Browsing by Subject "Nanoparticle detection"

Now showing 1 - 4 of 4

Open Access
High-throughput, high-resolution interferometric light microscopy of biological nanoparticles
(American Chemical Society, 2020-01) Yurdakul, C.; Avcı, O.; Matlock, A.; Devaux, A. J.; Quintero, M. V.; Özbay, Ekmel; Davey, R. A.; Connor, J. H.; Karl, W. C.; Tian, L.; Ünlü, M. Selim
Label-free, visible light microscopy is an indispensable tool for studying biological nanoparticles (BNPs). However, conventional imaging techniques have two major challenges: (i) weak contrast due to low-refractive-index difference with the surrounding medium and exceptionally small size and (ii) limited spatial resolution. Advances in interferometric microscopy have overcome the weak contrast limitation and enabled direct detection of BNPs, yet lateral resolution remains as a challenge in studying BNP morphology. Here, we introduce a wide-field interferometric microscopy technique augmented by computational imaging to demonstrate a 2-fold lateral resolution improvement over a large field-of-view (>100 × 100 μm2 ), enabling simultaneous imaging of more than 104 BNPs at a resolution of ∼150 nm without any labels or sample preparation. We present a rigorous vectorial-optics-based forward model establishing the relationship between the intensity images captured under partially coherent asymmetric illumination and the complex permittivity distribution of nanoparticles. We demonstrate high-throughput morphological visualization of a diverse population of Ebola virus-like particles and a structurally distinct Ebola vaccine candidate. Our approach offers a low-cost and robust label-free imaging platform for high-throughput and high-resolution characterization of a broad size range of BNPs.
Open Access
Nonlinear nanomechanical mass spectrometry at the single-nanoparticle level
(American Chemical Society, 2019) Yüksel, Mert; Orhan, Ezgi; Yanık, C.; Arı, Atakan B.; Demir, A.; Hanay, Mehmet Selim
Nanoelectromechanical systems (NEMS) have emerged as a promising technology for performing the mass spectrometry of large biomolecules and nanoparticles. As nanoscale objects land on NEMS sensors one by one, they induce resolvable shifts in the resonance frequency of the sensor proportional to their weight. The operational regime of NEMS sensors is often limited by the onset of nonlinearity, beyond which the highly sensitive schemes based on frequency tracking by phase-locked loops cannot be readily used. Here, we develop a measurement architecture with which to operate at the nonlinear regime and measure frequency shifts induced by analytes in a rapid and sensitive manner. We used this architecture to individually characterize the mass of gold nanoparticles and verified the results by performing independent measurements of the same nanoparticles based on linear mass sensing. Once the feasibility of the technique is established, we have obtained the mass spectrum of a 20 nm gold nanoparticle sample by individually recording about 500 single-particle events using two modes working sequentially in the nonlinear regime. The technique obtained here can be used for thin nanomechanical structures that possess a limited dynamic range.
Open Access
Sensing and characterization of single nanoparticles by vacuum-free nanoelectromechanical systems with an integrated polymeric lens
(2021-08) Erdoğan, Ramazan Tufan
Machines in the nanoscale dimension had the opportunity to become a top-notch choice to detect and characterize nanoparticles thanks to the rapid progress in micro-nano fabrication. Sensors that can detect and identify nanoparticles al-lowed the analysis of the physics on the scale of nanometers. In the last decade, nano-electromechanical systems are evolved with the integration of electronics to the mechanical nano dimensional structures to sense the mass of particles. Their small form factor, high sensitivity to mass changes, and compatibility with the microchip fabrication process placed NEMS in a position to be an excellent can-didate for sensing applications. In contrast, high sensitivity that is coming from their minuscule size of active area for mass detection comes with the cost of hav-ing minimal eﬃciency in capturing the nanoparticles in concern. Moreover, the need for vacuum equipment for the transportation of the nanoparticles conﬁned NEMS-MS applications to the laboratories. Here, we resolved these problems by integrating a polymeric lens on top of the NEMS sensors in order to transport and direct the incoming nanoparticles, utilizing the electric ﬁeld only, towards the minuscule active detection area; with exploiting change of the electric ﬁeld in between nanoparticle source and NEMS, due to the accumulating surface charges over the polymeric lens. Therefore, we executed mass sensing measurements and obtained the mass spectrum of the 40 nm diameter gold nanoparticles and 100 nm diameter polystyrene nanoparticles without diﬀerential vacuum equipment, with a rapid analysis time and high capture eﬃciency.
Open Access
Single nanoparticle sensing with nanoelectromechanical resonators operating at nonlinear regime
(2019-08) Yüksel, Mert
Machines working at the nanoscale dimensions o er an important technological opportunity for healthcare and biomedical screening. State-of-the-art nanomachines are usually operated at small displacements, since engineering tools for their control at large vibration amplitudes have so far been absent. Nanoelectromechanical Systems (NEMS) have emerged as a promising technology for performing the mass spectrometry of large biomolecules and nanoparticles. Nanoparticles constitute an important family in the nanotechnology toolbox, because they indicate potential pollutions early on, or can be designed to act as drug carriers for cancer therapy. As nanoscale objects land on NEMS sensor one by one, they induce resolvable shifts in the resonance frequency of the sensor proportional to their weight. The operational regime of NEMS sensors is often limited by the onset-of-nonlinearity, beyond which the highly sensitive schemes based on frequency tracking by phase-locked loops cannot be readily used. Here, we develop a measurement architecture to operate at the nonlinear regime and measure frequency shifts induced by analytes in a rapid and sensitive manner. We used this architecture to individually characterize the mass of gold nanoparticles and veri ed the results by performing independent measurements of the same nanoparticles based on linear mass sensing. Once the feasibility of the technique is established, we have obtained the mass spectrum of a 20 nm gold nanoparticle sample by individually recording about ve hundred single particle events using two modes working sequentially in the nonlinear regime. The technique obtained here can be used for thin nanomechanical structures which possess a limited dynamic range.