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Two‐photon excited fluorescence materials with sufficient responsiveness to magnetic field are essential for applications such as 3D mapping of magnetic field distributions based on magneto‐optical effect. In this study, a two‐photon excited magneto‐photoluminescence (MPL) in the intermolecular exciplex of 1,1‐bis[(di‐4‐tolylamino)phenyl]cyclohexane and tris(2,4,6‐trimethyl‐3‐(pyridin‐3‐yl)phenyl)borane (TAPC:3TPYMB) is observed. This MPL can be attributed to the promotion of delocalization of excitons in the exciplex under two‐photon excitation, resulting in a weakened spin‐exchange interaction and thereby enhancing the magnetic field‐sensitive spin conversion process. The temperature‐dependent MPL further validates the strong correlation between the delocalization of excitons in the exciplex and the enhanced MPL observed during temperature variation. Combining the penetration capability and magneto‐optical effect of two‐photon excited fluorescence in TAPC:3TPYMB exciplex, a novel magnetic sensor suitable for 3D mapping of magnetic field distributions is further developed. The present work not only enhances the understanding of the magneto‐optical coupling mechanism but also opens up opportunities for the application of molecular materials in opto‐spintronic devices. [ABSTRACT FROM AUTHOR]

With the significant growth in modern computing systems, dynamic random access memory (DRAM) has become a power/performance/energy bottleneck in data-intensive applications. Both the power management mechanism and downscaling method face decreasing performance or difficulties in the smaller footprint of the DRAM capacitor. Since optimizing the circuit of sense amplifier (SA) is an efficient method to reduce energy consumption, we propose two single bitline load sense amplifier (SBLSA) circuits, i.e., a redundant voltage discharged SBLSA (RVD-SBLSA) circuit and a bit aware SBLSA (BA-SBLSA) circuit, to improve conventional and single bitline write (SBW) circuits. The RVD-SBLSA circuit utilizes a clamp diode to discharge redundant voltage over VDD/2 with an additional working stage. The BA-SBLSA circuit abandons the single bitline load (SBL) circuit during read and write '1' operations. The RVD-SBLSA circuit can offer the lowest total energy consumption, and the BA-SBLSA circuit can make a better balance between energy consumption and latency. Through the simulation results, the proposed circuits can efficiently reduce energy consumption or balance energy consumption and latency and show huge potentials in very large-scale integrated circuits. [ABSTRACT FROM AUTHOR]

Simultaneously realizing high exciton density and high emission efficiency in light emitting devices is generally challenging because of the competition between exciton accumulation and its radiative recombination. Here, we demonstrate that the hybridized local and charge-transfer (HLCT) excited state in a twisted donor–acceptor molecule can be used to accumulate highly luminescent excitons, leading to both efficient optically pumped lasing and improved electrically injected luminescence. The twisted molecular structure brings the hybridization characteristics of both locally excited (LE) and charge-transfer (CT) states, where the LE component ensures the remarkable quantum yield (>60%) of radiative decay and the CT contribution prolongs the exciton lifetime to a few nanoseconds. By incorporating the HLCT molecule into the polymer semiconductor, optically pumped lasing is achieved from their microspheres, and the threshold is significantly reduced compared with that of the LE molecule. Magneto-photoluminescence measurement reveals that the introduction of CT characteristics is beneficial to the efficient accumulation of bright excitons at high pump intensity. Moreover, the HLCT molecule doped polymer is used as an active layer in organic light emitting diodes, in which the electroluminescence intensity is enhanced by 2 orders of magnitude compared with its LE counterpart especially at high electric current density. The magneto-electroluminescence of the HLCT material decreases at >50 mT fields and is opposite to its magneto-photoluminescence, which reveals the distinct contribution of the CT component in exciton accumulation under optical pump and electrical injection. These findings provide new insights into the design and synthesis of optical gain molecules towards high-performance organic lasers upon optical excitation as well as those under electrical injection conditions. [ABSTRACT FROM AUTHOR]

The construction of "photonic molecules" with controlled sizes and shapes is of particular interest for the integration of miniaturized devices into optoelectronic chips. Here, a general approach is reported that allows the assembly of colloidal microspheres into coupled microcavities with high yield and large scale, utilizing magnetostatic interactions between diamagnetic building blocks dispersed in a ferrofluid under an external field. By precisely designing the local field gradient around diamagnetic microspheres, "virtual templates" can be formed to produce various coupled photonic structures, including diatomic heterogeneous molecules and polyatomic chain molecules. The diatomic structures can modulate the optical resonance modes upon the coherent coupling between microsphere cavities and serve as single‐mode wavelength‐tunable microlasers. The chain photonic molecules, as coupled resonator optical waveguides, could modulate the light propagation and store photons up to tens of picoseconds. The magnetically controlled assembly method is demonstrated, which provides a promising way for the facile and efficient fabrication of coupled microstructures for fascinating photonic and optoelectronic applications. [ABSTRACT FROM AUTHOR]

High quality single crystals of bis-(8-hydroxyquinoline) zinc (ZnQ2), a π-conjugated molecular semiconductor with high thermal stability, good electron transport ability and excellent electroluminescence properties, were prepared by physical vapor deposition (PVD) method in a double zone tube furnace. X-ray single crystal diffraction (XSCD) indicates that the sample was ZnO2 tetramer, (ZnQ2)4, with the triclinic unit cell parameters: a = 10.8537(15) Å, b = 11.8814(16) Å, c = 13.0532(18) Å, α = 74.119(2)°, β = 73.449(2)°, γ = 70.999(2)°, volume = 1494.9(4) Å3 and Z = 1. The crystallization mechanism analysis suggests a classical crystal growth process at low temperatures (300 and 320 °C) and an existence of non-classical particle-attachment crystal growth pathway at high temperature (340 °C). The (ZnQ2)4 crystals also show enhanced photoluminescence (PL) intensities and narrower full width at half maximum (FWHM) compared with that of the ZnQ2 thin film. [ABSTRACT FROM AUTHOR]

Two‐photon excited chromophores are widely applied for photon upconversion in organic optoelectronics. In this work, efficient two‐photon excited fluorescence is observed from charge‐transfer cocrystals where the molecular architectures of donor and acceptor molecules are both centrosymmetric. The superior structural symmetry of cocrystals eliminates the second harmonic generation of incident near‐infrared laser. The nonlinear optical properties of cocrystals are found to be strongly correlated with the intermolecular charge‐transfer interaction, bringing a wide window of excitation wavelength for the upconverted light emission. The work demonstrates that the cocrystallization of small molecules provides opportunities for the design and synthesis of novel organic optofunctional materials. [ABSTRACT FROM AUTHOR]

Synthesis of single-crystalline micro/nanostructures with curved shapes is essential for developing extraordinary types of optoelectronic devices. Here, we use the strategy of liquid-phase nonconfinement growth to controllably synthesize edge-curved molecular microcrystals on a large scale. By varying the molecular substituents on linear organic conjugated molecules, it is found that the steric hindrance effect could minimize the intrinsic anisotropy of molecular stacking, allowing for the exposure of high-index crystal planes. The growth rate of high-index crystal planes can be further regulated by increasing the molecular supersaturation, which is conducive to the cogrowth of these crystal planes to form continuously curved-shape microcrystals. Assisted by nonrotationally symmetric geometry and optically smooth curvature, edge-curved microcrystals can support low-threshold lasing, and self-focusing directional emission. These results contribute to gaining an insightful understanding of the design and growth of functional molecular crystals and promoting the applications of organic active materials in integrated photonic devices and circuits.

The generation of reactive oxygen species (ROS) in photodynamic therapy (PDT) involves excited-state intermediates with both singlet and triplet spin configurations, which provides possibilities to modulate the ROS production in PDT under an external magnetic field. Here, we present that magnetically modulated ROS production can promote PDT efficacy and develop a magnetic-field-assisted PDT (magneto-PDT) method for effectively and selectively killing cancer cells. The photosensitization reaction between excited-state riboflavin and oxygen molecules is influenced by the applied field, and the overall magnetic field effect (MFE) shows a moderate increase at a low field (<1000 G) and then a boost up to the saturation ∼100% at a high field (>1000 G). It is found that the spin precession occurring in radical ion pairs (electron transfer from riboflavin to oxygen) facilitates the O 2 •- generation at the low field. In comparison, the spin splitting in an encounter complex (energy transfer from riboflavin to oxygen) benefits the production of 1 O 2 species at the high field. The field modulation on the two types of ROS in PDT, i.e., O 2 •- and 1 O 2 , is also demonstrated in living cells. The magneto-PDT strategy shows the capability to inhibit the proliferation of cancer cells (e.g., HeLa, RBL-2H3, and MCF-7) effectively and selectively, which reveals the potential of using the MFE on chemical reactions in biological applications.

The solid-to-solid crystallization processes of organic molecules have been poorly understood in view of the complexity and the instability of organic crystals. Here, we studied the crystallization of a π-conjugated small molecular semiconductor, bis-(8-hydroxyquinoline) copper (CuQ 2 ), by annealing the thin films at different temperatures. We observed a classical film-to-nanorods crystallization at 80 °C, a coexistence of classical and nonclassical nucleation and particle growth at 120 °C, and a nonclassical crystal growth at 150 °C. We found that the growth of the crystals followed the following processes: particle nucleation, particle growth, particle migration, nondirectional particle attachment, and structure reconstruction. We notice that the growth of CuQ 2 particles follows an outside-to-inside process. More interestingly, our experiments suggest that the submicron CuQ 2 particles are able to migrate dozens of micrometers at 150 °C., Competing Interests: The authors declare no competing financial interest.