Nanocone Arrays Research Articles

Highly sensitive miRNA detection of early-stage laryngeal carcinoma using a solid-state Au nanocone arrays fabricated LoC-SERS analysis system coupled with target-triggered dual cycle amplification strategy

Herein, with a target-triggered dual cycle amplification strategy, a novel lab-on-a-chip-based surface-enhanced Raman scattering (LoC-SERS) analysis system was established to analyze miRNAs quantitatively. Due to a more substantial complementary pairing effect, the presence of targets can replace the single-stranded DNA S1 (S1) from the single-stranded DNA F1 (F1) and single-stranded DNA S2 (S2) can replace and release the targets similarly. Thus, target can cyclically trigger the cycle Ⅰ and release S1 continuously. Cycle Ⅱ is the catalyzed hairpin assembly (CHA) event between the hairpin DNA 1 and hairpin DNA 2, which can connect the Ag-Au nanorods (Ag-AuNRs) to the surface of solid-state Au nanocone arrays (AuNCAs). Owing the dual cycle amplification strategy, localized surface plasmon resonance (LSPR) can be excited and significantly magnify the local electromagnetic field for SERS signal enhancement. Thus, ultrasensitive detection of miR-21 and miR-106b was achieved with the limit of detection as low as aM level. Attributed to the hydrophilic treatment and the design of capillary pump, the detection can be finished without any external pumps. Moreover, the system exhibited good practicability in the analysis of real serum samples obtained from Laryngeal carcinoma (LC) patients and healthy subjects. Therefore, the system is a promising candidate in clinical application and exhibited potential for the prediction, diagnosis, monitoring, and staging of LC.

0D/1D type Ⅱ CdS/TiO2 nanocone arrays/Ti hybrids for visible-light-driven rapid photocatalytic degradation of tetracycline: An insight investigation of the interfacial electron transport mechanism

The photocatalytic applications of TiO2 was limited by its rapid photogenerated charge recombination and low responsiveness to visible light. To address these challenges, we introduced a novel low-dimensional heterojunction, CdS quantum dots/TiO2 nanocone arrays on Ti mesh substrate (referred to as CTNC), facilitating efficient separation of photogenerated carriers under visible light. Effective type Ⅱ electron migration from TiO2 to CdS was established, enhancing charge separation, as confirmed by in situ irradiated Kelvin probe force microscopy (KPFM) and ultraviolet photoelectron spectroscopy (UPS). The comprehensive analysis of the photoelectric properties of conical TiO2 further confirmed the efficient separation of electron-hole pairs. Leveraging these advantages, the CTNC catalyst significantly degraded 83% of TC (20 mg/L) within 120 min (rate constant k = 0.029 min−1), outperforming CTNR (CdS quantum dots/TiO2 nanorod arrays on Ti substrate) by 2.6 times, and surpassing related low-dimension heterostructures of CdS/TiO2 in previously reported. Remarkably, CTNC exhibited exceptional TC degradation performance and stability on both fronts. The present study provides profound insights into enhancing the photocatalytic performance of TiO2 through morphology manipulation and the formation of heterojunctions responsive to visible light.

Probing the effect of precursor concentration on the growth and properties of titanium dioxide nanocones for environment safe solar cells.

Environment friendly third-generation solar cells sensitized by dyes, quantum dots, and perovskites are seen as promising energy alternatives. Among the various strategies, employing one-dimensional nanostructures that exemplify the smallest dimension for efficient carrier transport rate from the active layer to electron transport layer (ETL) in photovoltaic devices is attempted in this work. We herein report the synthesis of well-aligned 1-D TiO2 nanocones as ETL for photovoltaic thin films by varying the precursor concentration (0.03M, 0.04M, 0.05M) to track the evolution of growth. The hydrothermal approach is exploited to grow oriented rutile TiO2 nanocones on fluorine doped tin oxide (FTO) under neutral conditions. The examination of phase, crystallinity, morphology, and opto-electronic properties of the well-structured nanocone arrays is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), ultra violet diffuse reflectance spectroscopy (UV-DRS), Brunnauer-Emmett-Teller (BET) surface area analysis, and field-dependent dark and photoconductivity analysis. The XRD pattern confirms the formation of the tetragonal rutile phase. SEM micrographs and UV-DRS spectroscopy reveals that the length of the nanocones and the energy gap is found to be maximum for 0.04M concentration with a well-defined excitation band at 316nm. Significantly, a strong light-trapping effect that decreases the incident light reflections and correspondingly increases the light absorption is unveiled through photoconductive studies for the TiO2 nanocones at 0.04M having a surface area of 81.767 m2/g. The investigation essentially suggests that the as-prepared one-dimensional nanostructures would serve as efficient photoanodes in environment safe third-generation solar cells.

NiCo2S4 nanocone arrays on three-dimensional graphene with small hole diameters for asymmetric supercapacitor

Chemical vapor deposition (CVD) is utilized to fabricate 3D graphene (3D Gr) with small hole diameters using nickel nanoparticles sintered at high temperatures as the sacrificial template. NiCo2S4 nanocone arrays (NiCo2S4 NCAs) are vertically grown in situ on the 3D Gr by a seeding layer and hydrothermal synthesis process. The results show the hole diameters of 3D Gr are ∼ 3 µm. The small hole diameters of 3D Gr not only enhances the high electrical conductivity but also increases the contact area to the solution. Moreover, NiCo2S4 NCAs on the 3D Gr can provide more electrochemical redox activities and shorter channels for ion transport. NiCo2S4 NCAs/3D Gr is applied as a supercapacitor electrode, showing a specific capacitance of 948.9 F/g at 1 A/g. In addition, an asymmetric supercapacitor is assembled with the NiCo2S4 NCAs/3D Gr as the cathode material and the activated carbon as the anode material. The supercapacitor has an energy density of 64.1 Wh/kg at the power density of 1153.8 W/kg. It exhibits 90 % capacitance retention under 10, 000 charge and discharge cycles at 10 A/g.

A superhydrophilic NiFe electrode for industrial alkaline water electrolysis

NiFe-based materials are among the most promising alkaline oxygen evolution reaction (OER) catalysts because of their high intrinsic activities and abundance. Although many advanced NiFe-based catalysts have been developed, few exhibit simultaneous high activity, stability, good mass transfer, and cost-effective large-scale preparation. Furthermore, NiFe-based catalysts have rarely been studied in alkaline water electrolyzers (AWE) where the catalysts work under a large current density in an alkaline electrolyte at high temperatures and high concentrations with tight assembly pressure. This study successfully developes robust and highly active NiFe nanocone array (NA) catalysts that exhibit both fast and cost-effective mass production capabilities. Benefiting from the in situ-formed OER-active NiFe layered double hydroxide (LDH) and the superhydrophilic structure-induced fast mass transfer, the optimized NiFe NA sample presentes a low OER overpotential of 269 mV at 500 mA cm−2 in a 30 wt% KOH solution. The NiFe core-NiFe LDH shell structure and metallic bond between NiFe nanocones and the substrate are crucial for enabling the NiFe electrode to maintain a minimal potential increase of only 4% even after 250 h of testing at 500 mA cm−2 in a 30 wt% KOH solution. Moreover, the AWE using NiFe NA anodes and NiMo cathodes (NiFe//NiMo) works stably at 500 mA cm−2 under 80 °C in 30 wt% KOH solution and presents a power energy consumption of 4.0 kWh Nm−3 H2, much lower than that of the Ni mesh//Ni mesh counterpart and most commercial AWEs. This study, for the first time, evaluates the performance of NiFe electrodes in AWE and demonstrates their industrial application prospects in alkaline water electrolysis.

Solid-State Au Nanocone Arrays Substrate for Reliable SERS Profiling of Serum for Disease Diagnosis.

Surface-enhanced Raman scattering (SERS) is a widely used rapid and noninvasive method for detecting biological substances in serum samples and is commonly employed in disease screening and diagnosis. Solid-state nanoarray SERS substrates used in serum detection may cause spectral instability due to imperfections in the detection method. For the purpose of identifying optimal detection conditions, various dilution levels of the serum were tested in this study. The study found that a complete and stable serum SERS spectrum can be obtained when the serum is diluted by a factor of 50. The study reports the successful preparation of an Au nanocone array (Au NCA) plasmonic substrate with a uniform, controllable microstructure and high activity, achieved through a combination of PS colloidal sphere template-assisted reactive ion etching (RIE) process and magnetron sputtering deposition technology. Based on this substrate, a standard detection scheme was developed to obtain highly stable and repeatable serum SERS spectra. The study verified the reliability of the optimized serum detection scheme by comparing the SERS spectra of serum samples from healthy individuals and gastric cancer patients, and confirmed the potential benefits of the scheme for disease screening and diagnosis.

A dual-modification strategy for the preparation of super-amphiphobic nanofibrous membranes for high-efficiency oil aerosol separation

This study presents a highly effective FOTS-TiO2@SiO2 Nano fibrous membrane (NFM) with super-amphiphobic properties for oil aerosol purification. The membrane was fabricated by modifying the surface roughness of electrospun SiO2 NFM with a uniform array of TiO2 nanocones, followed by surface energy modification using 1H, 1H, 2H, 2H-perfluorooctyltrimethoxysilane (FOTS). The NFM exhibited exceptional contact angles towards both water (167.9°) and n-hexadecane (154.7°) as well as extremely low oil adhesion (38.7 μN). At a gas velocity of 3.2 m/min, the NFM demonstrated excellent oil aerosol separation performance, with a filtration efficiency of 99.87 % and a resistance of 10.0 kPa. The amphiphobic NFM also exhibited a good regeneration ability, with higher efficiency than SiO2 NFM after three rounds of filtration. These results suggest that the FOTS-TiO2@SiO2 NFM has promising potential for cleaning oil-bearing gas.

Combined SERS Microfluidic Chip with Gold Nanocone Array for Effective Early Lung Cancer Prognosis in Mice Model.

As the most common malignant tumor in the world, the prognosis of patients with advanced lung cancer remains poor even after treatment. There are many prognostic marker assays available, but there is still more room for the development of high-throughput and sensitive detection of circulating tumor DNA (ctDNA). Surface-enhanced Raman spectroscopy (SERS), a spectroscopic detection method that has received wide attention in recent years, can achieve exponential amplification of Raman signals by using different metallic nanomaterials. Integrating SERS with signal amplification strategy into the microfluidic chip and applying it to ctDNA detection is expected to be an effective tool for the prognosis of lung cancer treatment effect in the future. To construct a high-throughput SERS microfluidic chip integrated with enzyme-assisted signal amplification (EASA) and catalytic hairpin self-assembly (CHA) signal amplification strategies, using hpDNA-functionalized Au nanocone arrays (AuNCAs) as capture substrates and cisplatin-treated lung cancer mice to simulate the detection environment for sensitive detection of ctDNA in serum of lung cancer patients after treatment. The SERS microfluidic chip constructed by this scheme, with two reaction zones, can simultaneously and sensitively detect the concentrations of four prognostic ctDNAs in the serum of three lung cancer patients with a limit of detection (LOD) as low as the aM level. The results of the ELISA assay are consistent with this scheme, and its accuracy is guaranteed. This high-throughput SERS microfluidic chip has high sensitivity and specificity in the detection of ctDNA. This could be a potential tool for prognostic assessment of lung cancer treatment efficacy in future clinical applications.

Au/SiNCA-based SERS analysis coupled with machine learning for the early-stage diagnosis of cisplatin-induced liver injury.

Cisplatin has been widely applied in the clinical treatment of various cancers, whereas liver injury induced by its hepatotoxicity is still a severe issue. Reliable identification of early-stage cisplatin-induced liver injury (CILI) can improve clinical care and help to streamline drug development. Traditional methods, however, cannot achieve enough information at the subcellular level due to the requirement of the labeling process and low sensitivity. To overcome these, we designed an Au-coated Si nanocone array (Au/SiNCA) to fabricate the microporous chip as the surface-enhanced Raman scattering (SERS) analysis platform for the early diagnosis of CILI. A CILI rat model was established, and the exosome spectra were obtained. The principal component analysis (PCA)-representation coefficient-based k-nearest centroid neighbor (RCKNCN) classification algorithm was proposed as the multivariate analysis method to build the diagnosis and staging model. The PCA-RCKNCN model has been validated to achieve a satisfactory result, with accuracy and AUC of over 97.5%, and sensitivity and specificity of over 95%, indicating that SERS combined with the PCA-RCKNCN analysis platform can be a promising tool for clinical applications.

A SERS Biosensor Based on Functionalized Au-SiNCA Integrated with a Dual Signal Amplification Strategy for Sensitive Detection of Telomerase Activity During EMT in Laryngeal Carcinoma.

This paper aims to construct a surface-enhanced Raman spectroscopy (SERS) biosensor based on functionalized Au-Si nanocone arrays (Au-SiNCA) using a dual signal amplification strategy (SDA-CHA) to evaluate telomerase activity during epithelial-mesenchymal transition (EMT) in laryngeal carcinoma (LC). A SERS biosensor based on functionalized Au-SiNCA was designed with an integrated dual-signal amplification strategy to achieve ultrasensitive detection of telomerase activity during EMT in LC patients. Labeled probes (Au-AgNRs@4-MBA@H1) and capture substrates (Au-SiNCA@H2) were prepared by modifying hairpin DNA and Raman signal molecules. Using this scheme, telomerase activity in peripheral mononuclear cells (PMNC) could be successfully detected with a limit of detection (LOD) as low as 10-6 IU/mL. In addition, biological experiments using BLM treatment of TU686 effectively mimicked the EMT process. The results of this scheme were highly consistent with the ELISA scheme, confirming its accuracy. This scheme provides a reproducible, selective, and ultrasensitive assay for telomerase activity, which is expected to be a potential tool for the early screening of LC in future clinical applications.

LoC-SERS Platform Integrated with the Signal Amplification Strategy toward Parkinson's Disease Diagnosis.

Multiplexed detection of Parkinson's disease (PD) biomarkers is of great significance for early diagnosis and personalized treatment. In this study, we fabricated a robust surface-enhanced Raman scattering-enabled lab-on-a-chip (LoC-SERS) platform for simultaneous quantification of α-synuclein, phosphorylated tau protein 181, osteopontin, and osteocalcin. Herein, the antibody-DNA conjugate was designed to introduce the catalytic hairpin self-assembly (CHA) amplification into the protein detection. Au nano-stars (AuNSs) modified with Raman reporter molecules and hairpin-structure DNA 1 were applied as the SERS nanotags. Au-coated silicon nanocone array (Au/SiNCA) fabricated based on the maskless plasma etching-prepared high-density Si nanocone array (SiNCA) and surface ion sputtering was used as the capture substrate after the modification of hairpin-structure DNA 2. Benefitting from the antibody-DNA conjugate-induced CHA amplification, numerous AuNSs can be connected to the Au/SiNCA surface, which significantly amplify the plasmonic coupling effect for ultrasensitive SERS detection, and the limit of detection was less than the pg/mL level. The application of highly uniform Au/SiNCA and antibody-DNA conjugate endows the LoC-SERS platform excellent analytical performance, including superior reproducibility, satisfactory universality, and high sensitivity. In addition, a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice model was established, and satisfactory results were obtained in real sample analysis with the LoC-SERS platform, which may be enlightening for exploiting protein biomarkers in PD monitoring.

Grafting aryldiazonium cations to copper: Insights into wettability behavior of a highly hydrophobic coating with enhanced corrosion performance

This paper describes electrografting of various aryldiazonium salts on copper substrate. The wettability of the functionalized surface was measured to choose an aryldiazonium salt with the lowest surface free energy suitable for developing a hydrophobic surface. In this regard, a nickel film with a micro-nano structure was fabricated using an electrodeposition process followed by the modification with 4-dodecylbenzendiazonium salt. The surface morphology of the nickel coating revealed by a scanning electron microscope showed pine cone-like microstructure with nano-cone arrays randomly dispersed on each micro-protrusion. The wettability of the micro-nano nickel film was increased from 7 ° for as-prepared nickel coating to 140° after modification with 4-dodecylbenzendiazonium salt and it was unchanged by storing 7 days in the air. The corrosion performance of this highly hydrophobic surface was evaluated in 3.5 wt.% NaCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed a significant decrease in the corrosion current density (icorr), double layer capacitance (Cdl), and a simultaneous increase of the charge transfer resistance (Rct), indicating an improvement in anti-corrosion performance.

Au@Ag nanodome-cones array substrate for efficient residue analysis of food samples by surface-enhanced Raman scattering

A bioinspired Au@Ag nanodome-cones array (Au@Ag NDCA) surface-enhanced Raman scattering (SERS) chip was developed for efficient residue analyses of food samples. The cicada wing inspired Au@Ag NDCA chip was fabricated by a bottom-up method, Au nanocones array was firstly grown onto nickel foil by displacement reaction and cetyltrimethylammonium bromide guidance growth, and then silver shell with controllable thickness was coated onto the Au nanocones array by magnetron sputtering. The Au@Ag NDCA chip exhibited good SERS performances with high enhancement factor of 1.2 × 108, good uniformity with relative standard deviation (RSD) less than 7.5% (n = 25), good inter-batch reproducibility with RSD less than 9.4% (n = 9), and long-term stability over 9 weeks. By adapting a minimized sample preparation, Au@Ag NDCA chip combined with a 96-well plate could realize high-throughput SERS analyses of 96 samples with average analysis time less than 10 min. The substrate was applied for quantitative analyses of two food projects. One was 6-benzylaminopurine auxin residue in sprout samples with detection limit of 38.8 μg/L, recoveries of 93.3–105.4% and RSDs of 1.5–6.5%, and the other was an edible spice of 4-amino-5,6-dimethylthieno (2,3-d) pyrimidin-2(1H)-one hydrochloride additive in beverage samples with detection limit of 18.0 μg/L, recoveries of 96.2–106.6% and RSDs of 3.5–7.9%. All the SERS results were well confirmed by conventional high-performance liquid chromatographic methods with relative errors less than 9.7%. The robust Au@Ag NDCA chip exhibited good analytical performances possessed great potential for convenient and reliable analyses of food quality and safety.

Effects of geometric parameters on optical absorption characteristics of InGaN nanostructured arrays

In recent years, with the development of wide-spectrum response photodetectors, InGaN as a semiconducting material has been widely studied. The nanowire array structure has excellent trapping ability, but different structures and shapes have different absorption abilities. It is necessary to optimize the nanowire array continuously in order to obtain the highest absorption efficiency possible. Based on this background, we study the effects of the geometry and structural parameters of InGaN nanowires on the optical response properties. We define the cone ratio and fill factor, respectively, and compare the optical absorption characteristics of InGaN nanowires by using the finite difference time domain (FDTD) method. The calculation results show that the truncated nanocone arrays can enhance the light capture ability and obtain the high sensitivity of the cut-off wavelength. Its optical absorption is at least 15% higher than that of nanowires. Therefore, the research of this paper can provide a certain theoretical reference for the experiment and preparation of InGaN photocathode.

Ti3+ self-doped and nitrogen-annealed TiO2 nanocone arrays photoanode for efficient visible-LED-light-driven photoelectrocatalytic degradation of sulfamethazine

Developing efficient, durable and visible-light-driven photoanode with excellent environmental adaptability is of great significance for photoelectrocatalytic (PEC) degradation of organic pollutants. In this work, a novel Ti3+ self-doped and nitrogen-annealed TiO2 nanocone arrays (Ti3+-TiO2NCs(N2)) photoanode was prepared for efficiently photoelectrocatalytic degradation of sulfamethazine (SMT) under visible light emitting diode (LED) irradiation, which obtained 98.68% removal for initial SMT concentration of 10 mg/L within 60 min. The visible light harvesting and charge transfer of TiO2NCs were significantly improved after nitrogen annealing treatment. Additionally, the introduction of moderate Ti3+ sites further lowered charge transport resistance and introduced a new impurity energy level, which efficiently accelerated the transmission of photogenerated carriers and then generated more h+ and active species to degrade pollutants. After 15 recycling degradation experiments, Ti3+-TiO2NCs(N2) still obtained more than 97% SMT removal, demonstrating highly durable. Also, it exhibited promising application prospect for treatment of real wastewaters (secondary effluent, pharmaceutical wastewater and mariculture wastewater).

Study on photoemission of field assisted InGaN nanocone array photocathode

With the rise of group III nitride semiconductor materials, InGaN provides a great possibility for manufacturing high performance photocathodes with wide spectral response. In order to reduce the secondary absorption of photoelectrons by adjacent nanocones and improve the collection efficiency, we established a field-assisted negative electron affinity potential InGaN nanocone array photocathode. Finite difference time domain (FDTD) method is used to study the filling ratio, cone ratio, angle and photoemission performance of nanocone array assisted by external electric field. We found that the external electric field can greatly improve the collection efficiency and electron collection ratio of the nanocone array. The collection efficiency is increased to 41.2% and the electron collection ratio is increased to 65.4%, which is a significant improvement compared with that without external electric field. Therefore, the study in this paper can provide a certain theoretical reference for the preparation and performance improvement of InGaN nanocone array photocathode.

One-Pot Synthesis of Ag/AgCl Heterojunction Nanoparticles on Polyaniline Nanocone Arrays on Graphene Oxide for Microwave Absorption

Heterointerfaces in microwave absorption materials can induce dielectric polarization relaxation for superior microwave absorption capacity. Nevertheless, the construction of favorable hierarchical structures in dielectric heterogeneous materials remains a considerable challenge. Herein, Ag/AgCl heterojunction (HAg) nanoparticles are successfully decorated on polyaniline (PANI)/graphene oxide (GO) sheets through simple one-pot interfacial polymerization. The synthesized HAg/PANI/GO hybrid exhibits superior microwave absorption performance due to the multi-heterogeneous and hierarchical structures, which provides numerous interface polarizations, dipolar relaxations, and improved impedance matching. The minimum reflection loss of the optimum HAg/PANI/GO hybrid reaches −61.14 dB at 11.32 GHz with an effective absorption bandwidth of 4.77 GHz in the range from 9.70 to 14.47 GHz. This work provides ideas for producing multi-heterogeneous and hierarchical structures to reach a high microwave absorption performance.

Regulation of TiO2 nanoarrays on titanium implants for enhanced osteogenic activity and immunomodulation

The surface topography of implants plays a major role in osteogenesis and immunomodulation. In this study, three types of TiO2 nanoarrays including nanorod arrays with a diameter of 45 nm (TiO2-N), nanorod arrays with a diameter of 60 nm (TiO2-N N), and nanocone arrays (TiO2-NW) are prepared on titanium and the behavior of bone marrow stromal cells (BMSCs) and polarization of macrophages are studied. Compared to the planar titanium control, TiO2 nanoarrays facilitate osteogenesis of BMSCs and stimulate the pro-healing M2 phenotype. However, adhesion, spreading, proliferation, and osteogenic differentiation of BMSCs are more pronounced on TiO2-N N than both TiO2-N and TiO2-NW. TiO2-NN also produces the best immune microenvironment, while TiO2-NW is more favorable than TiO2-NN from the viewpoint of cell adhesion and spreading of osteoblasts.

Sulphur-dopant induced breaking of the scaling relation on low-valence Ni sites in nickel ferrite nanocones for water oxidation with industrial-level current density

The microstructure of active centers in bimetallic/multimetallic catalysts is under a long-time debate toward oxygen evolution reaction (OER). Here, sulfur doping NiFe2O4 nanocone arrays on iron foams (S-NiFe2O4/IF) is prepared via a scalable hydrothermal method. The favorable 3D nanocone arrays can offer large electrochemical surface area and allow for effective electrolyte access and O2 escape. Physical characterizations confirm low-valence Ni atoms in tetrahedron sites are more actives sites than high-valence Fe atoms in this S-doped bimetallic catalyst. Meanwhile, DFT calculations further verify the S introduction enhances the adsorption and dissociation of water, and optimizes the adsorption of OER intermediates on Ni sites. Therefore, the optimal S-NiFe2O4/IF achieves industrial-level 500 mA cm−2 at an overpotential of only 310 mV and maintains for 100 h in an alkaline medium. In addition, integrating S-NiFe2O4/IF into an anion-exchange membrane water electrolyzer can deliver a current density of 1.0 A cm−2 at 1.79 V.

Fabrication of ultrahigh aspect ratio Si nanopillar and nanocone arrays

High aspect ratio (HAR) structures have many promising applications such as biomedical detection, optical spectroscopy, and material characterization. Bottom-up self-assembly is a low-cost method to fabricate HAR structures, but it remains challenging to control the structure dimension, shape, density, and location. In this paper, an optimized top-down method using a combination of pseudo-Bosch etching and wet isotropic thinning/sharpening is presented to fabricate HAR silicon (Si) nanopillar and nanocone arrays. To achieve these structure profiles, electron beam lithography and reactive ion etching were carried out to fabricate silicon pillars having a nearly vertical sidewall, followed by thinning or sharpening by wet etching with a mixture of hydrofluoric (HF) acid and nitric acid (HNO3). For the dry etching step using the pseudo-Bosch process, the sidewall angle is largely dependent on the SF6/C4F8 gas flow ratio, and it was found that a vertical profile can be attained with a ratio of 22/38. For the wet etching process, a very large HNO3/HF volume ratio is shown to give smooth etching with a slow and controllable etching rate. The final structure profile also depends on the pattern density/array periodicity. When the array period is large, silicon nanopillar is thinned down, and its aspect ratio can reach 1:135 with a sub-100 nm apex. When the pillar array becomes very dense (periodicity much smaller than height), a very sharp nanocone structure is obtained after wet etching with an apex diameter under 20 nm.