Embedding metallic and semiconductor nanoparticles in a chalcogenide glass matrix effectively modifies the photonic properties. Such nanostructured materials could play an important role in optoelectronic devices, catalysis, and imaging applications. In this work, we fabricate and characterize germanium nanocrystals (Ge NCs) embedded in arsenic sulfide thin films by pulsed laser ablation in aliphatic amine solutions. Unstable surface termination of aliphatic groups and stable termination by amine on Ge NCs are indicated by Raman and Fourier-transform infrared spectroscopy measurements. A broad-band photoluminescence in the visible range is observed for the amine functionalized Ge NCs. A noticeable enhancement of fluorescence is observed for Ge NCs in arsenic sulfide, after annealing to remove the residual solvent of the glass matrix.Keywords: chalcogenide glass; laser ablation; nanocrystals; photoluminescence; solution process;

•Sterically hindered Mg dialkoxides and AlCl3 in THF reversibly electrodeposit Mg.•Positive relationship between ligand steric size and electrolyte performance.•Larger ligands improve anodic stability, cycling efficiency, and deposition purity.•The triphenylmethoxide-based electrolyte enhances reactivity of metallic Mg.While homoleptic magnesium dialkoxides (MgR2, R = alkoxide) have shown promise as precursors for magnesium-ion electrolytes, the effect of ligand steric bulk on the performance of electrolytes based on these compounds is not fully understood. Increasing steric hindrance, studied via R groups with additional phenyl moieties, produces electrolytes with sequentially lower deposition overpotentials (less than −90 mV), higher purity Mg deposits (ca. 100% Mg), and lower overall cell impedances. The two largest alkoxide ligands show consistent cycling behavior and low stripping and plating overpotentials over 200 constant-current plating/stripping cycles. A deep-red visual change and the presence of large solubilized magnesium particulates above 450 nm in size is observed in an electrolyte containing magnesium bis(triphenylmethoxide) and aluminum chloride in contact with an abraded magnesium anode. Further morphological and impedance characterization show that this electrolyte system rapidly activates the magnesium metal anode surface to produce low overpotentials and, as such, is a candidate for further investigation.

The ability to understand and visualize complex flow structures in microfluidic and biological systems relies heavily on the resolving power of three-dimensional (3D) particle velocimetry techniques. We propose a simple technique for acquiring volumetric particle information with the potential for microsecond time resolution. By utilizing a fast varifocal lens in a modified wide-field microscope, we capture both volumetric and planar information with microsecond time resolution. The technique is demonstrated by tracking particle motions in the complex, three-dimensional flow in a high Reynolds number laminar flow at a branching arrow-shaped junction.

Efficient large scale electrochemical energy storage systems, such as those based on multivalent ions, are a prerequisite for the realization of intermittent renewable energy sources. From the perspectives of both cost and environmental concerns, it is of critical importance that components of these systems are synthesized using sustainable chemical processes starting from their initial conception. Herein, we report on a fluorinated dialkoxide-based magnesium-ion electrolyte that is synthesized through an atom-efficient and scalable process without the use of any metal alkyls. The electrolyte composition results in high solution conductivity (4.77 mS cm−1 at 26.3 °C), low overpotentials, ca. 100% coulombic efficiency for electrodeposition/dissolution, and good performance in full battery cells using Chevrel phase Mo6S8.

The lack of electrolytes that simultaneously possess high Coulombic efficiency, conductivity, and voltage stability has hindered the deployment of rechargeable magnesium-ion batteries. With few exceptions, the tenacious oxide layer on magnesium metal has limited the scope of research to halide ion-based electrolytes, which help activate the electrode surface but also limit the working voltage window considerably. Herein, we demonstrate a new class of magnesium electrolytes based on fluoroalkoxyaluminate anions synthesized via a facile and scalable method and its incorporation in a full battery cell. Mixtures of magnesium and aluminum fluoroalkoxides in ethereal solvents result in solutions that can reversibly deposit magnesium metal with near unit efficiency in addition to achieving suitable oxidative stabilities (>3.5 V vs Mg/Mg2+ on glassy carbon and gold) and conductivities (>6 mS cm–1).

In this Research Article, we demonstrate pulsed laser processing of a silver nanowire network transparent conductor on top of an otherwise complete solar cell. The macroscopic pulsed laser irradiation serves to sinter nanowire-nanowire junctions on the nanoscale, leading to a much more conductive electrode. We fabricate hybrid silicon/organic heterojunction photovoltaic devices, which have ITO-free, solution processed, and laser processed transparent electrodes. Furthermore, devices which have high resistive losses show up to a 35% increase in power conversion efficiency after laser processing. We perform this study over a range of laser fluences, and a range of nanowire area coverage to investigate the sintering mechanism of nanowires inside of a device stack. The increase in device performance is modeled using a simple photovoltaic diode approach and compares favorably to the experimental data.Keywords: direct laser sintering; inorganic−organic heterojunction solar cell; nanowire network; solution processing; transparent electrode;

The effects of time delay and spatial separation between two adjacent laser pulses in blister-actuated laser-induced forward transfer are studied experimentally and computationally. Each laser pulse creates a blister that expands into a liquid film, forming liquid jets to transfer material from a donor substrate to an acceptor substrate. For a fixed separation between the two laser pulses, time-resolved imaging reveals a tilting of the second liquid jet toward or away from the first jet, depending on the time delay between pulses. Simulations of the same process reveal that the first jet perturbs the ink−air interface around it, and the initial angle of the liquid−air interface below the second laser pulse is shown to be a good predictor of the angle of the second jet. The time evolution of the initial interface angle at a fixed separation is then investigated analytically in terms of a viscously damped cylindrical capillary wave, initiating once the jet retracts or pinches off. This two-jet setup can be considered as a model system for high repetition rate printing, so these results reveal limits on the repetition rate and separation between pulses for LIFT such that materials are printed in desired patterns.

•Mechanical stress can be used to monitor SOH and SOC.•Stress is linearly related to state of health.•The linear stress-SOH relationship holds over range of cycling conditions.•Data suggests SEI growth is responsible for the observed stress-SOH relationship.•A phenomenological model can explain linear stress-SOH relationship.Despite the fundamental importance of state of health (SOH) and state of charge (SOC) measurement to lithium-ion battery systems, the determination of these parameters is challenging and remains an area of active research. Here we propose a novel method of SOH/SOC determination using mechanical measurements. We present the results of long term aging studies in which we observe stack stress to be linearly related to cell SOH for cells aged with different cycling parameters. The observed increases in stack stress are attributed to irreversible volumetric expansion of the electrodes. We discuss the use of stress measurements for SOC determination, which offers the advantage of being more sensitive to SOC than voltage as well as the ability to measure SOC in the presence of self discharge. Finally we present a simple model to explain the linear nature of the observed stress-SOH relationship. The inherent simplicity of the mechanical measurements and their relationships to SOH and SOC presented in this paper offer potential utility for the improvement of existing battery management systems.

•Stack stress is a dynamic quantity that evolves during electrochemical cycling.•The initial applied stack pressure determines how stress evolves during cycling.•Small stack stresses prevent layer delamination, benefiting long term performance.•Higher stress causes higher rates of capacity fade through cycleable lithium loss.•Stack stress leads to localized separator deformation and chemical degradation.The effects of mechanical stress on lithium-ion battery life are investigated by monitoring the stack pressure and capacity of constrained commercial lithium-ion pouch cells during cycling. Stack stress is found to be a dynamic quantity, fluctuating with charge/discharge and gradually increasing irreversibly over long times with cycling. Variations in initial stack pressure, an important controllable manufacturing parameter, are shown to produce different stress evolution characteristics over the lifetime of the cells. Cells manufactured with higher levels of stack pressure are found to exhibit shorter cycle lives, although small amounts of stack pressure lead to increased capacity retention over unconstrained cells. Postmortem analysis of these cells suggests a coupling between mechanics and electrochemistry in which higher levels of mechanical stress lead to higher rates of chemical degradation, while layer delamination is responsible for the capacity fade in unconstrained cells. Localized separator deformation resulting in nonuniform lithium transport is also observed in all cells.

This paper studies the fabrication and characterization of solution-processed chalcogenide waveguides by a microtrench filling method. In this process, channels are etched on substrates and backfilled with solution-dissolved arsenic sulfide before being annealed. The waveguides are homogeneous in elemental composition and have good mode confinement. Both simulation and experimental measurements confirm a dominant fundamental mode covering 2.5–2.8 μm. We measure an optical loss of 1.87 dB/cm, which to our knowledge is the lowest among solution-processed waveguides.Keywords: arsenic sulfide; chalcogenides; glass; microtrench filling; solution-process

We use AC impedance methods to investigate the effect of mechanical deformation on ion transport in commercial separator membranes and lithium-ion cells as a whole. A Bruggeman type power law relationship is found to provide an accurate correlation between porosity and tortuosity of deformed separators, which allows the impedance of a separator membrane to be predicted as a function of deformation. By using mechanical compression to vary the porosity of the separator membranes during impedance measurements it is possible to determine both the α and γ parameters from the modified Bruggeman relation for individual separator membranes. From impedance testing of compressed pouch cells it is found that separator deformation accounts for the majority of the transport restrictions arising from compressive stress in a lithium-ion cell. Finally, a charge state dependent increase in the impedance associated with charge transfer is observed with increasing cell compression.Highlights► We model and measure the resistance increase associated with separator deformation. ► We show a Bruggeman relation can model tortuosity changes in deformed separators. ► We measure the α and γ Bruggeman parameters for monolayer separator membranes. ► We measure in situ the impedance changes in a pouch cell under applied compression.

•We characterize pore formation in solution-processed As2S3 films.•Pore density increases with baking temperature and duration.•We explain this phenomenon with vacancy coalescence theory.•Pores are removed with an addition of 10% ethylenediamine.This paper studies the formation of nanopores in solution-processed amorphous arsenic sulfide films and provides an effective method to remove such pores. Nanopores are observed mainly in the bulk of the film after being annealed above 120 °C, and pore sizes are determined to increase with both baking temperature and duration. These observations are explained by a vacancy coalescence mechanism in the context of propylamine solvent. By adding a second solvent, ethylenediamine (EDA), to the original solution, we can essentially modify the material dissolution and annealing chemistry. Most pores are removed when 10% EDA is added, rendering a homogeneous film. The work presented here has great implications for improving the quality of optical chalcogenide components processed with solution methods. It also reinforces the pore formation mechanism that has been relevant to many solution-processed materials.

Solution-processing of chalcogenide glass materials has many benefits for the fabrication of photonic devices. We report on the structural properties of Ge23Sb7S70 glass during solution-processing. The molecular and micro-structure of the bulk glass and the n-propylamine solution, as well as the spin-coated thin films and post-irradiated films are analyzed by Raman spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. We find the vibrational spectral fingerprint of Ge4S104−-units in the amine solutions as well as in the spin-coated films, indicating a similar molecular structure of solutions and solution-processed films, which differs from the bulk glass. Moreover, the spin-coated films exhibit nanopores, and change their composition during irradiation such that sulfur escapes from the film while oxygen gets absorbed.

Directed electrochemical nanowire assembly is a promising high growth rate technique for synthesizing electrically connected nanowires and dendrites at desired locations. Here we demonstrate the directed growth and morphological control of edge-supported platinum nanostructures by applying an alternating electric field across a chloroplatinic acid solution. The dendrite structure is characterized with respect to the driving frequency, amplitude, offset, and salt concentration and is well-explained by classical models. Control over the tip diameter, side branch spacing, and amplitude is demonstrated, opening the door to novel device architectures for sensing and catalytic applications.

Lithium-ion batteries are well-known to be plagued by a gradual loss of capacity and power which occur regardless of use and can be limiting factors in the development of emerging energy technologies. Here we show that separator deformation in response to mechanical stimuli that arise under normal operation and storage conditions, such as external stresses on the battery stack or electrode expansion associated with lithium insertion/deinsertion, leads to increased internal resistance and significant capacity fade. We find this mechanically induced capacity fade to be a result of viscoelastic creep in the electrochemically inactive separator which reduces ion transport via a pore closure mechanism. By applying compressive stress on the battery structure we are able to accelerate aging studies and identify this unexpected, but important and fundamental link between mechanical properties and electrochemical performance. Furthermore, by making simple modifications to the electrode structure or separator properties, these effects can be mitigated, providing a pathway for improved battery performance.Highlights► Mechanical response of batteries is dominated by electrochemically inactive materials. ► Stresses as low as 1 MPa cause viscoelastic creep and pore closure in the separator. ► Varying the magnitude of the stress simulates long-time viscoelastic creep. ► Power fade and capacity loss observed due to limited ion transport in the separator. ► Results can be generalized to other intercalation electrode energy storage systems.

In this work we use laser direct-write (LDW) to fabricate patterned [Ru(dtb-bpy)3]2+(PF6-)2 electroluminescent devices under ambient processing conditions. Device fabrication is accomplished via laser micromachining of a transparent conducting oxide top electrode, LDW printing the active organo-metallic material, and vapor depositing the bottom electrode. Nuclear magnetic resonance spectroscopy is used to ensure the transfer of damage-free luminophore material. Devices tested in air are shown to exhibit emission spectra, luminous efficiencies, and lifetimes similar to literature values for devices fabricated in nitrogen environments. The versatility of laser direct-write printing is then demonstrated by printing multi-color luminophore patterns with diameters down to 10 μm for future use in high-resolution device fabrication. This approach is compatible with large-area organic electronics that require the fabrication of high-resolution architectures.Graphical abstractBlister-actuated Laser induced forward transfer (BA-LIFT) enables the damage-free patterning of ionic transition metal complexes that show extended electroluminescence in air.Highlights► Laser direct write printing of organo-metallic luminophores for light emitting diodes. ► Blister-actuated laser induced forward transfer protects material properties. ► Printed films are pin-hole free and exhibit good diode behavior. ► Long lifetimes of >40 min in air at 4 V with >6 cd/m2 are measured. ► Peak 93 cd/m2 at 11 V in air, and luminous efficiency of 0.4 Lm/W at 3 V are observed.

Laser-induced forward transfer (LIFT) is a high-resolution direct-write technique, which can print a wide range of liquid materials without a nozzle. In this process, a pulsed laser initiates the expulsion of a high-velocity micro-jet of fluid from a thin donor film. LIFT involves a novel regime for impulsively driven free-surface jetting in that viscous forces developed in the thin film become relevant within the jet lifetime. In this work, time-resolved microscopy is used to study the dynamics of the laser-induced ejection process. We consider the influence of thin metal and thick polymer laser-absorbing layers on the flow actuation mechanism and resulting jet dynamics. Both films exhibit a mechanism in which flow is driven by the rapid expansion of a gas bubble within the liquid film. We present high-resolution images of the transient gas cavities, the resulting ejection of high aspect ratio external jets, as well as the first images of re-entrant jets formed during LIFT. These observations are interpreted in the context of similar work on cavitation bubble formation near free surfaces and rigid interfaces. Additionally, by increasing the laser beam size used on the polymer absorbing layer, we observe a transition to an alternate mechanism for jet formation, which is driven by the rapid expansion of a blister on the polymer surface. We compare the dynamics of these blister-actuated jets to those of the gas-actuated mechanism. Finally, we analyze these results in the context of printing sensitive ink materials.

Thin film Ge23Sb7S70 chalcogenide glass has emerged as an important material system for photonic applications due to its high non-linear refractive index. However, one of the challenges is developing low-cost methods to deposit films of glassy material while retaining glass stoichiometry and high film quality. In this paper, we demonstrate a spin-coating technique for the deposition of such films. The dissolution mechanisms of Ge23Sb7S70 in different solvents are studied in order to select the optimal solvent for film deposition. We show that the use of amine-based solvents allow the deposition of stoichiometric films in contrast to alkaline solutions. Films with low surface roughness (RMS roughness <5 nm) and controlled thickness (100–600 nm) can be deposited from solutions. We also show that annealing the films in vacuum decreases the amount of residual solvent, the presence of which is expected to lead to variation in optical properties of the thin films.

The need to generate sub 100 nm features is of interest for a variety of applications including optics, optoelectronics, and plasmonics. To address this requirement, several advanced optical lithography techniques have been developed based on either multiphoton absorption polymerization or near-field effects. In this paper, we combine strengths from multiphoton absorption and near field using optical trap assisted nanopatterning (OTAN). A Gaussian beam is used to position a microsphere in a polymer precursor fluid near a substrate. An ultrafast laser is focused by that microsphere to induce multiphoton polymerization in the near field, leading additive direct-write nanoscale processing.

Efficient large scale electrochemical energy storage systems, such as those based on multivalent ions, are a prerequisite for the realization of intermittent renewable energy sources. From the perspectives of both cost and environmental concerns, it is of critical importance that components of these systems are synthesized using sustainable chemical processes starting from their initial conception. Herein, we report on a fluorinated dialkoxide-based magnesium-ion electrolyte that is synthesized through an atom-efficient and scalable process without the use of any metal alkyls. The electrolyte composition results in high solution conductivity (4.77 mS cm−1 at 26.3 °C), low overpotentials, ca. 100% coulombic efficiency for electrodeposition/dissolution, and good performance in full battery cells using Chevrel phase Mo6S8.

Solution-processing of chalcogenide glass materials has many benefits for the fabrication of photonic devices. We report on the structural properties of Ge23Sb7S70 glass during solution-processing. The molecular and micro-structure of the bulk glass and the n-propylamine solution, as well as the spin-coated thin films and post-irradiated films are analyzed by Raman spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. We find the vibrational spectral fingerprint of Ge4S104−-units in the amine solutions as well as in the spin-coated films, indicating a similar molecular structure of solutions and solution-processed films, which differs from the bulk glass. Moreover, the spin-coated films exhibit nanopores, and change their composition during irradiation such that sulfur escapes from the film while oxygen gets absorbed.