Chemical Etching Method Research Articles

An Oxysulfide Photocatalyst Evolving Hydrogen with an Apparent Quantum Efficiency of 30 % under Visible Light.

Photocatalytic water splitting is a simple means of converting solar energy into storable hydrogen energy. Narrow-band gap oxysulfide photocatalysts have attracted much attention in this regard owing to the significant visible-light absorption and relatively high stability of these compounds. However, existing materials suffer from low efficiencies due to difficulties in synthesizing these oxysulfides with suitable degrees of crystallinity and particle sizes, and in constructing effective reaction sites. The present work demonstrates the production of a Gd2 Ti2 O5 S2 (λ<650 nm) photocatalyst capable of efficiently driving photocatalytic reactions. Single-crystalline, plate-like Gd2 Ti2 O5 S2 particles with atomically ordered surfaces were synthesized by flux and chemical etching methods. Ultrafine Pt-IrO2 cocatalyst particles that promoted hydrogen (H2 ) and oxygen (O2 ) evolution reactions were subsequently loaded on the Gd2 Ti2 O5 S2 while ensuring an intimate contact by employing a microwave-heating technique. The optimized Gd2 Ti2 O5 S2 was found to evolve H2 from an aqueous methanol solution with a remarkable apparent quantum efficiency of 30 % at 420 nm. This material was also stable during O2 evolution in the presence of a sacrificial reagent. The results presented herein demonstrates a highly efficient narrow-band gap oxysulfide photocatalyst with potential applications in practical solar hydrogen production.

An Oxysulfide Photocatalyst Evolving Hydrogen with an Apparent Quantum Efficiency of 30 % under Visible Light

AbstractPhotocatalytic water splitting is a simple means of converting solar energy into storable hydrogen energy. Narrow‐band gap oxysulfide photocatalysts have attracted much attention in this regard owing to the significant visible‐light absorption and relatively high stability of these compounds. However, existing materials suffer from low efficiencies due to difficulties in synthesizing these oxysulfides with suitable degrees of crystallinity and particle sizes, and in constructing effective reaction sites. The present work demonstrates the production of a Gd2Ti2O5S2 (λ&lt;650 nm) photocatalyst capable of efficiently driving photocatalytic reactions. Single‐crystalline, plate‐like Gd2Ti2O5S2 particles with atomically ordered surfaces were synthesized by flux and chemical etching methods. Ultrafine Pt‐IrO2 cocatalyst particles that promoted hydrogen (H2) and oxygen (O2) evolution reactions were subsequently loaded on the Gd2Ti2O5S2 while ensuring an intimate contact by employing a microwave‐heating technique. The optimized Gd2Ti2O5S2 was found to evolve H2 from an aqueous methanol solution with a remarkable apparent quantum efficiency of 30 % at 420 nm. This material was also stable during O2 evolution in the presence of a sacrificial reagent. The results presented herein demonstrates a highly efficient narrow‐band gap oxysulfide photocatalyst with potential applications in practical solar hydrogen production.

Study on copper-assisted chemical etching of porous Si/Cu@C anode materials

The volume expansion and low electronic conductivity of silicon anodes are the main problems needed to be solved. In this paper, submicron silicon particles are used as raw materials and a two-step copper-assisted chemical etching method is used to construct porous structures, and asphalt is used as carbon source to finally prepare carbon coated copper modified porous silicon (pSi/Cu@C) composite anode material. The pSi/Cu@C shows excellent electrochemical performance. After 200 cycles at the rate of 0.5C (1C = 4.2 A g−1), the discharge specific capacity still remains 820 mAh g−1, while raw silicon anode material (Si-raw) presents a low discharge specific capacity of 229 mAh g−1. In addition, pSi/Cu@C maintains 774 mAh g−1 at 2C, showing good rate performance. In this paper, the method is simple and low cost, which is an effective modification method for silicon anode materials.

Surface modification of Polyether-ether-ketone for enhanced cell response: a chemical etching approach.

Polyether-ether-ketone (PEEK) is increasingly becoming popular in medicine because of its excellent mechanical strength, dimensional stability, and chemical resistance properties. However, PEEK being bioinert, has weak bone osseointegration properties, limiting its clinical applications. In this study, a porous PEEK structure was developed using a chemical etching method with 98wt% sulfuric acids and three post-treatments were performed to improve bone cell adhesion and proliferation. Four groups of PEEK samples were prepared for the study: Control (untreated; Group 1); Etched with sulfuric acid and washed with distilled water (Group 2); Etched with sulfuric acid and washed with acetone and distilled water (Group 3); and Etched with sulfuric acid and washed with 4wt% sodium hydroxide and distilled water (Group 4). Surface characterization of the different groups was evaluated for surface topology, porosity, roughness, and wettability using various techniques, including scanning electron microscopy, profilometer, and goniometer. Further chemical characterization was done using Energy-dispersive X-ray spectroscopy to analyze the elements on the surface of each group. Bone cell studies were conducted using cell toxicity and alkaline phosphatase activity (ALP) assays. The SEM analysis of the different groups revealed porous structures in the treatment groups, while the control group showed a flat topology. There was no statistically significant difference between the pore size within the treated groups. This was further confirmed by the roughness values measured with the profilometer. We found a statistically significant increase in the roughness from 7.22 × 10-3μm for the control group to the roughness range of 0.1µm for the treated groups (Groups 2-4). EDX analysis revealed the presence of a 0.1% weight concentration of sodium on the surface of Group 4, while sulfur weight percentage concentration was 1.1%, 0.1%, and 1.4% in groups 2, 3, and 4, respectively, indicating different surface chemistry on the surface due to different post-treatments. Cell toxicity decreased, and ALP activity increased in groups 3 and 4 over 7days compared with the control group. It is demonstrated that the surface modification of PEEK using a chemical etching method with post-processing with either acetone or sodium hydroxide provides a nano-porous structure with improved properties, leading to enhanced osteoblastic cell differentiation and osteogenic potential.

Fabrication and Characterization of Silicon Nanowires Heterojunction Solar Cell

Silicon nanowire arrays (SiNWs) are created utilizing the metal-assisted chemical etching method with an Ag metal as a catalyst and different etching time of 15, 30, and 60 minutes using n-Si (100). Physical properties such as structural, surface morphology, and optical properties of the prepared SiNWs are studied. The diameter of prepared SiNWs ranged from 20 to 280 nm, and the reflectance in the visible part of the wavelength spectrum was less than 1% for all prepared samples. The obtained energy gap of prepared SiNWs was around 2 eV, which is higher than the energy gap of bulk silicon. X-ray diffraction (XRD) has diffraction peaks at 68.70o for all prepared samples. The heterojunction solar cell was fabricated based on the n-SiNWs/ P3HT/PEDOT: PSS structure. The heterojunction solar cell produced for 60 minutes has the highest Jsc of 11.55 mA.cm-2 and a conversion efficiency of 0.93%. Based on SiNWs prepared for etching time of 15 min, the solar cell demonstrated Jsc and Voc of 2.73 mA/cm2 and 0.46 V, respectively, and a conversion efficiency of 0.34%.

Wet Chemical and Plasma Etching of Photosensitive Glass

Photosensitive glasses for radiation-induced 3D microstructuring, due to their optical transparency and thermal, mechanical, and chemical resistance, enable the use of new strategies for numerous microscale applications, ranging from optics to biomedical systems. In this context, we investigated the plasma etching of photosensitive glasses after their exposure and compared it to the established wet chemical etching method, which offers new degrees of freedom in microstructuring control and microsystem fabrication. A CF4/H2 etching gas mixture with a constant volumetric flow of 30 sccm and a variable H2 concentration from 0% to 40% was utilized for plasma-based etching, while for wet chemical etching, diluted hydrofluoric acid (1% ≤ cHF ≤ 20%) was used. Therefore, both etching processes are based on a chemical etching attack involving fluorine ions. A key result is the observed reversion of the etch selectivity between the initial glassy and partially crystallized parts that evolve after UV exposure and thermal treatment. The crystallized parts were found to be 27 times more soluble than the unexposed glass parts during wet chemical etching. During the plasma etching process, the glassy components dissolve approximately 2.5 times faster than the partially crystalline components. Unlike wet chemical etching, the surfaces of plasma etched photostructured samples showed cone- and truncated-cone-shaped topographies, which supposedly resulted from self-masking effects during plasma etching, as well as a distinct physical contribution from the plasma etching process. The influences of various water species on the etching behaviors of the homogeneous glass and partially crystallized material are discussed based on FTIR-ATR and in relation to the respective etch rates and SNMS measurements.

High-performance olfactory receptor-derived peptide sensor for trimethylamine detection on the pyramid substrate structure

In our daily life, people are commonly exposed to trimethylamine (TMA) and suffered from a variety of diseases. Therefore, we are desperately in need of the real-time monitoring of TMA with convenience and high sensitivity. In this study, a pyramid substrate structure was developed to manufacture a high-performance TMA sensor, where olfactory receptor-derived peptides (ORPs) as the sensing material were chemically connected to single-walled carbon nanotubes (SWCNTs). First, the pyramid structure on silicon substrates was fabricated by chemical etching method. Then, SWCNTs were attached to the pyramid structure substrate. After that, the surface of SWCNTs were modified with thioester in the ester exchange reaction and connected to the ORPs whose N-terminus bore a cysteine residue to the thioester by natural chemical ligation. Using this approach, the ORPs-CNTs sensor on pyramid Si substrate was capable of detecting gaseous TMA with a concentration as low as 0.01 ppt and the responsivity was improved significantly compare with the sensor on flat Si substrate as well. The sensor was also shown excellent sensitive and stable for TMA detection by selectivity and repeatability measurements. The results proved the availability and the potential usage of the pyramid structure for sensors fabrication and the potential of these TMA sensors applied in food safety, diseases monitoring and environmental protection.

Photocatalytic fuel cell based on integrated silicon nanowire arrays/zinc oxide heterojunction anode for simultaneous wastewater treatment and electricity production

Photocatalytic fuel cells (PFCs) convert organic waste into electricity, thereby providing a potential solution for remediating environmental pollution and solving energy crises. Most PFCs for energy generation applications use powder photocatalysts, which have poor mechanical stability, high internal resistance, and may detach from the substrate during reactions, leading to unstable performance. Integrated photoelectrodes can overcome the drawbacks of powder catalysts. In this study, an integrated photoanode was prepared based on a silicon nanowire arrays/zinc oxide (Si NWs/ZnO) heterojunction by combining metal-assisted chemical etching (MACE) and hydrothermal methods. The resulting photoanode was used to assemble a PFC for simultaneous electricity generation and Rhodamine (RhB) dye wastewater degradation. This PFC showed excellent cell performance under irradiation, with a short-circuit current density of 0.183 Am−2, an open-circuit voltage (OCV) of 0.72 V, and a maximum power density of 0.87 W m−2. It could also be used continuously 20 times while degrading > 90% of RhB. This performance was ascribed to the three-dimensional (3D) structure and large surface area of Si NWs, as well as the matched band structure of ZnO, which facilitated the efficient separation and transport of photogenerated carriers in Si NWs/ZnO. The integrated structure also shortened the carrier transport pathways and suppressed carrier recombination. This research provides a foundation for the development of efficient, stable, low-cost, small-scale PFCs.

Methods for Preparing Hierarchical Zeolites by Chemical Etching and Their Catalytic Applications: A Review

AbstractZeolites are widely used in petrochemical processes and refineries due to their well‐ordered microporous network and large surface area. However, the diffusion of reactants and products is hampered by the narrow microporous channels, causing limitations. To overcome this challenge, modifying the pore structure is crucial, and the chemical etching technique is a powerful tool that introduces mesopores and macropores, consequently enhancing mass transfer and accessibility. Diverse chemical etching methods have been invented, including exposure to both acids (organic/inorganic acids), alkali (organic/inorganic alkali), and neutral etchants (e. g., ammonium fluoride). This review summarizes and assesses the chemical etching methods and their relevance to catalytic cracking reactions, methanol to hydrocarbons (MTH), and biomass conversion. The potential of zeolites with modified pore structures has motivated researchers to develop novel methods to tackle the practical challenges associated with their applications.

Regrowth characteristics of semipolar (11–22) GaN epitaxial film on corroded semipolar GaN template

Semipolar (11–22) GaN epitaxial film was grown by metal-organic chemical vapor deposition (MOCVD) on a prismatic structure corroded (11–22) GaN template prepared by wet chemical etching method. The X-ray rocking curves (XRCs) of on-axis and off-axis (11–22) GaN reflection planes were measured, and the results demonstrate that (11–22) GaN epitaxial film grown on the corroded GaN template can improve the crystal quality by reducing the defects such as basal stacking faults (BSFs) and partial dislocations (PDs). The SEM analysis for the semipolar GaN epitaxial film grown on the corroded GaN template and untreated GaN template also show that the mosaic grain size of GaN epitaxial film grown on the corroded GaN template is larger than that untreated one. The photoluminescence (PL) spectrum of the semipolar GaN epitaxial film grown on the corroded GaN template may also indicate better crystal quality. Besides, we found that the recombination mechanism in BSFs defects was dominated by radiative recombination. In our case, our research demonstrates that the crystal quality of semipolar GaN epitaxial films can be improved by regrowing GaN film on corroded GaN template.

An Experimental Study on the Influence of the Fractal Characteristics of X80 Steel Surface Morphology on Water Ring Stability

The surface morphology of X80 steel with hydrophilic underwater oleophobic characteristic is described greater comprehensively and quantitatively in this work by combining fractal dimension and multifractal. X80 steel with hydrophilic underwater oleophobic surface characteristics was constructed using a chemical etching method. Then, with the aid of three wettability parameters—contact angle, rolling angle, and adhesion work—this study investigated the relationship between the surface fractal dimension of X80 and the stability of the water ring in the core annular flow. The results showed that: (1) the fractal dimension of X80 steel specimens increased first and then decreased with the increase of reaction time. Besides that, the value of it was greater than 2, indicating that the surface had obvious fractal characteristics. The spectral difference, Δf(α), and the spectral width, Δα, supplemented the description of the X80 steel surface morphology, which was consistent with the scanning electron microscope results. (2) When the maximum fractal dimension was 2.0808, the minimum contact angle of distilled water on its surface was 50.2°, and the maximum contact angle of underwater oil droplets was 166.4°. The larger the fractal dimension of X80 steel with hydrophilic underwater oleophobic properties, the more hydrophilic and underwater oleophobic it is. This illustrated that there was a strong binding force between the water and the X80 steel pipe wall, and hence the quality and efficiency of the core annular flow was improved, which was more conducive to the promotion of this technology in the field of heavy oil transportation.

Ligand chemistry for surface functionalization in MXenes: A review

AbstractSurface chemistry of MXenes is of significant interest due to its potential to control their final optoelectronic and physicochemical properties, and address the oxidation and dispersion stabilities of MXenes. Surface chemistry of MXenes can be manipulated by either MXene synthesis via chemical etching or post surface functionalization method. Although numerous reviews have explored MXene synthesis methods, there has been a lack of focus on post surface functionalization. This review aims to fill this gap by summarizing recent advancements in the MXene surface functionalization chemistry, and elucidating mechanisms, properties, and future perspectives of functionalized MXenes. We discuss organic ligand molecules, such as organic salts, catechols, phosphonates, carboxylates, and silanes, which can be employed to surface‐functionalize MXene through covalent or non‐covalent bond interaction. This comprehensive review offers valuable insights for scientists and engineers in utilizing functionalized MXenes across diverse applications, including EMI shielding, energy storage, electronics, optoelectronics, and sensors.image

Strong enhancement of the optical properties of SiNWs by the deposition of snowball-like V2O5 nanoparticles

In this work, the morphological and optical properties of vanadium pentoxide (V2O5) nanoparticles deposited on silicon nanowires (SiNWs) have been investigated. SiNWs are obtained by metal-assisted chemical etching (MACE) method. The deposition of vanadium pentoxide on SiNWs layer was performed by vacuum thermal evaporation system for different durations. Scanning electronic microscope (SEM) images show the formation of snowball-like V2O5 nanoparticles on the SiNWs surface. A large condensation of V2O5 elements was observed by increasing the evaporation time. The changes in bonds and chemical composition at the surface of the SiNWs-V2O5 nanocomposites were examined by Raman and Fourier transform infrared (FTIR) spectroscopies. The X-ray Diffraction (XRD) technique revealed the presence of orthorhombic structure of V2O5 layer with good crystallinity. The SiNWs-V2O5 composites show strong visible PL due to the contribution of the radiative band edge transitions of vanadium pentoxide. The emission of V2O5 layer is in the same energy range as that of SiNWs thus leading to a large increase in PL intensity. Optical band gap (Eog) was determined from UV–Vis-IR spectroscopy. The presence of vanadium pentoxide on the SiNWs surface causes an increase in the value of Eog from 1.851 to 2.075 eV. This increase was explained by Burstein-Moss effect.

CMOS-compatible electrochemical nanoimprint: High throughput fabrication of ordered microstructures on semiconductor wafer by using a glassy carbon mold

Metal assisted chemical etching (MACE), as an emerging wet chemical etching method for fabricating semiconductor micro/nano-structures (MNS), has attracted wide attentions because of the advantages of simple processes, high accuracy and no damages. However, the conventionally used noble metal catalysts (such as Au, Pt,) trapped in the micro/nano-structures are difficult to be removed or reused, not only harming the electronic performances of the CMOS devices but also increasing the fabrication cost. Here, we propose an electrochemical nanoimprint strategy by using a glassy carbon (GC) imprint mold. To overcome the poor electrocatalytic activity of GC, the GC imprint mold was connected to a Pt sheet in the cathodic chamber. To avoid the contaminations of metal and metallic cations in the fabricated MNS, the cathodic chamber was separated from the anodic one by a proton exchange membrane. By optimizing the technical parameters, including the contact pressure between GC imprint mold and GaAs wafer, the concentration of electron acceptor in the cathodic chamber, the imprinting time, etc., a remarkable corrosion rate of about 130 nm/min was achieved, comparable with that of platinum electrocatalyst. Furthermore, by using a GC imprint mold in the spatially separated corrosion cell, the contaminations caused by both the metal catalysts and metallic ions can be eliminated. Thus, this work provides a potential approach to the high throughput fabrication of CMOS-compatible semiconductor microdevices.

Construction of Si nanowires/ZnFe2O4/Ag photocatalysts with enhanced photocatalytic activity under visible light and magnetic field

The Si nanowires/ZnFe2O4/Ag composite photocatalyst is prepared by metal-assisted chemical etching and hydrothermal methods. Photoelectric conversion and photodegradation experiments show that the composite structure offers high photocatalytic performance under visible light. The photocurrent density of Si nanowires/ZnFe2O4/Ag is 1.76 mA/cm2, and the Methyl orange photodegradation rate is 19 % within 90 min. Furthermore, the photocatalytic activity of composite photocatalysts was studied under the magnetic field, which further improves the photocatalytic efficiency significantly. Energy band structure studies revealed that the interfacial contact in the Si nanowires/ZnFe2O4/Ag increases carrier transfer and charge separation, thereby improving photocatalytic performance. It can be seen from the I-V results that the Si nanowires/ZnFe2O4/Ag has a negative magnetoresistance. Therefore, in the presence of a magnetic field, photogenerated carriers can be more effectively transferred to the electrode surface to participate in the photocatalytic reaction with improved photocatalytic performance.

Emerging Porous Two-Dimensional Materials: Current Status, Existing Challenges, and Applications.

Two-Dimensional (2D) materials have attracted immense attention in recent years. These materials have found their applications in various fields, such as catalysis, adsorption, energy storage, and sensing, as they exhibit excellent physical, chemical, electronic, photonic, and biological properties. Recently, researchers have focused on constructing porous structures on 2D materials. Various strategies, such as chemical etching and template-based methods, for the development of surface pores are reported, and the porous 2D materials fabricated over the years are used to develop supercapacitors and energy storage devices. Moreover, the lattice structure of the 2D materials can be modulated during the construction of porous structures to develop 2D materials that can be used in various fields such as lattice defects in 2D nanomaterials for enhancing biomedical performances. This review focuses on the recently developed chemical etching, solvent thermal synthesis, microwave combustion, and template methods that are used to fabricate porous 2D materials. The application prospects of the porous 2D materials are summarized. Finally, the key scientific challenges associated with developing porous 2D materials are presented to provide a platform for developing porous 2D materials.

Surface evolution of fused silica hemispherical resonators and its influence on the quality factor

Investigating the surface loss mechanism of hemispherical resonators is essential to further improve the performance of hemispherical resonant gyroscopes. Although many studies have focused on the surface loss mechanism and surface treatment process of fused silica hemispherical resonators, the bulk fabrication of high-quality factor (Q factor) hemispherical resonators is still a significant factor limiting the widely applied hemispherical resonant gyroscopes. To address this practical need, this paper first analyzes the formation mechanism of surface defects and their effect on energy loss. Then, a cyclic chemical etching method using hydrofluoric acid as an etchant is proposed to significantly improve the Q factor of the hemispherical resonator by improving the surface morphology. Finally, a surface loss model was developed based on the experimental results to reveal the mechanism of the effect of surface morphology evolution on the change of the quality factor of the hemispherical resonator. The results show that the developed etching method can significantly improve surface quality with minimal damage to the substrate. The resonator’s Q factor increases to a final value of about 2 × 107 after chemical etching, which is improved by about 20 times. The developed loss model can screen hemispherical resonators with different performances according to the change of the Q factor during the etching process. The etching technique and screening method developed in this paper is essential for bulk fabricating high-quality factor hemispherical resonators.

Characterization of Prismatic Slip in SiC Crystals by Chemical Etching Method

In 4H-silicon carbide crystals, basal plane slip is the predominant deformation mechanism. However, prismatic slip is often observed in single crystals grown by the physical vapor transport method as the diameter expands to 6 inches or larger. Thermal modeling has shown that occurrence of prismatic slip is attributed to increased radial thermal gradients. While X-ray topography can be used to characterize the presence and extent of prismatic slip, the feasibility of using the chemical etching method to assess the extent of prismatic slip in an industrial setting is investigated. The distribution of scallop shaped etch pits oriented along the directions that correspond to prismatic dislocations, correlate well with the results of the thermal model that predicts the occurrence of prismatic slip dislocations. This capability of the etch pit method to characterize prismatic slip can be used to manage radial thermal gradients during PVT growth.

Influence of backside surface morphology on passivation and contact characteristics of TOPCON solar cells

Compared with P-PERC cells, the rear tunnel oxide/n + polysilicon passivation contact structure in N-TOPCon cells makes the influence of rear surface morphology more significant. In this work, the effects of different chemical etching methods and weight loss on the surface topography and passivation characteristics and contact resistance of SiOx/n + poly Si passivated contact structures were investigated by finely controlling the etching process. Studies have shown that for textured surfaces, both increasing the roundness of the pyramids (acid polishing) and flattening the pyramids (alkaline polishing) lead to a more uniform SiOx layer, which improves surface passivation. The significant deterioration of the contact resistance of the alkali-polished flat surface may be more due to the influence of the thickness of the tunnel oxide layer and the concentration of trailing P doping in the substrate. Acid polishing preserves the round pyramid structure but removes the sharp pyramid tips, improving contact passivation while ensuring good metal contact. It can better balance the contradiction between passivation characteristics (J0 ∼ 4.73fA/cm2, J0, metal ∼ 67.26fA/cm2, iVoc ∼ 740 mV) and contact characteristics (ρc, B ∼ 1.67mΩcm2), and achieve the highest average cell efficiency (24.05%).

SERS Nanowire Chip and Machine Learning-Enabled Classification of Wild-Type and Antibiotic-Resistant Bacteria at Species and Strain Levels.

Antimicrobial resistance (AMR) is a major health threat worldwide and the culture-based bacterial detection methods are slow. Surface-enhanced Raman spectroscopy (SERS) can be used to identify target analytes in real time with sensitivity down to the single-molecule level, providing a promising solution for the culture-free bacterial detection. We report the fabrication of SERS substrates having tightly packed silver (Ag) nanoparticles loaded onto long silicon nanowires (Si NWs) grown by the metal-assisted chemical etching (MACE) method for the detection of bacteria. The optimized SERS chips exhibited sensitivity down to 10-12 M concentration of R6G molecules and detected reproducible Raman spectra of bacteria down to a concentration of 100 colony forming units (CFU)/mL, which is a thousand times lower than the clinical threshold of bacterial infections like UTI (105 CFU/mL). A Siamese neural network model was used to classify SERS spectra from bacteria specimens. The trained model identified 12 different bacterial species, including those which are causative agents for tuberculosis and urinary tract infection (UTI). Next, the SERS chips and another Siamese neural network model were used to differentiate AMR strains from susceptible strains of Escherichia coli (E. coli). The enhancement offered by SERS chip-enabled acquisitions of Raman spectra of bacteria directly in the synthetic urine by spiking the sample with only 103 CFU/mL E. coli. Thus, the present study lays the ground for the identification and quantification of bacteria on SERS chips, thereby offering a potential future use for rapid, reproducible, label-free, and low limit detection of clinical pathogens.