Use of orally administered anhydrous crystalline maltose for relief of dry mouth

OBJECTIVES: To examine the safety and efficacy of anhydrous crystalline maltose (ACM) for treatment of dry mouth. DESIGN: ACM was delivered orally as a 200-mg lozenge given three times daily over a 12-week (study Alpha) or 24-week (study Omega) period to a total of 22 and 97 subjects, respectively. All participants had prominent complaints of persistent dry mouth associated with primary Sj?gren's syndrome. Patients were examined every 4 weeks in study Alpha and every 6 weeks in study Omega. SETTINGS: Patients were seen in outpatient clinics at a total of 33 sites within the United States. OUTCOME MEASURES: Unstimulated whole saliva output, a measure of basal salivary gland function, was determined at each visit. Symptoms associated with oral and ocular dryness were assessed at the same time with the use of 100-mm visual analog scales. Safety was assessed by physical examination and laboratory studies. RESULTS: During these clinical trials, a majority of subjects demonstrated an increase in unstimulated whole saliva output and the treatment exhibited an excellent safety profile. The ACM treatment in study Omega led to significant improvement in several subjective measures of oral and ocular comfort. CONCLUSIONS: In these two studies, ACM lozenges administered three times daily for 12 or 24 weeks improved salivary output and decreased complaints of dry mouth and eyes. Side effects were minimal, and treatment was without significant adverse events. This safe and simple intervention may provide clinical benefit to individuals with distressing dry mouth symptoms.     

Synthesis and characterization of low density porous nickel zinc ferrites

Ni–Zn ferrite has important applications in the field of soft magnetic materials due to its excellent magnetic properties, but its high bulk density hinders its promotion. Herein, an oxalate precursor was prepared by a coprecipitation method with metal sulfate and oxalic acid as raw materials. The low density porous Ni–Zn ferrite powder was prepared by thermal decomposition in an aerobic environment with the oxalate precursor. The microstructure, morphology, and dielectric and magnetic properties of Ni–Zn ferrite were studied by thermogravimetric and differential scanning calorimetry, X-ray powder diffraction, X-ray photoelectron spectroscopy, Fourier transform-infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, tap density testing for powder, vibrating sample magnetometry, specific surface and aperture analysis and vector network analysis. The results showed that the purity, morphology, grain size and saturation magnetization of Ni–Zn ferrite were controlled by many factors such as synthetic temperature, retaining time and environmental conditions. Under an oxygen atmosphere, pure Ni–Zn ferrite can be prepared from an oxalate precursor by a thermal process. The ferrite has a wood-splitting appearance and a multi-layered internal cavity structure, and the bulk density is only 1/3 of the general ferrite. It has good soft magnetic and microwave absorbing properties, which makes it a potential excellent material for microwave absorbers.

Ni–Zn ferrite has important applications in the field of soft magnetic materials due to its excellent magnetic properties, but its high bulk density hinders its promotion.     

Synthesis of self-assembled nucleobases and their anhydrous proton conductivity

We synthesized self-assembled nucleobases (SANs), such as 1-dodecylthymine (DOT) or 9-dodecyladenine (DOA), in which the nucleobase is immobilized on a long alkyl chain. The thermal stability of the SAN was increased by mixing with the acidic surfactant mono-dodecyl phosphate (MDP). Additionally, the SAN–MDP composite material showed proton conductivity of 4.62 × 10⁻⁴ S cm⁻¹ at 160 °C under anhydrous conditions. Additionally, the activation energy of the proton conduction was approximately 0.2 eV and this value was one order of magnitude higher than that of a typical humidified perfluorinated membrane, in which the proton can be moved by vehicle molecules, such as water molecules. In contrast, when the nucleobase without the immobilization of a long alkyl chain was mixed with MDP, the proton conductivity of these composite materials was two orders of magnitude less than that of the SAN–MDP composite. Therefore, we measured the XRD spectra of the SAN–MDP composite material. As a result, the SAN–MDP composite material showed a self-assembled structure with a two-dimensional proton conducting pathway, such as a lamellar structure, and that the anhydrous proton conduction was related to the interaction between the nucleobase of the SAN and the phosphate group of MDP. Consequently, the self-assembled nucleobase derivatives have the potential for use as novel anhydrous proton conductors with a two-dimensional proton conducting pathway.

We synthesized the proton conductive self-assembled nucleobase, such as 1-dodecylthymine and 9-dodecyladenine, in which the nucleobase is immobilized on a long alkyl chain.     

Synthesis,characterizations and electrochemical performances of anhydrous CoC2O4 nanorods for pseudocapacitive energy storage applications

To overcome the environmental challenges caused by utilization of fossil fuel based energy technologies and to utilize the full potential of renewable energy sources such as solar, wind and tidal, high power and high energy density containing large scale electrochemical energy storage devices are a matter of concern and a need of the hour. Pseudocapacitors with accessibility to multiple oxidation states for redox charge transfer can achieve a higher degree of energy storage density compared to electric double layer capacitors (EDLC) and the hybrid supercapacitor is one of the prominent electrochemical capacitors that can resolve the low energy density issues associated with EDLCs. Due to its open pore framework structure with superior structural stability and accessibility of Co^2+/3+/4 redox states, porous anhydrous CoC₂O₄ nanorods are envisaged here as a potential energy storage electrode in a pseudo-capacitive mode. Superior specific capacitance equivalent to 2116 F g⁻¹ at 1 A g⁻¹ in the potential window of 0.3 V was observed for anhydrous CoC₂O₄ nanorods in aqueous 2 M KOH electrolyte. A predominant pseudo-capacitive mechanism seems to be operative behind the high charge storage at electrodes as intercalative (Inner) and surface (outer) charge storage contributions were found to be 75% and 25% respectively. Further, in full cell asymmetric supercapacitor (ASC) mode in which porous anhydrous CoC₂O₄ nanorods were used as positive electrodes and activated carbon (AC) was utilised as negative electrodes within an operating potential window of 1.3 V, a highest specific energy of W h kg⁻¹ and specific power of ∼647 W kg⁻¹ at 0.5 A g⁻¹ current density were obtained with superior cycling stability. High cycling stability coupled with superior electrochemical storage properties make anhydrous CoC₂O₄ nanorods potential pseudo-capacitive electrodes for large scale energy storage applications.

With active participation of Co^2+/3+ redox couples in an oxalate framework, Anhydrous CoC₂O₄ nanorods display a capacitance equivalent to 2116 F g⁻¹ at 1 A g⁻¹ current rate in the potential window of 0.3 V in aqueous 2 M KOH electrolyte.     

Synthesis and characterization of carboxylated PBAMO copolymers as promising prepolymers for energetic binders

The carboxylated poly[3,3-bis(3-azidomethyl)oxetane] (PBAMO) copolymers (poly(BAMO-carboxylate)) were synthesized by substitution of poly[3,3-bis(3-chloromethyl)oxetane] (PBCMO) with potassium carboxylate and sodium azide in DMSO. The synthesized compounds were characterized using various analytical techniques, such as Fourier-transform infrared (FT-IR) spectroscopy, inverse-gated decoupling ¹³C-nuclear magnetic resonance (¹³C NMR) spectroscopy, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), calorimetry, friction, and impact sensitivity analysis. These poly(BAMO-carboxylate) compounds have better thermal properties, with lower glass transition temperatures (ranging from −43 °C to −51 °C) than PBAMO (−37 °C) and higher thermal decomposition temperatures (233–237 °C) than PBAMO (211 °C). Moreover, poly(BAMO_0.80-octanoate_0.20) and poly(BAMO_0.78-decanoate_0.22) have higher heats of combustion (5226 and 5665 kJ mol⁻¹, respectively) and negative formation enthalpies (−0.17 and −0.55 kJ g⁻¹, respectively), while PBAMO has lower heat of combustion (3125 kJ mol⁻¹) and positive formation enthalpy (0.06 kJ g⁻¹). The poly(BAMO-carboxylate) compounds have higher values (38–50 J) than that of PBAMO (14 J) in the impact sensitivities. This is a valuable study for improving the properties of PBAMO, which is a high energetic polymeric binder but difficult to handle because of its sensitivity. Therefore, poly(BAMO-carboxylate) could be a good candidate as a prepolymer for designing the energetic polymeric binder.

The carboxylated poly[3,3-bis(3-azidomethyl)oxetane] (PBAMO) copolymers (poly(BAMO-carboxylate)) were synthesized by substitution of poly[3,3-bis(3-chloromethyl)oxetane] (PBCMO) with potassium carboxylate and sodium azide in DMSO.     

Synthesis and characterization of supported stabilized palladium nanoparticles for selective hydrogenation in water at low temperature

Zirconia supported vacant phosphotungstate stabilized Pd nanoparticles (Pd–PW₁₁/ZrO₂) were prepared using a simple impregnation and post reduction method, characterized and their efficiency for selective C C hydrogenation of unsaturated compounds explored. The establishment of a hydrogenation strategy at low temperature using water as solvent under mild conditions makes the present system environmentally benign and green. The catalyst shows outstanding activity (96% conversion) with just a small amount of Pd(0) (0.0034 mol%) with high substrate/catalyst ratio (29 177/1), TON (28 010) and TOF (14 005 h⁻¹) for cyclohexene (as a model substrate) hydrogenation. The catalyst was recovered by simple centrifugation and reused for up to five catalytic cycles without alteration in its activity. The present catalyst was found to be viable towards different substrates with excellent activity and TON (18 000 to 28 800). A study on the effect of addenda atom shows that the efficiency of the catalyst can be enhanced greatly by increasing the number of counter protons. This challenging strategy would greatly benefit sustainable development in chemistry as it diminishes the use of organic solvents and offers economic and environmental benefits as water is cheap and non-toxic.

Zirconia supported vacant phosphotungstate stabilized Pd nanoparticles (Pd–PW₁₁/ZrO₂) are proved to be sustainable and excellent for the water mediated hydrogenation reaction with a very high substrate to catalyst ratio, TON and TOF.     

Synthesis,characterization and biological evaluation of dipicolylamine sulfonamide derivatized platinum complexes as potential anticancer agents

Three new Pt complexes, [PtCl₂(N(SO₂(2-nap))dpa)], [PtCl₂(N(SO₂(1-nap))dpa)] and [PtCl₂(N(SO₂pip)dpa)], containing a rare 8-membered ring were synthesized in good yield and high purity by utilizing the ligands N(SO₂(2-nap))dpa, N(SO₂(1-nap))dpa and N(SO₂pip)dpa, which contain a dipicolylamine moiety. Structural studies of all three complexes confirmed that the ligands are bound in a bidentate mode via Pt–N_(pyridyl) bonds forming a rare 8-membered ring. The intense fluorescence displayed by the ligands is quenched upon coordination to Pt. According to time dependent density functional theory (TDDFT) calculations, the key excitations of N(SO₂(2-nap))dpa and [PtCl₂(N(SO₂(1-nap))dpa)] involve the 2-nap-ligand-centered π → π* excitations. While all six compounds have shown antiproliferative activity against human breast cancer cells (MCF-7), the N(SO₂pip)dpa and N(SO₂(2-nap))dpa ligands and [PtCl₂((NSO₂pip)dpa)] complex have shown significantly high cytotoxicity, directing them to be further investigated as potential anti-cancer drug leads.

Three new Pt complexes, [PtCl₂(N(SO₂(2-nap))dpa)], [PtCl₂(N(SO₂(1-nap))dpa)] and [PtCl₂(N(SO₂pip)dpa)], containing a rare 8-membered ring were synthesized in good yield and high purity by utilizing ligands which contain a dipicolylamine moiety.     

Synthesis and characterization of hydroxyl-terminated butadiene-end-capped polyisobutylene and its use as a diol for polyurethane preparation

Hydroxyl-terminated telechelic polyisobutylene (PIB) was prepared through living cationic polymerization. A living PIB chain was formed using the t-Bu-m-DiCuOMe/TiCl₄ initiating system and then capped with 1,3-butadiene (BD) to prepare chlorine-terminated telechelic PIB. The chlorine-terminated telechelic PIB was then hydrolysed with tetrabutylammonium hydroxide to form hydroxyl-terminated PIB. Nuclear magnetic resonance spectroscopy confirmed hydrolysis completion. The hydroxyl-terminated PIB was subsequently used as a diol to react with 4,4-methylenebis(phenylisocyanate) (MDI) and produce a PIB-based polyurethane, which showed stronger acid resistance, hydrolysis stability and thermal oxidation stability than a commercial polyurethane.

We synthesised hydroxyl-terminated PIB through living cationic polymerisation. Then the hydroxyl-terminated PIB was subsequently used as a diol to produce a PIB-based polyurethane.     

Dissolution mechanism and release kinetics of phosphate controlled release glasses in aqueous medium.

Leach test of a phosphate controlled release glass (CRG) were conducted in aqueous medium under different conditions. Results show that the phosphate CRG dissolves congruently in deionized water. Its dissolution rate is dependent with the solution pH, temperature and concentrations of phosphate ions and calcium ions in the medium, but independent with the stirring speed of the solution. Analysis leads to a conclusion that the dissolution of phosphate glass is a reaction-controlled process. Discussions on the dissolution mechanisms show that the nature of the reaction in the hydrated layer is the dissociation of Na(+) ions from the phosphate chains under the attack of the penetrating water molecules. The velocity of formation and development of hydrated layer depends on the diffusion rate of water molecules inside glass. The dissolution is realized by the breakage of P-O-P bonds in the phosphate network within the hydrated layer. The chelating ability of polyphosphate with divalent cations play an important role in the dissolution process of phosphate CRGs and was found responsible for the accelerated or decelerated dissolution of the CRG in sodium hexametaphosphate (SHMP) or CaCl(2) solutions, respectively.     

壳聚糖/介孔生物活性玻璃多孔膜的制备和表征

背景：壳聚糖和介孔生物玻璃都具有良好的生物相容性和止血性能,但壳聚糖止血作用有限,介孔生物玻璃粉体方式止血,给应用带来不便。目的：制备壳聚糖/介孔生物玻璃复合多孔膜并检测材料的性能。方法：采用冷冻干燥法制备壳聚糖/介孔生物玻璃复合多孔膜。结果与结论：通过冷冻干燥法可以实现壳聚糖和介孔生物玻璃的均匀复合。制备的复合多孔膜的孔隙分布较均匀;多孔膜具有很好的吸水性,吸水率的大小与壳聚糖和介孔生物玻璃质量比相关;多孔膜的孔隙率高。     

壳聚糖/介孔生物活性玻璃多孔膜的制备和表征

背景:壳聚糖和介孔生物玻璃都具有良好的生物相容性和止血性能,但壳聚糖止血作用有限,介孔生物玻璃粉体方式止血,给应用带来不便。目的:制备壳聚糖/介孔生物玻璃复合多孔膜并检测材料的性能。方法:采用冷冻干燥法制备壳聚糖/介孔生物玻璃复合多孔膜。结果与结论:通过冷冻干燥法可以实现壳聚糖和介孔生物玻璃的均匀复合。制备的复合多孔膜的孔隙分布较均匀;多孔膜具有很好的吸水性,吸水率的大小与壳聚糖和介孔生物玻璃质量比相关;多孔膜的孔隙率高。     

Synthesis of highly crystalline LaFeO3 nanospheres for phenoxazinone synthase mimicking activity

LaFeO₃ nanospheres with an orthorhombic perovskite structure were synthesized by a sol–gel autocombustion method in the presence of different citric acid ratios (x = 2, 4, 8, and 16) and utilized for the photocatalytic conversion of o-aminophenol (OAP) to 2-aminophenoxazine-3-one (APX) for the first time. OAP is one of the most toxic phenolic derivatives used as a starting material in many industries; however, the dimerization product APX has diverse therapeutic properties. Photocatalytic conversion was carried out in ethanol/water and acetonitrile/water mixtures in the absence and presence of molecular oxygen at ambient temperature via the oxidative coupling reaction that mimics phenoxazinone synthase-like activity. The LaFeO₃ samples showed a superior photocatalytic activity of OAP to APX with rate constants of 0.43 and 0.92 min⁻¹ in the absence and presence of molecular oxygen, respectively. Thus, the LaFeO₃ nanozymes could be used as promising candidates in industrial water treatment and phenoxazinone synthase-like activity.

LaFeO₃ nanospheres were synthesized by a facile sol–gel autocombustion method and explored for the photocatalytic transformation of o-aminophenol to 2-aminophenoxazine-3-one.     

Synthesis and characterization of nanoceria for electrochemical sensing applications

Nanoceria (cerium oxide nanoparticles: CeO₂-NPs) has received significant attention due to its biocompatibility, good conductivity, and the ability to transfer oxygen. Nanoceria has been widely used to develop electrochemical sensors and biosensors as it could increase response time, sensitivity, and stability of the sensor. In this review, we discussed synthesis methods, and the recent applications employing CeO₂-NPs for electrochemical detection of various analytes reported in the most recent four years.

Nanoceria (cerium oxide nanoparticles: CeO₂-NPs) has received significant attention due to its biocompatibility, good conductivity, and the ability to transfer oxygen.     

Synthesis and characterization of comb-shaped copolymer as a filtration reducer and comparison with counterparts

A comb-shaped copolymer of 2-acrylamide-2-methyl propane sulfonic acid (AMPS), allyl polyoxyethylene ether (APEG), N-vinyl-2-pyrrolidone (NVP) and sodium styrene sulfonate (SSS) was synthesized by free-radical polymerization. The structure of the comb-shaped copolymer was characterized by Fourier transform infrared (FTIR) spectroscopy, and its molecular weight was determined by gel permeation chromatography (GPC). FTIR measurements and environmental scanning electron microscopy (ESEM) analysis were used to characterize the working mechanism of different filtrate loss reducers. Thermogravimetry and differential scanning calorimetry (TG-DSC) results showed that thermal degradation of the copolymer was significant only after 295.24 °C. The comb-shaped copolymer helped reduce filtration, while maintaining the rheological properties of the drilling fluid at high temperature and high salinity conditions as long PEG chains sterically stabilized colloids by protruding into the suspension. The filtration control of the comb-shaped copolymer was comparable to that of the sulfonated phenolic resin (SMP) mixture and outperformed AM/AMPS/NVP/SSS (NS-1) and polymeric product PAC in terms of high-temperature resistance and rheological advantages. The morphology of the comb-shaped copolymer was found with a compact 3-D film structure due to the intramolecular and intermolecular association by hydrogen bonding in the side chains. Small curly debris at high temperature and salinity remained capable of filtration control. The NS-1 had a lower temperature resistance, as large areas of flaky films thermally degraded into a small chain structure at 180 °C. Only separated filiform and coarse lines were found in PAC with a linear structure that makes the drilling fluid more viscous. Compact and structured films were formed with the SMP mixture at high temperature and salinity.

Comb-shaped copolymer as filtration reducer for high temperature and high salinity.     

Synthesis,characterization and antifungal activities of eco-friendly palladium nanoparticles

Palladium is a versatile catalyst, but the synthesis of palladium nanoparticles (PdNPs) is usually attained at a high temperature in the range of 160 °C to 200 °C using toxic reducing agents such as sodium borohydride. We report the synthesis of PdNPs using a low-cost and environmentally-friendly route at ambient temperatures. Quercetin diphosphate (QDP), a naturally-derived flavonoid, was employed as a reducing, capping, and stabilizing agent. The effect of temperature was optimized to produce perfectly spherical PdNP nanoparticles with sizes ranging from 0.1 to 0.3 microns in diameter. At relatively higher concentration of QDP, significantly smaller particles were produced with a size distribution of 1–7 nm. Perfectly spherical PdNP nanoparticles are a rare occurrence, especially under ambient room temperature conditions with fast reaction time. The formation of the nanoparticles was confirmed using UV-vis, TEM, EDS, and XRD. HRTEM demonstrated the lattice structure of the PdNPs. The synthesized PdNPs were also tested for their antifungal properties against Colletotrichum gloeosporioides and Fusarium oxysporum. Results showed that the size of the PdNPs played a critical role in their antifungal activity. However, for F. oxysporum, other factors beyond size could affect the antifungal activity including fine-scale, nutrient composition, and target organisms.

Palladium is a versatile catalyst, but the synthesis of palladium nanoparticles (PdNPs) is usually attained at a high temperature in the range of 160 °C to 200 °C using toxic reducing agents such as sodium borohydride.     

Synthesis,characterization and osteogenesis of phosphorylated methacrylamide chitosan hydrogels

Phosphorylated biopolymers can induce mineralization, mimic the process of natural bone formation, and have the potential as scaffolds for bone tissue engineering. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a low cytotoxicity phosphorus source, is mainly applied in vascularization and promoting blood compatibility and has been less researched for bone repair. In this study, phosphorylated methacrylamide chitosan (PMAC) hydrogel was prepared by mixing methacrylamide chitosan (MAC) and different mass of MPC with photoinitiator under UV irradiation. A series characterization tests showed that PMAC hydrogels were successful prepared and had a pretty good mineralization ability. Moreover, human fetal osteoblastic (hFOB) cells cultured on PMAC hydrogels exhibited not only highly viability but also the enhanced ALP activity and calcium deposition. The PMAC hydrogels have great potential in bone tissue engineering applications.

Phosphorylated biopolymers can induce mineralization, mimic the process of natural bone formation, and have the potential as scaffolds for bone tissue engineering.     

Synthesis,characterization, and properties of a novel aromatic ester-based polybenzoxazine

Polybenzoxazines with molecular design flexibility have excellent properties by using suitable raw materials. A new benzoxazine monomer terephthalic acid bis-[2-(6-methyl-4H-benzo[e][1,3]oxazin-3-yl)]ethyl ester (TMBE) with bis-ester groups has been synthesized from the simple esterification reaction of terephthaloyl chloride and 2-(6-methyl-4H-benzo[e][1,3]oxazin-3-yl)-ethanol (MB-OH). The chemical structure of TMBE was characterized by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (¹H-NMR, ¹³C-NMR). Polymerization behavior of TMBE was studied by differential scanning calorimetry (DSC) and FT-IR after each cure stage. The cross-linked polybenzoxazine (PTMBE) gave a transparent film through the thermal casting method. The dynamic mechanical analysis of PTMBE showed that the T_g was 110 °C. Thermogravimetric analysis reveals better thermal stability as evidenced by the 5% and 10% weight-loss temperatures (T_d5 and T_d10) of PTMBE, which were 263 and 289 °C, respectively, with a char yield of 27% at 800 °C. The tensile test of the film revealed that the elongation at break was up to 14.2%.

A novel benzoxazine monomer contain ester group was obtained by an indirect molecular design method. Its polymer showed excellent flexibility.     

Synthesis,characterization, and catalytic application of hierarchical nano-ZSM-5 zeolite

Hierarchical nano-ZSM-5 zeolites (Z5-X) with different grain sizes were synthesized by varying amounts of 3-glycidoxypropyltrimethoxysilane (KH-560) in the hydrothermal synthesis strategy. Moreover, the conventional ZSM-5zeolite(Z5), which was prepared without KH-560, was used as the reference sample. The crystalline phases, morphologies, porous characteristics, Si/Al molar ratios and acidic properties of all fresh catalysts were characterized using the X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning electron microscopy (SEM), N₂ adsorption–desorption, inductively coupled plasma atomic emission spectroscopy (ICP) and temperature programmed desorption of ammonia (NH₃-TPD) techniques. Results show that the grain size and strong acid amount of zeolite decreased with the increasing amount of KH-560. The micropore surface areas and the corresponding volume of Z5-X changed less compared with Z5. Consequently, the high shape-selectivity of zeolite was preserved well under the addition of KH-560. However, the mesopore surface areas and the corresponding volume increased significantly with the increasing amount of KH-560. Benefiting from the abundant hierarchical structure, the Z5-X catalysts exhibited a larger coke capacity than the Z5 catalyst. The coke depositions of all the deactivated catalysts were characterized by the thermogravimetric technique (TG), and the results are indicative of the decreased average rate of coke deposition with an increasing amount of KH-560, which could result from the gradually reduced strong acid amount and the nano-sized crystallites. The catalytic performance of methanol-to-aromatics (MTA) indicates that the Z5-0.12 catalyst exhibited higher catalytic activity and selectivity of BTX as the reaction was prolonged, which could result from the synergistic effect among the proper strong acid amount, the smaller zeolite grain size, and the abundant hierarchical structure.

The crystal size and strong acid amounts of ZSM-5 decrease and the mesopores increase with increasing of KH-560. High MTA catalytic performance could be obtained under synergistic effect of proper strong acid amount, smaller crystal size and abundant hierarchical structure.     

Gallium–tin alloys as a low melting point liquid metal for repetition-pulse-laser-induced high energy density state toward compact pulse EUV sources

Here, we show the easy-handling of a liquid gallium–tin alloy (Ga : Sn) as a laser target source for 13.5 nm light generation. The alloys have ∼30 °C freezing points according to a differential scanning calorimetry cooling process. A Nd:YAG laser (1064 nm, 1 ns, 7.1 × 10¹⁰ W cm⁻²) ablated the alloys, obtaining a similar extreme ultraviolet emission intensity to Sn despite a small quantity of Sn. Finally, we demonstrate a liquid metal alloy jet and droplets using a plastic nozzle for high-repetition target supply.

We show the near-room-temperature-handling of a liquid gallium–tin alloy (Ga:Sn) as a laser target source for 13.5 nm pulse repetition.

Liquid metals have generated interest in relation to electronics due to the possibilities of producing flexible circuitry, moldable parts, and stretchable electrodes.¹ Liquid metals can dissolve other metal ions, often further lowering the melting point through bond disruption.^1b In particular, gallium has shown strong potential as it exists readily in a liquid state at room temperature, with a non-oxygenated bulk and non-toxic properties. For example, gallium-based catalysts are exciting in terms of CO₂ reduction.^1cA cruder, but no less interesting, way of using liquid metals is in laser plasma generation. Laser plasma sources are of interest in fields such as extreme ultraviolet lithography (EUVL) and quantum beam generation.² EUVL generation is a process whereby a material, typically tin, is heated by a high-intensity laser pulse to ∼100 eV. The energy losses from the laser pulse (I_L) are excess heating to high ionization (I_ion), greater kinetic energy of ions and electrons (I_kin), and out-of-band radiation (I_oobrad) as follows:^2eI_L = I_kin + I_ion + I_rad + I_oobrad1In order to obtain the most favorable wavelength of 13.5 nm for the lithography optics, tin is the best element with the highest I_rad under optimized conditions.^2eThe light produced by this heating will be applied in the high volume manufacturing of semiconductors as a lithographic process. Currently, commercial EUVL sources are supplied as a test tool for lithography; powers at the intermediate focus are ever increasing (>125 W), and the source is highly available (>80%).³ However, more is needed from EUVL sources due to the need for higher throughput.⁴ Furthermore, practical issues remain problematic, such as the durability issue of the reflective optics.^4,5In addition to EUVL, compact EUV sources with different target sources, such as gas puff targets⁶ and low-density materials,⁷ are becoming attractive. These sources should be low cost, allowing exploration of different applications such as surface modification of materials⁸ and time-resolved ultraviolet photoelectron spectroscopy (UPS) studies, etc. By combining high-power laser compactness⁹ and emerging target materials and technologies,^7e,10 reliable quantum beam sources can be developed. Overall, laser plasma target materials play an important role in producing very high temperature plasmas, X-ray and higher quantum beam emission.To date, many works have focused on the technical optimization of EUV, such as the laser and target parameters.^10,11 However, optimizing the target source could be just as beneficial for EUV and other laser plasma sources; for example clever target design can improve laser conversion efficiency (CE).^11f This area is firmly established with the chemical synthesis of these low-density targets.^{7f,10,11b,11f} The plasma generated from well-defined low-density targets have lower self-reabsorption than full-density targets.^11a Dilution of tin is also an effective method for obtaining a high CE by-polymer,^11d and lithium dilution.^11f One criticism of minimum mass and well-defined low-density targets is that large laser systems would require a substantial design modification in order to be accommodated. However, an alternative dilution by a liquid metal droplet source would not suffer the same issues as liquid tin. This could be easily adapted to existing EUV design protocols, and should be considered for larger laser plasma sources. Furthermore, construction of new generations of EUV sources based on a low melting point liquid alloy would be simpler than liquid tin. Low melting point metals such as gallium or indium have caught the interest of EUV researchers.¹² One alloy that heavily utilizes gallium, commercially known as Galinstan®, is typically composed of Ga (62–95%), In (5–22%) and Sn (0–16%), and has a strong emission of 13.5 nm light due to the presence of Sn.^12a Therefore, Galinstan® could be highly desirable as a target source for EUVL given the very low reported melting point of −19 °C. However, low CE and the broad and flat shaped EUV spectrum due to the presence of indium (∼15/16 nm) and gallium (∼11/12 nm) restricts Galinstan® to metrology applications.^12b For EUV, the choice between utilization of gallium or indium is a decision for researchers. Such as a 50 : 50% Sn : In alloy has the same density as liquid Sn, and a melting point of ∼155 °C.¹³ On the other hand, gallium has a lower melting point than indium, meaning that alloys of gallium–tin could remain liquid at temperatures less than 100 °C. Although gallium has been mentioned on patents,¹⁴ there is a lack of accessible experimental data to assess the viability of gallium alloys as an EUV source.The aim of this work was to demonstrate that Ga : Sn alloys are an easy-handling liquid metal alternative to Sn as a laser plasma target source. Ga : Sn alloys of differing atomic (at%) ratios were synthesized, then characterized using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) with X-ray dispersive spectroscopy (EDS). A Nd:YAG laser (1 ns, 2 mJ) was used to generated EUV under similar conditions to previous work,¹⁵ with a grazing incidence spectrometer (GIS). As an example, we show that EUV emission intensity for the Ga : Sn alloy was equal to bulk Sn, depending on the alloy composition. The CE for the Ga : Sn alloy was also estimated in comparison with bulk tin using a calorimeter. We also show the emission properties of the alloy irradiated by 10 Hz exposure in order to demonstrate the potential as a practical and flexible laser plasma target source. Finally, our progress developing Ga : Sn jets and droplets is shown.DSC data shown in Fig. S1–S4^† exhibit consistency with the phase diagram reported;¹⁶ the endothermic peak on the liquidus and exothermic peaks at the solidus (27 °C), and supercooling solidus from the metastable state (–25 °C) are shown in