Cationic Agents Research Articles

Extractive Spectrophotometric Detection of Sn(II) Using 6-bromo-3-hydroxy-2-(5-methylfuran-2-yl)-4H-chromen-4-one.

For the determination of tin(II) traces, an extractive spectrophotometric approach is devised. The applied method serves a powerful tool for determination of tin(II), involves the formation of yellow colored complex after thebinding of 6-bromo-3-hydroxy-2-(5-methylfuran-2-yl)-4H-chromen-4-one (BHMF) and tin(II) in 1:2 stiochiometry in a slightly acidic medium (HCl). The complex shows absorbance at 434nm with respect of the blank reagent. The outcomes of spectral investigation for complexation showed a Beer's range of 0-1.3μg Sn mL-1, molar absorptivity, specific absorptivity and Sandell's complex sensitivity are 9.291 × 104 L mol-1cm-1, 0.490mLg-1cm-1 and 0.002040μgcm-2 at 434nm that was stable for two days. The interferences studyresults showed that this method is free from interferences, when tested with metal ions including Ag,Be, Bi, Ca,Cd, Ce, Co,Hg, Mo,Re,Pt, Se,Ti,U,V, W and other common cations, anions, and complexing agents. Theapplied method is quite simple, highly selective, and sensitive with good re-producibility. This method has been satisfactorily by utilizing the proposed procedure, and its applicability has been tested by analyzing synthetic samples and an alloy sample of gunmetal. The procedure assumes this because of the scarcity of better methods for determining tin(II). The results are in good agreement with the certified value.

Introducing highly polarizable cation in M-N-C type catalysts to boost their oxygen reduction reaction performance

The metal-nitrogen-carbon (M-N-C) type oxygen reduction reaction (ORR) catalysts are promising for hydroxide exchange membrane fuel cells, but catalysts with further improved performance are challenging. Here, we report the efficient improvement of the ORR activity of M-N-C catalysts by employing highly polarizable metal cation Ag+. Ag, Fe single atomic sites embedded in concave nitrogen doped carbon (Ag1Fe1/CNC) is successfully synthesized and shows high performance towards ORR, indicating by both the ultra-high half-wave potential of 0.917 V and membrane electrolyte assembly performance of peak power density up to 1.26 W cm−2. The binding energy of the ORR intermediates on the highly polarizable Ag site in Ag1Fe1/CNC was significantly tuned by the adjacent Fe site by more than 0.2 eV, and thus leading to a low theoretical ORR overpotential of only 0.398 V. The employment of the highly polarizable metal cation brings a novel and efficient approach to construct highly active catalysts.

Study on a cationic agent-based salt-free reactive dyeing process for cotton knit fabric and comparison with a traditional dyeing process

Since the majority of reactive dyes only have a moderate affinity for cotton, significant amounts of electrolytes are frequently needed to cause tiredness. As a result, wastewater contains significant amounts of salt and dye, and the increasing salinity of the rivers has an effect on the delicate biochemistry of aquatic life. The aim of the study was to find a sustainable dyeing process for cotton knit fabric using EPTMAC (2, 3-epoxypropyl trimethyl ammonium chloride) as a cationic agent and comparison of the cationic dyeing process (salt free dyeing) with the regular dyeing process (dyeing with salt). For this purpose, cotton knit fabric samples were dyed with reactive dyes following salt free process and with salt. Afterwards, color fastness (wash and rubbing), spectrophotometric evaluation, bursting strength test, analysis of dye bath discharge water and Scanning Electron Microscope (SEM) image of the dyed samples were carried out. Moreover, water consumption was also evaluated for the both cationic and regular dyeing process. In terms of color fastness, cationized dyed fabric showed no change to a slight loss in depth (rating of 4–5) for both wash and rubbing fastness. From the spectrophotometric evaluation, it was found that cationized dyed fabric appeared darker and less yellowish tone. Moreover, in case of bursting strength, cationized black, hot pink, and light pink colored fabrics possessed bursting strengths of 287 kPa, 337 kPa, and 440 kPa, correspondingly. After analysis of dye bath discharge water, Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Dissolved Solids (TDS) value of regular colored water samples were 45%, 39%, 54% greater than that of cationized dyed water samples respectively. Cationized dyed water value for Dissolved Oxygen (DO) was 6.39 mg/l, which was within the acceptable limit. The SEM image asserted that the cationized colored samples had consistent dye dispersion, greater adhesion, and no dye anomalies. Considering water consumption, it was found that 37%, 27% and 23% less amount of water required for dyeing dark, medium and light shade of cationized samples due to fewer washes after dyeing and elimination of fixing steps. In addition of that, total cost of cationic dyeing process was less due to less chemical consumption, less utility use, shorter process time and less amount of dyes needed. Cationic dyeing process is a sustainable practice of dyeing cotton fabric with reactive dyes that offers numerous advantages when compared to the regular dyeing process with less cost consumption and low amount of environmental pollution.

Tweaking the conjugation effects on a pair of new triazene compounds by targeted deprotonation: a spectroscopic and theoretical overview.

Triazene compounds (-NNN(H)-) exhibit versatility in biological, physical, and chemical applications. In their anionic form (-NNN-)(-), they can act as coordinating sites for metals, forming metallic complexes. In this study, two new isomeric triazene compounds with meta- and para-substituents in their neutral and anionic forms were investigated. A combination of detailed experimental spectroscopic characterization and computational chemistry analyses were employed. The new compounds, 1-(2-benzamide)-3-(3-nitrophenyl) triazene (m-TZN) and 1-(2-benzamide)-3-(4-nitrophenyl) triazene (p-TZN), were compared to 1,3-diphenyltriazene (dph-TZN) to understand the effects of functionalization and targeted triazene deprotonation. The anionic forms are stable, and our investigation suggests that these new compounds are suitable tridentate ligands that can act as chelating agents for metallic cations in stable complexes, similar to those found in vitamin B12. The absorption, vibrational, and electronic properties of the newly synthesized triazene compounds were extensively characterized using FT-IR/FT-Raman and UV-Vis spectroscopy. Their distinct molecular properties, intramolecular hydrogen bond effects, stability, and electronic transitions were investigated using the ORCA software. These analyses involved DFT and TD-DFT calculations at the ωB97X-D3/Def2-TZVP level of theory with THF CPCM implicit solvation to determine the molecular topology and electronic structure. The advanced STEOM-DLPNO-CCSD method for excited states was employed, enabling an in-depth analysis of ground and excited-state chemistry, accounting for precise electronic correlation and solvation effects. Explicit THF solvation was tested on the full TD-DFT ωB97X-D3/Def2-TZVP level and using ONIOM on the STEOM calculation. Reactivity was studied using Fukui functions, and action as chelating agents was investigated using GFN-xTB2 and DFT.

AEAg7(PS4)3 (AE = Ba, Sr): The homovalent substitution of lead by alkaline earth metals achieves the separation of the two phases and enlarges the band gap

Two alkaline earth metal-containing thiophosphate compounds, BaAg7(PS4)3 and SrAg7(PS4)3, were synthesized via the homovalent substitution of Pb2+ in PbAg7(PS4)3 by Ba2+ and Sr2+, respectively. The space group of BaAg7(PS4)3 (P21/c) and SrAg7(PS4)3 (P63/m) is the same as the low- and high-temperature phases of PbAg7(PS4)3, respectively. The two compounds exhibit structural similarity and possess three-dimensional honeycomb-shaped architectures. These honeycomb structures are arranged in a layered fashion via hexagonal rings, which arise from the sharing of edges or vertices between [AgS4] and [PS4] tetrahedral, accommodating discrete entities of Ba2+ and Sr2+ cations. BaAg7(PS4)3 melts congruently with a melting point of 760 °C and a solidification point of 675 °C, while the melting behaviour of SrAg7(PS4)3 was incongruently and thermally stable up to 689 °C under vacuum of 1 × 10−3 Pa. Moreover, the band gaps of BaAg7(PS4)3 (2.69 eV) and SrAg7(PS4)3 (2.85 eV) have a significant enlargement compared to PbAg7(PS4)3 (2.09 eV). The combination of d10 cation Ag+ with second-order Jahn-Teller distortion and alkaline earth metals cation enriches the system of new metal thiophosphates and provides ideas for exploring other functional materials.

Facile fabrication of robust and universal UV‐curable polyurethane composite coatings with antibacterial properties

AbstractThe colonization of bacteria and biofilm formation on the surface of medical devices is one of the main causes of nosocomial infections. The development of antimicrobial functional materials with robust and universal properties has been a hot research topic in this field. In this paper, a novel type of polyurethane composite coating was developed by a complementary combination of polyurethane and antibacterial agents. A photocurable anionic waterborne polyurethane was first synthesized using polycarbonate diol (PCDL), isophorone diisocyanate (IPDI), 2,2‐dimethylolpropionic acid (DMPA), and hydroxyethyl acrylate (HEA) as raw materials. Polyurethane composite coatings were prepared by associating cationic antibacterial agents with polyurethane molecules through electrostatic assembly, hydrophobic interactions and hydrogen bonding, and the mechanical properties, adhesion, and antibacterial properties of the polyurethane composite coatings were studied. The results showed that the polyurethane composite coatings had good mechanical properties, and the introduction of cationic antibacterial agents significantly improved the antibacterial ability of the polyurethane material. The antibacterial efficiency of polyurethane against E. coli and S. aureus reached 99% and exhibited durable antibacterial performance as well. Moreover, the polyurethane composite coatings showed excellent adhesion to a variety of substrates, demonstrating their potential application as a universal antimicrobial coating in the medical field.Highlights Construction of polyurethane composite with electrostatic self‐assembly method. Surface coating technology with fast curing, robustness, and universality. Excellent mechanical and antibacterial properties of composite coatings.

First-principles study on the effects of different valence VZn and Ag doping with Hi co-existence on the magnetism and photocatalysis of ZnO

In vacuum environment, metal organic chemical vapor deposition (MOCVD) method was used in experiments, with Ag doping and cation vacancy (VZn) doping in ZnO, where unintentional Hi cannot be avoided. However, studies on the effect of H interstitial physical properties are few. In this study, first-principles generalized gradient approximation plane-wave ultra-soft pseudopotential GGA + U approach within the frame of DFT is used to study the influences of VZn and Ag doping in different valencies with Hi on the magnetism and photocatalysis of ZnO.Under O-rich conditions, Zn34Ag2+HiO36(VZn0) has the best thermodynamic stability. Researches showed that Zn34Ag1+O36(VZn0) has a 2 μB magnetic moment, and magnetism is mainly generated by the roving electrons (O−) using the VZn as medium. Photocatalysis increases with the increase of Ag valence state. Especially, Zn34Ag2+HiO36(VZn0) has a relatively long electronic lifetime of 5.35 × 10−12 s, the strongest visible light absorption ability, relatively high carrier activity and relatively strong reduction ability.

Cationic β‐Scission of C−H and C−C Bonds for Selective Dimerization and Subsequent Sulfur‐Free RAFT Polymerization of α‐Methylstyrene and Isobutylene

AbstractA series of exo‐olefin compounds ((CH3)2C(PhY)−CH2C(=CH2)PhY) were prepared by selective cationic dimerization of α‐methylstyrene (αMS) derivatives (CH2=C(CH3)PhY) with p‐toluenesulfonic acid (TsOH) via β‐C−H scission. They were subsequently used as reversible chain transfer agents for sulfur‐free cationic RAFT polymerization of αMS via β‐C−C scission in the presence of Lewis acid catalysts such as SnCl4. In particular, exo‐olefin compounds with electron‐donating substituents, such as a 4‐MeO group (Y) on the aromatic ring, worked as efficient cationic RAFT agents for αMS to produce poly(αMS) with controlled molecular weights and exo‐olefin terminals. Other exo‐olefin compounds (R−CH2C(=CH2)(4‐MeOPh)) with various R groups were prepared by different methods to examine the effects of R groups on the cationic RAFT polymerization. A sulfur‐free cationic RAFT polymerization also proceeded for isobutylene (IB) with the exo‐olefin αMS dimer ((CH3)2C(Ph)−CH2C(=CH2)Ph). Furthermore, telechelic poly(IB) with exo‐olefins at both terminals was obtained with a bifunctional RAFT agent containing two exo‐olefins. Finally, block copolymers of αMS and methyl methacrylate (MMA) were prepared via mechanistic transformation from cationic to radical RAFT polymerization using exo‐olefin terminals containing 4‐MeOPh groups as common sulfur‐free RAFT groups for both cationic and radical polymerizations.

Cationic β-Scission of C-H and C--C Bonds for Selective Dimerization and Subsequent Sulfur-Free RAFT Polymerization of α-Methylstyrene and Isobutylene.

A series of exo-olefin compounds ((CH3)2C(PhY)-CH2C(=CH2)PhY) were prepared by selective cationic dimerization of α-methylstyrene (αMS) derivatives (CH2=C(CH3)PhY) with p-toluenesulfonic acid (TsOH) via β-C-H scision. They were subsequently used as reversible chain transfer agents for sulfur-free cationic RAFT polymerization of αMS via β-C-C scission in the presence of Lewis acid catalysts such as SnCl4. In particular, exo-olefin compounds with electron-donating substituents, such as a 4-MeO group (Y) on the aromatic ring, worked as efficient cationic RAFT agents for αMS to produce poly(αMS) with controlled molecular weights and exo-olefin terminals. Other exo-olefin compounds (R-CH2C(=CH2)(4-MeOPh)) with various R groups were prepared by different methods to examine the effects of R groups on the cationic RAFT polymerization. A sulfur-free cationic RAFT polymerization also proceeded for isobutylene (IB) with the exo-olefin αMS dimer ((CH3)2C(Ph)-CH2C(=CH2)Ph). Furthermore, telechelic poly(IB) with exo-olefins at both terminals was obtained with a bifunctional RAFT agent containing two exo-olefins. Finally, block copolymers of αMS and MMA were prepared via mechanistic transformation from cationic to radical RAFT polymerization using exo-olefin terminals containing 4-MeOPh groups as common sulfur-free RAFT groups for both cationic and radical polymerizations.

Binuclear Complexes Supported by a Tetrapyridyl Ligand with a Bending Anthraquinodimethane Linker.

A tetrapyridyl ligand with a bending anthraquinodimethane linker has been synthesized, and its complexation with coinage metals has been examined. The treatment of the ligand with Ag(I) and Au(I) cations afforded binuclear complexes, wherein the two metal centers were in close proximity to the inside space of the ligand. X-ray analyses corroborated with theoretical calculations indicated that the ligand has reasonable flexibility toward a bending deformation of the linker moiety to provide a ligand pocket suitable for the proximal binuclear complexes, even though such deformations accompany a non-negligible amount of energetic cost. On the other hand, treatment with 2 equiv of Cu(I) salt afforded a binuclear complex, in which both copper atoms were coordinated at the periphery of the ligand.

Wash fastness properties of pre-mordanting cotton fabrics dyed with natural dyes

With the awareness of the negative effects of synthetic products on the environment and human health, there is a global search for environmentally, friendly and sustainable consumer products with natural dyes. The concept of naturalness gains importance for textile products that are in direct contact with human body. Therefore, dyeing process of cellulosic based fabrics in different colours with natural dyes has been developed. In this study, cotton fabrics were dyed in different colours at 1% and 3% concentrations by pre-mordanting with a cationic mordanting agent, and the washing fastness of the fabrics was tested. Before dyeing the fabrics were pre-treated and made sustainable for dyeing. Tube dyeing was performed with five different commercial natural dyes at different concentrations using the HT dyeing technique. Cotton fabrics structures in different colours were obtained by using a thickening agent in dyeing and a colour chart that could be presented to the market was created. In the studies carried out, it was observed that the fastness results were quite good in the acceptable value range (3-5), although there were dyeing defect, especially in dark dyed fabrics. It was determined that the prepared dyes should be filtered in order to minimize the dyeing defect.

Improved bleached eucalyptus kraft pulp-based tissue papers incorporating wet-strength resins

Abstract Common tissue paper manufacturing trends aim at partial or total replacement of softwood pulp with hardwood pulp for its production, such as bleached eucalyptus kraft pulp (BEKP), in order to optimize the process and the final product properties such as softness. However, the use of a single type of hardwood fiber results in lower strengths of both wet and dry webs. To maintain necessary strength and desired properties, the incorporation of several additives is often required. In this context, low molecular weight polyethylene glycol (PEG) and different wet strength resins, such as polyamideamine-epichlorohydrin (PAE) and glyoxalated polyacrylamide (GPAM) resins, were combined to achieve an innovated product with improved properties. In particular, wet and dry tensile strength was significantly improved when combining PEG and wet strength resins, especially observed in tissue papers prepared with PAE resin, high-charge cationic agent and bulk applied aqueous PEG solution. Noteworthy that water absorption capacity and softness of tissue paper were not critically affected by PEG incorporation, regardless of application method used (in bulk or by spray).

Piezoelectric and Dielectric Properties in Bi0.5(Na,K)0.5TiO3-x Ag2O Lead-Free Piezoceramics.

Lead-free piezoceramics of Bi0.5(Na0.825K0.175)0.5TiO3 with varying concentrations of x mol% Ag2O (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, denoted as BNKT-xA) were fabricated using the solid-state technique. An extensive investigation was undertaken to analyze the structural, piezoelectric, and dielectric properties of these piezoceramics in the presence of Ag ions. There is no evidence of any secondary solid solution in the BNKT-xA piezoceramics. The ceramics with x mol% Ag2O in BNKT still demonstrate the presence of both rhombohedral (R) and tetragonal (T) phases. The addition of Ag+ is helpful to increase the relative density of the BNKT-xA piezoceramics. It is noteworthy that the BNKT-0.3 mol% A piezoceramics show remarkable improvements in their properties (d33 = 147 pC/N, kp = 29.6%, ε = 1199, tanδ = 0.063). These improvements may be ascribed to the denser microstructure and the preservation of morphotropic phase boundaries between R and T phases caused by the appropriate addition of Ag cations. The addition of Ag+ results in the relaxor behavior of the BNKT-xA ceramics, characterized by disorder among A-site cations. With the increase in temperature, the d33 value of BNKT-xA ceramics does not vary significantly in the range of 25 to 125 °C, ranging from 127 to 147 pC/N (with a change of d33 ≤ 13.6%). This finding shows that piezoelectric ceramics have a reliable performance over a certain operating temperature range.

Peptide nanostructures-based delivery of DNA nanomaterial therapeutics for regulating gene expression

Self-assembled branched DNA (bDNA) nanomaterials have exhibited their functionality in various biomedical and diagnostic applications. However, the anionic cellular membrane has restricted the movement of bDNA nanostructures. Recently, amphiphilic peptides have been investigated as cationic delivery agents for nucleic acids. Herein, we demonstrate a strategy for delivering functional bDNA nanomaterials into mammalian cells using self-assembled linear peptides. In this study, antisense oligonucleotides of vascular endothelial growth factor (VEGF) were inserted in the overhangs of bDNAs. Novel linear peptides have been synthesized and the peptide-bound bDNA complex formation was examined using various biophysical experiments. Interestingly, the W4R4-bound bDNAs were found to be exceptionally stable against DNase I compared to other complexes. The delivery of fluorescent-labeled bDNAs into the mammalian cells confirmed the potential of peptide transporters. Furthermore, the functional efficacy of the peptide-bound bDNAs has been examined through RT-PCR and western blot analysis. The observed results revealed that W4R4 peptides exhibited excellent internalization of antisense bDNAs and significantly suppressed (3- to 4-fold) the transcripts and translated product of VEGF compared to the control. In summary, the results highlight the potential use of peptide-based nanocarrier for delivering bDNA nanostructures to regulate the gene expression in cell lines.

Conductivity Enhancement of Graphene and Graphene Derivatives by Silver Nanoparticles

In this article, a facile way for the doping of graphene and graphene derivatives with silver nanoparticles at different Ag ratios is described. Ag nanoparticles were formed directly on the surface of two different graphene substrates dispersed in dimethylformamide by the reduction of Ag cations with NaBH4. A few layered graphene nanosheets (FLG) produced from graphite and reduced graphene oxide functionalized with amino arylsulfonates (f-rGO) were used as substrates. The final graphene/Ag nanoparticle hybrid in the form of solid, dense spots showed enhanced electrical conductivity, which can be attributed to the formation of conductive interconnections between the 2D nanosheets. Importantly, electrical conductivities of 20 and 167 103 S m−1 were measured for the hybrids of f-rGO and FLG, respectively, with the higher Ag percentage without an annealing process. A representative hybrid f-rGO with Ag nanoparticles was used for the development of a highly conductive water-based gravure ink with excellent printing properties.

Sustainable Dyeing and Finishing of Cotton Fabrics with Layer-by-Layer Technique

Large amounts of water, synthetic dyestuffs and chemicals are used in the wet processes of textile finishing, and at the end of these processes, liquors containing chemical substances create a waste load. For this reason, it is of great importance to develop new wet-finishing processes that use less water, dyestuffs and chemicals. For this purpose, the layer-by-layer deposition method (LbL) was used in this research as an environmentally friendly, sustainable method that can be used in wet-finishing processes to minimize chemical, water and energy consumption. The dyeing and functional finishing of cotton fabrics were carried out in one process by the LbL method. Cotton fabrics were pre-treated with a commercial cationic dye fixation agent and cationic charges were produced on the fabric surfaces. Reactive and direct dyestuff groups were used in the dyeing process of cotton fabrics and fluorocarbon was used in the functional finishing process. Eight and 12 dye/fluorocarbon layered structures were obtained by LbL deposition using a laboratory-type padder. Cotton fabrics were dyed and finished with the same dyes and fluorocarbon via the padding method and both samples were compared. The washing, rubbing and light color fastness properties, color strength and color difference of the dyed samples were tested. Tensile strength, air permeability, SEM graphs, contact angle, water and oil repellency analyses were performed for the treated fabrics.

Highly stable lithium sulfur batteries enhanced by flocculation and solidification of soluble polysulfides in routine ether electrolyte

Lithium-sulfur batteries (LSBs) are among the most promising next-generation high energy density energy-storage systems. However, practical application has been hindered by fundamental problems, especially shuttling by the higher-order polysulfides (PSs) and slow redox kinetics. Herein, a novel electrolyte-based strategy is proposed by adding an ultrasmall amount of the low-cost and commercially available cationic antistatic agent octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate (SN) into a routine ether electrolyte. Due to the strong cation–anion interaction and bridge-bonding with SN, rapid flocculation of the soluble polysulfide intermediates into solid-state polysulfide-SN sediments is found, which significantly inhibited the adverse shuttling effect. Moreover, a catalytic effect was also demonstrated for conversion of the polysulfide-SN intermediates, which enhanced the redox kinetics of Li–S batteries. Encouragingly, for cells with only 0.1 % added SN, an initial specific capacity of 783.6 mAh/g and a retained specific capacity of 565.7 mAh/g were found at 2C after 200 cycles, which corresponded to an ultralow capacity decay rate of only 0.014 % per cycle. This work may provide a simple and promising regulation strategy for preparing highly stable Li–S batteries.

Al2O3 interfacial layer derived hybrid conductive filament for the reliability enhancement of Ta2O5-based resistive random access memory

This study used an Al2O3 interfacial layer to improve the reliability characteristics of Ag/Ta2O5/Au resistive random access memory (RRAM), such as endurance and retention. The Ag/Ta2O5/Au device without the Al2O3 interfacial layer exhibited a high on/off ratio, low endurance, and poor retention. In Ag/Ta2O5/Au devices, it is difficult to precisely control the formation and rupture of conductive filaments (CFs) owing to the high diffusion coefficient of Ag cations. However, in the RS mechanism of Ag/Ta2O5/Au with an Al2O3 interfacial layer, a hybrid CF composed of Ag cations in Ta2O5 and oxygen vacancies in the Al2O3 layer was formed during the set process. During the reset process, the hybrid CF was stably ruptured by the recombination of oxygen vacancies and oxygen ions at the Al2O3 interfacial layer. This RS mechanism induces stable switching characteristics, improving endurance and retention. Therefore, Ag/Ta2O5/Au with an Al2O3 interfacial layer exhibits relatively high endurance (up to 700 cycles) and excellent retention (up to 1.0 × 104 s) while maintaining a high on/off ratio (>106) compared to those of the Ag/Ta2O5/Au device.

Crystal structure of Ag3Dy2(NO3)9 and qu-anti-tative comparison to isotypic compounds.

Single crystals of Ag3Dy2(NO3)9 (tris-ilver didysprosium nona-nitrate) were obtained from a mixture of AgNO3 and Dy(NO3)3·5 H2O. The new compound crystallizes in space group P4132 (No. 213) with a = 13.2004 (4) Å, V = 2300.2 (2) Å3, Z = 4. The Ag and Dy cations are coordinated by five and six bidentate nitrate anions, respectively. Ag3Dy2(NO3)9 is isostructural to several compounds that include alkali metals or ammonium and lanthanide cations, but silver and dysprosium are included for the first time and feature the smallest ion radii observed for this structure type to date. Crystal structures of isotypic compounds are compared.

Kinetically regulated one-pot synthesis of cationic gold nanoparticles and their size-dependent antibacterial mechanism

Cationic gold nanoparticles (cAuNPs) have been regarded as promising candidates for antibacterial applications due to their high surface charge density, favorable biocompatibility, and controllable surface chemistry. Nevertheless, the complicated fabrication process and unclear antibacterial mechanism have greatly hindered the further biomedical application of cAuNPs. Herein, we have developed a simple and controllable strategy for synthesizing cAuNPs with tailored size and antibacterial behavior by kinetically modulating the reaction process. Specifically, a functional ligand, (11-mercaptoundecyl)-N, N, N-trimethylammonium bromide (MUTAB), was chosen to chemically manipulate the positive surface charge of cAuNPs via a one-step strategy. The size of cAuNPs could be flexibly adjusted from 1.1 to 14.8 nm by simply elevating the stirring speed of the reaction from 0 to 1500 rpm. Further studies revealed that the antibacterial effect of cAuNPs was strongly correlated with the particle size. MUTAB-protected ultrasmall gold nanoclusters (MUTAB-AuNCs) were able to eradicate E. coli at a concentration as low as 1.25 μg mL–1, while the minimum inhibitory concentration of MUTAB-AuNPs with a large size for E. coli was 5 μg mL–1. Mechanistic investigation revealed that MUTAB-AuNPs were able to damage the bacterial membrane and stimulate the production of reactive oxygen species more effectively than MUTAB-AuNCs. Conversely, MUTAB-AuNCs were more active in inducing membrane depolarization in contrast to MUTAB-AuNPs, suggesting the unique size-dependent antibacterial manner of cAuNPs. This study presents a new strategy for the controlled preparation of cAuNPs with distinct sizes and antibacterial behavior, laying a valuable foundation for developing efficient cationic NP-based bactericidal agents.