Ion Precursors Research Articles

In situ generation of dispersed MoS2 catalysts from oil-soluble Mo-based ionic liquids for highly effective biolipids hydrodeoxygenation

Dispersed metal sulfides are promising catalysts for the hydroconversion of biolipids to produce second-generation biodiesel. In this work, oil-soluble Mo-based ionic liquids (ILs) were innovatively utilized as the precursors for in situ generation of MoS2 catalysts for the hydroconversion of biolipids. Taking methyl palmitate as the model compound, the excellent activity of in situ generated MoS2 from ionic liquid Mo-based precursors was obtained. The turnover frequencies (TOFs) reached up to 1.6 × 102 h−1 for methyl palmitate conversion and 83 h−1 for hexadecane (C16) yield at 320 °C and 0.5 h (42% conversion) under solvent-dilute conditions. The structures of in situ generated MoS2 catalysts were characterized to provide explanations for the catalytic results. Based on the product distributions, the pathway of methyl palmitate hydroconversion was proposed, and the kinetics of methyl palmitate hydroconversion was analyzed in further detail. Applying the Mo-based ILs in the hydroconversion of methyl palmitate and palm oil under solvent-free condition also granted high conversions of feeds and selectivities of HDO products.

Covalent Triazine Framework Encapsulated Ultrafine PdAu Alloy Nanoclusters as Additive-Free Catalysts for Efficient Hydrogen Production from Formic Acid

Dehydrogenation of formic acid (FA) represents a promising route for clean hydrogen production, the economic viability of which, however, is largely hindered by the catalyst inefficiency. Here, ultrafine Au–Pd bimetallic nanoclusters (NCs) confined within the cavities of bipyridyl covalent triazine frameworks (CTFs) are constructed via a metal-nitrogen coordination reduction strategy, which is enabled by the chelation between bidentate nitrogen sites of the bipyridine ligands and metal ion precursors. The resulting CTF-confined PdAu NCs exhibit a high initial turnover frequency up to 12,368 h–1 (333 K) toward the dehydrogenation of FA without any additives. The experimental and theoretical studies disclose that the pyridinic nitrogen sites of CTF not only facilitate the formation of monodisperse small-sized metal NCs via the anchoring and the pore confinement effect but also serve as a proton buffer which can store excess protons and thus suppress the recombination of adsorbed formate and hydrogen on the PdAu alloy surface. These findings would have significant implications for designing high-performance hydrogen production catalysts.

Thermal self-reduction of metal hydroxide acrylate monolayer nanoparticles leads formation of nanoparticulate and porous structured alloys.

Chemical and physical designs of alloy nanomaterials have attracted considerable attention for the development of highly functional materials. Although polyol processes using ionic precursors are widely used to synthesise alloy nanoparticles, the reduction potential of polyols limits their chemical composition, making it difficult to obtain 3d transition metals. In this study, we employed pre-synthesized metal hydroxide salt monolayer nanoparticles as precursors to obtain alloy nanoparticles. Simultaneous dehydroxylation of the hydroxide moiety and decomposition of the organic moiety allowed the formation of stable face-centred cubic metals passing through the metal carbide and metastable hexagonal close-packed metal phases. This self-reduction process enabled the formation of nanoparticulate bimetallic alloys and macroporous/mesoporous-structured bimetallic alloys by compositing hard/soft templates with pre-synthesized metal hydroxide salt nanoparticles. We believe that the strategy presented in this study can be used to design nanostructures and chemical compositions of multimetallic alloy nanoparticles as well as bimetallic systems.

Adsorption Thermodynamics, Modeling, and Kinetics Studies for the Removal of Lead Ions Using ZnO Nanorods

In the present investigation, zinc oxide nanorods (ZnO-NR) were synthesized via the hydrothermal method using ZnCl2 as a zinc ion precursor in the presence of cetyltrimethylammonium bromide. Synthesized ZnO-NR was featured using advanced techniques including XRD, PL, SEM, and UV-visible spectroscopy. The role of these assynthesized ZnO-NR was evaluated for the sequestration of lead ions in batch mode. The elimination of lead ions was achieved at pH 6-7 using a 0.06 g adsorbent dose, 25 min contact time, 25 mg/L initial lead ion concentration, 323 K temperature, and 200 rpm agitation speed. A thermodynamic study revealed the endothermic nature of lead ion sequestration onto ZnO-NR. The lead ion sequestration followed kinetic (pseudo-second-order) and isotherm (Langmuir) models. The lead ions were eliminated up to 142 mg/g at the optimum level of affecting variables. The ZnO-NR might be a potential adsorbent for lead ion removal from industrial effluents.

Full Stereocontrol in α-Glycosidation of 3-Deoxy-d-manno-2-octulosonic Acid (Kdo) Using Macrobicyclic Glycosyl Donors.

We describe a method for the α-selective glycosidation of 3-deoxy-d-manno-2-octulosonic acid (Kdo) using a macrobicyclic Kdo donor as the precursor of a bridgehead oxocarbenium ion, whose stereoselectivity is not affected by the substrate structure and reaction conditions. Strapping Kdo via tethering in the α-configuration at the C1 and C5 positions completely blocked nucleophilic attack to the β-face of the anomeric center by sterically hindering the bicyclic system, realizing full α-selectivity during glycosidation.

Green synthesis of zero-valent iron nanoparticles by Cleistocalyx operculatus leaf extract using microfluidic device for degradation of the Rhodamine B dye

Environmental pollution, in particular, the wastewater from the textile and dyeing production process is causing serious issues for the ecosystem and humans. It has been well-demonstrated that zero-valent iron nanoparticles (nZVI) are one of the most promising materials in the treatment of environmental pollutants. In this work, the Cleistocalyx operculatus leaf extract was employed as a green reductant for the synthesis of the nZVIs nanoparticles from iron ions precursor. Notably, a microfluidic device was also used as micro-reactor for the synthesis process of the nanoparticles, making it easy to control and optimise the morphologies and sizes of nZVI. The morphology and crystallinity of nZVI were characterised by scanning electron microscopy (SEM) and x-ray diffraction (XRD), respectively. The nZVIs prepared in a microfluidic reactor using Cleistocalyx operculatus leaf extract as reductant were in plate-like structure with the thickness of around 5 nm and the diameter in range of hundred nanometers. The removal efficiency of Rhodamin B (RhB) dye by the prepared nZVI was determined by ultraviolet-visible (UV–vis) spectroscopy. The results showed that the nZVI revealed high removal performance toward RhB with removal efficiency of higher than 90% after 30 min of treatment. The effects of dye’s concentration, time, and pH solution on the treatment performance of RhB were also studied.

ZnHCF@PB nanoparticles with reduced bandgap as a promising photocatalyst for the degradation of conventional and emerging water contaminants

The photocatalytic degradation of conventional and emerging pollutants (i.e., methyl, ethyl, and butyl parabens) was investigated under light irradiation with 315–1050 nm wavelength using core–shell zinc doped hexacyanoferrate@Prussian blue nanoparticles. Different synthesis parameters including precursors loading, drying temperature and different metal ions precursors were studied. The ten different composite systems obtained, were investigated for the photodegradation of methylene blue in deionized water. The optimal performance photocatalyst (20 mg/L) photodegrade 94% of 10 ppm methylene blue within 24 min. The optimized sample was further used for the photodegradation of methylene blue in municipal wastewater matrix; it completely degraded the methylene blue after 51 min. Finally, the developed nanoparticles were investigated for the photodegradation of parabens. The chemical oxygen demand showed 30% of parabens was degraded in the municipal wastewater matrix. The results of this research show that ZnHCF@PB nanoparticles could be used for the effective photocatalytic remediation of conventional and emerging pollutants, i.e., parabens. Statement of environmental implicationThrough this study, it is anticipated that ZnO-derived ZnHCF@PB NPs can achieve a bandgap of 1.11 eV, which is much lower than that of ZnO NPs (3.15 eV). Interestingly, ZnHCF@PB NPs were efficiently used for the degradation of conventional (i.e., dyes) and emerging contaminants (i.e., parabens) in deionized water and municipal wastewater matrices to mimic industrial wastewater.

Laser irradiation induced platinum-based bimetallic alloy nanoparticles in liquids for electrocatalytic hydrogen production

Designing effective catalysts with high performance for electrocatalytic hydrogen production remains a formidable challenge. Small-size bimetallic alloy nanoparticles (NPs) with the advantages of a large exposure of effective active sites and optimal geometric/electronic effects are of great interest in the field of electrocatalysis, yet a suitable strategy for synthesizing such unique structures is still highly expected. In this effort, we report a unique approach to synthesizing ultra-small bimetallic PtM (M=Ni, Co) alloy NPs (∼ 1.7 nm) on carbon supports by laser irradiation in liquids. The method is based on the effective absorption of pulse laser energy by carbon supports to generate instant high temperature, which allows the reduction of metallic ions precursors by ethanol molecules and ensures the subsequent formation of alloy NPs. The fast-cooling dynamic process stops the further growth of small-sized alloy NPs. Such bimetallic PtNi alloy NPs displayed much improved catalytic performance in the HER process. The overpotential is only 19 mV and 42 mV (10 mA cm−2) in acidic and alkaline conditions, which is much lower than that of commercial 20 % Pt/C (36 mV, 53 mV) catalyst. Density function theory calculation shows that Ni doping facilitates the hydrogen adsorption/desorption process of nearby surface Pt atoms.

Bacterial DNA Recognition by SERS Active Plasma-Coupled Nanogold.

It is shown that surface-enhanced Raman spectroscopy (SERS) can identify bacteria based on their genomic DNA composition, acting as a "sample-distinguishing marker". Successful spectral differentiation of bacterial species was accomplished with nanogold aggregates synthesized through single-step plasma reduction of the ionic gold-containing vapored precursor. A high enhancement factor (EF = 107) in truncated coupled plasmonic particulates allowed SERS-probing at nanogram sample quantities. Simulations confirmed the occurrence of the strongest electric field confinement within nanometric gaps between gold dimers/chains from where the molecular fingerprints of bacterial DNA fragments gained photon scattering enhancement. The most prominent Raman modes linked to fundamental base-pair molecular vibrations were deconvoluted and used to proceed with nitrogenous base content estimation. The genomic composition (percentage of guanine-cytosine and adenine-thymine) was successfully validated by third-generation sequencing using nanopore technology, further proving that the SERS technique can be employed to swiftly specify bioentities by the discriminative principal-component statistical approach.

Solution ALD: A Versatility Process for the Growth of Sulfides and Selenides

We have proposed and demonstrated a novel thin film deposition technique by transferring the principles of atomic layer deposition (ALD), known with gaseous precursors, towards precursors dissolved in a liquid. The technique can also be considered as a generalization of already established methods such as the ‘layer by layer’ growth or the ‘successive ion layer adsorption and reaction’ (SILAR). 'Solution ALD' (sALD) shares the fundamental properties of standard ‘gas ALD’ (gALD), specially the self-limiting growth and the ability to coat conformally deep pores. It has been already shown that it is possible to transfer standard reactions from gALD to sALD such as TiO2 deposition . However, sALD also offers novel opportunities such as overcoming the need for volatile and thermally robust precursors.To illustrate this, we establish sALD procedures for depositing films of non oxides layers such as Pb-compound deposition, MOF, selenides and sulfides. Those examples highlight how ionic, polar, or high-molecular weight precursors that only exist in the condensed phase are now rendered amenable to being utilized in surface-controlled thin film formation by sALD for depositing materials that would otherwise be more difficult or more expensive to achieve by gALD or hazardous. The deposition was achieved on small (2 cm*1 cm) and large samples (up to 10 cm*10 cm). The ALD behavior has been shown. The influence of the deposition parameters on the morphology, the crystalline structure and the chemical composition has been investigated by scanning electron microscopy, atomic force microscopy, grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy. Additionally, the nucleation is studied in function of chemical pretreatment to control the growth and allow selective deposition of SnS, SnSe and Sb2Se3.This particular ALD process offer the growth of high quality and crystalline layers in middle conditions with the use of low cost and environmental friendly precursors. Y. Wu, D. Döhler, M. Barr, E Oks,M. Wolf, L. Santinacci and J. Bachmann, Nano Lett. 2015, 15, 6379 J. Fichtner, Y. Wu, J. Hitzenberger, T. Drewello and J. Bachmann, ECS J. Solid State Sci. Technol. 2017, 6, N171

Formation of Ultimate Thin 2D Crystal of Pt in the Presence of Hexamethylenetetramine.

Platinum naturally crystalizes into a three-dimensional crystal due to its highly symmetrical fcc lattice, with a metallic bond which is non-directional and highly isotropic. This inherently means ultimately that 2D crystals of a few atoms thick growth are hardly available in this material. Here, we discovered that a combinative effect of formic acid reductant and hexamethylenetetramine surfactant during the reduction of their metal ions precursor can realize an ultimate thin 2D crystal growth in platinum. High-resolution transmission electron microscopy and filed-emission electron microscopy analysis have also discovered that the 2D crystal of Pt has 111 facets with a lateral dimension that can be up to more than 5 μm × 2 μm. The thickness of the 2D crystal of Pt is 1.55 nm. A mechanism for obtaining ultimate thin 2D crystal of Pt using the present approach is proposed.

Morphological Control of Nanoporous Copper Formed from Conversion Reaction Synthesis

The pore architecture of nanoporous copper (NP-Cu) plays a vital role in its technological applications. The synthesis of NP-Cu by the conversion reaction has been reported, where an ionic Cu precursor (salt or oxide) is chemically reduced with n-butyllithium to form a Cu metal nanocomposite, from which the Li-containing product is removed to form NP-Cu. Anions in the Cu compound precursors significantly affect the size of Cu in the nanocomposite due to the effect of lithium salt on Cu diffusion. Thermal annealing of the nanocomposites reveals that the activation energy for diffusion correlates with the melting point of the lithium salt, which is used as a proxy for their tendencies of forming defects, indicating that Cu diffusion takes place through the bulk phase of the salt rather than the Cu/salt interfaces. This experimentally observed behavior is consistent with the results from density functional theory calculations. Further, doping the lithium salt with Mg2+ increases the defect concentration and facilitates enhanced Cu diffusion. The choice of anion in the Cu salt precursor thus provides an effective tool to enable control of the nanoscale size of Cu and the resultant NP porosity.

Structural characterization and antibacterial activity of silver nanoparticles synthesized using a low-molecular-weight Royal Jelly extract

In recent years silver nanoparticles (Ag NPs) gained increased and widespread applications in various fields of industry, technology, and medicine. This study describes the green synthesis of silver nanoparticles (Ag NPs) applying a low-molecular-weight fraction (LMF) of Royal Jelly, the nanoparticle characterization, and particularly their antibacterial activity. The optical properties of NPs, characterized by UV–Vis absorption spectroscopy, showed a peak at ~ 430 nm. The hydrodynamic radius and concentration were determined by complementary dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). The particle morphology was investigated using transmission electron microscopy (TEM), and the crystallinity of the silver was confirmed by X-ray diffraction (XRD). The antibacterial activities were evaluated utilizing Gram-negative and Gram-positive bacteria and colony counting assays. The growth inhibition curve method was applied to obtain information about the corresponding minimum inhibitory concentrations (MIC) and the minimum bactericidal concentrations (MBC) required. Obtained results showed that (i) the sizes of Ag NPs are increasing within the increase of silver ion precursor concentration, (ii) DLS, in agreement with NTA, showed that most particles have dimensions in the range of 50–100 nm; (iii) E. coli was more susceptible to all Ag NP samples compared to B. subtilis.

Ultrathin nitrogen-doped defective carbon layer embedded with NiFe for solid zinc-air batteries

Developing a simple oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional catalyst construction strategy for zinc-air batteries (ZABs) has been a major challenge. Therefore, this study synthesized an ultrathin nitrogen-doped defective carbon layer embedded with nickel-iron (NiFe) (ZGNiFe@NG) by introducing zinc gluconate to the precursor. In situ generated NiFe nanoparticles facilitated the OER catalyzation kinetics process, nitrogen-doped graphene demonstrated a large specific surface area, providing more active sites to boost electron transfer and mechanical support for the NiFe nanoparticles. Additionally, the introduction of Zn ions can enrich carbon vacancies in the structure of composite catalyst, which is beneficial to the further improvement of catalytic activity. The investigations revealed that the obtained ZGNiFe@NG catalyst possessed a higher ORR half-wave potential of 0.81 V and a lower OER potential of 1.65 V of 10 mA cm−2, presenting a bifunctional catalytic activity toward ORR and OER than that of catalysts lacking the Zn ion precursor. Moreover, as expected, the fabricated solid-state flexible ZAB with ZGNiFe@NG catalyst delivered a high power density of 84.95 mW cm−2 at a current density of 112 mA cm−2 and could operate 65 h steadily. In summary, this work paves a way for designing a carbon matrix with dopants and defects to load NiFe nanoparticles as superior cathode materials of ZABs.

Polyoxometalate-assisted in situ growth of ZnMoO4 on ZnO nanofibers for the selective detection of ppb-level acetone

One-dimensional (1D) semiconductor composite nanofibers (NFs) with large specific surface areas, high length-to-diameter ratios, and abundant interfacial active sites have received widespread attention. In this work, a rationally designed 1D composite NFs architecture for detecting acetone is synthesized via a two-step process based on electrospinning followed by a thermal oxidation method. Utilizing the polyoxometalate (POM) as a molecular platform with high negative charges to combine transition metal ions precursors, highly dispersed ZnMoO4 can be in situ grown on the ZnO. By adjusting the content of POM (H3PMo12O40, denoted as PMo12) in the precursor solution, we can obtain a series of ZnMoO4 decorated ZnO NFs (ZnMoO4-ZnO NFs). Compared with the pristine ZnO NFs, the ZnMoO4-ZnO NFs sensor exhibited excellent sensing characteristics over a wide range of acetone concentrations (50 ppb-50 ppm), such as high sensitivity , relatively low detection concentration, and high selectivity. The primary mechanism for the improved acetone gas sensing properties of the ZnMoO4-ZnO NFs could be ascribed to the available charge transfer and unique structure within ZnMoO4-ZnO NFs.

Controlling Electronic Energy Structure of Near-IR-Responsive Ag(In,Ga)(S,Se)2 Quantum Dots for In Vivo Bioimaging

[Introduction] Since cancer is a leading cause of death worldwide, early diagnostic and treatment observation using biosensors becomes urgent. To date, the development of the biosensors is limited to the utilization of fluorescent probes such as organic dyes or fluorescent proteins, which suffer from various weakness[1]. Therefore, new probes that are more photostable than current organic fluorophores are needed.Semiconductor called quantum dots (QDs) of a few nanometers in size exhibit unique photochemical properties different from their bulk materials, owing to the quantum size effect. Binary QDs composed of group II−VI or IV−VI semiconductors, such as CdS, CdSe, and PbS, have been intensively investigated because of intense PL, high quantum yield, resistance to photo-bleaching, and broad excitation with narrow emission bands, which made them ideal for high contrast optical imaging of biological systems. However, notable toxicity associated with Cd and Pb causes serious limitations in practical use. Recently, mixed-cation QDs, such as ZnAgInS[2], AgInGaS[3], and AgInGaSe[4], have been an environmentally friendly alternative to conventional binary QDs. Their photochemical properties were controlled through the composition of QDs as well as their particle size. Controlling the composition of QDs containing multinary chalcogen elements, that is, mixed-anion QDs, is also expected to be another strategy to tune their physicochemical properties, but the method to prepare such QDs showing intense PL has not been developed well.In this study, we report the strategy to prepare Ag(In, Ga)(S, Se)2 (AIGSSe) QDs, of tunable photochemical properties, such as energy gap (Eg) and photoluminescence peak, with the ratio of Se/S in the particles. [Experimental] AIGSSe QDs were synthesized by a solution-phase synthesis method. A mixture of AgOAc, In(acac)3, and Ga(acac)3 was used as a metal ion precursor, and that of thiourea and selenourea was used as a chalcogen precursor. These were added to a test tube with a mixture solvent of oleylamine and dodecane thiol, in which the ratio of Se/(Se+S) varied from 0 to 1.0. The solution was heated at 100~250 °C, and then formed QDs were isolated by adding methanol. The resulting wet precipitates were washed several times with ethanol, followed by dissolving in chloroform. Thus-obtained AIGSSe QDs were surface-coated by GaSx shell to improve PL property. Furthermore, these QDs were incorporated into unilamellar liposomes of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) to make them dissolved in aqueous solution before being injected into the back of a mouse, and their PL intensity was measured. [Results and Discussion] The absorption onset was red-shifted from 580 nm to 830 nm with an increase in the Se/(S+Se) ratio in preparation, indicating that the Eg of QDs was decreased from 1.9 to 1.5 eV with an increase in the Se/(Se+S) ratio from 0 to 1.0 in QDs. Thus-obtained AIGSSe QDs exhibited broad PL peaks with relatively weak intensities. However, the surface coating of AIGSSe QDs with GaSx shell (AIGSSe@GaSx) remarkably enhanced the intensity of PL peak. The PL quantum yield (QY) of AIGSSe QDs varied in the range of 2~43%, but QDs with each Se/(S+Se) ratio exhibited increased QY after surface coating with GaSx shell. Especially, AIGSSe@GaSx with Se/(S+Se) = 0 had the highest QY value as much as 50%. The PL peak wavelength was red-shifted from 580 nm to 785 nm with a decrease in the Eg of AIGSSe core, the FWHM of PL peak being varied in the range of 0.147 ~ 0.357 eV.TEM measurement revealed that the AIGSSe@GaSx QDs were spherical, and their average size was almost constant at ca. 4 nm with narrow size distribution, regardless of Se/(Se+S) in preparation. AIGSSe@GaSx QDs with Se/(Se+S) = 0.50 exhibited a sharp PL peak at 785 nm in first biological window, which was suitable for in vivo imaging. These QDs were encapsulated with DSPC liposomes so that the QDs were dispersed in aqueous solution. Thus-obtained AIGSSe@GaSx QD-DSPC liposomes maintained a sharp band-edge PL peak even in an aqueous dispersion, in which the PLQY was slightly decreased from 25% in chloroform to 21% in aqueous dispersions but was high enough to be used as a near-IR PL probe. We successfully detected PL emission from the QDs through the skin of a mouse, and the PL intensity was proportional to the concentration of injected QDs. [References] [1] T. Jin, et al., J Mater Chem B, 2020, 8, 10686.[2] T. Kameyama, et al., J. Phys. Chem. C, 2018, 122, 13705.[3] T. Kameyama, et al., ACS Appl. Mater. Interfaces, 2018, 10, 42844.[4] T. Kameyama, et al., ACS Appl. Nano Mater., 2020, 3, 3275.

Nitrenium ion-based ipso-addition and ortho-cyclization of arenes under photo and iron dual-catalysis

In this work, N-acyloxybenzamide was developed as an efficient acyl nitrenium ion precursor. An iron-catalyzed acyl nitrenium-based ipso-addition and ortho-cyclization of arenes under photocatalysis is reported for the switchable synthesis of 3,4-dihydroquinolin-2-ones and 6,9-diene-2,8-diones. In the reaction, FeCl3 serves as the photocatalyst and SET reductant, and an acyl nitrenium ion was proposed as a key intermediate. It is assumed that the divergence for ipso-addition and ortho-cyclization is enabled by the substituents on the substrates. Reaction of para-substituted arenes predominantly goes through ipso-addition and CC migration, while that of meta-substituted arenes proceeds through ortho-cyclization.

Anion‐Induced Catalytic Reaction in a Solution‐Processed Molybdenum Oxide for Efficient Inverted Ternary Organic Photovoltaics

AbstractSolution‐processed transition metal oxides (TMOs) prepared from complex ion precursors are developed as promising scalable interfacial layers for non‐fullerene organic photovoltaics (OPVs); however, challenges remain in achieving defect‐free and highly oriented metal‐oxygen networks without post‐deposition treatments due to the presence of residual organic metal‐binding ligands in films. Herein, the novel strategy that the problematic organic metal‐binding ligands in TMO precursors can be successfully eliminated by an anion‐induced catalytic reaction (ACR) at room temperature is demonstrated, in which the low‐level anions induce electron redistribution and instability of TMO precursors, expediting binding ligand removal during the hydrolysis reaction. The subsequent condensation process facilitates a dimensionally confined and continuous metal‐oxygen network with a 20‐fold increase in electrical conductivity (from 8.4 × 10−4 to 1.8 × 10−2 S m−1) and superior work function tunability (from 5.1 to 5.3 eV) compared to the pristine film. The ACR‐derived TMO thin film on top of a ternary PBDB‐TF:Y6:PC71BM photoactive layer enables an inverted device configuration with improved efficiency of 17.6%, as well as enhanced stability over 70% of the initial efficiency for up to 100 h AM 1.5G illumination.

THE SEDIMENTATION BEHAVIOURS OF AlPO4 AND Fe3(PO4)2 PRECIPITATES IN SOLUTIONS OF SODIUM CARBOXYMETHYLCELLULOSE AT DIFFERENT TEMPERATURES

To evaluate the sedimentation of aluminium phosphate [AlPO4] and ferrous phosphate [Fe3(PO4)2] precipitates in sodium carboxymethylcellulose (Na-CMC) biopolymer at different temperatures, batch-wise precipitation and sedimentation tests of AlPO4 and Fe3(PO4)2 in solutions of Na-CMC were carried out at temperatures of 30, 40 and 50oC. The objective was to determine On-set Sedimentation Rate (OSR) and Sedimentation Volume Ratio (SVR) of the metal phosphates. Fixed volume of Na-CMC at different concentrations was mixed with constant volume and known concentration of phosphate ion precursor (disodium hydrogen phosphate solution) in a sedimentation measurement apparatus - PreSed Meter. The resulting solution was mixed separately with constant volume and known concentration of either aluminium ion or iron (II) ion precursor (either aluminium chloride or ferrous chloride solution). The settling of the precipitate so formed was monitored and recorded. Blank sedimentation tests, without Na-CMC, were also run. For every measurement, On-set Sedimentation Rate (OSR) and Sedimentation Volume Ratio (SVR) of the precipitates were computed. It was observed that in the absence of Na-CMC, AlPO4 precipitate readily dissolved into the medium immediately after stirring. Also, in the absence of Na-CMC, OSR and SVR of Fe3(PO4)2 precipitate increased directly with increased temperatures. The test results also indicated that AlPO4 precipitate suspension was poorly influenced by the biopolymer. Poor correlations in OSR (0.50 ≤ R2 ≥ 0.05) and SVR (0.49 ≤ R2 ≥ 0.005) indicating non-dependence with Na-CMC concentration, implying no chemical interactions with Na-CMC, were described for AlPO4 suspension at all temperatures investigated. For Fe3(PO4)2 suspension, good correlations in OSR (R2 = 0.94) and SVR (R2 = 0.93) indicating dependence with Na-CMC concentration, implying chemical interaction with Na-CMC, were obtained at high temperature (50oC). The observations imply that Na-CMC would be good stabilizing agent for drug formulations containing AlPO4. However, suspension of Fe3(PO4)2 in Na-CMC need not be stored in high temperature conditions.

Harnessing of Spatially Confined Perovskite Nanocrystals Using Polysaccharide-based Block Copolymer Systems.

Metal halide perovskite nanocrystals (PVSK NCs) are generally unstable upon their transfer from colloidal dispersions to thin film devices. This has been a major obstacle limiting their widespread application. In this study, we proposed a new approach to maintain their exceptional optoelectronic properties during this transfer by dispersing brightly emitting cesium lead halide PVSK NCs in polysaccharide-based maltoheptaose-block-polyisoprene-block-maltoheptaose (MH-b-PI-b-MH) triblock copolymer (BCP) matrices. Instantaneous crystallization of ion precursors with favorable coordination to the sugar (maltoheptaose) domains produced ordered NCs with varied nanostructures of controlled domain size (≈10-20 nm). Confining highly ordered and low dimension PVSK NCs in polysaccharide-based BCPs constituted a powerful tool to control the self-assembly of BCPs and PVSK NCs into predictable structures. Consequently, the hybrid thin films exhibited excellent durability to humidity and stretchability with a relatively high PL intensity and photoluminescence quantum yield (>70%). Furthermore, stretchable phototransistor memory devices were produced and maintained with a good memory ratio of 105 and exhibited a long-term memory retention over 104 s at a high strain of 100%.