About

Clifford Russell Bowers is a Professor in the Department of Chemistry at the University of Florida. His research focuses on nuclear magnetic resonance (NMR) spectroscopy, a technique that uses radio waves to elucidate the atomic-scale structure and dynamics of molecules and materials. Despite the broad applications of NMR in chemistry, medicine, and industry, its sensitivity is limited by weak nuclear magnetic interactions. To address this limitation, Professor Bowers' work utilizes hyperpolarization from parahydrogen, which is rapidly gaining traction in chemically selective biomedical magnetic resonance imaging. His current research interests include understanding the mechanisms of heterogeneous catalysis through parahydrogen spin labeling and developing a flow chemistry process for the continuous production of hyperpolarized metabolites in aqueous solution. Professor Bowers received his PhD in Chemistry from the California Institute of Technology in 1990. He completed postdoctoral training in Chemistry at the University of California, Berkeley under Alexander Pines from 1993 to 1994, and in Physics at the University of Stuttgart, Germany under Michael Mehring from 1991 to 1992. Throughout his career, he has been recognized with several awards including the National Academy of Medicine Healthy Longevity Catalyst Award in 2023, a Term Professorship at the University of Florida from 2018 to 2021, the Netherlands NWO Visiting Scientist Travel Award in 2012, the NSF CAREER Award in 1996, and a NATO-NSF Postdoctoral Fellowship from 1991 to 1992. In addition to his research, Professor Bowers is a faculty affiliate of the National High Magnetic Field Laboratory since 1994 and a member of multiple interdisciplinary centers at the University of Florida, including the Institute for Cooperative Upcycling of Polymers (iCOUP), the Center for Catalysis, the Center for Condensed Matter Sciences, the Center for Chemical Physics, and the Cancer Center. He has also served on the steering committee of the Bologna International Conference on Magnetic Resonance in Porous Media (MRPM) under the Ampere Society from 2016 to 2020.

Research topics

• Composite material
• Nanotechnology
• Photochemistry
• Chemistry
• Materials science
• Chemical engineering
• Organic chemistry

Selected publications

• Surface-Functionalized, Two-Dimensional Polymer Electrochromic Layers as Ultrafast, Multi-State Infrared Optical Gates

  Journal of the American Chemical Society · 2026-03-20

  article

  ) compared to an alkyl functionalized 2DP constructed from the same chromophores. The functionalized nanoporous surfaces enable rapid switching in these materials under either oxidative or reductive conditions, allowing us to access a range of robust, stable optical responses in a single electrochromic layer. These attributes led us to leverage surface-functionalized 2DPs as multistate infrared logic gates. Collectively, this work demonstrates that surface engineering of nanoporous crystalline lattices is a promising approach to co-optimize the electronic and ionic conductivities required to achieve rapidly switchable electrochromic layers. Beyond speed and efficiency, the demonstration of multistate infrared characteristics shows that electrochromic frameworks are useful in integrated optoelectronic circuits. This positions surface-engineered 2DPs as improved electrochromic coatings and a new material platform for photonic information processing and adaptive devices.

  PublisherDOI

• Unconventional Parahydrogen-Induced Hyperpolarization Effects in Chemistry and Catalysis: From Photoreactions to Enzymes

  ACS Catalysis · 2025-04-04 · 14 citations

  reviewOpen access

  activation mechanisms of hydrogenases. By providing a detailed review of these diverse phenomena, we aim to familiarize the reader with the versatility of PHIP and its potential applications for mechanistic studies and chemical analysis.

  PublisherDOI

• Soliton Based Dynamic Nuclear Polarization: An Overhauser Effect in Cyclic Polyacetylene at High Field and Room Temperature

  The Journal of Physical Chemistry Letters · 2024-03-18 · 3 citations

  articleOpen access

  Polyacetylene, a versatile material with an electrical conductivity that can span 7 orders of magnitude, is the prototypical conductive polymer. In this letter, we report the observation of a significant Overhauser effect at the high magnetic field of 14.1 T that operates at 100 K and room temperature in both linear and cyclic polyacetylene. Significant NMR signal enhancements ranging from 24 to 45 are obtained. The increased sensitivity enabled the characterization of the polymer chain defects at natural abundance. The absence of end methyl group carbon-13 signals provides proof of the closed-loop molecular structure of cyclic polyacetylene. The remarkable efficiency of the soliton based Overhauser effect DNP mechanism at high temperature and high field holds promise for applications and extension to other conductive polymer systems.

  PublisherOA PDFDOI

• Diversity of Parahydrogen-Induced Hyperpolarization Effects in Chemistry

  arXiv (Cornell University) · 2024-09-27 · 1 citations

  preprintOpen access

  Nuclear spin hyperpolarization utilizing parahydrogen has the potential for broad applications in chemistry, biochemistry, and medicine. This review examines recent chemical and biochemical insights gained using parahydrogen-induced polarization (PHIP). We begin with photo-induced PHIP, which allows the investigation of short-lived and photo-activated catalysis. Next, we review the partially negative line effect, in which distinctive lineshape helps to reveal information about rapid exchange with parahydrogen and the role of short-lived catalytic species. The NMR signal enhancement of a single proton in oneH-PHIP is discussed, challenging the underpinning concept of the necessity of pairwise hydrogenation. Furthermore, we examine metal-free PHIP facilitated by novel molecular tweezers and radicaloids, demonstrating alternative routes to conventional hydrogenation using metal-based catalysts. Although symmetric molecules incorporating parahydrogen are NMR silent, we showcase methods that reveal hyperpolarized states through post-hydrogenation reactions. We discuss chemical exchange processes that mediate polarization transfer between parahydrogen and a molecular target, expanding the reach of PHIP without synthesizing specialized precursors. We conclude this review by highlighting the role of PHIP in uncovering the H2 activation mechanisms of hydrogenases. By providing a detailed review of these diverse phenomena, we aim to familiarize the reader with the versatility of PHIP and its potential applications for mechanistic studies and chemical analysis.

  PublisherOA PDFDOI

• Wallace S. Brey, Jr. (June 6, 1922–July 13, 2023) – Founding editor of the Journal of Magnetic Resonance

  Journal of Magnetic Resonance · 2023-11-20

  article
  PublisherDOI

• Ultrasmall amorphous zirconia nanoparticles catalyse polyolefin hydrogenolysis

  Nature Catalysis · 2023 · 160 citations

  • Materials science
  • Chemical engineering
  • Chemistry

  Abstract Carbon–carbon bond cleavage reactions, adapted to deconstruct aliphatic hydrocarbon polymers and recover the intrinsic energy and carbon value in plastic waste, have typically been catalysed by metal nanoparticles or air-sensitive organometallics. Metal oxides that serve as supports for these catalysts are typically considered to be inert. Here we show that Earth-abundant, non-reducible zirconia catalyses the hydrogenolysis of polyolefins with activity rivalling that of precious metal nanoparticles. To harness this unusual reactivity, our catalytic architecture localizes ultrasmall amorphous zirconia nanoparticles between two fused platelets of mesoporous silica. Macromolecules translocate from bulk through radial mesopores to the highly active zirconia particles, where the chains undergo selective hydrogenolytic cleavage into a narrow, C 18 -centred distribution. Calculations indicated that C–H bond heterolysis across a Zr–O bond of a Zr(O) 2 adatom model for unsaturated surface sites gives a zirconium hydrocarbyl, which cleaves a C–C bond via β-alkyl elimination.

  PublisherOA PDFDOI

• Soliton based Dynamic Nuclear Polarization: an unexpected Overhauser effect in cyclic polyacetylene at high field and room temperature

  ChemRxiv · 2023-12-26 · 4 citations

  preprintOpen access

  Polyacetylene, a versatile material with an electrical conductivity that can span seven orders of magnitude, is the prototypical conductive polymer. In this letter, we report an unexpected and unprecedented Overhauser Effect that increases with temperature, observed under high magnetic field of 14.1 T, in both linear and cyclic polyacetylene. Significant NMR signal enhancements ranging from 24 to 45 are obtained. The heightened sensitivity enabled the characterization of chain defects at natural abundance. The absence of end methyl group carbon-13 signals provides proof of the closed-loop molecular structure of the cyclic polyacetylene. This efficiency of the soliton based Overhauser Effect DNP mechanism at high temperature and high field holds promise for applications and extension to other conductive polymer systems.

  PublisherOA PDFDOI

• Mesoporous Silica Encapsulated Platinum–Tin Intermetallic Nanoparticles Catalyze Hydrogenation with an Unprecedented 20% Pairwise Selectivity for Parahydrogen Enhanced Nuclear Magnetic Resonance

  The Journal of Physical Chemistry Letters · 2022-05-04 · 7 citations

  articleSenior authorCorresponding

  Supported noble metals offer key advantages over homogeneous catalysts for in vivo applications of parahydrogen-based hyperpolarization. However, their performance is compromised by randomization of parahydrogen spin order resulting from rapid hydrogen adatom diffusion. The diffusion on Pt surfaces can be suppressed by introduction of Sn to form Pt–Sn intermetallic phases. Herein, an unprecedented pairwise selectivity of 19.7 ± 1.1% in the heterogeneous hydrogenation of propyne using silica encapsulated Pt–Sn intermetallic nanoparticles is reported. This high level of selectivity exceeds that of all supported metal catalysts by at least a factor of 3. Moreover, the pairwise selectivity for alkyne hydrogenation is about 2 times higher than for alkene hydrogenation, an observation attributed to the higher coverage of the former and its effect on diffusion. Lastly, PtSn@mSiO2 nanoparticles exhibited improved coking resistance, and any loss of activity is shown to be fully reversible through high-temperature oxidation–reduction cycling.

  PublisherDOI

• Adiabatic Passage through Level Anticrossings in Systems of Chemically Inequivalent Protons Incorporating Parahydrogen: Theory, Experiment, and Prospective Applications

  Journal of the American Chemical Society · 2022-11-04 · 12 citations

  articleOpen accessSenior authorCorresponding

  Level anticrossings (LACs) are ubiquitous in quantum systems and have been exploited for spin-order transfer in hyperpolarized nuclear magnetic resonance spectroscopy. This paper examines the manifestations of adiabatic passage through a specific type of LAC found in homonuclear systems of chemically inequivalent coupled protons incorporating parahydrogen (pH2). Adiabatic passage through such a LAC is shown to elicit translation of the pH2 spin order. As an example, with prospective applications in biomedicine, proton spin polarizations of at least 19.8 ± 2.6% on the methylene protons and 68.7 ± 0.5% on the vinylic protons of selectively deuterated allyl pyruvate ester are demonstrated experimentally. After ultrasonic spray injection of a precursor solution containing propargyl pyruvate and a dissolved Rh catalyst into a chamber pressurized with 99% para-enriched H2, the products are collected and transported to a high magnetic field for NMR detection. The LAC-mediated hyperpolarization of the methylene protons is significant because of the stronger spin coupling to the pyruvate carbonyl 13C, setting up an ideal initial condition for subsequent coherence transfer by selective INEPT. Furthermore, the selective deuteration of the propargyl side arm increases the efficiency and polarization level. LAC-mediated translation of parahydrogen spin order completes the first step toward a new and highly efficient route for the 13C NMR signal enhancement of pyruvate via side-arm hydrogenation with parahydrogen.

  PublisherOA PDFDOI

• Perpetual hyperpolarization of allyl acetate from parahydrogen and continuous flow heterogeneous hydrogenation with recycling of unreacted propargyl acetate

  Journal of Magnetic Resonance Open · 2022-09-23 · 6 citations

  articleOpen accessSenior authorCorresponding

  A novel closed loop, continuous flow (CF) reactor system for parahydrogen enhanced nuclear magnetic resonance (NMR) of liquids via heterogeneous catalysis is introduced which enables recycling of unreacted liquid substrate reactant. This system consists of an HPLC pump, a liquid substrate reservoir incorporating a gas diffuser, an all-metal packed bed catalytic reactor, and an AF-2400 tube-in-tube gas permeable membrane for removal of normal H2. Two types of supported metal nanoparticle catalysts were tested: mesoporous silica encapsulated Pt3Sn intermetallic nanoparticles and a Rh on anatase TiO2 support. In the CF hydrogenation of propargyl acetate to allyl acetate, the hyperpolarized signals exhibited stability over 20 min of recirculation, with signal enhancements of up to 626 using 99% p-H2 and negligible leaching of the catalyst into the flowing solutions. These results demonstrate the practicality of performing systematic optimization of conditions for continuous flow catalysis and polarization transfer to heteronuclei with important implications for biomedical magnetic resonance imaging.

  PublisherDOI

Recent grants

• Understanding Surface-Mediated Hyperpolarization of Water and other Neat Liquids from Parahydrogen

  NSF · $470k · 2018–2021

• Heterogeneous Catalysts Tailored for Parahydrogen Induced Nuclear Spin Polarization

  NSF · $400k · 2015–2019

• Collaborative Research: Continuous-Flow Hyperpolarization of Liquids Utilizing Parahydrogen and Heterogeneous Catalysis

  NSF · $300k · 2021–2025

• Inducing molecular single file diffusion by co-adsorption in one-dimensional channels for gas separations and catalysis

  NSF · $372k · 2010–2013

Frequent coauthors

• Wenyu Huang

  China Pharmaceutical University

  36 shared

• Joshua D. Caldwell

  Vanderbilt University

  34 shared

• Sergey Vasenkov

  University of Florida

  26 shared

• Linda S. Shimizu

  University of South Carolina

  25 shared

• Ammon J. Sindt

  21 shared

• Eduard Y. Chekmenev

  The Barbara Ann Karmanos Cancer Institute

  21 shared

• Mark D. Smith

  University of South Carolina

  21 shared

• Yunpu Zhao

  Ames National Laboratory

  19 shared

Education

• PhD, Chemistry

  California Institute of Technology

  1990

• BA, Chemistry

  Bowdoin College

  1985

Awards & honors

• Healthy Longevity Catalyst Awardee (2023)
• Term Professor, University of Florida (2018–2021)
• Netherlands NWO Visiting Scientist Travel Award (2012)
• NSF CAREER AWARD (1996)
• NATO-NSF Postdoctoral Fellow (1991–1992)