Lewis Acid-base Reaction Research Articles

Increased stearic acid grafting density on silica nanoparticles via alumina-activation

Stearic acid (SA) has a low grafting density on silica nanoparticle (NP) surfaces. However, alumina coating on the particle surface effectively increases the surface reactivity with SA, significantly increasing the grafting density of SA. When the alumina coating amount reaches 15 %, the grafting density of SA increases by 350 % compared to that of the reference sample, while the water contact angle reaches 124°. The coated alumina is chemically bonded to the surfaces of the SiO2 particles. After alumina coating, the particle surface is loaded with electron acceptor sites with strong electron-receiving ability, allowing SA to undergo Lewis acid–base reactions with the particle surface.

Synergistic flame retardancy of aluminum diethylphosphinate and piperazine pyrophosphate/β‐cyclodextrin in polylactic acid

AbstractPolylactic acid has good biodegradability and processability, but its flammability and serious droplet characteristics limit its development and application. Therefore, developing safer flame‐retardant PLA materials is crucial. This research develops a novel flame‐retardant polylactic acid (PLA) material blend, utilizing aluminum diethylphosphinate (AlPi), piperazine pyrophosphate (PAPP), and β‐cyclodextrin. Optimal synergy occurs at a 5:1 PAPP/β‐CD mass ratio with 4 wt.% AlPi. This combination significantly reduces the heat release peak from 294.89 to 144.21 kW·m−2 and generates non‐combustible residues. The sample forms a stable, uniform carbon layer during combustion due to hydrogen bond crosslinking and Lewis acid–base reactions. The activation energy (Eα) is raised from 264.99 to 281.08 kJ·mol−1 between 312 and 402°C. Thus, an AlPi‐PAPP‐β‐CD based P‐C‐N composite flame retardant is investigated, offering a promising research direction for developing fire‐safe polylactic acid materials. This research may yield valuable insights for diverse applications.

Temperature‐Dependent Operando Raman Analysis of a WO3‐Based Metal‐Oxide Gas Sensor Detecting Triacetone Triperoxide

In this work, the surface reactions of the homemade explosive triacetone triperoxide on tungsten oxide (WO3) sensor surfaces are studied to obtain detailed information about the chemical reactions taking place. Semiconductor gas sensors based on WO3 nanopowders are therefore produced and characterized by scanning electron microscopy, X‐ray diffraction, and Raman spectroscopy. To analyze the reaction mechanisms at the sensor surface, the sensor is monitored online under operation conditions using Raman spectroscopy, which allows to identify the temperature‐dependent sensor reactions. By combining information from the Raman spectra with data on the changing resistivity of the underlying semiconductor, it is possible to establish a correlation between the adsorbed gas species and the physical properties of the WO3 layer. In the results, it is indicated that a Lewis acid–base reaction is the most likely mechanism for the increase in resistance observed at temperatures below 150 °C. In the results, at higher temperatures, the assumption of a radical mechanism that causes a decrease in resistance is supported.

Surface engineering for enhanced efficiency and stability of perovskite solar cells through Lewis acid-base modified tin oxide electron transport layers

The effective utilization of Lewis acid-base reactions plays a pivotal role in achieving high power conversion efficiency (PCE) in perovskite solar cells while ensuring exceptional stability. In this study, we introduce the Lewis acid-base reaction as a potent modification technique for enhancing the performance of the tin oxide (SnO2)-based electron transport layer (ETL) in perovskite solar cells. Devices employing this modified ETL exhibit an impressive efficiency of 22.2%, surpassing the reference devices with a single SnO2 ETL, which achieve only 19.5% efficiency. Moreover, these Lewis acid-base-modified ETLs demonstrate outstanding stability, retaining over 90% efficiency even after 1000 h of exposure under AM 1.5G lamp irradiation with negligible hysteresis effects. Further investigation reveals that the performance enhancement can be attributed to various mechanisms. The Lewis acid-base reaction not only mitigates inherent defects within the SnO2 layer but also significantly improves the deposition of subsequent perovskite layers. Our research makes a substantial contribution to the advancement of perovskite solar cell technology, providing a promising avenue for more efficient and durable energy conversion devices.

Critical role of dopant in NiOx hole transport layer for mitigating redox reactivity at NiOx/absorber interface in mixed cation perovskite solar cells.

Redox chemistry transpiring at the interface of NiOx hole transport layer (HTL) and perovskite absorber is a critical phenomenon leading to relatively low values of open circuit voltage (VOC) and fill factor (FF), in turn hampering the overall device performance and stability. In this work, for the first time, the hard acid electronic nature of vanadium (V) dopant in nickel oxide HTL is opportunely exploited to mitigate the undesirable Lewis acid-base reactions occurring at the HTL/mixed-cation perovskite interface. The findings of the study show that vanadium doping results in improved interfacial energetics along with decreased VOC loss, confirming that despite the increase in Ni3+/Ni2+ ratio with the vanadium dopant, the redox reaction catalyzed by Ni3+ ions is kept under check. Vanadium doping also aided in the realization of superior perovskite films with lower Urbach energy, which translated into one order increase in maximum photoinduced carrier generation rate per unit volume. Carrier dynamics investigations show fewer defect states (lower VTFL) and trap-assisted recombination (lower diode ideality factor), which optimize the devices' photovoltaic performance. These benefits collectively contribute to low-loss charge transfer across the NiOx/mixed-cation perovskite interface, which increases the relative efficiency by ∼30% for 5 wt% V-doped NiOx devices compared to pristine NiOx devices, augmented by an increase in device J-V parameters like open circuit voltage (VOC), short circuit current density (JSC), and fill factor (FF).

Flue gas suppression and environmental evaluation of deodorizer-modified rubber asphalt based on radar method

Rubber-modified asphalt (RMA) is associated with impaired storage stability and additional harmful emissions during application. Microwave-oil bath activation of waste rubber powder (WRP) to improve its compatibility with asphalt. The treatment of VOCs and malodorous gas emissions from RMA is carried out using powder deodorizers, liquid deodorizers and their combination. The storage stability, high and low temp rheological behavior of RMA were investigated. The effects and machinations of three deodorants on odor removal and VOCs inhibition of RMA were explored. The emission indexes based on the characteristic pollutants of VOCs and malodorous gases were proposed to conduct a comprehensive environmental impact assessment by the Radar method. The results show that the activated WRP has a fluffier morphology and is better encapsulated by the oil film, which enhances the storage stability of RMA. The incorporation of deodorant has not altered the viscoelastic properties of asphalt. The higher specific surfaced areas and extensive pore structures was contributed to the adsorption of VOCs molecules from asphalt. VOCs and odor gases from asphalt could be inhibited by liquid deodorizers based on Lewis acid-base reactions, addition reactions, catalytic reactions, and redox reactions. LMA was the most effective in decreasing odorant gases, with reductions of up to 92.6% and 90.8% for isobutanol and dimethyl disulfide, respectively. PMA had the optimal inhibitory activity for vinyl chloride, which was 67.7%. The decrease of total concentration of VOCs in RMA by PMA (powder deodorant-modified asphalt), LMA (liquid deodorant-modified asphalt), and CMA (complex deodorant-modified asphalt) could be calculated as 51.7%, 34.1% and 46.7% respectively. RMA had a high load on the environment, and the overall advantage of CMA was greater. The environmental impacts of the four modified asphalts were ranked as CMA < PMA < LMA < RMA. Therefore, the utilization of powder and liquid compounding was recommended to improve the environmental impact of RMA.

Selective recovery of lithium from spent lithium-ion batteries via mild hydrothermal driven Lewis acid-base reaction in aqua solution

Selective metal recovery from spent lithium-ion batteries has attracted wide attention since a high recovery rate and minimized environmental impact can be expected. However, either high temperature or high chemical consumption in order to realize effective lithium recovery is required, as the cathode inherent with high physiochemical stability, especially when the cobalt content is high (e.g. LiCoO2). Herein, we discover that Lewis acids in cathode scraps induce phase transition from LiCoO2 to Co(CoO2)2 and Li+, thus realizing fully selective recovery of lithium in a mild environment. Since Lewis acids are produced from scraps, the chemical consumption is reduced. Meanwhile, relying on the mild phase transition caused by Lewis acids, the morphology of the waste are maintained in the Co(CoO2)2 products, resulting in a comparable electrochemical performance with commercial Co3O4 anode materials. Consequently, a closed-loop route for recycling cathode scrap is established at mild conditions with low cost and environmental impact.

Thioacetamide‐Assisted Crystallization of Lead‐Free Perovskite Solar Cells for Improved Efficiency and Stability

Perovskite solar cells (PSCs) have made great strides in recent years, operating inside the theoretical Scholkely–Quisser efficiency limit with a certified power conversion efficiency (PCE) of 26.1%. However, lead toxicity from Pb‐based PSCs can harm the environment. As a result, the search for nontoxic and environmentally friendly substances to replace Pb in perovskites is the need of the hour. Tin has emerged as the most viable choice to replace Pb, due to its favorable electronic properties and smaller bandgaps of Sn‐based perovskites between 1.1 and 1.4 eV, strong charge carrier mobility, and high theoretical efficiency of 32%. Sn vacancies and point defects, on the other hand, are easily produced in Sn perovskites, leading to nonradiative recombination. Furthermore, interfacial flaws and traps impede further performance improvement. In this research, to produce high‐quality Pb‐free perovskites for high‐performance PSCs, a Lewis‐base thioacetamide (TAA) is added to the simple FASnI3 perovskite solution. FASnI3 and TAA additive‐based films effectively control perovskite film crystallinity and grain size via Lewis acid–base reaction. The champion FASnI3 + TAA‐based PSC achieves a maximum PCE of 10.67% while paving a facile way for other compositional perovskite analogues to be integrated into highly efficient and operationally stable PSCs.

Organic halide salts and PbI2 in improving the efficiency of perovskite solar cells

First developed in 2012, perovskite solar cells (PSC) have been attracting enormous attention for their high-power conversion efficiency, low manufacturing cost, easy annealing and fabricating techniques, good stability in ambient environments, and excellent overall performance. Skyrocketing from a PCE of 2.8% to 25.2%, PSCs are deemed as one of the most promising solar energy harvesters in the near future. However, due to the grain boundaries and some poor interface connections, there appear several defects that affect the efficiency and stability of PSCs. In this case, two primary methods are discussed in this review to minimize such limitations: the introduction of (1) PbI2 and (2) organic halide salts as additives to the perovskite film. By filling the vacancies at the grain boundary, promoting spatial electron–hole separation, generating Lewis acid–base reaction, and forming intermolecular interactions like hydrogen bonding, sulfide bonds, pi-conjunctions, etc., these additives serve as promising candidates for reducing the surface recombination of PSCs. Moreover, because of the hydrophobic characteristics of organic halide-based compounds and the thermal annealing process, the stability of PSCs can also be improved in both high-temperature and -humidity environments. Through presenting and compiling the results of recent studies on various additives, this review also proposes further development and next-generation strategies for minimizing the limitations and challenges in the future.

Quantitative detection of citrate for early stage diagnosing of prostate cancer: Discriminating normal to cancer in prostate tissues

Prostate cancer (PC) biomarker-citrate detection is clinically important to diagnose PC in early stages. Methylquinolinium iodide (Q) conjugated indole-phenylboronic acid (IB) was designed as a red-emissive QIB probe for the detection of citrate through Lewis acid–base reaction and intramolecular charge transfer (ICT) sensing mechanisms. Boronic acid acts as Lewis acid as well as citrate (Lewis base) recognition unit. The probe reacted with citrate, showing enhanced red emissions. Since the probe has excellent water solubility and great biocompatibility, practical application in biological systems is possible. Citrate was monitored precisely in the mitochondria organelle (in vitro) of living cells with a positive charge on QIB. Also, endogenous (in situ) citrate was detected quantitatively to discriminate non-cancerous and PC mice, observed strong and lower (negligible) emission intensity on non-cancerous and cancerous prostate tissues, respectively. Because, the concentration of citrate is higher in healthy prostate compared with PC prostate. Furthermore, the analysis of sliced prostate tissues can give PC-related information for clinical diagnosis to prevent and treat PC in the initial stages. Therefore, we believe that the present probe is a promising biochemical reagent in diagnosing PC.

One dimensional CeO2 nanorods/poly(ethylene oxide) solid composite electrolyte for all-solid-state lithium-ion batteries

The research of poly(ethylene oxide) (PEO)-based solid composite electrolyte with high ionic conductivity and excellent interfacial stability is the key to the development of all-solid-state lithium-ion batteries (ASSLIBs). Herein, uniform nanorod structured CeO2 fillers were controllably synthesized by electrospinning, which were subsequently filled into PEO polymer to prepare CeO2/PEO solid composite electrolyte. The addition of CeO2 nanorods can reduce both the glass transition temperature and the melting point of PEO polymer, and also interact with PEO and lithium bis(trifluoromethanesulphonyl)imide (LITFSI) by Lewis acid–base reaction. Therefore, the solid composite electrolyte exhibits a high ionic conductivity of 4.52 × 10−4 S/cm, a wide electrochemical stability window of about 4.8 V, and a good interfacial stability with Li at 55 °C. Moreover, the LiFePO4/Li ASSLIB divulges the discharging specific capacity of 165, 162, 156 and 146 mA⋅h/g at 0.2, 0.5, 1 and 2 C, respectively, and achieves the capacity retention of 90.3% after 150 cycles at 0.5 C. Consequently, one dimensional CeO2 nanorods can be considered as an alternative filler for polymeric solid electrolyte.

Defect engineering of ternary Cu–In–Se quantum dots for boosting photoelectrochemical hydrogen generation

AbstractHeavy‐metal‐free ternary Cu–In–Se quantum dots (CISe QDs) are promising for solar fuel production because of their low toxicity, tunable band gap, and high light absorption coefficient. Although defects significantly affect the photophysical properties of QDs, the influence on photoelectrochemical hydrogen production is not well understood. Herein, we present the defect engineering of CISe QDs for efficient solar‐energy conversion. Lewis acid–base reactions between metal halide–oleylamine complexes and oleylammonium selenocarbamate are modulated to achieve CISe QDs with the controlled amount of Cu vacancies without changing their morphology. Among them, CISe QDs with In/Cu = 1.55 show the most outstanding photoelectrochemical hydrogen generation with excellent photocurrent density of up to 10.7 mA cm−2 (at 0.6 VRHE), attributed to the suitable electronic band structures and enhanced carrier concentrations/lifetimes of the QDs. The proposed method, which can effectively control the defects in heavy‐metal‐free ternary QDs, offers a deeper understanding of the effects of the defects and provides a practical approach to enhance photoelectrochemical hydrogen generation.

Study on mercury adsorption mechanism of iron-modified biomass char in coal-fired flue gas based on density functional theory

As a new type of porous adsorbent, iron-modified biomass char (Fe10%-BC) may efficiently remove Hg0 from flue gas. However, the lack of in-depth research on the mercury adsorption mechanism of biomass char limits the development of this technology. The reaction path of mercury adsorption was quantitatively revealed by DFT (Density Functional Theory). The effects of oxygen-containing groups and adsorption atmosphere on Hg0 adsorption were analyzed. The results show that Hg0 adsorption by Fe10%-BC includes two stages, that is adsorption and oxidation. The modified biochar utilized the strong oxygen release/storage capacity of iron oxides, reacting with Hg0 by Lewis acid-base reaction. Oxygen-containing groups regulated molecular orbital energy level and surface charge distribution of iron-modified biomass char, affecting the adsorption capacity of Fe10%-BC. Aldehyde, ketone and carboxyl group promoted Hg0 adsorption performance of Fe10%-BC, and the effect from strong to weak was aldehyde group > ketone group > carboxyl group. Hydroxyl group inhibited mercury adsorption by Fe%10-BC. The adsorption atmosphere CO2，O2 and HCl promoted the mercury adsorption performance of the iron-based modified biomass char by forming new adsorption sites with the modified biomass char. SO2 consumed the high valence metal and lattice oxygen, forming competitive adsorption with Hg0. Hg0 adsorption efficiency of the modified biomass char decreased to 58%.

Contact/Noncontact‐Mode Thermoelectric Characteristics of Polytriarylamine/Lewis Acid Complex Films in Horizontal Device Geometry

Herein, the thermoelectric characteristics of polytriarylamine‐Lewis acid complex films were investigated by employing a horizontal device structure. Poly[N,N′‐bis(4‐butylphenyl)‐N,N′‐bis(phenyl)benzidine] (PolyTPD) is doped with tris(pentafluorophenyl)borane (BCF) via Lewis acid–base reactions by varying the BCF molar ratio (0–300 mol%). The resulting PolyTPD:BCF films are spun on glass substrates and silver electrodes are deposited leading to the horizontal type of organic thermoelectric devices (OTEDs). The OTEDs with the PolyTPD:BCF films are examined by varying temperature differences up to 45 K between two silver electrodes directly contacting hot/cold sources. Both device current and voltage are proportionally increased with the temperature difference, leading to higher powers at larger temperature differences, irrespective of BCF molar ratio. However, the highest current is achieved at 50 mol% owing to the highest electrical conductivity, even though the device voltage is slightly lower at 50 than 20 mol%. The origin of high electrical conductivity is assigned to the formation of radical cations in PolyTPD chains by BCF doping, which is influenced by the reaction time. The device current can be also generated by the illumination of IR radiation (noncontact mode) that is away from the OTEDs with the PolyTPD:BCF films.

Reactivity of Silylene with Gallium- and Boron Trihalide at Reductive Conditions Resulting in Unforeseen Products.

Herein, we report a one-pot reaction of gallium and boron halides with potassium graphite in the presence of benzamidinate stabilized silylene LSi-R, (L=PhC(Nt Bu)2 ). The reaction of LSiCl with an equivalent amount of GaI3 in the presence of KC8 leads to the direct substitution of one chloride group by gallium diiodide simultaneously additional coordination of silylene resulted in L(Cl)Si→GaI2 -Si(L)→GaI3 (1). In compound 1, the structure comprises two differently coordinated gallium atoms where one gallium presents between two silylenes and the other gallium is only coordinated by one silylene. In this Lewis acid-base reaction the oxidation states of the starting materials remain unchanged. The same is valid in the silylene boron adduct formation of L(t Bu)Si-BPhCl2 (2) and L(t Bu)Si-BBr3 (3). This new route provides access to galliumhalosilanes challenging to synthesize by any other method.

Quartz Crystal Microbalance Coated with Polyacrylonitrile/Nickel Nanofibers for High-Performance Methanol Gas Detection.

This study describes a sensor based on quartz crystal microbalance (QCM) coated by polyacrylonitrile (PAN) nanofibers containing nickel nanoparticles for methanol gas detection. The PAN/nickel nanofibers composites were made via electrospinning and electrospray methods. The QCM sensors coated with the PAN/nickel nanofiber composite were evaluated for their sensitivities, selectivities, and stabilities. The morphologies and elemental compositions of the sensors were examined using a scanning electron microscope-energy dispersive X-ray. A Fourier Transform Infrared spectrometer was used to investigate the elemental bonds within the nanofiber composites. The QCM sensors coated with PAN/nickel nanofibers offered a high specific surface area to enhance the QCM sensing performance. They exhibited excellent sensing characteristics, including a high sensitivity of 389.8 ± 3.8 Hz/SCCM, response and recovery times of 288 and 251 s, respectively, high selectivity for methanol compared to other gases, a limit of detection (LOD) of about 1.347 SCCM, and good long-term stability. The mechanism of methanol gas adsorption by the PAN/nickel nanofibers can be attributed to intermolecular interactions, such as the Lewis acid-base reaction by PAN nanofibers and hydrogen bonding by nickel nanoparticles. The results suggest that QCM-coated PAN/nickel nanofiber composites show great potential for the design of highly sensitive and selective methanol gas sensors.

Multi-stimuli, color switchable emitter by solvent induced polymorph synthesis

Polymorphism has drawn great attention in tuning organic solid-state luminescent materials by alteration of molecular packing structure and has considerable potential application in optoelectronic devices and fluorescence sensors. Herein, two polymorphs based on dicyanodistyrylbenzene (DCS) compound were obtained by solvent induced synthesis. We have comprehensively investigated photophysical properties (such as photoluminescence colors, lifetime and PL quantum yield) of the two polymorphs, blue one αDCFDCS (Aqua) and green one αDCFDCS (Green). The single crystal structure analysis and XRD powder pattern shows that there is a slightly packing dislocation in a-axis account for the difference between the two phases. Mechanical grinding can lead to an alternation in photoluminescence color from blue to green. The differential thermal analysis (DTA) measurement discloses αDCFDCS (Aqua) is the metastable state of the compound. Both of two polymorphs show thermochromic and can be reversibly switched upon heating and cooling, which is attributing to the crystal cell expansion with the temperature increasing revealed by in situ XRD. Moreover, fuming with NH3 also causes the color change via Lewis acid base reaction. Upon heating or being exposed to HCl, it will return to the original state. The results of the polymorphism not only provide an insight into molecular packing and emission properties, but also pave the way for understanding the solid luminescence change by the multi-stimuli response.

Electronic and surface modulation of 2D MoS2 nanosheets for an enhancement on flexible thermoelectric property

Two-dimensional materials have potential applications for flexible thermoelectric materials because of their excellent mechanical and unique electronic transport properties. Here we present a functionalization method by a Lewis acid-base reaction to modulate atomic structure and electronic properties at surface of the MoS2 nanosheets. By AlCl3 solution doping, the lone pair electronics from S atoms would enter into the empty orbitals of Al3+ ions, which made the Fermi level of the 1T phase MoS2 move towards valence band, achieving a 1.8-fold enhancement of the thermoelectric power factor. Meanwhile, benefiting from the chemical welding effect of Al3+ ions, the mechanical flexibility of the nanosheets restacking has been improved. We fabricate a wearable thermoelectric wristband based on this improved MoS2 nanosheets and achieved 5 mV voltage output when contacting with human body. We think this method makes most of the transition metal chalcogenides have great potential to harvest human body heat for supplying wearable electronic devices due to their similar molecular structure.

First-principles study of mercaptoundecanoic acid molecule adsorption and gas molecule penetration onto silver surface: an insight for corrosion protection.

Recently, 11-mercaptoundecanoic acid (MUA) molecule has attracted attention as a promising passivation agent of Ag nanowire (NW) network electrode for corrosion inhibition, but the underneath mechanism has not been elaborated. In this work, we investigate adsorption of MUA molecule on Ag(1 0 0) and Ag(1 1 1) surface, adsorption of air gas molecules of H2O, H2S and O2 on MUA molecular end surface, and their penetrations into the Ag surface using the first-principles calculations. Our calculations reveal that the MUA molecule is strongly bound to the Ag surface with the binding energies ranging from -0.47 to -2.06 eV and the Ag-S bond lengths of 2.68-2.97 Å by Lewis acid-base reaction. Furthermore, we find attractive interactions between the gas molecules and the MUA@Ag complexes upon their adsorptions and calculate activation barriers for their migrations from the outermost end of the complexes to the top of Ag surface. It is found that the penetrations of H2O and H2S are more difficult than the O2 penetration due to their higher activation barriers, while the O2 penetration is still difficult, confirming the corrosion protection of Ag NW network by adsorbing the uniform monolayer of MUA. With these findings, this work can contribute to finding a better passivation agent in the strategy of corrosion protection of Ag NW network electrode.

Air-processed MAPbI3 perovskite solar cells achieve 20.87% efficiency and excellent bending resistance enabled via a polymer dual-passivation strategy.

In recent years, air-processed MAPbI3 perovskite solar cells (PSCs) have attracted widespread interest from researchers worldwide because of their simple and low-cost fabrication process. Nonetheless, the ambient conditions usually bring about many adverse effects, such as imperfect crystallization and numerous defects in perovskite films, which seriously impact both the photoelectric performance and stability of the device. Therefore, in this work, a polymer dual-passivation strategy was employed by introducing ammonium polyphosphate (APP) as an additive to the green anti-solvent to accurately modify the perovskite layer. APP, which has abundant phosphate and ammonium groups, could simultaneously fill the I/Pb vacancies by Lewis acid-base reactions to restrain defect formation and improve the power conversion efficiency (PCE) of the ultimate device. On the other hand, the long molecular chains of the polymer with a certain flexural ability were easily congregated at the grain boundaries of the perovskite grains, thus enhancing the bending resistance. Consequently, high-quality perovskite films with a dense morphology and large grain size were obtained. Because of the reduced defect density and suppressed non-radiative recombination, the optimal PSC attained a champion PCE of 20.87% with negligible hysteresis. Furthermore, the non-encapsulated APP-modified flexible device also exhibited excellent bending resistance. Only 20% of its normalized PCE was lost after 150 bending cycles at room temperature. This simple, green, low-cost, and reliable strategy for preparing high-efficiency PSCs with good stability can facilitate its commercialization.