High-sensitivity narrow­band T-shaped cantilever Fabry-perot acoustic sensor for photoacoustic spectroscopy.

Photoacoustic spectroscopy (PAS) has been rapidly developed and applied to different detection scenarios. The acoustic pressure detection is an important part in the PAS system. In this paper, an ultrahigh sensitivity Fabry-Perot acoustic sensor with a T-shaped cantilever was proposed. To achieve the best acoustic pressure effect, the dimension of the cantilever structure was designed and optimized by finite element analysis using COMSOL Multiphysics. Simulation results showed that the sensitivity of such T-shaped cantilever was 1.5 times higher than that based on a rectangular cantilever, and the resonance frequency of T-shaped cantilever were able to modulate from 800 Hz to 1500 Hz by adjusting the multi-parameter characteristics. Experimental sensing results showed that the resonance frequency of T-shaped Fabry-Perot acoustic sensor was 1080 Hz, yielding a high sensitivity of 1.428 µm/Pa, with a signal-to-noise ratio (SNR) of 84.8 dB and a detectable pressure limit of 1.9 µPa/Hz1/2@1 kHz. We successfully used such acoustic sensor to measure acetylene (C2H2) concentration in the PAS. The sensitivity of PAS for C2H2 gas was 3.22 pm/ppm with a concentration range of 50 ppm ∼100 ppm, and the minimum detection limit was 24.91ppb.

Achieving consistency of flexible surface acoustic wave sensors with artificial intelligence.

Flexible surface acoustic wave technology has garnered significant attention for wearable electronics and sensing applications. However, the mechanical strains induced by random deformation of these flexible SAWs during sensing often significantly alter the specific sensing signals, causing critical issues such as inconsistency of the sensing results on a curved/flexible surface. To address this challenge, we first developed high-performance AlScN piezoelectric film-based flexible SAW sensors, investigated their response characteristics both theoretically and experimentally under various bending strains and UV illumination conditions, and achieved a high UV sensitivity of 1.71 KHz/(mW/cm²). To ensure reliable and consistent UV detection and eliminate the interference of bending strain on SAW sensors, we proposed using key features within the response signals of a single flexible SAW device to establish a regression model based on machine learning algorithms for precise UV detection under dynamic strain disturbances, successfully decoupling the interference of bending strain from target UV detection. The results indicate that under strain interferences from 0 to 1160 µÎµ the model based on the extreme gradient boosting algorithm exhibits optimal UV prediction performance. As a demonstration for practical applications, flexible SAW sensors were adhered to four different locations on spacecraft model surfaces, including flat and three curved surfaces with radii of curvature of 14.5, 11.5, and 5.8 cm. These flexible SAW sensors demonstrated high reliability and consistency in terms of UV sensing performance under random bending conditions, with results consistent with those on a flat surface.

Morin reverses P-glycoprotein-mediated multidrug-resistance in KBChR-8-5 cancer cell lines.

Multidrug resistance (MDR) during clinical chemotherapy for cancer has been considered a major obstacle to treatment efficacy. The involvement of adenosine triphosphate-binding cassette (ABC) transporters in the MDR mechanism significantly reduces the efficacy of chemotherapeutics. This study investigates the potential of morin, a dietary bioflavonoid, to overcome colchicine resistance in KBChR-8-5 MDR cells. The P-gp inhibitory activity by morin was measured by calcein-AM drug efflux assay. Western blot analysis was employed to evaluate P-gp messenger RNA and protein expressions following morin treatment. Flow cytometry analysis and acridine orange/ethidium bromide fluorescence staining were utilised to investigate the induction of apoptosis and cell cycle arrest upon treatment with morin and paclitaxel in combination. Additionally, polymerase chain reaction (PCR) array analysis was conducted to study the gene expression profiles related to MDR, apoptosis and cell cycle arrest during treatment with morin, paclitaxel or their combination. Morin exhibited a strong binding interaction with human P-gp. This was corroborated by drug efflux assays, which showed a reduction in P-gp efflux function with increasing morin concentration. Furthermore, morin and paclitaxel combination potentiated the induction of apoptosis and G2/M phase cell cycle arrest. Morin treatment significantly downregulated the gene expression of ABCB1 and P-gp membrane expressions in MDR cells. Additionally, PCR array gene expression analysis revealed that the combination treatment with morin and paclitaxel upregulated proapoptotic and cell cycle arrest genes while downregulating ABCB1 gene and antiapoptotic genes. Thus, morin effectively reversed paclitaxel resistance in KBChR-8-5 drug-resistant cancer cells and concluded that morin resensitized the paclitaxel resistance in KBChR8-5 drug-resistant cancer cells.

A nanonewton force sensor using a U-shape tapered microfiber interferometer.

Nanomechanical measurements, especially the detection of weak contact forces, play a vital role in many fields, such as material science, micromanipulation, and mechanobiology. However, it remains a challenging task to realize the measurement of ultraweak force levels as low as nanonewtons with a simple sensing configuration. In this work, an ultrasensitive all-fiber nanonewton force sensor structure based on a single-mode-tapered U-shape multimode-single-mode fiber probe is proposed and experimentally demonstrated with a limit of detection of ~5.4 nanonewtons. The use of the sensor is demonstrated by force measurement on a human hair sample to determine the spring constant of the hair. The results agree well with measurements using an atomic force microscope for the spring constant of the hair. Compared with other force sensors based on optical fiber in the literature, the proposed all-fiber force sensor provides a substantial advancement in the minimum detectable force possible, with the advantages of a simple configuration, ease of fabrication, and low cost.

Capillary wave tweezer.

Precise control of microparticle movement is crucial in high throughput processing for various applications in scalable manufacturing, such as particle monolayer assembly and 3D bio-printing. Current techniques using acoustic, electrical and optical methods offer precise manipulation advantages, but their scalability is restricted due to issues such as, high input powers and complex fabrication and operation processes. In this work, we introduce the concept of capillary wave tweezers, where mm-scale capillary wave fields are dynamically manipulated to control the position of microparticles in a liquid volume. Capillary waves are generated in an open liquid volume using low frequency vibrations (in the range of 10-100 Hz) to trap particles underneath the nodes of the capillary waves. By shifting the displacement nodes of the waves, the trapped particles are precisely displaced. Using analytical and numerical models, we identify conditions under which a stable control over particle motion is achieved. By showcasing the ability to dynamically control the movement of microparticles, our concept offers a simple and high throughput method to manipulate particles in open systems.

Fundamentals of Monitoring Condensation and Frost/Ice Formation in Cold Environments Using Thin-Film Surface-Acoustic-Wave Technology.

Moisture condensation, fogging, and frost or ice formation on structural surfaces cause severe hazards in many industrial components such as aircraft wings, electric power lines, and wind-turbine blades. Surface-acoustic-wave (SAW) technology, which is based on generating and monitoring acoustic waves propagating along structural surfaces, is one of the most promising techniques for monitoring, predicting, and also eliminating these hazards occurring on these surfaces in a cold environment. Monitoring condensation and frost/ice formation using SAW devices is challenging in practical scenarios including sleet, snow, cold rain, strong wind, and low pressure, and such a detection in various ambient conditions can be complex and requires consideration of various key influencing factors. Herein, the influences of various individual factors such as temperature, humidity, and water vapor pressure, as well as combined or multienvironmental dynamic factors, are investigated, all of which lead to either adsorption of water molecules, condensation, and/or frost/ice in a cold environment on the SAW devices. The influences of these parameters on the frequency shifts of the resonant SAW devices are systematically analyzed. Complemented with experimental studies and data from the literature, relationships among the frequency shifts and changes of temperature and other key factors influencing the dynamic phase transitions of water vapor on SAW devices are investigated to provide important guidance for icing detection and monitoring.

Progress in wearable acoustical sensors for diagnostic applications.

With extensive and widespread uses of miniaturized and intelligent wearable devices, continuously monitoring subtle spatial and temporal changes in human physiological states becomes crucial for daily healthcare and professional medical diagnosis. Wearable acoustical sensors and related monitoring systems can be comfortably applied onto human body with a distinctive function of non-invasive detection. This paper reviews recent advances in wearable acoustical sensors for medical applications. Structural designs and characteristics of the structural components of wearable electronics, including piezoelectric and capacitive micromachined ultrasonic transducer (i.e., pMUT and cMUT), surface acoustic wave sensors (SAW) and triboelectric nanogenerators (TENGs) are discussed, along with their fabrication techniques and manufacturing processes. Diagnostic applications of these wearable sensors for detection of biomarkers or bioreceptors and diagnostic imaging have further been discussed. Finally, main challenges and future research directions in these fields are highlighted.

5.7 GHz Ultrasensitive Shear Horizontal-Surface Acoustic Wave Humidity Sensor Based on LiNbO3/SiO2/SiC Heterostructures with a Sensitive Layer of Polyethyleneimine-SiO2 Nanocomposites.

Humidity sensing and water molecule monitoring have become hot research topics attributed to their potential applications in monitoring breathing/physiological conditions of humans, air conditioning in greenhouses, and soil moisture in agriculture. However, there is a huge challenge for highly sensitive and precision humidity detection with wireless and fast responsive capabilities. In this work, a hybrid/synergistic strategy was proposed using a LiNbO3/SiO2/SiC heterostructure to generate shear-horizontal (SH) surface acoustic waves (SAWs) and using a nanocomposite of polyethylenimine-silicon dioxide nanoparticles (PEI-SiO2 NPs) to form a sensitive layer, thus achieving an ultrahigh sensitivity of SAW humidity sensors. Ultrahigh frequencies (1∼15 GHz) of SAW devices were obtained on a high-velocity heterostructure of LiNbO3/SiO2/SiC. Among the multimodal wave modes, we selected SH waves for humidity sensing and achieved a high mass-sensitivity of 5383 MHz · mm2 · µg-1. With the PEI-SiO2 NP composite as the sensitive layer, an ultrahigh sensitivity of 2.02 MHz/% RH was obtained, which is two orders of magnitude higher than those of the conventional SAW humidity sensors (∼202.5 MHz frequency) within a humidity range of 20-80% RH.

High-precision prediction of blood glucose concentration utilizing Fourier transform Raman spectroscopy and an ensemble machine learning algorithm.

Raman spectroscopy has gained popularity in analyzing blood glucose levels due to its non-invasive identification and minimal interference from water. However, the challenge lies in how to accurately predict blood glucose concentrations in human blood using Raman spectroscopy. This paper researches a novel integrated machine learning algorithm called Bagging-ABC-ELM. The optimal input weights and biases of extreme learning machine (ELM) model are obtained by artificial bee colony (ABC) algorithm. The bagging algorithm is used to obtain a better the stability of the model and higher performance than ELM algorithm. The results show that the mean value of coefficient of determination is 0.9928, and root mean square error is 0.1928. Compared to other regression models, the Bagging-ABC-ELM model exhibited superior prediction accuracy, robustness, and generalization capability. The Bagging-ABC-ELM model presents a promising alternative for analyzing blood glucose levels in clinical and research settings.

Power-controlled acoustofluidic manipulation of microparticles.

Recently, surface acoustic wave (SAW) based acoustofluidic separation of microparticles and cells has attracted increasing interest due to accuracy and biocompatibility. Precise control of the input power of acoustofluidic devices is essential for generating optimum acoustic radiation force to manipulate microparticles given their various parameters including size, density, compressibility, and moving velocity. In this work, an acoustophoretic system is developed by employing SAW based interdigital electrode devices. Power meters are applied to closely monitor the incident and reflected powers of the SAW device, which are associated with the separation efficiency. There exists a range of input powers to migrate the microparticles to the pressure node due to their random locations when entering the SAW field. Theoretical analysis is performed to predict a proper input power to separate mixtures of polystyrene microspheres, and the end lateral position of microspheres being acoustically separated. The separation efficiency of four sizes of microspheres, including 20 µm, 15 µm, 10 µm, and 5 µm, is calculated and compared with experimental results, which suggest the input power for separating the mixture of these microspheres. The study provides a practical guidance on operating SAW devices for bioparticle separation using the incident power as a control parameter.

The novel π-d conjugated TM2B3N3S6 (TM = Mo, Ti and W) monolayers as highly active single-atom catalysts for electrocatalytic synthesis of ammonia.

Recently, single-atom catalysts (SACs) are receiving significant attention in electrocatalysis fields due to their excellent specific activities and extremely high atomic utilization ratio. Effective loading of metal atoms and high stability of SACs increase the number of exposed active sites, thus significantly improving their catalytic efficiency. Herein, we proposed a series (29 in total) of two-dimensional (2D) conjugated structures of TM2B3N3S6 (TM means those 3d to 5d transition metals) and studied the performance as single-atom catalysts for nitrogen reduction reaction (NRR) using density functional theory (DFT). Results show that TM2B3N3S6 (TM = Mo, Ti and W) monolayers have superior performance for ammonia synthesis with low limiting potentials of -0.38, -0.53 and -0.68 V, respectively. Among them, the Mo2B3N3S6 monolayer shows the best catalytic performance of NRR. Meanwhile, the π conjugated B3N3S6 rings undergo coordinated electron transfer with the d orbitals of TM to exhibit good chargeability, and these TM2B3N3S6 monolayers activate isolated N2 according to the "acceptance-donation" mechanism. We have also verified the good stability (i.e., Ef < 0, and Udiss > 0) and high selectivity (Ud = -0.03, 0.01 and 0.10 V, respectively) of the above four types of monolayers for NRR over hydrogen evolution reaction (HER). The NRR activities have been clarified by multiple-level descriptors (ΔG*N2H, ICOHP, and Ɛd) in the terms of basic characteristics, electronic property, and energy. Moreover, the aqueous solution can promote the NRR process, leading to the reduction of ΔGPDS from 0.38 eV to 0.27 eV for the Mo2B3N3S6 monolayer. However, the TM2B3N3S6 (TM = Mo, Ti and W) also showed excellent stability in aqueous phase. This study proves that the π-d conjugated monolayers of TM2B3N3S6 (TM = Mo, Ti and W) as electrocatalysts show great potentials for the nitrogen reduction.

Open source board based acoustofluidic transwells for reversible disruption of the blood-brain barrier for therapeutic delivery.

BACKGROUND: Blood-brain barrier (BBB) is a crucial but dynamic structure that functions as a gatekeeper for the central nervous system (CNS). Managing sufficient substances across the BBB is a major challenge, especially in the development of therapeutics for CNS disorders. METHODS: To achieve an efficient, fast and safe strategy for BBB opening, an acoustofluidic transwell (AFT) was developed for reversible disruption of the BBB. The proposed AFT was consisted of a transwell insert where the BBB model was established, and a surface acoustic wave (SAW) transducer realized using open-source electronics based on printed circuit board techniques. RESULTS: In the AFT device, the SAW produced acousto-mechanical stimulations to the BBB model resulting in decreased transendothelial electrical resistance in a dose dependent manner, indicating the disruption of the BBB. Moreover, SAW stimulation enhanced transendothelial permeability to sodium fluorescein and FITC-dextran with various molecular weight in the AFT device. Further study indicated BBB opening was mainly attributed to the apparent stretching of intercellular spaces. An in vivo study using a zebrafish model demonstrated SAW exposure promoted penetration of sodium fluorescein to the CNS. CONCLUSIONS: In summary, AFT effectively disrupts the BBB under the SAW stimulation, which is promising as a new drug delivery methodology for neurodegenerative diseases.

Highly-Exposed Co-CoO Derived from Nanosized ZIF-67 on N-Doped Porous Carbon Foam as Efficient Electrocatalyst for Zinc-Air Battery.

Non-precious-metal based electrocatalysts with highly-exposed and well-dispersed active sites are crucially needed to achieve superior electrocatalytic performance for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) toward zinc-air battery (ZAB). Herein, Co-CoO heterostructures derived from nanosized ZIF-67 are densely-exposed and strongly-immobilized onto N-doped porous carbon foam (NPCF) through a self-sacrificial pyrolysis strategy. Benefited from the high exposure of Co-CoO heterostructures and the favorable mass and electron transfer ability of NPCF, the Co-CoO/NPCF electrocatalyst exhibits remarkable performance for both ORR (E1/2  = 0.843 V vs RHE) and OER (Ej = 10 mA cm-2  = 1.586 V vs RHE). Further application of Co-CoO/NPCF as the air-cathode in rechargeable ZAB achieves superior performance for liquid-state ZAB (214.1 mW cm-2 and 600 cycles) and flexible all-solid-state ZAB (93.1 mW cm-2 and 140 cycles). Results from DFT calculations demonstrate that the electronic metal-support interactions between Co-CoO and NPCF via abundant C-Nx sites is favorable for electronic structure modulation, accounting for the remarkable performance.

A phase transition model in dual-amorphous water undergoing liquid-liquid transition.

An in-depth understanding of liquid-liquid phase transition (LLPT) in condensed water will gain insight into anomalous behaviors of dual-amorphous condensed water. Despite numerous experimental, molecular simulation, and theoretical studies, it is yet to achieve a widely accepted consensus with convinced evidence in the condensed matter physics for two-state liquid-liquid transition of water. In this work, a theoretical model is proposed based on the Avrami equation, commonly used to describe first-order phase transitions, to elucidate complex homogeneous and inhomogeneous condensation from high-density liquid (HDL) water to low-density liquid (LDL) water for both pure and ionic dual-amorphous condensed water. This model unifies the coupling effects of temperature and electrolyte concentration based on the new theoretical framework. The Adam-Gibbs theory is then introduced to characterize the synergistic motion and relaxation behavior of condensed water. Variations in the configurational entropy under electrostatic forces are further explored, and an analytical 2D cloud chart is developed to visualize the synergistic effect of temperature and electrolyte concentration on the configurational entropy of ionic water. The constitutive relationships among viscosity, temperature, and electrolyte concentration are derived to analyze their synergistic effects under different condensation fractions of LDL and HDL. The Stokes-Einstein relation and free volume theory are further used to analyze diffusion coefficients and densities (or apparent density) during both pure and ionic LLPT. Finally, theoretical results obtained from these models are compared with experimental results reported in literature to validate the accuracy and applicability of the proposed models, which offer significant benefits and advancements in effectively predicting physical property changes of dual-amorphous condensed water.

Impact Dynamics of Non-Newtonian Droplets on Superhydrophobic Surfaces.

Droplet impact behavior on a solid surface is critical for many industrial applications such as spray coating, food production, printing, and agriculture. For all of these applications, a common challenge is to modify and control the impact regime and contact time of the droplets. This challenge becomes more critical for non-Newtonian liquids with complex rheology. In this research, we explored the impact dynamics of non-Newtonian liquids (by adding different concentrations of Xanthan into water) on superhydrophobic surfaces. Our experimental results show that by increasing the Xanthan concentration in water, the shapes of the bouncing droplet are dramatically altered, e.g., its shape at the separation moment is changed from a conventional vertical jetting into a "mushroom"-like one. As a result, the contact time of the non-Newtonian droplet could be reduced by up to ∼50%. We compare the impact scenarios of Xanthan liquids with those of glycerol solutions having a similar apparent viscosity, and results show that the differences in the elongation viscosity induce different impact dynamics of the droplets. Finally, we show that by increasing the Weber number for all of the liquids, the contact time is reduced, and the maximum spreading radius is increased.

An enhanced tilted-angle acoustic tweezer for mechanical phenotyping of cancer cells.

Acoustofluidic devices becomes one of the emerging and versatile tools for many biomedical applications. Most of the previous acoustofluidic devices are used for cells manipulation, and the few devices for cell phenotyping with a limitation in throughput. In this study, an enhanced tilted-angle (ETA) acoustofluidic device is developed and applied for mechanophenotyping of live cells. The ETA Device consists of an interdigital transducer which is positioned along a microfluidic channel. An inclination angle of 5° is introduced between the interdigital transducer and the liquid flow direction. The pressure nodes formed inside the acoustofluidic field in the channel deflect the biological cells from their original course in accordance with their mechanical properties, including volume, compressibility, and density. The threshold power for fully converging the cells to the pressure node is used to calculate the acoustic contrast factor. To demonstrate the ETA device in cell mechanophenotyping, and distinguishing between different cell types, further experimentation is carried out by using A549 (lung cancer cells), MDB-MA-231 (breast cancer cells), and leukocytes. The resulting acoustic contrast factors for the lung and breast cancer cells are different from that of the leukocytes by 27.9% and 21.5%, respectively. These results suggest this methodology can successfully distinguish and phenotype different cell types based on the acoustic contrast factor.

Dual-Wave Acoustofluidic Centrifuge for Ultrafast Concentration of Nanoparticles and Extracellular Vesicles.

Extracellular vesicles (EVs) are secreted nanostructures that play various roles in critical cancer processes. They operate as an intercellular communication system, transferring complex sets of biomolecules from cell to cell. The concentration of EVs is difficult to decipher, and there is an unmet technological need for improved (faster, simpler, and gentler) approaches to isolate EVs from complex matrices. Herein, an acoustofluidic concentration of extracellular vesicles (ACEV) is presented, based on a thin-film printed circuit board with interdigital electrodes mounted on a piezoelectric substrate. An angle of 120° is identified between the electrodes and the reference flat of the piezoelectric substrate for simultaneous generation of Rayleigh and shear horizontal waves. The dual waves create a complex acoustic field in a droplet, resulting in effective concentration of nanoparticles and EVs. The ACEV is able to concentrate 20 nm nanospheres within 105 s and four EV dilutions derived from the human prostate cancer (Du145) cell line in approximately 30 s. Cryo-electron microscopy confirmed the preservation of EV integrity. The ACEV device holds great potential to revolutionize investigations of EVs. Its faster, simpler, and gentler approach to EV isolation and concentration can save time and effort in phenotypic and functional studies of EVs.

Metal-organic framework-derived trimetallic oxides with dual sensing functions for ethanol.

Metal-organic framework (MOF)-derived metal oxide semiconductors have recently received extensive attention in gas sensing applications due to their high porosity and three-dimensional architecture. Still, challenges remain for MOF-derived materials, including low-cost and facile synthetic methods, rational nanostructure design, and superior gas-sensing performances. Herein, a series of Fe-MIL-88B-derived trimetallic FeCoNi oxides (FCN-MOS) with a mesoporous structure were synthesized by a one-step hydrothermal reaction followed by calcination. The FCN-MOS system consists of three main phases: α-Fe2O3 (n-type), CoFe2O4, and NiFe2O4 (p-type), and the nanostructure and pore size can be controlled by altering the content of α-Fe2O3, CoFe2O4, and NiFe2O4. The sensors based on FCN-MOS exhibit a high response of 71.9, a good selectivity towards 100 ppm ethanol at 250 °C, and long-term stability up to 60 days. Additionally, the FCN-MOS-based sensors show a p-n transition gas sensing behavior with the alteration of the Fe/Co/Ni ratio.

Integrated label-free erbium-doped fiber laser biosensing system for detection of single cell Staphylococcus aureus.

A critical challenge to realize ultra-high sensitivity with optical fiber interferometers for label free biosensing is to achieve high quality factors (Q-factor) in liquid. In this work a high Q-factor of 105, which significantly improves the detection resolution is described based on a structure of single mode -core-only -single mode fiber (SCS) with its multimode (or Mach-Zehnder) interference effect as a filter that is integrated into an erbium-doped fiber laser (EDFL) system for excitation. In the case study, the section of core-only fiber is functionalized with porcine immunoglobulin G (IgG) antibodies, which could selectively bind to bacterial pathogen of Staphylococcus aureus (S. aureus). The developed microfiber-based biosensing platform called SCS-based EDFL biosensors can effectively detect concentrations of S. aureus from 10 to 105 CFU/mL, with a responsivity of 0.426 nm wavelength shift in the measured spectrum for S. aureus concentration of 10 CFU/mL. The limit of detection (LoD) is estimated as 7.3 CFU/mL based on the measurement of S. aureus with minimum concentration of 10 CFU/mL. In addition, when a lower concentration of 1 CFU/mL is applied to the biosensor, a wavelength shift of 0.12 nm is observed in 10% of samples (1/10), indicating actual LoD of 1 CFU/mL for the proposed biosensor. Attributed to its good sensitivity, stability, reproducibility and specificity, the proposed EDFL based biosensing platform has great potentials for diagnostics.

Significantly Stabilizing Hydrogen Evolution Reaction Induced by Nb-Doping Pt/Co(OH)2 Nanosheets.

High stability and efficiency of electrocatalysts are crucial for hydrogen evolution reaction (HER) toward water splitting in an alkaline media. Herein, a novel nano-Pt/Nb-doped Co(OH)2 (Pt/NbCo(OH)2 ) nanosheet is designed and synthesized using water-bath treatment and solvothermal reduction approaches. With nano-Pt uniformly anchored onto NbCo(OH)2 nanosheet, the synthesized Pt/NbCo(OH)2 shows outstanding electrocatalytic performances for alkaline HER, achieving a high stability for at least 33 h, a high mass activity of 0.65 mA µg-1 Pt, and a good catalytic activity with a low overpotential of 112 mV at 10 mA cm-2 . Both experimental and theoretical results prove that Nb-doping significantly optimizes the hydrogen adsorption free energy to accelerate the Heyrovsky step for HER, and boosts the adsorption of H2 O, which further enhances the water activation. This study provides a new design methodology for the Nb-doped electrocatalysts in an alkaline HER field by facile and green way.