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Design of lanthanide-based metal-organic frameworks with enhanced near-infrared emission
摘要： A strategy based on the use of ligand steric hindrance and metal doping is reported for the design and synthesis of near-infrared (NIR) emitting lanthanide-based metal–organic frameworks (MOFs). The lanthanide ions are free of coordinated solvents, and the resulting NIR-MOFs are highly emissive and exhibit long luminescence lifetimes.
关键词： metal doping,ligand steric hindrance,lanthanide-based metal–organic frameworks,luminescence,near-infrared emission
更新于2025-09-23 15:21:01
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Electrochemiluminescent biosensor with DNA link for selective detection of human IgG based on steric hindrance
摘要： A highly selective DNA-based electrochemiluminescence (ECL) based biosensor is described for the detection of human IgG. It is exploiting the effect of steric hindrance that affects the strength of the ECL signal in the presence of IgG. Digoxin-linked signalling DNA was specifically bound to IgG, and this causes steric hindrance which limits the ability of DNA to hybridize with capturing DNA attached to a gold electrode. Europium (II) doped CdSe quantum dots were covalently linked to the DNA in order to generate the ECL signal. Using this steric hindrance hybridization method, the ECL signal of the biosensor were proportional to the concentration of IgG with a wide linear range and a 14 pM detection limit. Conceivably, the method can be expanded to the detection of a wide range of proteins for which homologous recognition elements are available.
关键词： Digoxin-linked signalling DNA,Electrochemiluminescence,Human IgG,Steric hindrance effects,Biosensor,Europium (II) doped CdSe quantum dots
更新于2025-09-23 15:21:01
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Synthesis of second-order nonlinear optical chromophores with conjugated steric hindrances for electro-optics @850 nm
摘要： Electro-optic materials at the shortwave infrared window (850 nm) of optical fiber is significant for free-space telecommunication and short-distance local area network. However, most of current high-performance organic nonlinear optical chromophores (absorption bandgap ~1.5 eV) are designed for the operation windows of 1310 nm (O band) or 1550 nm (C band), which are not transparent at 850 nm (bandgap ~1.45 eV). The design and synthesis of chromophores for 850 nm is more challenging because regular bandgap engineering to improve microcroscopic nonlinearity (μβ value) might be not available due to the bandgap restriction (optical transparency) @ 850 nm. In this respect, this manuscript utilizes the strategy of suitable site-isolation in molecular engineering to optimize comprehensive performance of chromophores for electro-optics @850 nm. Vilsmeier formylation is facilitated on symmetric or asymmetric donor-π-donor intermediate dyes to form donor-π-acceptor (D-π-A) chromophores C1 and C2 with tuneable conjugated steric hindrance (site-isolator). Without significant red-shift of absorption spectra, conjugated steric hindrance groups contribute to large enhancement of chromophores’ μβ values and ensure optical transparency @ 850 nm. The μβ values of C1 (6706 ? 10-48 esu) and C2 (7279 ? 10-48 esu) with conjugated site-isolation groups are much higher than previously reported chromophores for 850 nm. The structure-property relation reveals that a suitable site-isolator is extremely significant for realizing highly efficient translation of microscopic hyperpolarizability into macroscopic electro-optic coefficients. As a results, electro-optic coefficients of 94 pm/V @ 830 nm are achieved. To the best of our knowledge, this is the highest value for organic electro-optics materials @ 850 nm.
关键词： Electro-optic materials,Vilsmeier formylation,conjugated steric hindrance,site-isolation,nonlinear optical chromophores
更新于2025-09-23 15:19:57
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Enhancing Charge Transfer and Photoelectric Characteristics for Organic Solar Cells
摘要： The main purpose of this work is to analyze the effect of steric hindrance on the photoelectric performance of three different donor sensitizers (ZHG5, ZHG6, and ZHG7) by molecular theory simulation engineering. Photoelectric physical and photoelectric chemical parameters are investigated by means of frontier molecular orbital, global reactivity descriptors, optical absorption properties, fluorescent lifetime, charge density difference, and influence of external electric field. The results showed that the performance of the quinoxaline sensitizer was deteriorated by gradually increasing the steric hindrance to auxiliary donors. The optical properties of the hybridization of cir-coronene graphene quantum dot (GR) with the three dyes have been revealed, and the results show that graphene quantum dots can indeed improve the optical properties of solar cells. In addition, nine new molecules were designed by inserting six functional groups; it is found that inserting -CN in the acceptor part of the molecular structure is beneficial to the performance of the sensitizer.
关键词： donor sensitizers,steric hindrance,functional groups,graphene quantum dot,photoelectric performance,molecular theory simulation
更新于2025-09-16 10:30:52
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A highly sensitive and selective “off-on” porphyrin-based fluorescent sensor for detection of thiophenol
摘要： Thiophenol and its derivatives easily cause damage to aquatic bioorganisms, animals and even human being, therefore, fluorescent probes for detecting thiophenol with sensitive and selective characters are highly popular. In this study, a highly sensitive and selective porphyrin-based fluorescent sensor (M1) was reported for detection of thiophenol based on the steric hindrance effect, where the recognition unit, 7-nitrobenzo[c][1,2,5]oxadiazolyl group is linked to aromatic ortho-position in the porphyrin, and correspondingly the fluorescence of fluorescein is efficiently quenched. Its time of fluorescence response for thiophenol was only 60s, and its fluorescence responses for the other anions/molecules were all far lower than the relative fluorescence ratio values for thiophenol, which means that the porphyrin-based fluorescent sensor is rapid, sensitive and selective to detection of thiophenol. This approach offers some useful insights for designing sensitive and selective fluorescent turn-on sensors in the detection assays for other analytes.
关键词： thiophenol,7-nitrobenzo[c][1,2,5]oxadiazolyl group,steric hindrance effect,the porphyrin-based fluorescent sensor
更新于2025-09-09 09:28:46
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Branched Side Chains Govern Counterion Position and Doping Mechanism in Conjugated Polythiophenes
摘要： Predicting the interactions between a semi-conducting polymer and dopant is not straightforward due to the intrinsic structural and energetic disorder in polymeric systems. Although the driving force for e?cient charge transfer depends on a favorable o?set between the electron donor and acceptor, we demonstrate that the e?cacy of doping also relies on structural constraints of incorporating a dopant molecule into the semiconducting polymer ?lm. Here, we report the evolution in spectroscopic and electrical properties of a model conjugated polymer upon exposure to two dopant types: one that directly oxidizes the polymeric backbone and one that protonates the polymer backbone. Through vapor phase in?ltration, the common charge transfer dopant, F4-TCNQ, forms a charge transfer complex (CTC) with the polymer poly(3-(2′-ethyl)hexylthiophene) (P3EHT), a conjugated polymer with the same backbone as the well-characterized polymer P3HT, resulting in a maximum electrical conductivity of 3 × 10?5 S cm?1. We postulate that the branched side chains of P3EHT force F4-TCNQ to reside between the π-faces of the crystallites, resulting in partial charge transfer between the donor and the acceptor. Conversely, protonation of the polymeric backbone using the strong acid, HTFSI, increases the electrical conductivity of P3EHT to a maximum of 4 × 10?3 S cm?1, 2 orders of magnitude higher than when a charge transfer dopant is used. The ability for the backbone of P3EHT to be protonated by an acid dopant, but not oxidized directly by F4-TCNQ, suggests that steric hindrance plays a signi?cant role in the degree of charge transfer between dopant and polymer, even when the driving force for charge transfer is su?cient.
关键词： semiconducting polymer,electrical conductivity,steric hindrance,dopant,charge transfer
更新于2025-09-09 09:28:46