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This comprehensive review highlights the recent technological advancements in the realm of polymer-modified porous silicon (PSi) biosensors, mainly over the past two years. The cost-effective fabrication process and high internal surface area, tuneable pore size, and photonic properties make PSi a compelling transducing substrate for biosensing applications across diverse research fields. Notably, there has been a significant trend in the last few years toward increasing polymers' utilization for modifying porous silicon features. This strategic use of polymers aims to enhance the sensitivity and specificity of biosensors, catering to a wide array of targets of interest. The conjugation of polymers with PSi represents a noteworthy technological advancement, contributing significantly to refining biosensor performances in terms of target detection, selectivity, and stability. This review offers a comprehensive overview of recent developments, elucidating the distinctive features of optical biosensors based on polymer-modified PSi, with particular attention to the evolving role of polymers in augmenting sensor capabilities. [Display omitted] • Hybrid porous silicon-based optical sensors. • Optical quantification of small analytes. • Enhanced detection features by polymer properties. • Next generation of organic-inorganic optical transducers. [ABSTRACT FROM AUTHOR]

With the advent of silicon‐based semiconductors, a plethora of previously unknown technologies became possible. The development of lightweight low‐dimensional organic semiconductors followed soon after. However, the efficient charge/electron transfers enabled by the non‐porous 3D structure of silicon is rather challenging to be realized by their (metal‐)organic counterparts. Nevertheless, the demand for lighter, more efficient semiconductors is steadily increasing resulting in a growing interest in (metal‐)organic semiconductors. These novel materials are faced with a variety of challenges originating from their chemical design, their packing and crystallinity. Although the effect of molecular design is quite well understood, the influence of dimensionality and the associated change in properties (porosity, packing, conjugation) is still an uncharted area in (metal‐)organic semiconductors, yet highly important for their practical utilization. In this Minireview, an overview on the design and synthesis of porous semiconductors, with a particular emphasis on organic semiconductors, is presented and the influence of dimensionality is discussed. [ABSTRACT FROM AUTHOR]

Mesoporous nanoparticles have a larger surface area and therefore, suitable for dye‐sensitised solar cells and photocatalytic applications. This Letter presents the analysis of solvothermal derived as‐prepared TiO2 and doped TiO2 nanocrystals by utilising acetone as the solvent. The as‐prepared and doped TiO2 nanoparticles endorsed the presence of anatase phase along with the slightly deviated diffraction peaks with the reduced crystallite size as a result of doping. Surface morphology analyses evidenced the mesoporous microspheres of nanoparticles, whereas the stoichiometry study exhibited the elementary peaks in the as‐prepared and doped samples. The estimated optical bandgaps are found to be 2.68, 2.92, 2.48 and 2.88 eV in accordance with the doped TiO2 with copper, tin, barium and zinc–magnesium as compared to 3.16 eV of TiO2. Doped samples evidenced the enhanced scattering capability, whereas tin and zinc–magnesium co‐doped samples demonstrated the highest diffuse reflectance in a broad wavelength range from 550 to 800 nm. [ABSTRACT FROM AUTHOR]

Arguably the most controllable way to control the charge density in various semiconductors, is by electrochemical doping. However, electrochemically injected charges usually disappear within minutes to hours, which is why this technique is not yet used to make semiconductor devices. In this manuscript, electrochemical doping of different semiconductor films (ZnO Quantum Dots (QDs), PbS QDs, and P3DT) is investigated in various high melting‐point nitrile‐based solvents. It is shown that by charging the semiconductors at elevated temperatures, then cooling down to room temperature where these solvents are frozen, the doping stability increases immensely. Measurements performed in cyanoacetamide show that ion transport is entirely halted at room temperature, and that the n‐type conductivity is stable for days, and only drops marginally (≈10%) in several weeks. For p‐doped P3DT films, the conductivity is even completely stable during the entire 76 days of the measurement. In an ambient atmosphere, the p‐type doping is stable, while the n‐type doping disappears in several hours, as electrons react with molecular oxygen. Finally, a pn‐junction diode made of a PbS QD film is demonstrated. These results highlight the possibility of using solidified electrolytes for electrochemical doping and for obtaining semiconductor devices wherein the doping density is controlled electrochemically. [ABSTRACT FROM AUTHOR]

This work examined the possibility of overcoming narrow band optical absorption of organic dyes in the range of 350–700nm via surface plasmon effect mediated by RF‐sputtered tungsten (W) thin film on mesoporous TiO2 for dye‐sensitised solar cells (DSSCs) application. The UV–visible spectroscopic measurement showed optical absorption of W‐film in the spectral range of 350–700nm with a dominant characteristic feature in the range of 350–550nm. W‐thin film‐coated TiO2 was used as an electron acceptor in DSSCs and observed ∼28% enhancement in short circuit current density compared to that of in a pristine TiO2‐based DSSC which did not use W‐thin film on TiO2. It is attributed to the local field‐induced enhancement in optical absorption which resulted in improved exciton generation and effective charge transport in DSSCs enabled by W‐thin film coating onto mesoporous TiO2. [ABSTRACT FROM AUTHOR]

Hierarchical porous zinc oxide (ZnO)/silver (Ag) microspheres were prepared by two‐step method. The porous ZnO microspheres were prepared firstly, and then Ag nanoparticles were evenly anchored on the surface of ZnO microspheres by Sn2+ activation method. The results show that ZnO is wurtzite phase, and Ag particles are only coated on the surface of ZnO microspheres. Compared with pure ZnO, there are two obvious absorption peaks of Ag‐doped ZnO, which corresponds to the ultraviolet absorption peak of ZnO and the plasma resonance absorption peak of Ag, respectively. The intensities of photoluminescence peak of ZnO/Ag microspheres are significantly lower than that of pure ZnO. Moreover, ZnO/Ag microspheres show higher photocatalytic activity than ZnO, which may be attributed to the existence of highly dispersed Ag. [ABSTRACT FROM AUTHOR]

Abstract The optical scattering properties of porous polyimide (PI) films were investigated for the light-extraction layer in organic light-emitting diodes (OLEDs). By adjusting mixing ratios of different non-solvents during the immersion precipitation process, the light scattering at the generated porous PIs can be precisely tuned. Analyzed from the final OLED devices based on prepared scattering substrates, we found that the light-output characteristics of fabricated devices are correlated with the optical scattering properties, which depends on both the size of generated pores inside porous PIs and the surface roughness at the air-interface. From the help of Mie scattering and Surface scattering simulations, a systematic approach has been performed to explain the influence of the generated micro-structure on both the optical scattering and OLED-performance. Graphical abstract Image 1 Highlights • Porous light-extraction layers for OLEDs with coated polyimides by immersion precipitation. • Fine control of optical scattering properties through tuning mixing ratios of two non-solvents. • Tuning capabilities of light-outcoupling efficiency and angular emission property in OLEDs. • Systematic approach to correlate optical scattering of porous films with OLED performance. • Analysis of influences of the pore-structures using both Mie scattering and surface scattering. [ABSTRACT FROM AUTHOR]

Abstract As researchers can control the nanostructure of the nanoporous membrane based on block copolymer precursors, it is considered to be an ideal device for separation and purification. However, the challenge still remains to make ultrathin, economic, nanopore sized and charged isoporous membranes without post-treatment. Hence, a simple, energy saving and sacrificial layer free technique was adopted to bridge the gap between the uniformly spread PS- b -PAA nanospheres and the ultrathin, negatively charged nanoporous membrane. The flux of the membrane is as high as 350 L m−2 h−1 bar−1, while the effective pore size is only ca. 8 nm. It can separate not only the nanoparticles based on their size differences, but can also separate similarly sized proteins based on the charge differences efficiently. Moreover, nanofibers and lamellae formed nanoporous membranes have now been fabricated. The effective pore size can be customized, and can even be smaller than 1.5 nm for the lamellae formed membrane. Graphical abstract Nanopore sized membranes based on block copolymer micelles, i.e. , nanospheres, nanofibers and lamellae were fabricated in this work. These membranes exhibited higher permeability and sieving performance fx1 [ABSTRACT FROM AUTHOR]

High efficiency, lightweight, and tunable microwave absorbing materials have drawn tremendous attention. Here, we have synthesized layered GeP5 bulk at high temperature and high pressure. Then, the GeP5 nanosheets are obtained by an efficient liquid-phase exfoliation method and display excellent microwave absorption performance as a microwave absorber. The reflection loss (RL) can achieve below −10 dB in a wide range of thicknesses and microwave frequencies. For further meeting the lightweight demand of microwave absorption materials, porous germanium (GeP5-570) is obtained from GeP5 via the annealing treatment. Microwave absorption characteristics can be significantly improved after annealing treatment. The minimum RL values of porous germanium (GeP5-570) can reach −37.8 dB at a microwave frequency of 4.7 GHz under a thickness of 2.9 mm. The effective absorption bandwidth (RL< −10 dB) of GeP5-570 is 11.8–14.3 GHz with a thickness of 1.2 mm. In addition, the RL value can attain −20 dB in the frequency range of 3.8–16.1 GHz with various thicknesses from 1.0 to 3.5 mm. [ABSTRACT FROM AUTHOR]

Hybrid metal halide semiconductors are a unique family of materials with immense potential for numerous applications. For this to materialize, environmental stability and toxicity deficiencies must be simultaneously addressed. We report here a porous, visible light semiconductor, namely, (DHS)Bi 2 I 8 (DHS = [2.2.2] cryptand), which consists of nontoxic, earth-abundant elements, and is water-stable for more than a year. Gas- and vapor-sorption studies revealed that it can selectively and reversibly adsorb H 2 O and D 2 O at room temperature (RT) while remaining impervious to N 2 and CO 2 . Solid-state NMR measurements and density functional theory (DFT) calculations verified the incorporation of H 2 O and D 2 O in the molecular cages, validating the porous nature. In addition to porosity, the material exhibits broad band-edge light emission centered at 600 nm with a full width at half-maximum (fwhm) of 99 nm, which is maintained after 6 months of immersion in H 2 O. Moreover, (DHS)Bi 2 I 8 exhibits bacteriocidal action against three Gram-positive and three Gram-negative bacteria, including antibiotic-resistant strains. This performance, coupled with the recorded water stability and porous nature, renders it suitable for a plethora of applications, from solid-state batteries to water purification and disinfection.

The pure and Tb-doped In2O3 beaded-porous nanotubes (BPNTs) are fabricated by simple electrospinning method. The crystal phase, morphology and chemical composition of the obtained samples were analyzed by characteristic techniques (XRD, FE-SEM, TEM, EDS, XPS, etc.). The mechanism of forming BPNTs structure was studied, and phase separation plays a key role in the process of formation. A series of sensing tests toward formaldehyde gas showed that 6 mol% Tb-doped In2O3 BPNTs exhibited the best sensing performance: high response (75-50 ppm), shorter response and recovery times (2 s and 12 s), low limit of detection (LOD, 1.27-100 ppb), good selectivity and long-term stability, etc. The significantly improved gas sensing properties were mainly resulted from their high surface basicity, enriched defects (oxygen vacancies), small crystallite size and complex porous structures. [ABSTRACT FROM AUTHOR]

Copyright of Nanosistemi, Nanomateriali, Nanotehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Deep eutectic mixtures were deployed for the preparation of porous layered [Sn3Se7]n2n− single crystals. The perforation on the layers accentuates the negative temperature dependence of its band gap, resulting in remarkable thermochromic performance. Substitution of the hydroxo group by the methyl group provides an enhanced hydrophobicity for the organic template, leading to an anhydrous product with a remarkably improved thermal stability and thus reversible thermochromic properties. [ABSTRACT FROM AUTHOR]

Copyright of Nanosistemi, Nanomateriali, Nanotehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this work, CdS films were obtained on the technology of chemical surface deposition on porous semiconductor substrates. The morphology and chemical composition of the obtained structures were studied. The possibility of using CdS/porous-Si/p-Si heterostructures as photovoltaic solar energy converters is considered. [ABSTRACT FROM AUTHOR]

Palladium doping enhances the hydrogen storage capacity of nanoporous carbons. The purpose of this work is to asses the effect of the carbonaceous support on the adsorption of hydrogen on Pd clusters. Hydrogen adsorbs on Pd clusters following two channels: molecular adsorption and dissociative chemisorption. These two adsorption channels are investigated on free Pd clusters and Pd clusters supported on pristine and defective (with vacancies) graphene using the Density Functional Formalism. Pd 6 is taken as case study. Free Pd 6 can adsorb twelve hydrogen molecules in the molecular form, a number higher than the nine and eight molecules that can be adsorbed on the cluster supported on pristine graphene and on a graphene vacancy, respectively. However the most stable adsorption channel is, in all cases, the dissociative chemisorption of hydrogen. As the cluster is being loaded with hydrogen, there is a competition between the two adsorption channels. Pd 6 supported on a graphene vacancy is able to dissociate three hydrogen molecules, whereas the free cluster can dissociate up to seven molecules. In both cases, six additional molecules can be adsorbed in the molecular form. The higher saturation limit obtained for the free clusters is explained in terms of the steric and chemical effects of the supporting layer. These effects are of primarily importance to asses the role of the Pd dopant on the adsorption and storage of hydrogen on nanoporous carbons. [ABSTRACT FROM AUTHOR]

Use of porous GaP is proposed as substrates for supercapacitors. Porous substrates are prepared by electrochemical etching. A method of producing of porous GaP is presented. Analysis of the morphology of resulting structures based on porous GaP is investigated. Obtained materials were assayed to evaluate the possibility of replacing activated carbon for electrodes of supercapacitors. [ABSTRACT FROM AUTHOR]

We present a study on the fraction of porosity for dealloyed nanoporous Au leafs. Nanoporous Au is attracting great scientific interest due to its peculiar plasmonic properties and the high exposed surface (∼10 m 2 /g). As examples, it was used in prototypes of chemical and biological devices. However, the maximization of the devices sensitivity is subjected to the maximization of the exposed surface by the nanoporous Au, i. e. maximization of the porosity fraction. So, we report on the analyses of the porosity fraction in nanoporous Au leafs as a function of the fabrication process parameters. We dealloyed 60 μm-thick Au 23 Ag 77 at.% leafs and we show that: a) for dealloying time till to 6 h, only a 450 nm-thick surface layer of the leafs assumes a nanoporous structure with a porosity fraction of 32%. For a dealloying time of 20 h the leafs result fragmented in small black pieces with a porosity fraction increased to 60%. b) After 600 °C-30 minutes annealing of the previous samples, the nanopores disappear due to the Au/residual Ag inter-diffusion. c) After a second dealloying process on the previously annealed samples, the surface nanoporous structure is, again, obtained with the porosity fraction increased to 50%. [ABSTRACT FROM AUTHOR]

Pores in single crystalline semiconductors come in many forms (e.g., pore sizes from 2 nm to > 10 µm; morphologies from perfect pore crystal to fractal) and exhibit many unique properties directly or as nanocompounds if the pores are filled. The various kinds of pores obtained in semiconductors like Ge, Si, III-V, and II-VI compound semiconductors are systematically reviewed, emphasizing macropores. Essentials of pore formation mechanisms will be discussed, focusing on differences and some open questions but in particular on common properties. Possible applications of porous semiconductors, including for example high explosives, high efficiency electrodes for Li ion batteries, drug delivery systems, solar cells, thermoelectric elements and many novel electronic, optical or sensor devices, will be introduced and discussed.

Abstract The growth mechanism of currentline-oriented pores in n-type InP has been studied by Fast-Fourier-Transform Impedance Spectroscopy (FFT IS) applied in situ during pore etching and by theoretical calculations. Several pore growth parameters could thus be extracted in situ that are otherwise not obtainable. These include the space-charge-region (SCR) width, the SCR potential, the capacitance at the pore tips, and the avalanche breakdown field strength. It could be demonstrated that the system adjusts itself in such a way that the potential across the space-charge-region at the pore tips is kept constant within a certain bandwidth of the applied potential. This provides for a constant field strength at the pore tips, ensuring that avalanche breakdown occurs, generating the necessary holes for the electrochemical dissolution of InP.

We review our approach to the generation of nanoporous materials, both semiconducting and metallic, which leads to the existence of nanopores within the bulk structure. This method, which we have named as the expanding lattice method, is a novel transferable approach which consists first of constructing crystalline supercells with a large number of atoms and a density close to the real value and then lowering the density by increasing the volume. The resulting supercells are subjected to either ab initio or parameterized—Tersoff-based—molecular dynamics processes at various temperatures, all below the corresponding bulk melting points, followed by geometry relaxations. The resulting samples are essentially amorphous and display pores along some of the “crystallographic” directions without the need of incorporating ad hoc semiconducting atomic structural elements such as graphene-like sheets and/or chain-like patterns (reconstructive simulations) or of reproducing the experimental processes (mimetic simulations). We report radial (pair) distribution functions, nanoporous structures of C and Si, and some computational predictions for their vibrational density of states. We present numerical estimates and discuss possible applications of semiconducting materials for hydrogen storage in potential fuel tanks. Nanopore structures for metallic elements like Al and Au also obtained through the expanding lattice method are reported.

A nanoporous Pirani sensor based on anodic aluminum oxide (AAO) is proposed, and the quantitative relationship between the performance of the sensor and the porosity of the AAO membrane is characterized with a theoretical model. The proposed Pirani sensor is composed of a metallic resistor on a suspended nanoporous membrane, which simultaneously serves as the sensing area and the supporting structure. The AAO membrane has numerous vertically-tufted nanopores, resulting in a lower measurable pressure limit due to both the increased effective sensing area and the decreased effective thermal loss through the supporting structure. Additionally, the suspended AAO membrane structure, with its outer periphery anchored to the substrate, known as a closed-type design, is demonstrated using nanopores of AAO as an etch hole without a bulk micromachining process used on the substrate. In a CMOS-compatible process, a 200 µm 200 µm nanoporous Pirani sensor with porosity of 25% was capable of measuring the pressure from 0.1 mTorr to 760 Torr. With adjustment of the porosity of the AAO, the measurable range could be extended toward lower pressures of more than one decade compared to a nonporous membrane with an identical footprint. [ABSTRACT FROM AUTHOR]

A new material platform is presented to manipulate heat and charge transportation in steady-state conditions. More precisely, we investigate the conceptual realization of a concentric composite made of the same isotropic and homogeneous semiconductor material with layers of different porosity, and show the possibility of a simultaneous cloaking performance in such a device for both heat flux and electric current without disturbing external fields. The background medium in the composite is a porous material with a periodical 3D cubic lattice of spherical hollow pores while the cylindrical shell is made from the same bulk material with zero porosity. A sound analytical expression is found for the volume fraction of the pores at which bi-functional cloaking effect can be realized. To validate our theoretical results, we also demonstrate the temperature and heat flux profiles as well as the voltage and current profiles in numerical simulations for a composite consisting of bulk (cylindrical shell) and porous (background) n-type silicon layers. [ABSTRACT FROM AUTHOR]

The integration of nano- and microfluidic technologies enables the construction of tunable interfaces to physical and biological systems across relevant length scales. The ability to perform chemical manipulations of miniscule sample volumes is greatly enhanced through these technologies and extends the ability to manipulate and sample local fluidic environments at subcellular, cellular, and community or tissue scales. Here, the authors describe the development of a flexible surface micromachining process for the creation of nanofluidic channel arrays integrated within SU-8 microfluidic networks. The use of a semiporous, silicon rich, silicon nitride structural layer allows for a rapid removal of the sacrificial silicon dioxide during the nanochannel fabrication. Nanochannel openings that form the interface to biological samples are customized using focused ion beam milling. The compatibility of these interfaces with on-chip microbial culture is demonstrated. [ABSTRACT FROM AUTHOR]

The authors report on Coulomb blockade effect in the PtSi/porous Si Schottky barrier. A model of two‐dimensional multi‐tunnelling junction (2D‐MTJ) can explain the blockade characteristic of this barrier. Using the SIMON simulator, the electrical characteristics of the proposed model were investigated. The results show that simulated current–voltage curves achieve a reasonable fit with the measured data and the present model can be used to study the PtSi/porous Si Schottky barrier behaviour. In accordance with both the studies, Coulomb blockade phenomenon is observed in current oscillation and single‐electron effect of this device at low temperatures (5 K) is justified using the 2D‐MTJ model. In addition, it indicates that by increasing the current value with temperature and for high drain voltages, PtSi/porous Si Schottky barrier behaves like a single island single‐electron tunnelling (SET) junction as previously reported by Raissi , et al. [ABSTRACT FROM AUTHOR]

We present the chemical synthesis of hexaniobate nanotubes using two routes, (1) starting material K4Nb6O17 and (2) parent material of H4Nb6O17 via ion exchange. The as-synthesized materials were exfoliated by adjusting the pH to 9-10 using tetra-n-butylammonioum hydroxide (TBA+OH-), leading to a formation of hexaniobate nanotubes. In order to understand morphology a full characterization was conducted using SEM, HRTEM, BET and powder-XRD. The photocatalytic activity was evaluated using photolysis method using Bromocresol Green (BG) and Methyl Orange (MO) as model contaminants. Results indicate a nanotube porous oxide with large porous and surface area; the photocatalytic activity is about 95% efficient when comparing with commercial TiO2. [ABSTRACT FROM AUTHOR]

LEDs with enhanced light extraction efficiency and sensors with improved sensitivity have been developed using porous semiconductors. Here, the growth of porous GaN epitaxial layers oriented along the [0001] crystallographic direction on Al2O3, SiC, AlN and GaN substrates is demonstrated. A lattice mismatch between the substrate and the porous GaN layer directly affects the structure and porosity of the porous GaN layer on each substrate. Deposition of unintentionally doped n-type porous GaN on non-porous p-type GaN layers allows for the fabrication of high quality rectifying p-n junctions, with potential applications in high brightness unencapsulated GaN-based light emitting diodes and high surface area wide band gap sensor devices. [ABSTRACT FROM AUTHOR]

Functionalized nanoporous materials have been developed recently as bio/chemical sensing materials. Due to the huge specific surface of the nano-materials for molecular adsorption, high hopes have been placed on gravimetric detection with micro/nano resonant cantilevers for ultra-sensitive sensing of low-concentration bio/chemical substances. In order to enhance selectivity of the gravimetric resonant sensors to the target molecules, it is crucial to modify specific groups onto the pore-surface of the nano-materials. By loading the nanoporous sensing material onto the desired region of the mass-type transducers like resonant cantilevers, the micro-gravimetric bio/chemical sensors can be formed. Recently, such micro-gravimetric bio/chemical sensors have been successfully applied for rapid or on-the-spot detection of various bio/chemical molecules at the trace-concentration level. The applicable nanoporous sensing materials include mesoporous silica, zeolite, nanoporous graphene oxide (GO) and so on. This review article focuses on the recent achievements in design, preparation, functionalization and characterization of advanced nanoporous sensing materials for micro-gravimetric bio/chemical sensing. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, thermal transport properties study of partially amorphous porous silicon obtained by irradiation with swift (110MeV) uranium ions is reported. A photoacoustic technique allows thermal conductivity evaluation of the samples with enhanced amorphous fraction (>80%). In particular, 3-fold thermal conductivity decrease is shown to be achieved for the completely amorphous porous silicon layers in comparison with as-prepared non-irradiated porous samples. [Copyright &y& Elsevier]

In this paper, a highly ordered three-dimensional Co3O4@MnO2 hierarchical porous nanoneedle array on nickel foam is fabricated by a facile, stepwise hydrothermal approach. The morphologies evolution of Co3O4 and Co3O4@MnO2 nanostructures upon reaction times and growth temperature are investigated in detail. Moreover, the as-prepared Co3O4@MnO2 hierarchical structures are investigated as anodes for both supercapacitors and Li-ion batteries. When used for supercapacitors, excellent electrochemical performances such as high specific capacitances of 932.8 F g−1 at a scan rate of 10 mV s−1 and 1693.2 F g−1 at a current density of 1 A g−1 as well as long-term cycling stability and high energy density (66.2 W h kg−1 at a power density of 0.25 kW kg−1), which are better than that of the individual component of Co3O4 nanoneedles and MnO2 nanosheets, are obtained. The Co3O4@MnO2 NAs are also tested as anode material for LIBs for the first time, which presents an improved performance with high reversible capacity of 1060 mA h g−1 at a rate of 120 mA g−1, good cycling stability, and rate capability. [ABSTRACT FROM AUTHOR]

The intense interactions of guest molecules with the pore walls of nanoporous materials is the subject of continued fundamental research. Stimulated by their thermal energy, the guest molecules in these materials are subject to a continuous, irregular motion, referred to as diffusion. Diffusion, which is omnipresent in nature, influences the efficacy of nanoporous materials in reaction and separation processes. The recently introduced techniques of microimaging by interference and infrared microscopy provide us with a wealth of information on diffusion, hitherto inaccessible from commonly used techniques. Examples include the determination of surface barriers and the sticking coefficient's analogue, namely the probability that, on colliding with the particle surface, a molecule may continue its diffusion path into the interior. Microimaging is further seen to open new vistas in multicomponent guest diffusion (including the detection of a reversal in the preferred diffusion pathways), in guest-induced phase transitions in nanoporous materials and in matching the results of diffusion studies under equilibrium and non-equilibrium conditions. [ABSTRACT FROM AUTHOR]

For thermal sensors and devices, porous silicon is a comparably novel alternative to standard materials such as thin glass substrates or silicon nitride membranes. These materials are primarily characterized by their thermal conductivity and heat capacity, as well as temperature stability and mechanical fragility. In this paper, we present details of the porous silicon technology for full wafer porosification as well as static and dynamic device and material characterization. The reduction of thermal conductivity is estimated with the dynamic 3ω technique and compared with pure silicon and silica glass wafers. Thin film microheaters have been deposited on the samples as proof of concept for the characterization and comparison of thermal insulation, heat capacity, as well as thermal and mechanical stability. [ABSTRACT FROM PUBLISHER]

Abstract: Dye-sensitized solar cell (DSSC) provides credible alternative concept for inorganic solid-state photovoltaic devices. The conversion efficiency of DSSC is mainly based on the dye coated on the porous semiconductor TiO2 film. The use of natural dyes in solar cells is a promising development to this technology because it cuts down the high cost of noble metals and chemical synthesis. Therefore, this type of solar cell has attracted considerable attention from the academic and industrial communities. Numerous kinds of pigments, such as anthocyanin, carotenoid, chlorophyll, and flavonoid, extracted from various plant components, such as leaves, fruits, and flowers, have been tested as sensitizers. The photostability of the DSSC sensitizer material must be capable of undergoing many redox cycles without decomposition, and must also have the ability to carry attachment groups, such as phosphonate or carboxylate, to promptly graft it to the TiO2 oxide. This paper highlights and discusses the development of natural dye photosensitizers and the mechanisms affecting the dye stability. [Copyright &y& Elsevier]

Metal-assisted chemical etching is a facile method to produce micro-/nanostructures in the near-surface region of gallium nitride (GaN) and other semiconductors. Detailed studies of the production of porous GaN (PGaN) using different metal catalysts and GaN doping conditions have been performed in order to understand the mechanism by which metal-assisted chemical etching is accomplished in GaN. Patterned catalysts show increasing metal-assisted chemical etching activity to n-GaN in the order Ag < Au < Ir < Pt. In addition, the catalytic behavior of continuous films is compared to discontinuous island films. Continuous metal films strongly shield the surface, hindering metal-assisted chemical etching, an effect which can be overcome by using discontinuous films or increasing the irradiance of the light source. With increasing etch time or irradiance, PGaN morphologies change from uniform porous structures to ridge and valley structures. The doping type plays an important role, with metal-assisted chemical etching activity increasing in the order p-GaN < intrinsic GaN < n-GaN. Both the catalyst identity and the doping type effects are explained by the work functions and the related band offsets that affect the metal-assisted chemical etching process through a combination of different barriers to hole injection and the formation of hole accumulation/depletion layers at the metal-semiconductor interface. [ABSTRACT FROM AUTHOR]

Abstract: We report on the electrochemical preparation of porous GaAs substrates in fluoride-iodide aqueous electrolytes for the lattice mismatched epitaxial growth from the vapor phase. The aim is to gain control over the uniformity of the pore nucleation layer and pore branching below this layer to achieve structures with a high degree of porosity and periodicity while leaving minimum damage on the substrate surface. Layers of In x Ga1-x As with varying In content are grown on GaAs substrates with different pore geometries and depths. Substantial differences in the surface morphology and photoluminescence efficiency of the layers grown on porous and conventional substrates are observed. [Copyright &y& Elsevier]

Abstract: In this work the effect of OH on the electronic states of H-passivated 3Ctructures, was studied by means of Density Functional Theory. We compare the electronic band structure for a [111]-oriented nanowire with total H, OH passivation and a combination of both. Also the electronic states of a porous silicon carbide case (PSiC) a C-rich pore surface in which the dangling bonds on the surface are saturated with H and OH was studied. The calculations show that the surface replacement of H with OH radicals is always energetically favorable and more stable. In all cases the OH passivation produced a similar effect than the H passivation, with electronic band gap of lower energy value than the H-terminated phase. When the OH groups are attached to C atoms, the band gap feature is changed from direct to indirect. The results indicate the possibility of band gap engineering on SiC nanostructures through the surface passivation species. [Copyright &y& Elsevier]

This paper reports the optimization of electrode geometry on macroporous silicon biosensor for improved bacteria detection. Macroporous silicon of 8 μm thickness and 55% porosity has been fabricated on a 10-20 Ω-cm wafer using hydrofluoric acid and dimethyl sulfoxide. The electrode configurations selected for optimization are coplanar rectangular types with simple two-electrode, interdigitated comb finger-like electrode, and a combination of simple electrode and comb-shaped electrode designs. With these configurations, 14 different patterns have been generated with varying lengths and spacing within the technological constraints of low cost screen printing method of electrode fabrication with a wide range of effective exposed area from 0.04 to 0.6 mm2 by techniques from design of experiments. The sensitivity toward bacteria detection for all the patterns has been estimated by computation of an area utilization factor (AUF) which has been defined as the ratio of the effective area occupied by the captured bacteria to the effective exposed area available for capture. From the AUF values, eight patterns have been selected which are above a lower cut-off threshold for experimentation with E.coli O157 in the range of 102CFU/ml to 106 CFU/ml. It has been observed that the pattern with the highest AUF is capable of detecting 102CFU/ml E.coli O157 with a sensitivity of 11% without any pre-concentration which was not possible in the earlier reports of macroporous silicon. [ABSTRACT FROM PUBLISHER]

Abstract: Water splitting at a semiconductor/solution interface with the only input of sunlight to generate hydrogen is one of the most attractive strategies to produce and store chemical energy. In the present study we have investigated carrier dynamics and interfacial kinetics of mesoporous TiO2 in an aqueous solution. The applicability of the transmission line model for mesoporous semiconductors has been validated to identify chemical capacitance, transport resistance and charge transfer resistance in this system by testing samples of different thicknesses in the dark and under illumination. We found that both transport resistance and chemical capacitance scale well with sample thickness, while charge transfer resistance scales with thickness when the FTO substrate is not exposed to the solution. Otherwise, there is a competition between charge transfer through TiO2 and through the FTO substrate. Under illumination, the electron density is dominated by photogenerated carriers at biases below the open circuit potential, whereas at higher bias, the applied potential determines the electron density. Evidence of charge transfer via surface states has been experimentally observed and corroborated with a physical model, which explicitly includes charge transfer through a monoenergetic trap for electron and holes. This study may lay the basis for understanding more complex processes at anodic potentials on the TiO2/solution interface where water splitting reactions take place. [Copyright &y& Elsevier]

Abstract: Ion irradiation of GaSb causes not only defect formation but also leads to the formation of a porous structure. To study the behaviour of this structural modification, GaSb was irradiated with 6MeV Iodine ions and ion fluences from 5×1012 to 6×1015 ions/cm2. The samples were investigated by step height measurements and scanning electron microscopy (SEM). Experiments were performed with two different procedures: (CI) Continuous Irradiation of samples followed by measurements of the step height in air and (SI) Stepwise Irradiation of samples with measurements of the step height in air between subsequent irradiations. Samples irradiated continuously, show a linear increase of the step height with increasing ion fluence up to 1.5×1014 ions/cm2 followed by a steeper, linear increase for higher ion fluences up to a step height of 32μm. This swelling is induced by a formation of voids, and the two different slopes can be explained by a transformation from isolated voids to a rod like structure. For samples irradiated accordingly to procedure (SI), the step height shows the same behaviour up to an ion fluence of 1.5×1014 ions/cm2 resulting in a step height of ≈3μm but then decreases with further irradiation. The latter effect is caused by a compaction of the porous structure. [Copyright &y& Elsevier]

We report on the preparation of Ga( x)In(1− x)P/GaAs lattice matched heterostructures by liquid phase epitaxy and their electrochemical etching to prepare porous networks. We show that the process of formation of pores strongly depends on the electrolyte, on the applied current/voltage anodization regime, and that illumination is a crucial factor in obtaining fine porous structures with a high degree of self-organization. [ABSTRACT FROM AUTHOR]

Abstract: The anodic etching of n +-type GaAs (100) substrate in HCl aqueous solution has been investigated experimentally using an in situ current–voltage J (V) and capacitance–voltage C (V) measurements. In situ current–voltage, J (V), characteristics of the n +-GaAs/HCl interface exhibit the presence of three potential regions, which are attributed to different reaction mechanisms between HCl and n +-type GaAs surface. Also, current peaks appear in the J (V) characteristics which delimit the different potential regions. According to the Mott–Schottky relation, the characteristic C −2 (V) exhibits the presence of two linear regions separated by a shoulder at about 1.15V. This shoulder indicates the formation of porous GaAs/HCl interface. Scanning electron microscopy (SEM) images shows that GaAs etched in HCl can produce various surface morphologies depending on the anodization current density. Reasonable assumptions on the dissolution mechanisms according to the variety of morphologies are given. [Copyright &y& Elsevier]

Pores in single crystalline semiconductors come in many forms (e.g., pore sizes from 2 nm to > 10 μm; morphologies from perfect pore crystal to fractal) and exhibit many unique properties directly or as nanocompounds if the pores are filled. The various kinds of pores obtained in semiconductors like Ge, Si, III-V, and II-VI compound semiconductors are systematically reviewed, emphasizing macropores. Essentials of pore formation mechanisms will be discussed, focusing on differences and some open questions but in particular on common properties. Possible applications of porous semiconductors, including for example high explosives, high efficiency electrodes for Li ion batteries, drug delivery systems, solar cells, thermoelectric elements and many novel electronic, optical or sensor devices, will be introduced and discussed. [ABSTRACT FROM AUTHOR]