species. The BB bacteriochlorophyll molecule that lies between P and the carotenoid on the inactive electron transfer branch is involved in triplet energy transfer between P and the carotenoid. To expand the high-resolution spectral and kinetic information available for describing the mechanism, we investigated the triplet excited state formation and energy transfer pathways in the reaction center of Rhodobacter sphaeroides using pump-probe transient absorption spectroscopy over a broad spectral region on the nanosecond to microsecond time scale at both room temperature and at 77 K. Wild-type reaction centers were compared with a reaction center mutant (M182HL) in which BB is replaced by a bacteriopheophytin (Φ), as well as to reaction centers that lack the carotenoid. In wild-type reaction centers, the triplet energy transfer efficiency from P to the carotenoid was essentially unity at room temperature and at 77 K. However, in the M182HL mutant reaction centers, both the rate and efficiency of triplet energy transfer were decreased at room temperature, and at 77 K, no triplet energy transfer was observed, attributable to a higher triplet state energy of the bacteriopheophytin that replaces bacteriochlorophyll in this mutant. Finally, detailed time-resolved spectral analysis of P, carotenoid, and BB (Φ in the M182HL mutant) reveals that the triplet state of the carotenoid is coupled fairly strongly to the bridging intermediate BB in wild-type and Φ in the M182HL mutant, a fact that is probably responsible for the lack of any obvious intermediate 3BB/3Φ transient formation during triplet energy transfer.

Cobaltocenium substituents as electron acceptors in photosynthetic model dyads

Cobaltocenium carboxylic acid hexafluorophosphate has been attached to a zinc(II) meso-tetraphenyl porphyrin chromophore via an amide linkage. Optical and electrochemical studies reveal that the metallocene and the porphyrin interact only negligibly in the ground state of the dyad. Photoinduced charge-shift from the zinc porphyrin to the cobaltocenium substituent to give the zinc porphyrin radical cation and the cobaltocene occurs upon exciting the porphyrin with light. Steady state emission, time-resolved fluorescence and transient absorption pump–probe spectroscopy in addition to density functional theory calculations suggest that the charge shift to the cobaltocenium substituent can occur from several excited states of the porphyrin, namely from the S2, S1 and T1 states. The triplet states of the cobaltocenium substituent (3E1g) and the triplet state of the zinc porphyrin (T1) are higher in energy than the charge-shifted state. This energy sequence of states of the dyad is beneficial for photoinduced charge-shift reactions.

Pump-probe micro-spectroscopy by means of an ultra-fast acousto-optics delay line

We demonstrate femtosecond pump-probe transient absorption spectroscopy using a programmable dispersive filter as an ultra-fast delay line. Combined with fast synchronous detection, this delay line allows for recording of 6 ps decay traces at 34 kHz. With such acquisition speed, we perform single point pump-probe spectroscopy on bulk samples in 80 μs and hyperspectral pump-probe imaging over a field of view of 100 μm in less than a second. The usability of the method is illustrated in a showcase experiment to image and discriminate between two pigments in a mixture.

CW Optical Limiting Study in Disperse Yellow Dye-doped PMMA-MA Polymer Films

<div><p><em>Molecules with high two-photon absorption (TPA) cross section and the molecules which have reverse saturation absorption (RSA) cross section are of great interest today because of their application in three-dimensional optical data storage and photonic switches. During last forty years, several techniques have been developed to determine the two-photon absorption cross-sections and reverse saturation absorption cross-sections of the materials. This includes direct methods, such as nonlinear transmission and Z-scan methods and indirect methods, such as two-photon excited fluorescence and two-photon pump-probe transient absorption spectroscopy. During recent years, the organic dye-doped polymer films getting more attention due to their advantages to fabricate photonics devices. In this paper, we have studied the nonlinear optical properties like nonlinear absorption and nonlinear refraction of an azo dye Disperse yellow-7 (DY-7) doped in Polymethyl methacrylate-methacrylic acid (PMMA-MA) polymer matrix using open aperture and closed aperture Z-scan experimental methods using continuous wave (CW) laser. The optical limiting properties of these films are also studied in Type 1 and Type 2 configurations at different input power using continuous wave (CW) laser beams of 532 nm wavelength.</em></p></div>

Ultrafast carrier dynamics, band-gap renormalization, and optical properties of ZnSe nanowires

In this paper, we present a comprehensive study of the carrier dynamics and optical properties of ZnSe nanowires (NWs). The transparency of the sample, obtained by the growth of the ZnSe NWs on glass, allowed us to perform transmittance, reflectance, photoluminescence (PL), time-resolved PL, and pump-probe transient absorption spectroscopy on as-grown samples. All measurements were performed at room temperature. Strong light trapping at the band-gap energy has been observed in reflectivity measurements. Fast transient absorption bleaching due to band filling and band-gap renormalization has been observed. The band-gap renormalization has a rise time constant of about 170 fs and a decay time of about 4 ps. Fast transient absorption bleaching is also observed at energies below the band gap, suggesting that intrinsic processes prevail over extrinsic photoinduced transitions in our high-quality NWs. The PL reveals the presence at room temperature of excitonic emission that shows a decay time of 0.5 ns. All of these features indicate that our ZnSe NWs have quality comparable to epitaxial films and can be used for optical devices and nonlinear optics.

Effect of Silver Nanoparticles on the Photophysics of Riboflavin: Consequences on the ROS Generation

Metal-enhanced singlet oxygen, O2(1Δg), generation is a desirable effect to augment the amount of O2(1Δg) produced upon irradiation of organic sensitizers. Herein, we employed pectin for stabilizing 9 nm silver nanoparticles and showed that these particles are able to form a ground-sate complex with riboflavin (Rf). Pump–probe transient absorption spectroscopy and laser flash-photolysis experiments proved that the excited state of the riboflavin–Ag complex feeds the triplet state of the sensitizer, which results in an enhanced intersystem crossing process. The higher amounts of riboflavin triplet states formed in the presence of the nanoparticles result in higher yields of singlet oxygen and hydrogen peroxide produced in the irradiated colloidal suspensions. As a result, not only the effect on singlet oxygen but also the effect on superoxide radical ion should contribute to a better performance of Riboflavin as a sensitizer applied to the photodynamic therapy of tumors.

Ultrafast Dynamics of Plasmon-Exciton Interaction of Ag Nanowire- Graphene Hybrids for Surface Catalytic Reactions.

Using the ultrafast pump-probe transient absorption spectroscopy, the femtosecond-resolved plasmon-exciton interaction of graphene-Ag nanowire hybrids is experimentally investigated, in the VIS-NIR region. The plasmonic lifetime of Ag nanowire is about 150 ± 7 femtosecond (fs). For a single layer of graphene, the fast dynamic process at 275 ± 77 fs is due to the excitation of graphene excitons, and the slow process at 1.4 ± 0.3 picosecond (ps) is due to the plasmonic hot electron interaction with phonons of graphene. For the graphene-Ag nanowire hybrids, the time scale of the plasmon-induced hot electron transferring to graphene is 534 ± 108 fs, and the metal plasmon enhanced graphene plasmon is about 3.2 ± 0.8 ps in the VIS region. The graphene-Ag nanowire hybrids can be used for plasmon-driven chemical reactions. This graphene-mediated surface-enhanced Raman scattering substrate significantly increases the probability and efficiency of surface catalytic reactions co-driven by graphene-Ag nanowire hybridization, in comparison with reactions individually driven by monolayer graphene or single Ag nanowire. This implies that the graphene-Ag nanowire hybrids can not only lead to a significant accumulation of high-density hot electrons, but also significantly increase the plasmon-to-electron conversion efficiency, due to strong plasmon-exciton coupling.