Modulating Crystallization and Defect Passivation by Butyrolactone Molecule for Perovskite Solar Cells.

The attainment of a well-crystallized photo-absorbing layer with minimal defects is crucial for achieving high photovoltaic performance in polycrystalline solar cells. However, in the case of perovskite solar cells (PSCs), precise control over crystallization and elemental distribution through solution processing remains a challenge. In this study, we propose the use of a multifunctional molecule, α-amino-γ-butyrolactone (ABL), as a modulator to simultaneously enhance crystallization and passivate defects, thereby improving film quality and deactivating nonradiative recombination centers in the perovskite absorber. The Lewis base groups present in ABL facilitate nucleation, leading to enhanced crystallinity, while also retarding crystallization. Additionally, ABL effectively passivates Pb2+ dangling bonds, which are major deep-level defects in perovskite films. This passivation process reduces recombination losses, promotes carrier transfer and extraction, and further improves efficiency. Consequently, the PSCs incorporating the ABL additive exhibit an increase in conversion efficiency from 18.30% to 20.36%, along with improved long-term environmental stability. We believe that this research will contribute to the design of additive molecular structures and the engineering of components in perovskite precursor colloids.

Particle Swarm Predictions of a SrB8 Monolayer with 12-Fold Metal Coordination.

Materials containing planar hypercoordinate motifs greatly enriched the fundamental understanding of chemical bonding. Herein, by means of first-principles calculations combined with global minimum search, we discovered the two-dimensional (2D) SrB8 monolayer, which has the highest planar coordination number (12) reported so far in extended periodic materials. In the SrB8 monolayer, bridged B8 units are forming the boron monolayer consisting of B12 rings, and the Sr atoms are embedded at the center of these B12 rings, leading to the Sr@B12 motifs. The SrB8 monolayer has good thermodynamic, kinetic, and thermal stabilities, which is attributed to the geometry fit between the size of the Sr atom and cavity of the B12 rings, as well as the electron transfer from Sr atoms to electron-deficient boron network. Placing the SrB8 monolayer on the Ag(001) surface shows good commensurability of the lattices and small vertical structure undulations, suggesting the feasibility of its experimental realization by epitaxial growth. Potential applications of the SrB8 monolayer on metal ions storage (for Li, Na, and K) are explored.

Two-Dimensional TeB Structures with Anisotropic Carrier Mobility and Tunable Bandgap.

Two-dimensional (2D) semiconductors with desirable bandgaps and high carrier mobility have great potential in electronic and optoelectronic applications. In this work, we proposed α-TeB and ß-TeB monolayers using density functional theory (DFT) combined with the particle swarm-intelligent global structure search method. The high dynamical and thermal stabilities of two TeB structures indicate high feasibility for experimental synthesis. The electronic structure calculations show that the two structures are indirect bandgap semiconductors with bandgaps of 2.3 and 2.1 eV, respectively. The hole mobility of the ß-TeB sheet is up to 6.90 × 102 cm2 V-1 s-1. By reconstructing the two structures, we identified two new horizontal and lateral heterostructures, and the lateral heterostructure presents a direct band gap, indicating more probable applications could be further explored for TeB sheets.

Highly efficient and recyclable catalyst: porous Fe3O4-Au magnetic nanocomposites with tailored synthesis.

In this work, we reported the tailored design of highly efficient Fe3O4-Au magnetic nanocomposite (MNP) catalysts. Fe3O4 nanocrystals with three different morphologies have been developed with engineered amounts of urea, and the plausible mechanism has been proposed. Then by controlling the amount of Au seeds, Fe3O4-Au MNPs with different morphologies and tunable Au deposition have been realized. Characterizations including x-ray diffraction (XRD), transmission electron microscopy (TEM), Mössbauer spectra, and elemental mapping are implemented to unveil the structural and physical characteristics of the successfully developed Fe3O4-Au MNPs with different morphologies. The catalytic ability of Fe3O4-Au MNPs with different morphologies have been compared by applying them to degrading RhB and 4-NP, meanwhile the correlation between the amount of Au seeds and the turnover frequency as well as the catalytic ability of Fe3O4-Au MNPs is investigated systematically. We found that the flower-like Fe3O4-Au MNPs with 20 ml Au seeds added achieved the best degradation efficiency of 96.7%, and their catalytic ability were almost unchanged after recycling. Out study sheds the light into the tailored design of highly efficient and recyclable catalysts for RhB and 4-NP.

Improved Charge Transfer and Hot Spots by Doping and Modulating the Semiconductor Structure: A High Sensitivity and Renewability Surface-Enhanced Raman Spectroscopy Substrate.

Here, we develop a new method to improve the surface-enhanced Raman spectroscopy (SERS) activity of ZnO using Mg doping combined with noble metals. Highly aligned silver nanoparticles (AgNPs) decorated on an array of Mg-doped ZnO (MZO@Ag) were fabricated. Using rhodamine 6G as the probe molecule, SERS indicated that the MZO@Ag substrate possesses perfect sensitivity, homogeneity, and chemical stability. The enhancement mechanism of this substrate was analyzed in detail, and finite-difference time-domain (FDTD) simulations were used to examine "hot spot" distribution which generated gaps between the balls, the rods, and the stems. FDTD simulation calculated ( E/ E0)4 to be 2.5 × 106. Furthermore, the prepared substrates could degrade the target molecules in situ irradiated by visible light irradiation over the course of 40 min and then efficiently recover detectability through a recycling process. Our substrates were easy to fabricate, self-cleaning, and reusable. They are expected to provide new opportunities for the use of SERS in biological sensors, biomedical diagnostics, and food safety.

ZnO nanoparticles on MoS2 microflowers for ultrasensitive SERS detection of bisphenol A.

A heterojunction microcomposite was synthesized that consists of ZnO nanoparticles (ZnO NPs) anchored on MoS2 microflowers (MoS2 MFs). The material is shown to enable trace level detection of the pollutant bisphenol A (BPA). The microcomposite was characterized by XRD, XPS, SEM and TEM. In addition, coupling reaction between phenolic estrogens and Pauly's reagents was adopted to greatly enhance the SERS signal. BPA display a characteristic Raman band at 1592 cm-1 which can be used for its selective detection. The assay is highly sensitive and has a 1 nM detection limit which is the lowest among the reported semiconductor substrates. Graphical abstract MoS2/ZnO MCs SERS substrate broke through the application barrier of semiconductor composite materials in SERS substrates. It also sheds light on a deeper understanding of the charge-transfer based enhancement mechanism.

Controllable Preparation of SERS-Active Ag-FeS Substrates by a Cosputtering Technique.

In this work, we introduced an ordered metal-semiconductor molecular system and studied the resulting surface-enhanced Raman scattering (SERS) effect. Ag-FeS nanocaps with sputtered films of different thicknesses were obtained by changing the sputtering power of FeS while the sputtering power of Ag and the deposition time remained constant. When metallic Ag and the semiconductor FeS are cosputtered, the Ag film separates into Ag islands partially covered by FeS and strong coupling occurs among the Ag islands isolated by FeS, which contributes to the SERS phenomenon. We also investigated the SERS enhancement mechanism by decorating the nanocap arrays produced with different FeS sputtering powers with methylene blue (MB) probe molecules. As the FeS sputtering power increased, the SERS signal first increased and then decreased. The experimental results show that the SERS enhancement can mainly be attributed to the surface plasmon resonance (SPR) of the Ag nanoparticles. The coupling between FeS and Ag and the SPR displacement of Ag vary with different sputtering powers, resulting in changes in the intensity of the SERS spectra. These results demonstrate the high sensitivity of SERS substrates consisting of Ag-FeS nanocap arrays.

Crystal Structures and Electronic Properties of Oxygen-rich Titanium Oxides at High Pressure.

Pressure is well-known to significantly change the bonding patterns of materials and lift the reactivity of elements, leading to the synthesis of unconventional compounds with fascinating properties. Titanium-oxygen (Ti-O) compounds (e.g., TiO2) are attracting increasing attention due to their attractive electronic properties and extensive industrial applications (e.g., photocatalysis and solar cells). Using the effective CALYPSO structure searching method combined with first-principles calculations, we theoretically explored various oxygen-rich Ti-O compounds at pressures ranging from 0 to 200 GPa. Our results revealed, unexpectedly, that pressure stabilizes two hitherto unknown stoichiometric oxygen-rich Ti2O5 and TiO3 compounds. Ti2O5 crystallized in P-421 c structure, whose remarkable feature is that it contains a peroxide group (O22-) with an O-O distance of 1.38 Å at 150 GPa. The trioxide TiO3 is an ionic metal and is the oxygen-richest compound known thus far in the Ti-O system. It adopts a high symmetry (space group Pm-3 n) structure consisting of a 12-fold coordinated face-sharing TiO12 icosahedron, where Ti has the highest coordination number with O among all Ti-O structures. The underlying mechanisms for the stabilization of Ti2O5 and TiO3 lie in the higher coordination number and denser structure packing. Our current results unravel the unusual oxygen-rich stoichiometry of Ti-O compounds and provide further insight into the diverse electronic properties of Ti oxides under high pressure.

Fabrication of P(NIPAAm-co-AAm) coated optical-magnetic quantum dots/silica core-shell nanocomposites for temperature triggered drug release, bioimaging and in vivo tumor inhibition.

ZnS:Mn2+ quantum dots (QDs) Fe3O4 QDs/SiO2/P(NIPAAm-co-AAm) core-shell-shell nanocomposites have been successfully fabricated by free radical polymerization method. The average diameter and LCST of ZnS:Mn2+ QDs Fe3O4 QDs/SiO2/P(NIPAAm-co-AAm) (NIPAAm:AAm=90:10) nanocomposites was about 200 nm and 41.1°. It possessed a strong yellow-orange emission peak centered at 589 nm from the Mn2+ 4T1-6A1 transition and the desired superparamagnetic property at room temperature. The DOX encapsulation efficiency and loading capacity was 88% and 15.3 wt%, respectively. The nanocomposites showed the faster drug release behavior at 43 °C than that at 25 °C in vitro release experiment, and exhibited no significant cytotoxicity against the HeLa, HepG2 and HEK293 cell lines. Red fluorescence was observed in the cytoplasm of HeLa cells, confirming its application for biolabeling. Effective tumor inhibition was realized in vivo without the induction of toxicity in mice. ZnS:Mn2+ (QDs) Fe3O4 QDs/SiO2/P(NIPAAm-co-AAm) nanocomposites showed the red fluorescence in the cytoplasm of HeLa cells, faster drug release behavior at 43 °C than that at 25 °C in vitro, and effective tumor inhibition in vivo, confirming its application for drug delivery.

Mercury species induced frequency-shift of molecular orientational transformation based on SERS.

We proposed a novel readout method based on a peculiar phenomenon in which the vibrational frequencies of a SERS-active probe (dimethyldithiocarbamic acid sodium salt, DASS) can be affected when there is mercury species. Compared to the SERS intensity-dependent quantitative determination method, SERS frequency-shift-based methods have several advantages: smaller standard deviation, perfect linear relationship, and higher accuracy and sensitivity. In addition, the SERS frequency-shift-based method was not affected by irreproducible aggregation of the SERS substrate and instrumental factors, which greatly improved the application prospect of SERS-based detection. The DASS-modified silver nanoparticles produced a highly sensitive sensor specific to mercury species. Upon the addition of a solution of mercury species to the chip, the mercury species specifically binds to the sulfur atoms, which induces a frequency shift of the band at 1374 cm(-1). The detection limit of the proposed method for Hg(2+) is as low as 10(-8) M. In addition, the proposed method exhibited the same phenomenon for organic mercury. Moreover, these results suggest that the proposed platform possesses the potential for sensitive, selective, and high-throughput on-site mercury pollution monitoring in resource-constrained settings.

Biocompatible ZnS:Mn(2+) quantum dots/SiO2 nanocomposites as fluorescent probe for imaging HeLa cell.

ZnS:Mn(2+) quantum dots (QDs) were successfully embedded in SiO2 spheres by a reverse microemulsion method. The results showed that the monodispersed core/shell nanocomposites were uniform in size, with the majority of the SiO2 nanoparticles containing one QD in the center of the sphere. The shell thickness of SiO2 increased from 7 to 18 nm as the hydrolysis time of TEOS increased from 20 to 40 h. The quantum yield (QY) of the yellow-orange emission (coming from the Mn(2+) ions (4)T1-(6)A1 transition) for the ZnS:Mn(2+)(3 %) QDs and ZnS:Mn(2+)(3 %) QDs@SiO2 (when t = 40 h) nanocomposites was measured to be 34.5 and 22.4 %, respectively. All samples showed no significant cytotoxicity against the HeLa cells even at a high concentration of 500 µg/ml after incubation for 24 h. The red fluorescence can be observed in the cytoplasm of the HeLa cell, further proving its biolabeling applications.

Ordered nanocap array composed of SiO2-isolated Ag islands as SERS platform.

SERS-active substrate is fabricated by cosputtering Ag and SiO2 onto two-dimensional polystyrene (PS) colloidal particle templates in a magnetron sputtering system. When Ag and SiO2 are cosputtered onto ordered PS templates, the SiO2-isolated Ag island (SiO2-Ag) nanocap arrays with nanogaps and nanoscaled surface roughness form on PS particles, in which "hot spots" are facilely engineered on three-dimensional nanostructures. The surface-enhanced Raman scattering (SERS) activities of the SiO2-Ag nanocap arrays vary nonmonotonically and depend on the film thickness and surface roughness strongly. Under the optimized conditions, the SERS signal intensity of 4-aminothiophenol (PATP) is employed to evaluate the SERS ability (4.41 × 10(5)). The addition of SiO2 not only avoids photobleaching and background fluorescence but also decreases the oxidation rate of Ag and increases the stability of Ag particles. The results demonstrate the potential applications of this technique in reproducible SERS substrate.

Ni and O co-modified MoS2 as universal SERS substrate for the detection of different kinds of substances.

Surface-enhanced Raman scattering (SERS) has attracted extensive attention as an ultrasensitive detection method. However, the poor biocompatibility and expensive synthesis cost of noble metal SERS substrates have become non-negligible factors that limit the development of SERS technology. Metal chalcogenide semiconductors as an alternative to noble metal SERS substrates can avoid these disadvantages, but the enhancement effect is lower than that of noble metal substrates. Here, we report a method to co-modify MoS2 by Ni and O, which improves the carrier concentration and mobility of MoS2. The SERS effect of the modified MoS2 is comparable to that of noble metals. We found that the improved SERS performance of MoS2 can be attributed to the following two factors: strong interfacial dipole-dipole interaction and efficient charge transfer effect. During the doping process, the incorporation of Ni and O enhances the polarity and carrier concentration of MoS2, enhances the interfacial interaction of MoS2, and provides a basis for charge transfer. During the annealing process, the introduction of O atoms into the S defects reduces the internal defects of doped MoS2, improves the carrier mobility, and promotes the efficient charge transfer effect of MoS2. The final modified MoS2 as a SERS substrate realizes low-concentration detection of bilirubin, cytochrome C, and trichlorfon. This provides promising guidance for the practical inspection of metal chalcogenide semiconductor substrates.

Ultrasensitive dual-enhanced sandwich strategy for simultaneous detection of Escherichia coli and Staphylococcus aureus based on optimized aptamers-functionalized magnetic capture probes and graphene oxide-Au nanostars SERS tags.

In this work, a novel surface-enhanced Raman scattering (SERS) sandwich strategy biosensing platform has been established for simultaneously detecting Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Fe3O4@SiO2-Au nanocomposites (NCs) with varying amounts of Au nanocrystals were prepared, and the effect of interparticle gaps on SERS activity was studied by finite-difference time-domain (FDTD) method. The optimal magnetic SERS-active substrates (FS-A5) were functionalized with the specific aptamers to act as capture probes. Meanwhile, graphene oxide-Au nanostars (GO-Au NSs) decorated with Raman reporters and aptamers were used as SERS tags. The loading density of Au NSs on GO was tuned to change the number of SERS active sites. In this proposal, E. coli and S. aureus were first captured by capture probes and then bound with SERS tags to form a sandwich-like structure, which caused enhanced electromagnetic field because of the dual enhancement strategy. Under optimal conditions, SERS platform could detect E. coli and S. aureus simultaneously, and the detection limit was as low as 10 cfu/mL. Our sandwich assay-based dual-enhanced SERS platform provides a new idea for simultaneously detecting multiple pathogens with high selectivity and sensitivity, and thus will have more hopeful prospects in the field of food safety.

Toward low-cost and sustainable SERS substrate: novel ultrasensitive AMS5 nanoflowers.

Surface-enhanced Raman scattering (SERS) is an analytical technique for the rapid detection of low-concentration analytes. However, the lack of uniform, stable, and recyclable substrate limits its wide applications. Here, Ag-doped MoS2 (AMSx) was prepared by the hydrothermal method. Band structures, LSV, and EIS characteristics confirmed that Ag doping can reduce the indirect band gap and increase the charge transfer between substrates and molecules. As a SERS substrate, AMSx displays excellent reproducibility, stability, and recyclability, which is beneficial for the application of the SERS substrate. Meanwhile, AMSx has excellent sensitivity with an enhancement factor of 4.07 × 106, comparable to that of precious metals. In addition, AMSx exhibits ultrahigh sensitivity in sensing bilirubin and Bisphenol A (BPA); the corresponding detection limit of both is 10-9 M, also better than that of previously reported semiconductors. This work provided a novel idea to synthesize low-cost ultrasensitive SERS substrates and the strategy of improving metal-chalcogenide semiconductor sensing.

Novel Engineered Carbon Cloth-Based Self-Cleaning Membrane for High-Efficiency Oil-Water Separation.

A novel engineered carbon cloth (CC)-based self-cleaning membrane containing a Cu:TiO2 and Ag coating has been created via hydrothermal and light deposition methods. The engineered membrane with chrysanthemum morphology has superhydrophilic and underwater superoleophilic performance. The cooperativity strategy of Cu doping and Ag coating to the TiO2 is found to be critical for engineering the separation efficiency and self-cleaning skill of the CC-based membrane under visible light due to the modulated bandgap structure and surface plasmon resonance. The CC-based membrane has excellent oil-water separation performance when Cu is fixed at 2.5 wt% and the Ag coating reaches a certain amount of 0.003 mol/L AgNO3. The contact angle of underwater oil and the separation efficiency are 156° and 99.76%, respectively. Furthermore, the membrane has such an outstanding self-cleaning ability that the above performance can be nearly completely restored after 30 min of visible light irradiation, and the separation efficiency can still reach 99.65% after 100 cycles. Notably, the membrane with exceptional wear resistance and durability can work in various oil-water mixtures and harsh environments, indicating its potential as a new platform of the industrial-level available membrane in dealing with oily wastewater.

Multi-dimensional plasmonic coupling system for efficient enrichment and ultrasensitive label-free SERS detection of bilirubin based on graphene oxide-Au nanostars and Au@Ag nanoparticles.

Rapid and sensitive detection of free bilirubin (BR) is essential for early diagnosis of jaundice and other hepatobiliary diseases. Inspired by sandwich immunoassay strategy, a multi-dimensional plasmonic coupling SERS platform composed of graphene oxide-Au nanostars nanocomposites (GANS NCs) and Au@Ag nanoparticles (NPs) was designed for label-free detection of BR. Specifically, GANS NCs were first prepared, and their excellent SERS activity was ascribed to synergistic enhancement effect of electromagnetic enhancement and chemical enhancement. Furthermore, SERS spectroscopy was used to monitor the adsorption process of BR. Subsequently, secondary reinforcing Au@Ag NPs were directly added, ultimately resulting in a multi-dimensional plasmonic coupling effect. The SERS enhancing mechanism of coupled system was discussed through electromagnetic field simulations. Interestingly, the high-density hotspots generated by strong plasmonic coupling in GANS-Au@Ag substrate could lead to more extraordinary SERS enhancing behavior compared to GANS NCs. Sensing efficiency of the SERS platform was examined by BR with a detection limit down to 10-11 M. Besides, GANS-Au@Ag NCs performed high uniformity and reproducibility. This work not only opens up a new avenue for construction of multi-dimensional plasmonic coupling system, but also offers a new biosensing technology for label-free diagnosis of BR-related diseases, thereby expecting to be applied in clinical diagnosis.

Managing intermediate phase transition of perovskite film with gearbox-like molecule for efficient and stable solar cells.

The smooth and dense light-absorbing layer is an essential factor in polycrystalline solar cells to achieve high photovoltaic performance, while it remains challenging in perovskite solar cells because of the difficulty balancing the speed of crystal nucleation and growth in a solution way. Here, we explored a perovskite nucleation/growth compatible model via manipulating the intermediate complex induced by n-hexylamine (NHA) molecule, guiding us to adjustments perovskite nucleation and growth process. We found that the NHA can act as a gearbox-like molecule to sequentially reduce the perovskite nucleation barrier, promote the nucleation velocity, and retard the perovskite growth simultaneously to obtain uniform perovskite films; correspondingly, this modulation also yields the buried interface with fewer voids and low defects density. In addition, the hydrophobic NHA with long alkyl chain improves the moisture tolerance of the perovskite. The treated solar cell power conversion efficiency was 21.91 %. Importantly, in âˆ¼ 70 % humidity at 25 °C for 30 days, the efficiency of the device declined less than 5 %, exhibiting a good stability performance.

Break through the Steric Hindrance of Ionic Liquids with Carbon Quantum Dots to Achieve Efficient and Stable Perovskite Solar Cells.

Overcoming the negative impact of residual ionic liquids (ILs) on perovskite films based on an in-depth understanding of chemical interactions between ionic liquids and preparing perovskite precursor solutions is a great challenge when aiming to simultaneously achieve long-term stability and high efficiency within IL-based perovskite solar cells (PSCs). Herein, 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), a type of IL, was introduced into the perovskite precursor solution, and carbon quantum dots (CQDs) were further introduced into the antisolvent to enhance the photovoltaic properties of PSCs. Both ILs and CQDs synergistically manipulate the crystallization process and passivate defects to obtain high-quality perovskite films. Besides serving as passivation sites to strengthen the collaboration between additives and perovskite materials, the cointroduction of CQDs further promotes the carrier transport process since it not only provides carrier channels at grain boundaries but also forms better energy alignment, which effectively overcomes the charge transfer loss caused by the steric hindrance of ILs. Based on such a synergistic effect of ILs and CQDs, the n-i-p MAPbI3-based PSCs achieve the highest efficiency of 20.84% with improved stability. This simple and low-cost synergistic integration method will subsequently provide direction for optimizing ILs to improve the photovoltaic performance of PSCs.

A co-precipitation route for the preparation of eco-friendly Cu-Al-layered double hydroxides with efficient tetracycline degradation.

The construction of novel efficient catalysts for the treatment of organic pollutants in the aqueous environment is essential. The lamellar-like Cu-Al layered double hydroxides (CuAl-LDHs) with various mole ratios were synthesized by a simple route of co-precipitation, and the corresponding degradation characteristic was tested for the removal of tetracycline (TC) using PMS activation. The degradation efficiency of TC over CuAl-LDHs increased up to 93% within 10 min for the Cu/Al mole ratio of 3:1 and almost not changed at a higher mole ratio. For further calcining the optimal catalyst at 300 ℃, the degradation efficiency of TC was found to be increased to 96%. Sulfuric radicals and singlet oxygen were analyzed to be the main reason for the change in degradation characteristics, which was proved by radical quenching experiments and electron paramagnetic resonance technique. The parameters including PMS concentration, catalyst dosage, and reaction temperature on the TC degradation as well as the degradation mechanism for PMS activation were elaborated. The best proportion of CuAl-LDHs owned splendid stability and catalytic activity after reusing, which showed enormous potential in practical application.