lasers. [1][2][3][4][5][6][7][8][9][10][11] However, the toxicity of PQDs limit their practical applications. Bivalent manganese (Mn 2+ ) doping was widely studied in semiconductor materials like CdS, ZnS, [12][13][14][15] and as identical valance with Pb 2+ in lead halide perovskite, Mn 2+ can be introduced into CsPbX 3 host by substituting Pb 2+ to reduce the usage of Pb 2+ heavy metal ions. Additionally, energy transfer (ET) from perovskite host to Mn 2+ dopants can result in extra Mn 2+ red luminescence assigned to d-d transition. [16] Compared to II-VI group semiconductors, PQDs are regarded as appropriate hosts to efficiently sensitize Mn 2+ emission benefited from their high absorption coefficient, narrow emission width, and long excited-state lifetime. [17] The primary parameter to influence energy transfer and Mn emission intensity is energy difference (ΔE g ) between bandto-band emission of PQD and 4 T 1 → 6 A 1 transition of Mn 2+ . [18] When ΔE g value (0.7-0.9 eV) is appropriate, an intense Mn emission can be obtained; however, decreasing ΔE g intensifies back transfer (BT) from doped Mn 2+ centers to the perovskite host, leading to the weakening or even disappearing of Mn 2+ luminescence. [18][19][20] CsPbCl 3 PQDs have been reported to be the ideal host for efficiently transferring excitonic energy to Mn 2+ because of their appropriate bandgap of 3.0 eV. [18] When Cl was gradually replaced by Br, the bandgap of CsPb(Cl/Br) 3 PQDs becomes smaller and ET from PQDs to Mn 2+ is inefficient, leading to weak Mn 2+ luminescence. As tabulated in Table S1 (Supporting Information), for a classic Cs-hot-injection method using PbBr 2 and MnCl 2 as the precursors, the as-prepared Mn:CsPb(Cl/Br) 3 with excitonic emission at blue region (430-480 nm) has a low PLQY (31%) and Mn 2+ emission can be barely observed; [17] for a room-temperature supersaturated crystallization method, a high-content MnCl 2 precursor is required, causing low PLQY of excitonic emission and concentration quenching of Mn 2+ luminescence. [21,22] Furthermore, Mn:CsPb(Cl/Br) 3 PQDs can also be fabricated by a postsynthetic cation exchange and the bandgap of exciton can be tuned over a wide range, but the maximal PLQY is only 28%. [23] More recently, strong Mn 2+ emission Recently, Mn 2+ -doped CsPb(Cl/Br) 3 perovskite nanocrystals (NCs), showing the advantages of dual-color emissions via exciton-to-dopant energy transfer and reduced usage of toxic Pb 2+ heavy metal ions by nontoxic Mn 2+ substitution, are widely explored. However, photoluminescence quantum yields (PLQYs) for Mn 2+ -doped CsPb(Cl/Br) 3 NCs still need to be further improved. Here, a halogen-hot-injection strategy is developed to prepare Mn:CsPb(Cl 0.6 Br 0.4 ) 3 NCs with the maximal PLQY of 65%. With this method, intense blue narrowband emission from excitonic recombination and orange broadband emission from Mn 2+ 4 T 1 → 6 A 1 transition can be simultaneously achieved. The competitive luminescence between perovskite NCs and Mn 2+ dopants is systematically investigated by contr...

Chlorine-promoted doping of Mn(ii) in CsPbCl3 perovskites is achieved by employing manganese acetate as a Mn(ii) precursor for the first time.

Motor imagery-based brain–computer interfaces (MI-BCIs) have great application prospects in motor enhancement and rehabilitation. However, the capacity to control a MI-BCI varies among persons. Predicting the MI ability of a user remains challenging in BCI studies. We first calculated the relative power level (RPL), power spectral entropy (PSE) and Lempel–Ziv complexity (LZC) of the resting-state open and closed-eye EEG of different frequency bands and investigated their correlations with the upper and lower limbs MI performance (left hand, right hand, both hands and feet MI tasks) on as many as 105 subjects. Then, the most significant related features were used to construct a classifier to separate the high MI performance group from the low MI performance group. The results showed that the features of open-eye resting alpha-band EEG had the strongest significant correlations with MI performance. The PSE performed the best among all features for the screening of the MI performance, with the classification accuracy of 85.24%. These findings demonstrated that the alpha bands might offer information related to the user’s MI ability, which could be used to explore more effective and general neural markers to screen subjects and design individual MI training strategies.