Highly Efficient Red/Near-Infrared Phosphorescence from Doped Crystals.

Organic red/near-infrared (NIR) room temperature phosphorescence (RTP) materials with low toxicity and facile synthesis are highly sought after, particularly for applications in biotechnology and encryption. However, achieving efficient red/NIR RTP emitters has been challenging due to the weak spin-orbit coupling of organics and the rapid nonradiative decay imposed by the energy gap law. Here we demonstrate highly efficient red/ NIR RTP with boosted quantum yields (Φp) of up to 32.96% through doping the thionated derivatives of phthalimide (PAI) (MTPAI and DTPAI) into PAI crystals. The red-shifted photoluminescence (PL) stems from a combination of the external heavy atom effect and the formation of emissive clusters centered around electron-rich sulfur atoms. Furthermore, the dopants enhance exciton generation efficiency and facilitate energy transfer from smaller PAI units to larger aggregates, leading to dramatically increased Φp. This strategy proves universal, opening possibilities for acquiring long-wavelength RTP with tunable photophysical properties. The doped crystals exhibit promising applications in optical waveguides and encryption paper/ink. This research provides a practical approach to obtaining long-wavelength RTP materials and offers valuable insights into the mechanisms governing host-guest systems.

Photochromic luminescence of organic crystals arising from subtle molecular rearrangement.

Photoluminescence (PL) colour-changing materials in response to photostimulus play an increasingly significant role in intelligent applications for their programmability. Nevertheless, current research mainly focuses on photochemical processes, with less attention to PL transformation through uniform aggregation mode adjustment. Here we show photochromic luminescence in organic crystals (e.g. dimethyl terephthalate) with PL varying from dark blue to purple, then to bright orange-red, and finally to red. This change is attributed to the emergence of clusters with red emission, which is barely achieved in single-benzene-based structures, thanks to the subtle molecular rearrangements prompted by light. Crucial to this process are the through-space electron interactions among molecules and moderate short contacts between ester groups. The irradiated crystals exhibit reversible PL transformation upon sufficient relaxation, showing promising applications in information storage and smart optoelectronic devices. This research contributes to the development of smart photochromic luminescent materials with significant PL colour transformations through molecular rearrangement.

Bioelectrochemical systems for enhanced nitrogen removal with minimal greenhouse gas emission from carbon-deficient wastewater: A review.

Nitrogen pollution and the rising amount of wastewater generation are calling for advanced wastewater treatments, which is particularly necessary for carbon-deficient wastewater that contains multi-species inorganic nitrogen, since conventional heterotrophic denitrification processes cannot remove nitrogen completely when carbon sources are insufficient. For that, bioelectrochemical systems (BES) have been recently developed because they can simultaneously produce electricity and remove resistant nitrogen from the carbon-deficient wastewater. However, the simultaneous removal of multi-species inorganic nitrogen cannot be achieved by electroautotrophic denitrification using BES alone. Moreover, the efficiency of nitrogen removal and power generation has been thwarted by the low energy output, high internal resistance of the device, and electron competition in non-denitrification pathways. This review article discusses the latest developments for nitrogen removal through BES-enhanced denitrification and elucidates multiple coupled BES-based denitrification pathways to remove multi-species inorganic nitrogen simultaneously. Focus points of the research area include coupling BES technologies with emerged methods, electron transfer enhancement, and avoiding electron competition that improves performance with less cost. The prospect of reducing emissions of greenhouse gases is also critically reviewed, in the hope of reducing potential intermediate products of denitrification, such as nitrous oxide (a potent greenhouse gas), through multi-factor regulation. We imply that BES is a good choice for future scale-up applications of MFC coupled with MEC to treat carbon-deficient wastewater. Overall, this review will provide useful information for the development of advanced technologies to treat carbon-deficient wastewater with less emission of greenhouse gases.

Accessing Excitation- and Time-Responsive Afterglows from Aqueous Processable Amorphous Polymer Films through Doping and Energy Transfer.

Smart afterglow materials in response to excitation and delay time, including crystals, polymeric films, and carbon dots, have attracted considerable attention on account of their fundamental value in photophysics and promising applications in optoelectronics. However, the fabrication of amorphous and flexible polymer films with fine control remains underexplored. Herein, new doped polymer films based on sodium alginate and aromatic carboxylates are developed, which demonstrate following advantages: (i) easy and fast fabrication through the aqueous solution process, (ii) flexible, transparent, and re-dissolvable characteristics, (iii) multi-tunable afterglow colors from blue to red and even white with fine control. Specifically, even better controllability can be achieved through co-doping and triplet-to-singlet Förster resonance energy transfer (TS-FRET). Multimode advanced anti-counterfeiting of these materials is demonstrated using their excitation- and time-dependent as well as TS-FRET-mediated afterglow colors.

Chirality Transfer in Carbon Dot-Composited Sol-Gel Systems for Excitation-Dependent Circularly Polarized Luminescence.

In situ control of a circularly polarized luminescent (CPL) signal is desirable but rarely addressed. Even to compare with traditional chemical regulations, controlling the CPL signal at the material level using simple physical manipulation (such as photoexcitation) can be more convenient and preferable. In this work, we have constructed carbon dot-based composite luminescent materials with CPL activity. The materials can exist in the sol-gel state in a mixture solvent by chiral co-assembly, and chirality transfer occurred in the supramolecular assemblies and induced the CPL activity. Owing to the unique luminescent properties of the carbon dot component, the obtained CPL signal of the composite system is therefore excitation-dependent. The control ability of the CPL signal may allow the composite materials to find potential usage in advanced chirality-related fields.

An excitation-dependent ratiometric dual-emission strategy for the large-scale enhancement of fluorescent tint control.

An alternative and convenient strategy for preparing carbon dots (CDs) with multicolor and dual-emission fluorescence is described. For this dual-emission characteristic, the short-wavelength emission reveals unique excitation-dependent fluorescence behavior, during which the long-wavelength emission remains unshifted regardless of the excitation. Consequently, such excitation-dependent ratiometric dual emission can be applied into a fluorescent tint control of this material between the cold and warm white-light regions. This unique property allows the CDs to be further translated into film sheets for visual detection of the irradiation source, and to also be conjugated with calf thymus DNA for multichannel bioimaging. These results offer new insights for the development of easy-to-handle techniques for material luminescent color tuning.