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Does the wavelength dependent photoisomerization process of the p?coumaric acid come out from the electronic state dependent pathways?
摘要： Similar to the anion photoactive yellow protein (PYP) chromophore, the neutral form of the PYP chromophore was also found to exhibit a the wavelength-dependent photoisomerization quantum yield. The isomerization quantum yield increases with the increasing excitation energy on the S1 state, while decreases when being excited to the S2 state. Does this wavelength dependent product yield come out from the specific reaction pathways of the S1 and S2 states? This would mean that, the relaxation pathway of the S2 state is distinct from that of the S1 state and does not involve twisting motion. Does it break Kasha's rule by exhibiting a direct transition from the S2 state to the ground state? The underlying mechanism needs further in. In this article, we employed the on-the-fly dynamics simulations and static electronic structure calculations to reveal the deactivation mechanism of the neutral form of the PYP chromophore. Our results indicated that the C_C twisting motion dominates the S1 state decay process. In contrast, for the decay process of the S2 state, an ultrafast transition from the S2 to the S1 state through a planar conical intersection is observed, and the excess energy activates a new reaction channel to the ground state characterized by a puckering distortion of the ring. This pathway competes with the photoisomerization channel. No direct transition from S2 to S0 is observed, hence Kasha's rule is valid for this process. Our calcualtions can provide a reasonable explanation of the wavelength-dependent isomerization quantum yield of neutral PYP chromophore, and we hope it can provide theoretical foundations for comparing the effect of protonation state on the dynamcal behaviors of PYP chromophore.
关键词： Wavelength dependent,Photoisomerization,Fluorescent protein,Nonadiabatic process
更新于2025-09-23 15:23:52
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Substituted stilbene-based oxime esters used as highly reactive wavelength-dependent photoinitiators for LED photopolymerization
摘要： Six novel oxime carboxylate photoinitiators were designed on the basis of a π-conjugated (E)-1-(4-styryl-phenyl)-1-one subunit. Different substituent groups were introduced into three distinctive sites of the chromophore to rationalize their related electronic and structural effects on free-radical photoinitiating reactivities. The electronic properties, photodissociation mechanism, and structure–reactivity relationships were investigated by UV–visible spectroscopy, DFT calculations, real-time 1H NMR, electron spin resonance spectroscopy, and photo-DSC. We demonstrate that the structural change affecting the photoinitiating properties corresponds to a para-substitution effect on the stilbene subunit using an electron-acceptor group. Such a structural change leads to a 10-fold enhancement in initiation efficiency (Φi) upon visible irradiation of light-emitting diodes. The photoinitiating performances of these new derivatives are strikingly sensitive to the excitation wavelengths, leading to an impressive enhancement of Φi by more than three orders of magnitude from 365 nm to 405 nm irradiation. This wavelength-dependent reactivity previously observed for commercially available oxime esters can be generalized in our series and has high potential photocuring applications in low-power visible LEDs.
关键词： photocuring,photoinitiators,LED photopolymerization,oxime esters,wavelength-dependent
更新于2025-09-16 10:30:52
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Wavelength-dependent surface plasmon coupling electrochemiluminescence biosensor based on sulfur doped carbon nitride quantum dots for K-RAS gene detection
摘要： Although graphite phase carbon nitride quantum dots (GCN QDs) showed some advantages in the electrochemiluminescence (ECL) analytical research, the low ECL efficiency limited the potential sensing application. Herein, we synthesized sulfur doped graphite phase carbon nitride quantum dots (S-GCN QDs) to fabricate a sandwich sensor based on amplified surface plasmon coupling ECL (SPC-ECL) mode. Sulfur doping can change the surface states of QDs effectively and produced new element vacancy. As a result, the ECL efficiency of S-GCN QDs was 2.5 times over GCN QDs. Furthermore, compared with the big gap between the ECL peak of GCN QDs (620 nm) and the absorption peak of Au NPs, the doped sulfur elements in S-GCN QDs generated new ECL emission peaks at 555 nm, which was closed to the absorption peak of Au NPs at 530 nm. Due to the wavelength-dependent surface plasmon coupling effect, the ECL peak of S-GCN QDs at 555 nm had greater amplitude of enhancement in the sensing system. The proposed biosensor can quantify the K-RAS gene from 50 fM to 1 nM with a limit of detection (LOD) of 16 fM. We were the first to provide insight into the role of wavelength-dependent surface plasmon coupling in enhancing the sensitivity of ECL biosensor.
关键词： wavelength-dependent surface plasmon coupling effect,sulfur doped GCN QDs,K-RAS gene,Electrochemiluminescence
更新于2025-09-16 10:30:52