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Porous silicon nanoparticles (pSiNPs) are of increased interest for use in drug delivery systems, as catalysts, and as biomedical imaging agents. The most common synthesis of pSiNPs involves electrochemical anodization of a silicon wafer, followed by ultrasonic fracture of the resulting mesoporous film to form well-defined nanoparticles. A major source of loss in this process is the ultrasonic fracture step. This work presents a method of synthesizing gram-scale quantities of pSiNPs with high yield and high reproducibility using an ultrasonic bath equipped with a sample rotation stage and a refrigerator (4 °C) and a higher ultrasound frequency with power delivered in a pulsed modality compared with the static ultrasound "cleaning baths" commonly used for this purpose. The optimal processing conditions are determined by adjusting the pSi film mass, solvent volume, and iteration number of on/off cycles used in sonication. The approach provides pSiNPs with a narrow size distribution (∼170 nm, PDI = 0.149), higher yields (59%), and an approximately 12-fold reduction in the total processing time, allowing the preparation of gram-scale quantities of pSiNPs from single-crystal silicon wafers with high reproducibility in a single 24 h process. The performance of the produced pSiNPs is validated in a drug delivery application in which loading and release of the anthracycline drug doxorubicin are compared with pSiNPs prepared in a conventional cleaning bath ultrasonicator. [ABSTRACT FROM AUTHOR]

Photodynamic therapy (PDT) is a clinically approved minimally invasive therapy for malignant diseases. Indocyanine green (ICG) is a prominent photosensitive agent for PDT, but it has intrinsic drawbacks such as aggregation, instability, and photolytic degradation. Although numerous nanoparticle-based approaches have been studied to overcome such issues, there are still limitations such as potential immunogenicity and unprecise and inefficient delivery to the tumor. In this study, we disclosed a nanoformulation (SIWV-pSiNP-(ICG)), SIWV peptide-functionalized glioblastoma (GBM) homing, and ICG-incorporated porous silicon nanoparticles (pSiNPs). The nanoformulation demonstrated an enhanced photodynamic property under NIR light irradiation with improved stability of the incorporated ICG. The SIWV-pSiNP-(ICG) also showed significant targeting ability to the GBM cells with nontoxicity and laser-triggered ROS generation in situ. As a result, the SIWV-pSiNP-(ICG) showed superior therapeutic efficacy (anticancer efficiency) with excellent biocompatibility in the GBM xenograft mice. This work presents a novel and efficient strategy to enhance PDT efficacy for the targeted GBM therapy. [ABSTRACT FROM AUTHOR]

A hybrid composite of silver nanoparticles (AgNPs) and porous silicon microparticles (pSiMPs) was developed and applied for the computed tomography (CT) scanning of the lungs as an image-guided localization agent. We confirmed the grafting of AgNPs on oxidized pSiMPs template using various analytical equipment, including a scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS). The hybrid composite showed a high CT contrast intensity (>1000 HU) that enabled us to produce and view images of the lungs. In addition, it showed the ability to maintain a strong CT signal at the injected area of the rabbit's lungs, up to an hour, without spreading. The lack of toxicity and immune response indicated that the composite could be fully utilized as a new image-guided localization agent of CT scans for lung cancer surgery.

Achieving high signal-to-noise ratio in chemical and biological sensors enables accurate detection of target analytes. Unfortunately, below the limit of detection (LOD), it becomes difficult to detect the presence of small amounts of analytes and extract useful information via any of the conventional methods. In this work, we examine the possibility of extracting "hidden signals" using deep neural network to enhance gas sensing below the LOD region. As a test case system, we conduct experiments for H 2 sensing in six different metallic channels (Au, Cu, Mo, Ni, Pt, Pd) and demonstrate that deep neural network can enhance the sensing capabilities for H 2 concentration below the LOD. We demonstrate that this technique could be universally used for different types of sensors and target analytes. Our approach can extract new information from the hidden signals, which can be crucial for next-generation chemical sensing applications and analytical chemistry.

Crystalline Si and III-V compound semiconductors with appropriate band edge positions for the reduction of water have been widely utilized in photoelectrochemical (PEC) cells for the hydrogen evolution reaction (HER). However, the high cost of manufacturing those PEC cell photoabsorbers makes it difficult to achieve cost-effective hydrogen production. To overcome this issue, a new approach to fabricate a photoabsorber with low cost yet high performance for the HER is highly necessary. Here, we present a controlled fracture method, the so-called spalling process, to fabricate a cost-effective thin semiconductor applicable to the PEC HER. Using this method, a wafer-scale thin Si, whose thickness can be controlled from a few micrometers to sub-50 μm, was fabricated from a thick Si mother substrate without material loss. Pt nanoparticle-decorated 16 μm thick spalled Si with an np + rear junction exhibited an HER onset potential of 332 mV (vs reversible hydrogen electrode (RHE)) and a photocurrent density of 20.1 mA cm -2 at 0 V (vs RHE), which are the best performances among previously reported planar-type thin Si-based photocathodes. Finally, we demonstrated that 20 μm thick GaAs could also be successfully fabricated by the spalling process, while exhibiting a PEC HER performance comparable to 350 μm thick bulk GaAs.

Because of their low price, design flexibility, and sustainability, organic-based electrode materials are considered one of the most promising next-generation alternatives to inorganic materials in Li-ion batteries. However, a clear understanding of the changes in the molecular crystal structure during Li-ion insertion/extraction and its relationship to excess capacity (over theoretical capacity) is still lacking. Herein, the tetralithium 1,2,4,5-benzenetetracarboxylate (Li 4 C 10 H 2 O 8 , Li 4 BTC) salt was prepared using a simple ion-exchange reaction at room temperature and under solvothermal conditions (100 °C). The solvothermally synthesized salt (Li 4 BTC-S) exhibited a well-ordered nanosheet morphology, whereas the room-temperature salt (Li 4 BTC-R) was comprised of irregularly shaped particles. During the cycling of Li 4 BTC-S, molecular rearrangement occurred to reduce the stress caused by repeated Li-ion insertion/extraction, resulting in a change in the crystal structure from triclinic to monoclinic and an increased free volume. This contributed to an increase in the reversible capacity to 1016 mAh g -1 during the initial 25 cycles at 0.1 A g -1 , and finally the capacity stabilized at ca. 600 mAh g -1 after 100 cycles, which is much higher than its theoretical capacity (234 mAh g -1 ). Compared with Li 4 BTC-R, Li 4 BTC-S delivered a higher reversible capacity of 190 mAh g -1 at a high current density of 2 A g -1 , with an excellent long-term cyclability of up to 1000 cycles, which was attributed to the straight free volume columns and the low-charge-transfer limitation.

Polymeric binder is extremely important for Si-based anode in lithium-ion batteries due to large volume variation during charging/discharging process. Here, natural rubber-incorporated chitosan networks were designed as a binder material to obtain both adhesion and elasticity. Chitosan could strongly anchor Si particles through hydrogen bonding, while the natural rubber could stretch reversibly during the volume variation of Si particles, resulting in high cyclic performance. The prepared electrode exhibited the specific capacities of 1350 mAh/g after 1600 cycles at the current density of 8 A/g and 2310 mAh/g after 500 cycles at the current density of 1 A/g. Furthermore, the cycle test with limiting lithiation capacity was conducted to study the optimal binder properties at varying degree of the volume expansion of silicon, and it was found that the elastic property of binder material was strongly required when the large volume expansion of Si occurred.

In this study, we demonstrate that lignin, which constitutes 30-40 wt % of the terrestrial lignocellulosic biomass and is produced from second generation biofuel plants as a cheap byproduct, is an excellent precursor material for sodium-ion battery (NIB) anodes. Because it is rich in aromatic monomers that are highly cross-linked by ether and condensed bonds, the lignin material carbonized at 1300 °C (C-1300) in this study has small graphitic domains with well-developed graphene layers, a large interlayer spacing (0.403 nm), and a high micropore surface area (207.5 m 2 g -1 ). When tested as an anode in an NIB, C-1300 exhibited an initial Coulombic efficiency of 68% and a high reversible capacity of 297 mA h g -1 at 50 mA g -1 after 50 cycles. The high capacity of 199 mA h g -1 at less than 0.1 V with a flat voltage profile and an extremely low charge-discharge voltage hysteresis (<0.03 V) make C-1300 a promising energy-dense electrode material. In addition, C-1300 exhibited an excellent high-rate performance of 116 mA h g -1 at 2.5 A g -1 and showed stable cycling retention (0.2% capacity decay per cycle after 500 cycles). By comparing the properties of the lignin-derived carbon with oak sawdust-derived and sugar-derived carbons and a low-temperature carbonized sample (900 °C), the reasons for the excellent performance of C-1300 were determined to result from facilitated Na + -ion transport to the graphitic layer and the microporous regions that penetrate through the less defective and enlarged interlayer spacings.

Stable and robust open-circuit voltage (V OC ) is essential to achieve a long lifetime for polymer solar cells (PSCs). Here, we investigate the V OC burn-in loss mechanism on the basis of the analysis of electroluminescence quantum efficiency (EQE EL ) and impedance measurements in amorphous PSCs, with an inverted structure having different electron transport layers (ETLs) of ZnO nanoparticles (NPs) and the sol-gel processed ZnO layer. We found that both charge recombination and energetic disorder account for a substantial proportion of the V OC burn-in loss. Moreover, varying the ETL significantly affected the degree of V OC burn-in loss, although relative contribution of these two factors remained constant. To accurately extract charge recombination-induced V OC loss, we applied a novel yet effective method that relates the EQE EL of PSCs to charge recombination-induced V OC loss. Additional analyses, including those focused on light intensity (P light )-dependent V OC and density of states, will provide an inclusive perspective on the degradation mechanism of V OC and development of stable PSCs.

Atomic-scale direct probing of active sites and subsequent elucidation of the structure-activity relationship are important issues involving oxide-based electrocatalysts to achieve better electrochemical conversion efficiency. By generating Ruddlesden-Popper (RP) two-dimensional homologous faults via simple control of the cation nonstoichiometry in LaNiO 3 thin films, we demonstrate that strong tetragonal distortion of [NiO 6 ] octahedra is induced by more than 20% elongation of Ni-O bonds in the faults. In addition to direct visualization of the elongation by scanning transmission electron microscopy, we identify that the distorted [NiO 6 ] octahedra in the faults show considerably higher electrocatalytic activities than other surface sites during the electrochemical oxygen evolution reaction. This unequivocal evidence of the octahedral distortion and its impact on electrocatalysis in LaNiO 3 suggests that the formation of RP-type faults can provide an efficient way to control the octahedral geometry and thereby remarkably enhance the oxygen catalytic performance of perovskite oxides.

We report the influence of post-treatment via the external pressure on the device performance of quantum dot (QD) solar cells. The structural analysis together with optical and electrical characterization on QD solids reveal that the external pressure compacts QD active layers by removing the mesoscopic voids and enhances the charge carrier transport along QD solids, leading to significant increase in JSC of QD solar cells. Increasing the external pressure, by contrast, accompanies reduction in FF and VOC, yielding the trade-off relationship among JSC and FF and VOC in PCE of devices. Optimization at the external pressure in the present study at 1.4-1.6 MPa enables us to achieve over 10% increase in PCE of QD solar cells. The approach and results show that the control over the organization of QDs is the key for the charge transport properties in ensemble and also offer simple yet effective mean to enhance the electrical performance of transistors and solar cells using QDs.

We investigate the use of chitosan (CS) as a new cross-linkable and water-soluble binder for the Si anode of Li-ion batteries. In contrast to the traditional binder utilizing a hydrogen bond and/or van der Waals force-linked anode electrodes, CS can easily form a 3D network to limit the movement of Si particles through the cross-linking between the amino groups of CS and the dialdehyde of glutaraldehyde (GA). Chemical, mechanical, and morphological analyses are conducted by Fourier transform infrared spectroscopy, tensile testing, and scanning electron microscopy. The cross-linked Si/CS-GA anode exhibits an initial discharge capacity of 2782 mAh g(-1) with a high initial Coulombic efficiency of 89% and maintained a capacity of 1969 mAh g(-1) at the current density of 500 mA g(-1) over 100 cycles.

To exploit the benefits of nanostructuring for enhanced hydrogen evolution reaction (HER), we employed coaxial electrospinning to synthesize single-layered WS2 nanoplates anchored to hollow nitrogen-doped carbon nanofibers (WS2@HNCNFs) as efficient electrocatalysts. For comparison, bulk WS2 powder and single layers of WS2 embedded in nitrogen-doped carbon nanofibers (WS2@NCNFs) were synthesized and electrochemically tested. The distinctive design of the WS2@HNCNFs enables remarkable electrochemical performances showing a low overpotential with reduced charge transfer resistance, a small Tafel slope, and excellent durability. The experimental results highlight the importance of nanostructure engineering in electrocatalysts for enhanced HER.

Despite recent advances in molecular simulation technologies, analysis of high-molecular-weight structures is still challenging. Here, we propose an automated model reduction procedure aiming to enable modular analysis of these structures. It employs a component mode synthesis for the reduction of finite element protein models. Reduced models may consist of real biological subunits or artificial partitions whose dynamics is described using the degrees of freedom at the substructural interfaces and a small set of dominant vibrational modes only. Notably, the proper number of dominant modes is automatically determined using a novel estimator for eigenvalue errors without calculating the reference eigensolutions of the full model. The performance of the proposed approach is thoroughly investigated by analyzing 50 representative structures including a crystal structure of GroEL and an electron density map of a ribosome.

We present a systematic derivation of double-hybrid density functional (DHDF) based on the polynomial series expansion of adiabatic connection formula in the closed interval λ = [0,1] without a loss of generality. Because of the tendency of Wλ having a small (but not negligible) curvature at equilibrium, we first evaluate the chemical validity of quadratic approximation for Wλ using the large GMTKN30 benchmark database. The resulting functional, obtained analytically and denoted by quadratic adiabatic connection functional-PT2 (QACF-2), is found to be robust and accurate (2.35 kcal/mol of weighted total mean absolute deviation error, WTMAD), comparable or slightly improved compared to other flavors of existing parameter-free DHDFs (2.45 or 3.29 kcal/mol for PBE0-2 or PBE0-DH, respectively). The nonlocal expansion coefficients obtained for the current QACF-2 (aHF = 2/3, aPT2 = 1/3) also offer some interesting observation, in that the latter analytical coefficients are very similar to the empirically optimized coefficients in some of the best DHDFs today with high accuracy (1.5 kcal/mol). Effects of quadratic truncation in QACF-2 have been further assessed and justified by estimating the higher-order corrections to be as much as 0.54 kcal/mol. The present derivation and numerical experiments suggest that the quadratic λ dependence, despite its simplicity, is a surprisingly good approximation to the adiabatic connection that can serve as a good starting point for further development of accurate parameter-free density functionals.

In this study, we developed a novel inorganic thin film solar cell configuration in which bulk heterojunction was formed between indium tin oxide (ITO) nanorods and CuInS(2) (CIS). Specifically, ITO nanorods were first synthesized by the radio frequency magnetron sputtering deposition method followed by deposition of a dense TiO(2) layer and CdS buffer layer using atomic layer deposition and chemical bath deposition method, respectively. The spatial region between the nanorods was then filled with CIS nanoparticle ink, which was presynthesized using the colloidal synthetic method. We observed that complete gap filling was achieved to form bulk heterojunction between the inorganic phases. As a proof-of-concept, solar cell devices were fabricated by depositing an Au electrode on top of the CIS layer, which exhibited the best photovoltaic response with a V(oc), J(sc), FF, and efficiency of 0.287 V, 9.63 mA/cm(2), 0.364, and 1.01%, respectively.

Purification is a widely used technique to calculate idempotent density matrices from a Hamiltonian in large-scale electronic structure calculations. However, the initial guess of a density matrix usually contains large errors, which require many iterations to remove them, using standard recursive schemes such as those derived by McWeeny or Holas. In this Letter, we propose a way to obtain a converged density matrix much more rapidly by removing the stability conditions that the functions have fixed points and vanishing derivatives at 0 and 1, assumptions usually made in most traditional purification methods. That is, by extending the recursive function space, which gives the approximated step function via the generalized nonpurifying intermediate functions, and optimizing them, we reduce the purification cost approximately by a factor of 1.5 compared to grand canonical purification algorithms for the linear alkanes, diamondoid, and a protein endothelin that has a very small band gap.

Periodically polarity inverted (PPI) ZnO templates were fabricated using molecular beam epitaxy by employing MgO buffer layers. The polarity of ZnO film was controlled by the transformation of crystal structure from hexagonal to rocksalt due to the thickness of the MgO buffer layers. The polarity of ZnO in the PPI template was confirmed by AFM and PRM measurement. Higher growth rate and lower current value under positive supplied voltage in the region of Zn-polar were measured with comparing to that of O-polar. Holographic lithographic technique was employed for the realization of submicron pattern of periodical inverted polar ZnO over large area. After reaction using a carbothermal reduction, spatially well-separated ZnO nanorods with pitch of submicron were only observed in the Zn-polar regions. The possible reason for the difference of surface characteristics was considered as being due to the configuration of dangling bonds according to polarity.

A new coating process is described (deposition from two immiscible supercritical phases, or DISP) in which a solution of supercritical carbon dioxide (scCO2) with a desired solute is displaced by supercritical helium (scHe). After depressurization, the solute is deposited on substrates initially submerged in the coating solvent. Micron-sized particles and thin films of sucrose octaacetate (SOA) were formed on silicon wafer substrate coupons from DISP at relatively low temperatures and pressures (< or = 6500 psi and < or = 60 degrees C). The particle size, film thickness, and morphology of SOA were characterized as a function of coating conditions-solution concentrations, withdrawal velocities, and pressures. Particles in the range of 1-14 microm in diameter were deposited at low solute concentrations (< or = 0.2 wt % at 4500 psi), whereas films in the range of 0.1-0.5 microm in thickness were deposited at higher solute concentrations (> or = 1.5 wt % at 4500 psi). Particle sizes decreased with increasing displacement velocity and increasing pressure. Estimates of characteristic times for diffusion and nucleation indicate that DISP is a diffusion-limited process. Optical microscopy and atomic force microscopy (AFM) were used to characterize film morphology, including defect formations and film roughness. Highly uniform films with low root-mean-square (RMS) roughness (approximately 10 angstroms) were obtained at a low displacement velocity of 0.0035 cm/s, while ring-like defect structures were observed in films deposited at a higher displacement velocity of 0.035 cm/s. The film thickness and morphology of the films deposited from DISP were compared with films from normal dip coating with typical organic solvents (acetone and toluene). Films deposited from scCO2 by DISP were much thicker, more uniform, and exhibited much fewer drying defects and lower RMS roughness compared with films from the organic solvents.

Ultrathin organic films of sucrose octaacetate (SOA) were deposited on 12.5 cm diameter silicon wafer substrates using high-pressure free meniscus coating (hFMC) with liquid CO2 (l-CO2) as a coating solvent. The dry film thickness across the wafer and the morphology of deposited films were characterized as a function of coating conditions-withdrawal velocity, solution concentration, and evaporation driving force (deltaP). When no evaporation driving force was applied (deltaP = 0), highly uniform films were deposited with thickness in the range of 8-105 angstroms over the entire concentration range (3-11 wt%). Uniform films were also obtained at low concentrations (3-5 wt%) with a low evaporation driving force (deltaP = 0.0138 MPa). However, films deposited at medium to high concentrations (7-11 wt%) were thicker (110-570 angstroms) and less uniform, with larger nonuniformities at higher applied evaporation driving forces. Optical microscopy and atomic force microscopy (AFM) were used to characterize film morphology including drying defects and film roughness. Films deposited without evaporation had no apparent drying defects and very low root-mean-square (RMS) roughness (1.4-3.8 angstroms). Spinodal-like dewetting morphologies including holes with diameters in the range of 100-300 nm, and surface undulations were observed in films deposited at medium concentration (7 wt%) and low deltaP (0.0138-0.0276 MPa). At higher concentrations and higher evaporative driving forces, spinodal-like dewetting morphologies disappeared but concentric ring defect structures were observed with diameters in the range 20-125 microm. The film thickness and morphology of SOA films deposited from 1-CO2 hFMC were compared to those deposited from toluene and acetone under normal dip coating. Films deposited from l-CO2 hFMC were much thinner, more uniform, and exhibited much fewer drying defects and lower RMS roughness.