Periodic Reporting for period 2 - AETSOM (Engineering a solution to the “resolution gap” problem for probing local optoelectronic properties in low-dimensional materials)
Periodo di rendicontazione: 2023-09-01 al 2024-08-31
The native length scales of most optical and optoelectronic processes within low-dimensional materials and next-generation devices are well below the diffraction limit of light, and many of their defining properties are determined by material physics that occur at single-digit nanometer length scales. Their direct investigation and elucidation – crucial for future applications – therefore requires the ability to probe light matter interactions at resolutions an order of magnitude better than what is generally achievable with existing approaches. The aim of this action was to develop a breakthrough capability for achieving single-nanometer optical resolution, by combining the strengths of scanning probe microscopy with those of atomic energy transfer within and from lanthanide doped upconverting nanoparticles – and to utilize this approach to investigate and overcome longstanding scientific questions and challenges that are currently preventing technological breakthroughs in novel-material-based devices.
Throughout this action, the researcher has led the design and optimization of a cutting-edge microscopy system, which combines the capability of probing single nanoparticles with two different probes – and hence modalities – simultaneously. This advanced technique allows for the correlative interrogation of both optical and mechanical properties, at the sub-nanoparticle scale. This ultra-stable, ultra-high-resolution, capability, marries off an atomic force microscope with an inverted optical microscope – to enable the application of mechanical forces on the nanoscale from above with the simultaneous measurement of optical emission (and optical excitation) from below – allowing for elucidation of mechano-optical properties of nanoscale materials with unprecedented mechanical and optical resolutions.
Using this capability, the researcher has studied a novel class of lanthanide-doped upconverting nanoparticles – discovered in the host laboratory at the start of the action (Lee, et al., Nature 2021), and termed “photon-avalanching” nanoparticles. Through a chain reaction, photon-avalanching nanoparticles translate small changes in input to exceptionally large changes in output, and possess the steepest nonlinear response of any nanoscale material. The researcher isolated a single photon-avalanching nanoparticle and pressed upon it with the microscope tip (a needle 10,000 times thinner than a human hair) while optically imaging its emission from below – and discovered that the avalanche is extremely sensitive to miniscule physical forces. Tiny mechanical forces (equivalent to the weight of a grain of salt, divided by 1,000,000) lead to giant changes in the optical signal observed.
Photon avalanching excitation wavelengths and (upconverted) emission wavelengths are both in the near-infrared – benign wavelengths that can penetrate deeply into devices, or, alternately, into human tissue – without causing harm or damage to either. This exceptional characteristic of complete addressability with near-infrared allows for remote interrogation of nanoscale forces without the need for an electrical or mechanical extension; input and output are controlled via deeply-penetrating near-infrared. Hence, photon-avalanching nanoparticles are ideally suited for remote nanoscale sensing of mechanical force, especially from subsurface or interfacial sites.
Throughout the course of the action, the researcher has leveraged this extreme responsiveness of the avalanche to mechanical force to design different nanoparticles that react differently to different scales of force. Exploiting new nanoparticle schemes with precisely engineered energy transfer between the lanthanides within and photon avalanching mechanisms, the researcher has demonstrated novel force-dependent avalanche modalities, from emission intensity changes to emission wavelength changes, with unprecedented mechanical sensitivities.
The results of this action have been disseminated and presented on various platforms around the globe: from international conferences ranging from multidisciplinary to specialized, to outreach events targeting general audiences of various ages and backgrounds.
Using this capability, the researcher has studied a novel class of lanthanide-doped upconverting nanoparticles – discovered in the host laboratory at the start of the action (Lee, et al., Nature 2021), and termed “photon-avalanching” nanoparticles. Through a chain reaction, photon-avalanching nanoparticles translate small changes in input to exceptionally large changes in output, and possess the steepest nonlinear response of any nanoscale material. The researcher isolated a single photon-avalanching nanoparticle and pressed upon it with the microscope tip (a needle 10,000 times thinner than a human hair) while optically imaging its emission from below – and discovered that the avalanche is extremely sensitive to miniscule physical forces. Tiny mechanical forces (equivalent to the weight of a grain of salt, divided by 1,000,000) lead to giant changes in the optical signal observed.
Photon avalanching excitation wavelengths and (upconverted) emission wavelengths are both in the near-infrared – benign wavelengths that can penetrate deeply into devices, or, alternately, into human tissue – without causing harm or damage to either. This exceptional characteristic of complete addressability with near-infrared allows for remote interrogation of nanoscale forces without the need for an electrical or mechanical extension; input and output are controlled via deeply-penetrating near-infrared. Hence, photon-avalanching nanoparticles are ideally suited for remote nanoscale sensing of mechanical force, especially from subsurface or interfacial sites.
Throughout the course of the action, the researcher has leveraged this extreme responsiveness of the avalanche to mechanical force to design different nanoparticles that react differently to different scales of force. Exploiting new nanoparticle schemes with precisely engineered energy transfer between the lanthanides within and photon avalanching mechanisms, the researcher has demonstrated novel force-dependent avalanche modalities, from emission intensity changes to emission wavelength changes, with unprecedented mechanical sensitivities.
The results of this action have been disseminated and presented on various platforms around the globe: from international conferences ranging from multidisciplinary to specialized, to outreach events targeting general audiences of various ages and backgrounds.
This research has achieved “the holy grail” in mechanical sensing: the invention of remotely addressable, with unprecedented mechanical sensitivity and extremely large dynamic range, nanoscale force sensors. This breakthrough work directly addresses the long-standing challenge of measuring and monitoring mechanical forces in complex systems – a challenge defined by the lack of probes possessing the combination of all of the above-mentioned capabilities. This realization is expected to immediately upend the current state of mechanical sensing, in fields as diverse as robotics, biophysics, energy storage, and medicine. Nanoscale forces lie in the heart of most processes and systems, be they engineered or natural. The inability to directly measure these magnitudes of forces, on these spatial scales, in a noninvasive way, has been a roadblock to unraveling and achieving better understanding of the roles these forces play, and hence a barricade to developing remedies in the inevitable case of malfunction. From detecting detrimental expansions within lithium-ion batteries to early diagnosis of stiffening environments of cancerous cells – these remote sensors of force are to disrupt the current state of the art, and impact the world for the better.