Surface-Engineered Li4Ti5O12 Nanostructures for High-Power Li-Ion Batteries

Materials with high-power charge–discharge capabilities are of interest to overcome the power limitations of conventional Li-ion batteries.In this study,a unique solvothermal synthesis of Li4Ti5O12 nanoparticles is proposed by using an off-stoichiometric precursor ratio.A Li-deficient off-stoichiometry leads to the coexistence of phaseseparated crystalline nanoparticles of Li4Ti5O12 and TiO2 exhibiting reasonable high-rate performances.However,after the solvothermal process,an extended aging of the hydrolyzed solution leads to the formation of a Li4Ti5O12 nanoplate-like structure with a self-assembled disordered surface layer without crystalline TiO2.The Li4Ti5O12 nanoplates with the disordered surface layer deliver ultrahighrate performances for both charging and discharging in the range of 50–300C and reversible capacities of 156 and 113 mAh g−1 at these two rates,respectively.Furthermore,the electrode exhibits an ultrahigh-charging-rate capability up to 1200C(60 mAh g−1;discharge limited to 100C).Unlike previously reported high-rate half cells,we demonstrate a high-power Li-ion battery by coupling Li4Ti5O12 with a high-rate LiMn2O4 cathode.The full cell exhibits ultrafast charging/discharging for 140 and 12 s while retaining 97 and 66% of the anode theoretical capacity,respectively.Room-(25℃),low-(−10℃),and high-(55℃)temperature cycling data show the wide temperature operation range of the cell at a high rate of 100C.

Facile fabrication of TiO_2 nanoparticle–TiO_2 nanofiber composites by co-electrospinning–electrospraying for dye-sensitized solar cells

We report a facile method for the fabrication of TiO2 nanofiber-nanoparticle composite （FP） via. simulta- neous electrospraying and electrospinning for dye-sensitized solar cell （DSC） applications. The loading of nanoparticles on the fibers is controlled by varying their feed rates during electrospinning. The FP composites having three different particle loading are prepared by the methodology and the FP with the highest particle loading （denoted as FP-3 in the manuscript） showed the best overall efficiency of 9.15% in comparison to the other compositions of the FP （FP-2, 8.15% and FP-1, Z51%, respectively） and nanofibers （F） and nanoparticles （P） separately （7.21 and 7.81, respectively）. All the material systems are characterized by spec- troscopy, microscopy, surface area measurements and the devices are characterized by current-voltage （I-V）, incident photon-to-current conversion efficiency （IPCE）, electrochemical impedance measurements, etc. I-V, dye-loading and reflectance measurements throw light on the overall performance of the DSC devices.

WO_(3) passivation layer-coated nanostructured TiO_(2): An efficient defect engineered photoelectrode for dye sensitized solar cell

Major loss factors for photo-generated electrons due to the presence of surface defects in titanium dioxide(Ti O_2)were controlled by RF-sputtered tungsten trioxide(WO_3) passivation. X-ray photoelectron spectroscopy assured the coating of WO3 on the Ti O_2 nanoparticle layer by showing Ti 2 p, W 4 f and O 1 s characteristic peaks and were further confirmed by X-ray diffraction studies. The coating of WO_3 on the Ti O_2 nanoparticle layer did not affect dye adsorption significantly. Dye sensitized solar cells(DSSCs) fabricated using WO_3-coated Ti O_2 showed an enhancement of ~10% compared to DSSCs fabricated using pristine Ti O_2-based photo-electrodes. It is attributed to the WO_3 passivation on Ti O_2 that creates an energy barrier which favored photo-electron injection by tunneling but blocked reverse electron recombination pathways towards holes available in highest occupied molecular orbital of the dye molecules. It was further evidenced that there is an optimum thickness(duration of coating) of WO_3 to improve the DSSC performance and longer duration of WO_3 suppressed photo-electron injection from dye to Ti O_2 as inferred from the detrimental effect in short circuit current density values. RF-sputtering yields pinhole-free,highly uniform and conformal coating of WO_3 onto any area of interest, which can be considered for an effective surface passivation for nanostructured photovoltaic devices.

Synthesis and Characterization of Polymeric Composites Embeded with Silver Nanoparticles

Silver nanoparticles were synthesized by chemical reduction method. The Ag nanoparticles (AgNP) were characterized using UV-Vis spectroscopy which shows an absorption band at 420 nm confirming the formation of nanoparticles. For any practical application of the silver nanoparticles it is necessary to stabilize it which can be done by making a composite. In the present studies three polymers were chosen such that AgNP could be put to some practical use. Polyvinyl Alcohol (PVA), Polypyrrole (Ppy) and Carboxymethyl cellulose (CMC) are important for use in textiles, electronics and food/drug technologies respectively. Polymeric composites of PVA, PPy, and CMC were prepared by mixing the aqueous solutions of the respective polymers and the colloidal suspension of preformed silver nanoparticles. Various compositions containing 1% to 5% of Ag nanoparticles were prepared. Thin films of these composites were characterized by UV-Vis spectroscopy, X-ray diffraction and Scanning electron microscopy. X-ray diffraction showed the presence of the peaks at 2θ values of 38.1°, 44.2°, 64.4 and 78.2° corresponding to cubic phase of silver metal. SEM photographs revealed the presence of Ag nanoparticles of sizes varying from 40 to 80 nm. The electrical conductivity of these materials was studied using the four probe method. The conductivity was found to increase from 10–6 for control samples to 10–3 S/cm after the formation of the nanocomposites.

Parallelization of frequency domain quantum gates:manipulation and distribution of frequency-entangled photon pairs generated by a 21 GHz silicon microresonator

Harnessing the frequency dimension in integrated photonics offers key advantages in terms of scalability,noise resilience,parallelization,and compatibility with telecom multiplexing techniques.Integrated ring resonators have been used to generate frequency-entangled states through spontaneous four-wave mixing.However,state-of-the-art integrated resonators are limited by trade-offs among size,spectral separation,and efficient photon pair generation.We have developed silicon ring resonators with a footprint below 0.05 mm^(2)providing more than 70 frequency channels separated by 21 GHz.We exploit the narrow frequency separation to parallelize and independently control 34 single qubit-gates with a single set of three off-the-shelf electro-optic devices.We fully characterize 17 frequency-bin maximally entangled qubit pairs by performing quantum state tomography.We demonstrate for the first time,we believe,a fully connected five-user quantum network in the frequency domain.These results are a step towards a generation of quantum circuits implemented with scalable silicon photonics technology,for applications in quantum computing and secure communications.

Synthesis of Co3O4 Nanoparticles Wrapped Within Full Carbon Matrix as an Anode Material for Lithium Ion Batteries

A facile polyol-assisted pyro-synthesis method was used to synthesize Co3O4 nanoparticles embedded into carbon matrix without using any conventional carbon source. The surface analysis by scanning electron microscopy showed that the Co3O4 nanoparticles（-20 ± 5 nm） are tightly enwrapped within the carbon matrix. CHN analysis determined the carbon content was only 0.11% in the final annealed sample. The Co3O4@carbon exhibited high capacities and excellent cycling performance as an anode at various current rates（such as 914.4 and 515.5 mAh g^-1 at 0.25 and1.0 C, respectively, after 50 cycles; 318.2 mAh g^-1 at a high current rate of 5.0 C after 25 cycles）. This superior electrochemical performance of the electrode can be attributed to the various aspects, such as,（1） the existence of carbon matrix, which acts as a flexible buffer to accommodate the volume changes during Li^＋ion insertion/deinsertion and facilitates the fast Li^＋and electron transfer and（2） the anchoring of Co3O4 nanoparticles within the carbon matrix prevents particles agglomeration.

Recent developments in self-powered smart chemical sensors for wearable electronics

The next generation of electronics technology is purely going to be based on wearable sensing systems. Wearable electronic sensors that can operate in a continuous and sustainable manner without the need of an external power sources, are essential for portable and mobile electronic applications. In this review article, the recent progress and advantages of wearable self-powered smart chemical sensors systems for wearable electronics are presented. An overview of various modes of energy conversion and storage technologies for self-powered devices is provided. Self-powered chemical sensors (SPCS) systems with integrated energy units are then discussed, separated as solar cell-based SPCS, triboelectric nano-generators based SPCS, piezoelectric nano-generators based SPCS, energy storage device based SPCS, and thermal energy-based SPCS. Finally, the outlook on future prospects of wearable chemical sensors in self-powered sensing systems is addressed.

Alginate nanobeads interspersed fibrin network as in situ forming hydrogel for soft tissue engineering

Hydrogels are a class of materials that has the property of injectability and in situ gel formation.This property of hydrogels is manipulated in this study to develop a biomimetic bioresorbable injectable system of alginate nanobeads interspersed in fibrin network.Alginate nanobeads developed by calcium cross-linking yielded a size of 200e500 nm.The alginate nanobeads fibrin hydrogel was formed using dual syringe apparatus.Characterization of the in situ injectable hydrogel was done by SEM,FTIR and Rheometer.The developed hydrogel showed mechanical strength of 19 kPa which provides the suitable compliance for soft tissue engineering.Cytocompatibility studies using human umbilical cord blood derived mesenchymal stem cells showed good attachment,proliferation and infiltration within the hydrogel similar to fibrin gel.The developed in situ forming hydrogel could be a suitable delivery carrier of stem cells for soft tissue regeneration.

Conducting polymer PEDOT:PSS coated Co_(3)O_(4) nanoparticles as the anode for sodium-ion battery applications

Metal oxides are considered as potential anodes for sodium-ion batteries(SIBs).Nevertheless,they suffer from poor cycling and rate capability.Here,we investigate conductive polymer coating on Co_(3)O_(4)nanoparticles varying with different percentages.X-ray diffraction,electron microscopy and surface chemical analysis were adopted to analyze coated and uncoated Co_(3)O_(4)nanoparticles.Conducting polymer,poly(3,4-ethylene dioxythiophene)polystyrene sulfonate(PEDOT:PSS),has been utilized for coating.Improved specific capacity and rate capability for an optimal coating of 0.5 wt.%were observed.The 0.5 wt.%coated sample outperformed the uncoated one in terms of capacity,rate capability and coulombic efficiency.It delivered a reversible capacity of 561 mAh·g^(−1)at 100 mA·g^(−1)and maintained a capacity of 318 mAh·g^(−1)at a high rate of 1 A·g^(−1).Increasing the PEDOT:PSS coating percentage led to lower performance due to the thicker coating induced kinetic issues.Ex-situ analysis of the 0.5 wt.%coated sample after 100 cycles at 1 A·g^(−1)was characterized for performance correlation.Such a simple,cost-effective and wet-chemical approach has not been employed before for Co_(3)O_(4)as the SIB anode.

Silicon photonics phase and intensity modulators for flat frequency comb generation

Flat electro-optical frequency combs play an important role in a wide range of applications,such as metrology,spectroscopy,or microwave photonics.As a key technology for the integration of optical circuits,silicon photonics could benefit from on-chip,tunable,flat frequency comb generators.In this article,two different architectures based on silicon modulators are studied for this purpose.They rely on a time to frequency conversion principle to shape the comb envelope.Using a numerical model of the silicon traveling-wave phase modulators,their driving schemes are optimized before their performances are simulated and compared.A total of nine lines could be obtained within a 2 dB flatness,with a line-spacing ranging from 0.1 to 7 GHz.Since this tunability is a major asset of electro-optical frequency combs,the effect of segmenting the phase modulators is finally investigated,showing that the flat lines spacing could be extended up to 39 GHz by this method.

Orbital angular momentum based intra- and interparticle entangled states generated via a quantum dot source

Engineering single-photon states endowed with orbital angular momentum (OAM) is a powerful toolfor quantum information photonic implementations. Indeed, due to its unbounded nature, OAM is suitable forencoding qudits, allowing a single carrier to transport a large amount of information. Most of the experimentalplatforms employ spontaneous parametric down-conversion processes to generate single photons, evenif this approach is intrinsically probabilistic, leading to scalability issues for an increasing number of qudits.Semiconductor quantum dots (QDs) have been used to get over these limitations by producing on-demand pure and indistinguishable single-photon states, although only recently they have been exploitedto create OAM modes. Our work employs a bright QD single-photon source to generate a complete set ofquantum states for information processing with OAM-endowed photons. We first study hybrid intraparticleentanglement between OAM and polarization degrees of freedom of a single photon whose preparationwas certified by means of Hong–Ou–Mandel visibility. Then, we investigate hybrid interparticle OAM-based entanglement by exploiting a probabilistic entangling gate. The performance of our approach isassessed by performing quantum state tomography and violating Bell inequalities. Our results pave theway for the use of deterministic sources for the on-demand generation of photonic high-dimensionalquantum states.

Chitosan based metallic nanocomposite scaffolds as antimicrobial wound dressings

Chitosan based nanocomposite scaffolds have attracted wider applications in medicine,in the area of drug delivery,tissue engineering and wound healing.Chitosan matrix incorporated with nanometallic components has immense potential in the area of wound dressings due to its antimicrobial properties.This review focuses on the different combinations of Chitosan metal nanocomposites such as Chitosan/nAg,Chitosan/nAu,Chitosan/nCu,Chitosan/nZnO and Chitosan/nTiO2 towards enhancement of healing or infection control with special reference to the antimicrobial mechanism of action and toxicity.

Transplantation of engineered exosomes derived from bone marrow mesenchymal stromal cells ameliorate diabetic peripheral neuropathy under electrical stimulation

Diabetic peripheral neuropathy(DPN)is a long-term complication associated with nerve dysfunction and uncontrolled hyperglycemia.In spite of new drug discoveries,development of effective therapy is much needed to cure DPN.Here,we have developed a combinatorial approach to provide biochemical and electrical cues,considered to be important for nerve regeneration.Exosomes derived from bone marrow mesenchymal stromal cells(BMSCs)were fused with polypyrrole nanoparticles(PpyNps)containing liposomes to deliver both the cues in a single delivery vehicle.We developed DPN rat model and injected intramuscularly the fused exosomal system to understand its long-term therapeutic effect.We found that the fused system along with electrical stimulation normalized the nerve conduction velocity(57.60±0.45 m/s)and compound muscle action potential(16.96±0.73 mV)similar to healthy control(58.53±1.10 m/s;18.19±1.45 mV).Gastrocnemius muscle morphology,muscle mass,and integrity were recovered after treatment.Interestingly,we also observed paracrine effect of delivered exosomes in controlling hyperglycemia and loss in body weight and also showed attenuation of damage to the tissues such as the pancreas,kidney,and liver.This work provides a promising effective treatment and also contribute cutting edge therapeutic approach for the treatment of DPN.

Nonlinear integrated photonics

The field of nonlinear photonics is in full development. This special issue of Photonics Research takes you through the current issues of this fast-growing field of research, drawing on the current state of the art and seeking, through a selection of articles, to outline some trends for the future.