No abstract

Circularly polarized light (CPL) is central to photonic technologies. A key challenge lies in developing a general route for generation of CPL with tailored chiroptical activity using low-cost raw materials suitable for scale-up. This study presents that cellulose films with photonic bandgaps (PBG) and left-handed helical sense have an intrinsic ability for circular polarization leading to PBG-based CPL with extraordinary |g | values, well-defiend handedness, and tailorable wavelength by the PBG change. Using such cellulose films, incident light ranging from near-UV to near-IR can be transformed to passive L-CPL and R-CPL with viewing-side-dependent handedness and |g | values up to 0.87, and spontaneous emission transformed to R-CPL emission with |g | values up to 0.68. Unprecedented evidence is presented with theoretical underpinning that the PBG effect can stimulate the R-CPL emission. The potential of cellulose-based CPL films for polarization-based encryption is illustrated. The evaporation-induced self-assembly coupled with nanoscale mesogens of cellulose nanocrystals opens new venues for technological advances and enables a versatile strategy for rational design and scalable manufacturing of organic and inorganic CPL films for photonic applications.

representatives of this category. [21] Early attempts to render inorganic quantum dots with chiroptical activity involve the use of chiral stabilizers. Experimental studies showed that stabilizer-modified quantum dots, such as CdS and CdTe, enabled circular dichroism, however, they were circularly polarized luminescenceinactive. [22,23] Theoretical calculations suggested that the chiral stabilizers caused distortion of the surface layer, however, the core of quantum dots remained achiral, which may explain the circularly polarized luminescence inactivity. [24] It was later hypothesized that enclosing quantum dots in a chiral environment may render quantum dots with circularly polarized luminescence activity, indeed, such a hypothesis found experimental evidences in a chiral nanostructure of apoferritin encapsulating CdS. [25] This lead to new chiral inorganic nanomaterials based on quantum dots and some novel approaches for circularly polarized luminescence generation. Representative work include CdSe quantum dots grafted with chiral cysteine, [26] CdTe nanowires embedded in stretchable twisted fibers [4] and chiral nanostructures of chalcogenide quantum dots. [27] However, these inorganic nanostructures are inadequate for applications due to their tedious synthesis procedures and low CPL strength with dissymmetry factors in the range of 10 −3 -10 −4 . It is clear that circularly polarized luminescent quantum dot nanomaterials with high strength, precise handedness, tunable wavelengths, and suitable for scale-up are highly desirable.Carbon dots are remarkable inorganic phosphors with distinct features such as tunable photoluminescence, high emission intensity, photostability, biocompatibility, and easy availability, which are superior to many inorganic quantum dots. [28][29][30][31] They are promising for bioimaging, sensing, light emitting diodes, energy storage, photocatalysis, and optoelectronic applications. [32][33][34][35][36][37][38] It can be anticipated that conferring circularly polarized luminescence on carbon dots will avail novel circularly polarized luminescent nanomaterials for biomedicine and nanoscience. Such materials, to the best of our knowledge, are not reported to date.Cellulose nanocrystals are renewable, biocompatible, and low-cost nanomaterials. They have intrinsic ability to selfassemble forming a left-handed chiral nematic organization that can be preserved upon drying. [39][40][41] Taking advantage of this property, a realm of cellulose nanocrystal-based helical Circularly polarized luminescent carbon dot nanomaterials of self-organized helical superstructures based on cellulose nanocrystals enable strong, right-handed, and multicolor tunable circularly polarized luminescence with extraordinary dissymmetry factors up to −0.74. The effects of emission intensity and carbon dots loading on the strength of the righthanded circularly polarized luminescence are experimentally observed and theoretically explained. Potentials of the carbon dots-cellulose nanomaterials for circularly polarized ...

Stimuli‐responsive selective reflection of circularly polarized light in a broad wavelength range is of significance from scientific and technological viewpoints. Herein, chiral photonic cellulose films are fabricated which exhibit selective reflection of circularly polarized light responsive to mechanical and chemical stimuli. The chiral photonic cellulose films are highly deformable with the strain‐at‐break up to 40.8%, which is the highest among reported chiral photonic cellulose films. Selective reflection of left‐handed circularly polarized light responsive to bending and uniaxial tensioning across the entire visible spectrum is demonstrated, as well as reversible response to water vapor (10–100% relative humidity) from the visible to the near‐infrared region with Δλmax = 492 nm. The stimuli response is realized by alterable helical organization based on supramolecular chemistry. The current work provides a general strategy for rational design of multistimuli‐responsive selective reflection of circularly polarized light, and a soft material platform for scalable camouflaging and security materials.

RGB color-tunable "turn-on" electrofluorochromic (EFC) devices with high color purity (457 nm for blue, 539 nm for green, and 641 nm for red), relatively quick response/fading speeds and remarkable fluorescence contrast ratios are successfully fabricated. They exhibit great potential for increasingly important multistage encrypted information storage and displays.

No abstract

Converting CO 2 into fuels and other value-added chemicals via an electrochemical reduction method has recently attracted great interest. However, there are still challenges to find suitable catalysts with high selectivity toward the formic acid formation. Here, we report the bimetallic CuSn-based catalyst to reduce CO 2 to formic acid by optimizing the ratio of Cu to Sn to achieve the optimal selectivity. The catalyst is generated on laser-induced graphene. Among the catalysts, CuSn-4 with Cu/Sn atomic ratio close to 1:2 shows a faradaic efficiency of 99% toward formic acid with a high partial current density of 26 mA/cm 2 . Density functional theory calculations demonstrate that OCHO* intermediate formation is more favorable than that of COOH* on Sn sites, while OCHO* intermediate formation is moderate on Cu sites. The synergetic catalytic effect between Cu and Sn would further favor HCOOH formation. This study provides significant insight into the mechanism of formic acid formation.

but also avoiding the reaction of CO 2 with alkaline electrolytes. [11] Therefore, efficient CO 2 -to-CO conversion is important. Currently, the CO production process mainly operates in alkali or neutral media for high Faraday efficiency (FE). [12][13][14][15][16] However, CO 2 reacts with the electrolyte to form carbonate or bicarbonate in alkali or neutral media, leading to short-lived catalysis, electrolyte loss, and substantial CO 2 loss (>50%). [17,18] The carbonate or bicarbonate formation in CO 2 RR significantly increases the operating costs and severely limits its prospects. [11] CO 2 RR in acidic media can eliminate carbonate or bicarbonate formation and thus facilitate efficient CO 2 utiliza-