Enhanced photocatalytic activity of porous TiO2 containing C/P/K derived from grapefruit peel.

Grapefruit peel possesses a porous structure and a significant specific surface area. In this study, we introduce an innovative and eco-friendly approach for synthesizing porous TiO2. This was accomplished by employing grapefruit peel as a bio-template and tetrabutyl titanate as the precursor, utilizing a two-step rotary impregnation-calcination process. The TiO2 faithfully reproduced the structural characteristics of the grapefruit peel across different scales, simultaneously incorporating C, P, K elements from the original grapefruit peel into the final samples. The fabricated samples were analyzed using XRD, XPS, SEM, TEM, BET, and UV-vis DRS. The results showed that the TiO2 displays an anatase phase, and possesses a high specific surface area. The investigation of photocatalytic performance demonstrated that the CPK-TiO2-10 sample exhibited outstanding photocatalytic activity against Rhodamine B (RhB) solution, achieving complete degradation within 60 minutes. Additionally, the total organic carbon (TOC) removal rate reached 91.34% after 60 minutes of irradiation. The sample maintained a high degradation efficiency, even after five recycling cycles. This exceptional performance can be attributed to its porous structure, enriched with pores and a larger surface area, as well as the beneficial effects of doping with C, P, K elements in TiO2.

Waste Biomass-Mediated Synthesis of TiO2/P, K-Containing Grapefruit Peel Biochar Composites with Enhanced Photocatalytic Activity.

In this study, TiO2/P, K-containing grapefruit peel biochar (TiO2/P, K-PC) composites were synthesized in situ biomimetically using grapefruit peel as the bio-template and carbon source and tetrabutyl titanate as the titanium source. This was achieved using the two-step rotary impregnation-calcination method. Adjusting the calcination temperature of the sample in an air atmosphere could regulate the mass ratio of TiO2 to carbon. The prepared samples were subjected to an analysis of their compositions, structures, morphologies, and properties. It demonstrated that the prepared samples were complexes of anatase TiO2 and P, K-containing carbon, with the presence of graphitic carbon. They possessed a unique morphological structure with abundant pores and a large surface area. The grapefruit peel powder played a crucial role in the induction and assembly of TiO2/P, K-PC composites. The sample PCT-400-550 had the best photocatalytic activity, with the degradation rate of RhB, MO, and MB dye solutions reaching more than 99% within 30 min, with satisfactory cyclic stability. The outstanding photocatalytic activity can be credited to its unique morphology and the efficient collaboration between TiO2 and P, K-containing biochar.

[Improvement and application on the estimation model of windbreak and sand fixation function based on remote sensing soil moisture factor]. / åŸºäºŽé¥æ„ŸåœŸå£¤æ¹¿åº¦å› å­çš„é˜²é£Žå›ºæ²™åŠŸèƒ½ä¼°ç®—æ¨¡åž‹æ”¹è¿›åŠåº”ç”¨.

Soil moisture factor is one of the important parameters in the study of wind and sand fixation functions of ecosystems. Traditional methods often use potential evaporation, rainfall, and irrigation observed by meteorological stations to estimate soil moisture, which has significant limitations in terms of spatial continuity and data availability. Based on the development of remote sensing technology in soil moisture detection, we selected four remote sen-sing indicators for soil moisture (MODIS evapotranspiration ratio method, SMAP soil moisture ratio method, visible shortwave infrared drought index method, and remote sensing humidity index method) to improve the estimation of soil moisture factor in the modified wind erosion equation model (RWEQ), and used the improved algorithm to analyze the spatiotemporal variations and driving factors of wind prevention and sand fixation services in the northwest region of Liaoning Province from 2001 to 2021. The results showed that the MODIS evapotranspiration ratio method had the highest correlation with traditional meteorological methods in calculating soil moisture. The formula obtained by fitting the two could be used to improve the calculation of soil moisture factor in the RWEQ model. From 2001 to 2021, the wind prevention and sand fixation capacity in the northwest region of Liaoning Province showed strong spatial distribution characteristics in the northern and eastern regions, while weak in the central and western regions. According to Mann-Kendall trend testing, 72.7% of the regions in northwest Liaoning Province were showing an upward trend in their ability to prevent wind and fix sand. The application of geographic detector models for driving factor analysis showed that the change in wind and sand fixation capacity was a process of multiple factors interacting with each other, greatly influenced by soil type, annual wind speed, and economic development level. Moreover, the interaction between various driving factors had a higher impact on wind and sand fixation than that of single factors. The results could improve the RWEQ model estimation and provide technical support for the long-term analysis of ecological function formation mechanisms and driving forces in the northwest region of Liaoning.

Calcium Imaging in Mouse Superior Colliculus.

The superior colliculus (SC), an evolutionarily conserved midbrain structure in all vertebrates, is the most sophisticated visual center before the emergence of the cerebral cortex. It receives direct inputs from ~30 types of retinal ganglion cells (RGCs), with each encoding a specific visual feature. It remains elusive whether the SC simply inherits retinal features or if additional and potentially de novo processing occurs in the SC. To reveal the neural coding of visual information in the SC, we provide here a detailed protocol to optically record visual responses with two complementary methods in awake mice. One method uses two-photon microscopy to image calcium activity at single-cell resolution without ablating the overlaying cortex, while the other uses wide-field microscopy to image the whole SC of a mutant mouse whose cortex is largely undeveloped. This protocol details these two methods, including animal preparation, viral injection, headplate implantation, plug implantation, data acquisition, and data analysis. The representative results show that the two-photon calcium imaging reveals visually evoked neuronal responses at single-cell resolution, and the wide-field calcium imaging reveals neural activity across the entire SC. By combining these two methods, one can reveal the neural coding in the SC at different scales, and such combination can also be applied to other brain regions.

Charge and energy transfer dynamics in single colloidal quantum dots/monolayer MoS2 heterostructures.

The charge and energy transfer dynamics in colloidal CdSeTe/ZnS quantum dots (QDs)/monolayer molybdenum disulfide (MoS2) heterostructures have been investigated by time-resolved single-dot photoluminescence (PL) spectroscopy. A time-gated method is used to separate the PL photons of single QDs from the PL photons of monolayer MoS2, which are impossible to be separated by the spectral filter due to their spectral overlap. It is found that the energy transfer from MoS2 to single QDs increases the exciton generation of the QDs by 37.5% and the energy transfer from single QDs to MoS2 decreases the PL quantum yield of the QDs by 66.9%. In addition, it is found that MoS2 increases the discharging rate of single QDs by 59%, while the charging rate remains unchanged. This investigation not only provides valuable insight into the exciton generation and recombination at the single-dot level across such hybrid 0D-2D interfaces but also promotes the application of the hybrid system in various optoelectronic devices.

Photon-Energy-Dependent Reversible Charge Transfer Dynamics of Double Perovskite Nanocrystal-Polymer Nanocomposites.

Combining steady-state photoluminescence and transient absorption (TA) spectroscopy, we have investigated the photoinduced charge transfer dynamics between lead-free Mn-doped Cs2NaIn0.75Bi0.25Cl6 double perovskite (DP) nanocrystals (NCs) and conjugated poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). Upon ultraviolet-A excitation, the photoinduced absorption feature of DP NCs/MDMO-PPV nanocomposites disappeared, and the stimulated emission weakened in the TA spectrum. This was due to charge transfer from the MDMO-PPV polymers to DP NCs. Upon a higher photon-energy ultraviolet-C excitation, stimulated emission and photoinduced absorption features vanished, indicating there existed a reversible charge transfer from DP NCs to MDMO-PPV polymers. Reversible charge transfer of Mn-doped DP NCs/MDMO-PPV nanocomposites was tuned by varying the excitation photon-energy. The manipulation of reversible charge transfer dynamics in the perovskite-polymer nanocomposites opens a new avenue for optical and optoelectronic applications.

Biexciton Dynamics in Single Colloidal CdSe Quantum Dots.

The investigation of biexciton dynamics in single colloidal quantum dots (QDs) is critical to biexciton-based applications. Generally, a biexciton exhibits an extremely low photoluminescence (PL) quantum yield as well as very fast PL decay due to strong nonradiative Auger recombination, making it difficult to investigate the biexciton dynamics. Here, we develop a quantitative method based on intensity- and time-resolved photon statistics to investigate the biexciton dynamics in single colloidal QDs. This robust method can be used under high-excitation conditions to determine the absolute radiative and Auger recombination rates of both neutral and charged biexciton states in a single QD level, and the corresponding ratios between the two states agree with the theoretical predictions of the asymmetric band structures of CdSe-based QDs. Furthermore, the surface traps are found to provide additional nonradiative recombination pathways for the biexcitons, and their contributions are quantified by the method.

miRNA-324/-133a essential for recruiting new synapse innervations and associative memory cells in coactivated sensory cortices.

After the integrative storage of associated signals, a signal induces the recollection of its associated signal, or the other way around. This associative memory is essential to associative thinking, logical reasoning, imagination and computation. In terms of cellular mechanisms underlying associative memory, new mutual synapse innervations are formed among those coactivated neurons, so that they are recruited to be associative memory cells or associative memory neurons. These associative memory cells receive new synapse innervations alongside innate synapse inputs and encode signals carried by these inputs. We proposed to examine microRNAs as initiative factors for recruiting new synapse innervations and associative memory cells. In a mouse model of associative memory characterized as the reciprocal retrieval of associated whisker and odor signals, barrel and piriform cortical neurons gain their ability to encode whisker and odorant signals based on the newly formed synapse innervations between these coactivated cortices besides innate synapse inputs. miRNA-324 and miRNA-133a are required for recruiting these new synapse innervations and associative memory cells as well as sufficient for facilitating their recruitments, but not for innate synapse inputs. Therefore, the coactivation of sensory cortices through microRNA as initiative factor to recruit new mutual synapse innervations and associative memory cells for associative memory.

Coactivations of barrel and piriform cortices induce their mutual synapse innervations and recruit associative memory cells.

After associative learning, a signal induces the recall of its associated signal, or the other way around. This reciprocal retrieval of associated signals is essential for associative thinking and logical reasoning. For the cellular mechanism underlying this associative memory, we hypothesized that the formation of synapse innervations among coactivated sensory cortices and the recruitment of associative memory cells were involved in the integrative storage and reciprocal retrieval of associated signals. Our study indicated that the paired whisker and olfaction stimulations led to an odorant-induced whisker motion and a whisker-induced olfaction response, a reciprocal form of associative memory retrieval. In mice that showed the reciprocal retrieval of associated signals, their barrel and piriform cortical neurons became mutually innervated through their axon projection and new synapse formation. These piriform and barrel cortical neurons gained the ability to encode both whisker and olfaction signals based on synapse innervations from the innate input and the newly formed input. Therefore, the associated activation of sensory cortices by pairing input signals initiates their mutual synapse innervations, and the neurons innervated by new and innate synapses are recruited to be associative memory cells that encode these associated signals. Mutual synapse innervations among sensory cortices to recruit associative memory cells may compose the primary foundation for the integrative storage and reciprocal retrieval of associated signals. Our study also reveals that new synapses onto the neurons enable these neurons to encode memories to new specific signals.

Coordinated Plasticity between Barrel Cortical Glutamatergic and GABAergic Neurons during Associative Memory.

Neural plasticity is associated with memory formation. The coordinated refinement and interaction between cortical glutamatergic and GABAergic neurons remain elusive in associative memory, which we examine in a mouse model of associative learning. In the mice that show odorant-induced whisker motion after pairing whisker and odor stimulations, the barrel cortical glutamatergic and GABAergic neurons are recruited to encode the newly learnt odor signal alongside the innate whisker signal. These glutamatergic neurons are functionally upregulated, and GABAergic neurons are refined in a homeostatic manner. The mutual innervations between these glutamatergic and GABAergic neurons are upregulated. The analyses by high throughput sequencing show that certain microRNAs related to regulating synapses and neurons are involved in this cross-modal reflex. Thus, the coactivation of the sensory cortices through epigenetic processes recruits their glutamatergic and GABAergic neurons to be the associative memory cells as well as drive their coordinated refinements toward the optimal state for the storage of the associated signals.

An electric field induced reversible single-molecule fluorescence switch.

We report that by applying an electric field to a single squaraine-derived rotaxane (SR) molecule on bare glass, the fluorescence can be completely quenched. The molecule undergoes a reversible fluorescence switch between a zero-field "on" state and a high-field "off" state, which is attributed to intramolecular electron transfer within the SR molecule.

Electron transfer-based single molecule fluorescence as a probe for nano-environment dynamics.

Electron transfer (ET) is one of the most important elementary processes that takes place in fundamental aspects of biology, chemistry, and physics. In this review, we discuss recent research on single molecule probes based on ET. We review some applications, including the dynamics of glass-forming systems, surface binding events, interfacial ET on semiconductors, and the external field-induced dynamics of polymers. All these examples show that the ET-induced changes of fluorescence trajectory and lifetime of single molecules can be used to sensitively probe the surrounding nano-environments.

Electric field induced fluorescence modulation of single molecules in PMMA based on electron transfer.

We present a method to modulate the fluorescence of non-polar single squaraine-derived rotaxanes molecules embedded in a polar poly(methyl methacrylate) (PMMA) matrix under an external electric field. The electron transfer between single molecules and the electron acceptors in a PMMA matrix contributes to the diverse responses of fluorescence intensities to the electric field. The observed instantaneous and non-instantaneous electric field dependence of single-molecule fluorescence reflects the redistribution of electron acceptors in PMMA induced by electronic polarization and orientation polarization of polar polymer chains in an electric field.