Enhancing Triplet-Triplet Annihilation Upconversion of Pyrene Derivatives for Photoredox Catalysis via Molecular Engineering.

Triplet-triplet annihilation upconversion (TTA-UC) has the potential to enhance photoredox catalysis yield. It includes a sensitizer and an annihilator. Efficient and stable annihilators are essential for photoredox catalysis, yet only a few examples are reported. Herein, we designed four novel pyrene annihilators (1, 2, 3 and 4) via introducing aryl-alkynyl groups onto pyrene to systematically modulate their singlet and triplet energies. Coupled with platinum octaethylporphyrin (PtOEP), the TTA-UC efficiency is enhanced gradually as the number of aryl-alkynyl group increases. When combining 4 with palladium tetraphenyl-tetrabenzoporphyrin (PdTPTBP), we achieved the highest red-to-green upconversion efficiency (22.4±0.3 %) (out of a 50 % maximum) so far. Then, this pair was used to activate photooxidation of aryl boronic acid under red light (630 nm), which achieved a great improved reaction yield compared to that activated by green light directly. The results not only provide a design strategy for efficient annihilators, but also show the advantage of applying TTA-UC into improving the photoredox catalysis yield.

Unraveling the excited-state vibrational cooling dynamics of chlorophyll-a using femtosecond broadband fluorescence spectroscopy.

Understanding the dynamics of excited-state vibrational energy relaxation in photosynthetic pigments is crucial for elucidating the mechanisms underlying energy transfer processes in light-harvesting complexes. Utilizing advanced femtosecond broadband transient fluorescence (TF) spectroscopy, we explored the excited-state vibrational dynamics of Chlorophyll-a (Chl-a) both in solution and within the light-harvesting complex II (LHCII). We discovered a vibrational cooling (VC) process occurring over ∼6 ps in Chl-a in ethanol solution following Soret band excitation, marked by a notable ultrafast TF blueshift and spectral narrowing. This VC process, crucial for regulating the vibronic lifetimes, was further elucidated through the direct observation of the population dynamics of higher vibrational states within the Qy electronic state. Notably, Chl-a within LHCII demonstrated significantly faster VC dynamics, unfolding within a few hundred femtoseconds and aligning with the ultrafast energy transfer processes observed within the complex. Our findings shed light on the complex interaction between electronic and vibrational states in photosynthetic pigments, underscoring the pivotal role of vibrational dynamics in enabling efficient energy transfer within light-harvesting complexes.

Incoherent ultrafast energy transfer in phycocyanin 620 from Thermosynechococcus vulcanus revealed by polarization-controlled two dimensional electronic spectroscopy.

Phycocyanin 620 (PC620) is the outermost light-harvesting complex in phycobilisome of cyanobacteria, engaged in light collection and energy transfer to the core antenna, allophycocyanin. Recently, long-lived exciton-vibrational coherences have been observed in allophycocyanin, accounting for the coherent energy transfer [Zhu et al., Nat. Commun. 15, 3171 (2024)]. PC620 has a nearly identical spatial location of three α84-ß84 phycocyanobilin pigment pairs to those in allophycocyanin, inferring an existence of possible coherent energy transfer pathways. However, whether PC620 undergoes coherent or incoherent energy transfer remains debated. Furthermore, accurate determination of energy transfer rates in PC620 is still necessary owing to the spectral overlap and broadening in conventional time-resolved spectroscopic measurements. In this work, the energy transfer process within PC620 was directly resolved by polarization-controlled two dimensional electronic spectroscopy (2DES) and global analysis. The results show that the energy transfer from α84 to the adjacent ß84 has a lifetime constant of 400 fs, from ß155 to ß84 of 6-8 ps, and from ß155 to α84 of 66 ps, fully conforming to the Förster resonance energy transfer mechanism. The circular dichroism spectrum also reveals that the α84-ß84 pigment pair does not form excitonic dimer, and the observed oscillatory signals are confirmed to be vibrational coherence, excluding the exciton-vibrational coupling. Nodal line slope analysis of 2DES further reveals that all the vibrational modes participate in the energy dissipation of the excited states. Our results consolidate that the ultrafast energy transfer process in PC620 is incoherent, where the twisted conformation of α84 is suggested as the main cause for preventing the formation of α84-ß84 excitonic dimer in contrast to allophycocyanin.

Molecular mechanism of Xiaohuoluo wan for rheumatoid arthritis by integrating in vitro and in vivo chemomics and network pharmacology.

The cause of rheumatoid arthritis (RA) is unclear. Xiaohuoluo wan (XHLW) is a classical Chinese medicine that is particularly effective in the treatment of RA. Given the chemical composition of XHLW at the overall level has been little studied and the molecular mechanism for the treatment of RA is not clear, we searched for the potential active compounds of XHLW and explored their anti-inflammatory mechanism in the treatment of RA by flexibly integrating the high-resolution ultra-performance liquid chromatography-mass spectrometry (UPLC-MS)-based in vitro and in vivo chemomics, network pharmacology, and other means. The results of the study identified that the active compounds of XHLW, such as alkaloids, nucleosides, and fatty acids, may play an anti-inflammatory role by regulating key targets such as IL-2, STAT1, JAK3, and MAPK8, inducing immune response through IL-17 signaling pathway, T-cell receptor, FoxO, tumor necrosis factor (TNF), and so forth, inhibiting the release of inflammatory factors and resisting oxidative stress and other pathways to treat RA. The results of this study provide referable data for the screening of active compounds and the exploration of molecular mechanisms of XHLW in the treatment of RA.

Observation of photoinduced polarons in semimetal 1T-TiSe2.

In this work, ultrafast carrier dynamics of mechanically exfoliated 1T-TiSe2flakes from the high-quality single crystals with self-intercalated Ti atoms are investigated by femtosecond transient absorption spectroscopy. The observed coherent acoustic and optical phonon oscillations after ultrafast photoexcitation reveal the strong electron-phonon coupling in 1T-TiSe2. The ultrafast carrier dynamics probed in both visible and mid-infrared regions indicate that some photogenerated carriers localize near the intercalated Ti atoms and form small polarons rapidly within several picoseconds after photoexcitation due to the strong and short-range electron-phonon coupling. The formation of polarons leads to a reduction of carrier mobility and a long-time relaxation process of photoexcited carriers for several nanoseconds. The formation and dissociation rates of the photoinduced polarons are dependent on both the pump fluence and the thickness of TiSe2sample. This work offers new insights into the photogenerated carrier dynamics of 1T-TiSe2, and emphasizes the effects of intercalated atoms on the electron and lattice dynamics after photoexcitation.

Effects of the Separation Distance between Two Triplet States Produced from Intramolecular Singlet Fission on the Two-Electron-Transfer Process.

To harvest two triplet excitons of singlet fission (SF) via a two-electron transfer efficiently, the revelation of the key factors that influence the two-electron-transfer process is necessary. Here, by using steady-state and transient absorption/fluorescence spectroscopy, we investigated the two-electron-transfer process from the two triplet excitons of intramolecular SF (iSF) in a series of tetracene oligomers (dimer, trimer, and tetramer) with 7,7,8,8-tetracyanoquinodimethane (TCNQ) as an electron acceptor in solution. Quantitative two-electron transfer could be conducted for the trimer and tetramer, and the rate for the tetramer is faster than that for the trimer. However, the maximum efficiency of the two-electron transfer in the dimer is relatively low (∼47%). The calculation result of the free energy change (ΔG) of the second-electron transfer for these three compounds (-0.024, -0.061, and -0.074 eV for the dimer, trimer, and tetramer, respectively) is consistent with the experimental observation. The much closer ΔG value to zero for the dimer should be responsible for its low efficiency of the two-electron transfer. Different ΔG values for these three oligomers are attributed to the different Coulomb repulsive energies between the two positive charges generated after the two-electron transfer that is caused by their various intertriplet distances. This result reveals for the first time the important effect of the Coulomb repulsive energy, which depends on the intertriplet distance, on the two-electron transfer process from the two triplet excitons of iSF.

Covalent Microporous Polymer Nanosheets for Efficient Photocatalytic CO2 Conversion with H2 O.

It is still a challenging target to achieve photocatalytic CO2 conversion to valuable chemicals with H2 O as an electron donor. Herein, 2D imide-based covalent organic polymer nanosheets (CoPcPDA-CMP NSs), which integrate cobalt phthalocyanine (CoPc) moiety for reduction half-reaction and 3,4,9,10-perylenetetracarboxylic diimide moiety for oxidation half-reaction, are constructed as a Z-scheme artificial photosynthesis system to complete the overall CO2 reduction reaction. Owing to the outstanding light absorption capacity, charge separation efficiency, and electronic conductivity, CoPcPDA-CMP NSs exhibit excellent photocatalytic activity to reduce CO2 to CO using H2 O as a sacrificial agent with a CO production rate of 14.27 µmol g-1 h-1 and a CO selectivity of 92%, which is competitive to the state-of-the-art visible-light-driven organic photocatalysts towards the overall CO2 reduction reaction. According to a series of spectroscopy experiments, the authors also verify the photoexcited electron transfer processes in the CoPcPDA-CMP NSs photocatalytic system, confirming the Z-scheme photocatalytic mechanism. The present results should be helpful for fabricating high-performance organic photocatalysts for CO2 conversion.

Robust Biological Hydrogen-Bonded Organic Framework with Post-Functionalized Rhenium(I) Sites for Efficient Heterogeneous Visible-Light-Driven CO2 Reduction.

A robust 2,2'-bipyridine (bpy)-derived biological hydrogen-bonded framework (HOF-25) has been realized depending on guanine-quadruplex with the assistance of π-π interaction, which reacts with Re(CO)5 Cl to give a post-functionalized HOF-25-Re. X-ray absorption fine structure spectroscopic study on HOF-25-Re confirms the covalent attachment of Re(bpy)(CO)3 Cl segments to this HOF. Robust and recycled HOF-25-Re bearing photocatalytic Re(bpy)(CO)3 Cl centers displays good heterogeneous catalytic activity towards carbon dioxide photoreduction in the presence of [Ru(bpy)3 ]Cl2 and triisopropanolamine in CH3 CN under visible-light irradiation, with both high CO production rate of 1448 µmol g-1 h-1 and high selectivity of 93 %. Under the same conditions, the experimental turnover number of HOF-25-Re (50) is about 8 times as that of the homogeneous control Re(bpy)(CO)3 Cl. The sustainably regenerated HOF-25-Re via crystallization and post-modification processes shows recovered photocatalytic performance.

Study on the Ultrafast Process of Perovskite Nanoparticles Modified by Different Alkyl Chains.

Three kinds of perovskite nanoparticles encapsulated with different chain lengths of alkylammonium, (CH3NH3)x(CH3(CH2)3NH3)(1-x)PbBr3 (NP-C4), (CH3NH3)x(CH3(CH2)7NH3)(1-x)PbBr3 (NP-C8), and (CH3NH3)x(CH3(CH2)11NH3)(1-x)PbBr3 (NP-C12), are successfully prepared. X-ray powder diffraction experiments demonstrate that these three nanoparticles are all pure cubic phase. However, the compositions of these three nanoparticles are significantly different, as revealed by steady-state absorption spectra. NP-C4 mainly consists of 2D perovskite with m (number of unit cell layers) = 1 and 3D perovskite. Instead, NP-C8 and NP-C12 are mainly composed of 2D perovskite with m = 3, 4, and 5. Time-resolved fluorescence spectra and femtosecond transient absorption spectra suggest the presence of energy transfer from 2D perovskite to 3D perovskite in these three nanoparticles. More importantly, the energy-transfer rate gradually decreases from NP-C4 to NP-C12. This result suggests that the composition of perovskite nanoparticles and their corresponding photophysical properties can be controlled by the chain length of alkylammonium. This provides a new insight for preparing novel perovskite nanoparticles for special applications.

Evaluation of Fused Aromatic-Substituted Diketopyrrolopyrrole Derivatives for Singlet Fission Sensitizers.

Singlet fission (SF) is a spin-allowed carrier multiplication process that has potential to overcome the Shockley-Queisser limit of solar energy conversion efficiency for single-junction solar cells. It is of importance to prescreen appropriate SF candidates for both basic research and practical applications of SF. Besides common polycyclic aromatic hydrocarbons (PAHs), diketopyrrolopyrrole (DPP) derivatives also undergo efficient SF. A series of DPP derivatives with fused aromatic substituents were investigated considering their conjugation length, constitution, and the introduction of terminal substituents. A comparison of SF properties between nonfused and fused aromatic-substituted DPP derivatives was carried out. Detailed analysis focused on elucidating the relationship between the frontier molecular orbital energies, multiple diradical characters, and SF-relevant excited-state energy levels. Compared to nonfused aromatic-substituted DPP derivatives, fused aromatic-substituted DPP derivatives which contain three aromatic units (thiophene or furan) still share more appropriate energy levels for SF sensitizers. Changing the five-membered aromatic units with benzene ring and introducing -F, -OMe, and -COOH as terminal substituents are both effective ways to improve their performance as SF sensitizers. The results of this research help us to understand the SF properties of DPP derivatives deeply and are beneficial for the design of new DPP-based SF sensitizers.

Strong Visible-Light-Absorbing Cuprous Sensitizers for Dramatically Boosting Photocatalysis.

Developing strong visible-light-absorbing (SVLA) earth-abundant photosensitizers (PSs) for significantly improving the utilization of solar energy is highly desirable, yet it remains a great challenge. Herein, we adopt a through-bond energy transfer (TBET) strategy by bridging boron dipyrromethene (Bodipy) and a CuI complex with an electronically conjugated bridge, resulting in the first SVLA CuI PSs (Cu-2 and Cu-3). Cu-3 has an extremely high molar extinction coefficient of 162 260 m-1 cm-1 at 518 nm, over 62 times higher than that of traditional CuI PS (Cu-1). The photooxidation activity of Cu-3 is much greater than that of Cu-1 and noble-metal PSs (Ru(bpy)3 2+ and Ir(ppy)3 + ) for both energy- and electron-transfer reactions. Femto- and nanosecond transient absorption and theoretical investigations demonstrate that a "ping-pong" energy-transfer process in Cu-3 involving a forward singlet TBET from Bodipy to the CuI complex and a backward triplet-triplet energy transfer greatly contribute to the long-lived and Bodipy-localized triplet excited state.

Tuning the singlet fission relevant energetic levels of quinoidal bithiophene compounds by means of backbone modifications and functional group introduction.

Efficient singlet fission (SF) has been obtained in quinoidal bithiophene, end-capped with dicyanomethylene groups (QBT). However, QBT suffers from low triplet state energy [E(T1)] because of its biradicaloid nature, which results in a great driving force for SF but also a large loss of energy during the SF process. This is not favorable for the application of SF in solar cells. Modifications to the molecular structure of QBT were performed to optimize the SF relevant excited state energy levels and its diradical character in the present study. This includes chalcogen replacement, the fusing of the heterocyclic ring between the two thiophene rings, and the introduction of side substituents. Detailed analysis focused on the correlation between the molecular structure of the QBT derivatives and their diradical character y0, bond length alternation (BLA), molecular orbitals, and SF relevant excited state energy levels. The results show that electron-donating substituents, particularly groups introduced at the inner ß-positions of the thiophene ring, can increase E(T1) and reduce the energy loss of SF significantly under the premise of exothermic SF. These results would be beneficial to the development of new SF candidates for application in solar cells.

Effects of aromatic substituents on the electronic structure and excited state energy levels of diketopyrrolopyrrole derivatives for singlet fission.

Singlet fission (SF) is a spin-allowed process, which is expected to be a feasible strategy to realize photon downward conversion. To achieve a significant increase in the photoelectric conversion efficiency of solar cells, SF molecules should have not only a high SF efficiency, but also suitable energies of the first singlet excited state [E(S1)] and the first triplet excited state [E(T1)] to act as SF sensitizers in solar cells. Aryl-substituted diketopyrrolopyrrole (DPP) is one of the few organic molecules, which can undergo SF efficiently after photoexcitation. In order to find suitable DPP-based SF sensitizers for solar cells, we designed a series of DPP derivatives by varying aromatic substituents, including changing the conjugation and constitution of aromatic substituents, as well as introducing side-substituents on the aromatic substituents. Detailed analysis focused on the molecular structures, the frontier molecular orbitals, multiple diradical characters, and SF relevant excited-state energy levels. The results indicate that introduction of no more than two aromatic rings and modification of the aromatic rings with side-substituents are both practical ways to get suitable SF sensitizers for solar cells. This work would give a deep understanding of DPP-based SF molecules, and pave the way towards the development of new DPP-based SF sensitizers for solar cells.

Intramolecular singlet fission in a face-to-face stacked tetracene trimer.

A covalently linked tetracene trimer with a "face-to-face" stacked structure was prepared and its molecular structure is characterized by 1H NMR, MALDI-TOF mass spectroscopy, and elemental analysis. The minimized molecular structure reveals that three tetracene subunits within this trimer adopt a partially "face-to-face" stacked configuration. Its absorption spectrum differs significantly from that of the monomeric and dimeric counterparts in solution due to the strong ground state interactions between the neighboring tetracene subunits. Its fluorescence is almost quenched completely. An ultrafast fluorescence decay component is observed in its fluorescence dynamics, indicating the presence of an ultrafast nonradiative decay channel in the trimer. The nonradiative channel is proved to be intramolecular singlet fission (iSF) by femto-second transient absorption studies. Different from the strongly coupled triplet state observed in the corresponding dimer, weakly coupled triplet states can be formed in this trimer. The triplet quantum yield of trimer 4 can reach up to 126% in solution.

Synthesis and photophysical properties of a "face-to-face" stacked tetracene dimer.

A covalently linked tetracene dimer has been prepared and its molecular structure is characterized by (1)H NMR and MALDI-TOF mass spectroscopy, and elemental analysis. The minimized molecular structure reveals that the tetracene subunits in a dimer adopt a "face-to-face" stacked configuration. Its absorption spectrum differs significantly from that of the monomeric counterpart in solution, suggesting the presence of strong interactions between the two tetracene subunits. In solution, the fluorescence spectrum is dominated by a band at around 535 nm, due to an oxidative impurity. In the longer wavelength range, a short-lived lower energy emission can be identified as the intrinsic emission of the dimer. In a polystyrene matrix or at low temperatures, the lifetime of the lower energy emission lengthens and it becomes more prominent. We suggest that the interactions between the two tetracene subunits produce a short-lived, lower energy "excimer-like" state. The fluorescence decays show no observable dependence on an applied magnetic field, and no obvious evidence of significant singlet fission is found in this dimer. This research suggests that even though there are strong electronic interactions between the tetracene subunits in the dimer, singlet fission cannot be achieved efficiently, probably because the formation of "excimer-like" states competes effectively with singlet fission.

Covalently linked perylenetetracarboxylic diimide dimers and trimers with rigid "J-type" aggregation structure.

Covalently linked perylenetetracarboxylic diimide (PDI) dimers (D1 and D2) and trimers (T1 and T2) with slipped "face-to-face" stacked structure are prepared and their molecular structures are characterized by 1H NMR, MALDI-TOF mass spectroscopy and elemental analysis. The rigid molecular structures of these compounds make it easier to establish a direct correlation between the aggregate structure and the photophysical properties. The minimized molecular structures of these compounds reveal that they are all "face-to-face" stacked aggregates with large longitudinal displacement. Their absorption spectra show red-shifted bands, suggesting the presence of "J" type excitonic coupling between the PDI subunits in these compounds. However, their steady state and time resolved fluorescence spectra revealed that the emission from the "excimer-like" states dominates the fluorescence of these compounds, this is similar to that of "H-type" aggregates and may be ascribed to the "face-to-face" stacked structure. In the fluorescence spectra of these compounds, a minor "J-type" emission can be identified for the compounds with a relatively large longitudinal displacement. An increase in the number of subunits in one aggregate from 2 to 3 also brings about distinctive changes in their photophysical properties, which can be ascribed to the changes in the stacking structure caused by the steric hindrance.

Green synthesis of 3D core-shell SnS2/SnS-Cd0.5Zn0.5S multi-heterojunction for efficient photocatalytic H2 evolution.

Low charge carrier separation efficiency is one of the key factors restricting photocatalytic hydrogen evolution performance. It is an effective strategy to build heterojunctions to steer charge migration. Herein, a series of x-SnS2/SnS-Cd0.5Zn0.5S (x-SS-CZS) nanosphere composites with varying mass ratios of SnS2/SnS (SS) were prepared through in situ hydrothermal synthesis. Moreover, XRD, TEM, and XPS were used to characterize the 3D core-shell SS-CZS multi-heterojunction composite. The 5-SS-CZS heterojunction composite with 5 wt% content of SS exhibits a remarkable hydrogen evolution rate of 168.85 mmol g-1 h-1, which is 5.4 times higher than that of pristine twin CZS (31.08 mmol g-1 h-1) and 1.9 times higher than that of 5-SnS2-CZS (88.21 mmol g-1 h-1). Furthermore, the composite catalyst showed excellent photostability after four cycles of reactions under visible light illumination. The apparent quantum yield at λ = 420 nm could reach up to 24.78%. The excellent hydrogen evolution performance of 5-SS-CZS nanospheres is ascribed to the following factors: (1) a core-shell catalyst with broad spectral absorption improves light utilization efficiency, (2) hybrid material with large surface area provides more active sites and shows the highest H2 activity, (3) a multi-heterojunction composite extends the lifetime of photoinduced carriers and accelerates charge separation and migration, and (4) SS as a hole trapping agent enhances the photocatalytic stability performance. This work proposes a possible photocatalytic mechanism, while also providing a novel approach for the synthesis of highly active and stable photocatalysts.

Automated information extraction model enhancing traditional Chinese medicine RCT evidence extraction (Evi-BERT): algorithm development and validation.

Background: In the field of evidence-based medicine, randomized controlled trials (RCTs) are of critical importance for writing clinical guidelines and providing guidance to practicing physicians. Currently, RCTs rely heavily on manual extraction, but this method has data breadth limitations and is less efficient. Objectives: To expand the breadth of data and improve the efficiency of obtaining clinical evidence, here, we introduce an automated information extraction model for traditional Chinese medicine (TCM) RCT evidence extraction. Methods: We adopt the Evidence-Bidirectional Encoder Representation from Transformers (Evi-BERT) for automated information extraction, which is combined with rule extraction. Eleven disease types and 48,523 research articles from the China National Knowledge Infrastructure (CNKI), WanFang Data, and VIP databases were selected as the data source for extraction. We then constructed a manually annotated dataset of TCM clinical literature to train the model, including ten evidence elements and 24,244 datapoints. We chose two models, BERT-CRF and BiLSTM-CRF, as the baseline, and compared the training effects with Evi-BERT and Evi-BERT combined with rule expression (RE). Results: We found that Evi-BERT combined with RE achieved the best performance (precision score = 0.926, Recall = 0.952, F1 score = 0.938) and had the best robustness. We totally summarized 113 pieces of rule datasets in the regulation extraction procedure. Our model dramatically expands the amount of data that can be searched and greatly improves efficiency without losing accuracy. Conclusion: Our work provided an intelligent approach to extracting clinical evidence for TCM RCT data. Our model can help physicians reduce the time spent reading journals and rapidly speed up the screening of clinical trial evidence to help generate accurate clinical reference guidelines. Additionally, we hope the structured clinical evidence and structured knowledge extracted from this study will help other researchers build large language models in TCM.

Synergistic optimization of triple phase junctions and oxygen vacancies over MnxCd1-xS/Ov-WO3 for boosting photocatalytic hydrogen evolution.

Strengthening the separation of photogenerated charge carriers is crucial for improving the efficiency of photocatalytic hydrogen evolution. Herein, t-Mn0.5Cd0.5S/Ov-WO3 (t-MCSW) triple-phase junctions with rich oxygen vacancies were developed using the calcination-hydrothermal method. The corresponding morphology and structure of the samples were examined by XRD, TEM and XPS. The formation of the S-scheme heterostructure in t-MCSW has also been confirmed with in situ XPS, work function analysis and free radical capture tests. The experimental results demonstrate that t-MCSW-7 exhibited optimal activity (194.2 mmol g-1 h-1), which was about 4 times higher than that of the individual Mn0.5Cd0.5S (t-MCS, 48.8 mmol g-1 h-1). The apparent quantum yield of t-MCSW-7 is 29.14% at 420 nm, and the material exhibits excellent stability after seven cycles of photocatalytic reaction. The excellent photocatalytic activity of t-MCSW-7 is attributed to more efficient separation of charge carriers by triple-phase junctions connected by homojunctions and heterojunctions. Moreover, the existence of oxygen vacancies broadens absorption spectra and accelerates surface charge transfer. The synergistic effect of phase junctions and oxygen vacancies leads to an enhancement of hydrogen evolution activity. This work provides a new idea for preparing efficient photocatalysts.

Femtosecond fluorescence conical optical parametric amplification spectroscopy.

Parametric superfluorescence (PSF), which originated from the optical amplification of vacuum quantum noise, is the primary noise source of femtosecond fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS). It severely affects the detection limit of FNOPAS to collect the femtosecond time-resolved spectra of extremely weak fluorescence. Here, we report the development of femtosecond fluorescence conical optical parametric amplification spectroscopy (FCOPAS), aimed at effectively suppressing the noise fluctuation from the PSF background. In contrast to traditional FNOPAS configurations utilizing lateral fluorescence collection and dot-like parametric amplification, FCOPAS employs an innovative conical fluorescence collection and ring-like amplification setup. This design enables effective cancellation of noise fluctuation across the entire PSF ring, resulting in an approximate order of magnitude reduction in PSF noise compared to prior FNOPAS outcomes. This advancement enables the resolution of transient fluorescence spectra of 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) dye molecules in ethanol, even at an optically dilute concentration of 10-6 mol/l, with significantly enhanced signal-to-noise ratios. This improvement will be significant for extremely weak fluorescence detection on the femtosecond time scale.