About

Howard Fairbrother is a Professor and Associate Chair in the Department of Chemistry at Johns Hopkins University. His research involves aspects of environmental, analytical, physical, and materials science, with a focus on understanding the mechanisms of depositing nanostructures and exploring the environmental implications and applications of nanomaterials. His group develops a molecular level understanding of deposition processes used to create nanostructures, collaborating with researchers at the University of Florida and the University of Iceland to investigate surface chemistry and physics associated with focused electron beam induced deposition (FEBID) of metallic nanostructures using organometallic precursors. Fairbrother's research also encompasses the study of engineered nanomaterials, particularly carbon nanotubes, examining their environmental impact and potential applications. His projects include exploring the release rates of carbon nanotubes and quantum dots from polymer nanocomposites, investigating the photochemistry of carbon-based nanomaterials such as carbon nanotubes, graphene, and carbon dots, and assessing how heteroatoms influence the flame retarding properties of carbon nanotubes. Additionally, his work considers the effect of carbon nanotube incorporation on biofilm formation and biodegradation properties of polymers. His experimental approach employs a wide array of techniques, including Atomic Force Microscopy, X-ray Photoelectron Spectroscopy, Mass Spectrometry, Infrared Spectroscopy, UV-Vis Spectroscopy, Transmission Electron Microscopy, and Scanning Electron Microscopy. The Fairbrother lab maintains and operates surface analytical laboratories at Johns Hopkins University, which are accessible to researchers both within and outside the university.

Selected publications

• Probing the Environmental Persistence of Inorganic Nanoparticles and Micro(nano)plastics by Single-Particle ICP-MS

  Environmental Science & Technology · 2026-03-31

  articleSenior authorCorresponding

  The need to better understand the environmental persistence of nanomaterials has driven the development of new analytical methods designed to detect, quantify, and characterize inorganic nanoparticles (NPs) and micro(nano)plastics (MNPs). After two decades of refinement, single-particle inductively coupled plasma mass spectrometry (spICP-MS) has emerged as a powerful analytical technique capable of studying their environmental persistence, by providing high sensitivity, element-specific data on particle size distribution and number concentration. Moreover, spICP-MS can examine NPs/MNPs in environmental samples (i.e., low particle concentrations within complex heterogeneous matrices) where most analytical methods struggle. Herein, we present the underlying analytical principles and current state of spICP-MS, as well introduce the near-term future improvements to the methodology (e.g., multielement detection, enhanced instrumentation) that will enable more sensitive detection, lower particle size limits, and "fingerprinting" of NPs in laboratory studies and environmental samples. We highlight case studies that demonstrate the ability of spICP-MS to elucidate the importance of size, composition, and solution properties in regulating the stability, transformation, and transport of inorganic NPs and MNPs. Throughout, we provide our perspective not only on the unique advantages and success of spICP-MS but also on the challenges associated with existing analytical limits, and indicate scenarios where more experimental studies and instrumentation advances are needed to improve our understanding of NP/MNP persistence.

  PublisherDOI

• Nacre-Inspired Composite Coatings with Hierarchical Architecture for Durable Surface Protection

  Chemistry of Materials · 2026-02-13

  articleOpen accessCorresponding

  A bioinspired multilayer coating is developed for the protection of built cultural heritage, emulating the hierarchical architecture of natural nacre. The system is fabricated through the alternating deposition of mineralized calcium carbonate (CaCO3) and organic layers composed of chitosan and cellulose nanofibrils (CNFs), with poly(acrylic acid) (PAA) acting as a mineralization-directing agent. A CO2-controlled environment promotes the formation of continuous crystalline CaCO3 layers with strong interfacial adhesion to marble substrates. The resulting composite multilayers exhibit stratified organization and mechanical properties comparable to those of the biogenic minerals. Nanoindentation and stiffness mapping reveal hardness and modulus values in the range of natural nacre, along with enhanced reinforcement with increasing numbers of multilayers. Mechanical durability under acidic conditions confirms the preservation of both structural integrity and aesthetic compatibility, with color changes remaining below perceptual thresholds (ΔEab < 5). The observed crack resistance, cohesive strength, and mechanical compatibility with the substrate highlight the effectiveness of the layered architecture for dissipating stress and inhibiting damage propagation. These results contribute to the development of an emerging class of bioinspired protective coatings that integrate mechanical resilience, chemical stability, and visual compatibility by establishing a groundwork for advanced materials tailored to the complex demands of cultural heritage conservation.

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• Uptake and impact of carbon dots and their copper complex on tomato health

  Environmental Science Nano · 2026-01-01

  article

  This work describes the synthesis of copper-loaded carbon dots and their application for suppressing Fusarium disease in tomatoes. These carbon dots could be an effective tool for delivering copper or chelating out heavy metals in plants.

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• Self‐Organized Metal‐Carbon Multilayers Formed by Ion Beam Induced Deposition from Trimethyl(methylcyclopentadienyl)platinum(IV)

  Advanced Functional Materials · 2025-12-19

  articleSenior authorCorresponding

  Abstract Films deposited from Trimethyl(methylcyclopentadienyl)platinum(IV) (MeCpPtMe 3 ) using 1–1.2 keV Ar + and H 2 + ion beams with low deposition rates (&lt;100 nm h −1 ) exhibit spontaneous formation of well‐ordered alternating layers of ≈8 nm platinum and carbon, in marked contrast to the heterogeneous distribution of Pt produced from MeCpPtMe 3 during typical ion or electron beam induced deposition (IBID/EBID). Top‐down scanning electron microscopy (SEM) images and optical microscopy show a series of light and dark rings corresponding to the number of layers in the deposit. The Pt‐rich layers consist of platinum grains with diameters of up to 10 nm, larger than the ≈5 nm diameter Pt grains typically observed for IBID deposits from this precursor. Formation of self‐organized layers is postulated to occur as a result of the initial decomposition of MeCpPtMe 3 on the growth surface, followed by ion enhanced diffusion and recoil implantation, whose effects are concentrated near the surface by the low penetration depth of low‐energy ions. During recoil implantation, the movement of Pt atoms is preferentially downward, as the Pt atom trajectories are relatively unaffected by the light C atom matrix, resulting in enriched Pt layers with large grains. In contrast, C atoms are displaced by Pt atoms, maintaining a C rich surface layer during growth.

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• Differential Effects of Biodegradable Polymers and Polymer-Phosphorus Composites on Tomato Performance and Phosphorus Uptake

  ACS Agricultural Science & Technology · 2025-07-11

  articleSenior authorCorresponding

  While biopolymers have the potential to enhance agrochemical delivery and mitigate environmental impacts such as runoff, previous plant studies have often been limited to examining single biopolymers in isolation. This approach has hindered effective comparisons of plant outcomes due to variations in plant type, growth duration, and soil characteristics. The current study addresses this gap by incorporating six separate milled biopolymers: pectin, starch, chitosan, polycaprolactone (PCL), polylactic acid (PLA), or polyhydroxybutyrate (PHB) into soil and directly comparing their impacts on tomato (Solanum lycopersicum) plants cultivated under identical environmental parameters. Plant outcomes were also studied when biopolymers were modified via the inclusion of two phosphorus (P) salts, forming two types of Polymer-P-containing salt composites with amorphous CaPO4 (CaP) and CaHPO4 (DCP). Our results revealed that chitosan-based treatments significantly improved tomato root and shoot biomass, with increases of 200–300% compared to the control plants. Chitosan-CaP and Chitosan-DCP also enhanced P uptake, though the effect was significantly more pronounced in the former, suggesting a synergy between chitosan and CaP. Neither Chitosan-P-containing salt treatment, however, mitigated P leaching from soil when compared to CaP or DCP applied in isolation. The two most hydrophilic biopolymers, pectin and starch, as well as their P-salt-containing counterparts, showed the most substantial reductions in biomass (∼80%) with respect to control plants, while similarly lowering P uptake and P retention in soil compared to CaP- and DCP-only plants. PCL- and PHB-based treatments also adversely influenced biomass and plant P, though these effects were not as drastic as those observed with pectin and starch. PLA-based soil amendments had no effect on any plant performance metric, though PLA-CaP, specifically, was the only treatment to appreciably mitigate P leaching (−63%). Based on these findings, subsequent tomato growth experiments were conducted over a longer 8-week period with CaP, DCP, Chitosan, Chitosan-CaP, and Chitosan-DCP. While all chitosan-treated plants showed similar enhancements in biomass, plants treated with Chitosan-CaP and Chitosan-DCP were the only ones to fruit, demonstrating the benefit of using chitosan in conjunction with a P source as compared to either treatment in isolation. These findings contribute to an expanding body of evidence that biopolymer carriers can offer a more sustainable approach to improving the precision of nutrient delivery, while also highlighting the pivotal role of biopolymer and nutrient type in the development of these carriers.

  PublisherDOI

• Emerging investigator series: release and phototransformation of benzophenone additives from polystyrene plastics exposed to sunlight

  Environmental Science Processes & Impacts · 2025-01-01

  articleOpen access

  dependence, the presence of sunlight (active release) altered the concentration of leached benzophenones in solution depending on the relative photostability of the compounds. In accelerated lab-based studies using >300 nm irradiation, a second stage of increased additive release was observed for prolonged irradiation times, an effect ascribed to distinct stages of PS photodegradation. LC-HRMS analysis identified various photodegradation products, including carboxylic acids and hydroxylated species. Quencher experiments indicated that these transformation products were produced by the formation of excited triplet states and hydroxyl radicals generated by benzophenone photoexcitation. Hydroxyl radicals are also likely responsible for the complete mineralization of irradiated benzophenones as evidenced by total organic carbon analysis. This work identifies the impact of photolysis on both additive release and transformation of benzophenones.

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• Author response for "Emerging investigator series: release and phototransformation of benzophenone additives from polystyrene plastics exposed to sunlight"

  2025-07-11

  peer-review
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• Unexpected Reactivity of Commercially Relevant Phthalates with Free Chlorine

  ACS ES&T Water · 2025-10-23 · 2 citations

  articleSenior authorCorresponding

  Phthalates are the most prevalent plasticizers in poly(vinyl chloride) (PVC), the most commonly used polymer for drinking water distribution pipes. Though typically considered inert to the free chlorine necessary for drinking water disinfection, we found that certain commercially relevant phthalates leach from PVC and transform in the presence of free chlorine. The extent of aqueous phthalate leaching was alkyl chain length-dependent; the greatest leaching was observed for the most soluble 1-carbon chain phthalate, which was unaffected by free chlorine. In contrast, 2- and 4-carbon chain phthalates leached significantly less, and their concentrations decreased further in the presence of free chlorine. These observations were rationalized by experiments showing increased chlorine consumption with increasing phthalate alkyl chain length, indicative of structure-dependent chemical transformations of the parent phthalate with free chlorine. Using gas and liquid chromatography, high-resolution mass spectrometry, and nuclear magnetic resonance spectroscopy, we identified 13 disinfection byproducts of diisobutyl phthalate, 2 of which were confirmed using reference materials. The presence of both chlorinated and hydroxylated transformation products suggests reactions with both free chlorine and chlorine-derived reactive intermediates. This study underscores the need for consideration of chemical structure in predicting phthalate reactivity and highlights potential exposure risks in drinking water infrastructure.

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• Extreme Ultraviolet and Beyond Extreme Ultraviolet Lithography using Amorphous Zeolitic Imidazolate Resists Deposited by Atomic/Molecular Layer Deposition

  ChemRxiv · 2025-06-18 · 2 citations

  preprintOpen access

  Amorphous zinc-imidazolate (aZnMIm) resists show potential to meet the demands for next generation high-numerical aperture (high-NA) metal-containing extreme ultraviolet (EUV) resist materials given their ease of deposition by atomic/molecular layer deposition (ALD/MLD) at thicknesses of 20 nm and below. This study demonstrates that aZnMIm thin films, previously identified as high-resolution electron beam resists, can also function as negative tone EUV photoresists. Water development achieves high sensitivity (5 mJ/cm²) but leaves significant residue, while acetic acid development results in poor contrast. A hybrid approach—water followed by acetic acid—enables residue-free development with a sensitivity of 181 mJ/cm². Dry development using 1,1,1,5,5,5-hexafluoroacetylacetone (hfacH) is also possible, but shows lower sensitivity (375 mJ/cm²) compared to wet development methods. EUV photoelectron spectroscopy (PES), reflectometry/EUV absorption, total electron yield (TEY), residual gas analysis (RGA), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to investigate the effects of EUV irradiation on aZnMIm resists. Reflectometry experiments reveal an aZnMIm EUV absorption coefficient of 6.2 µm-1, while PES and TEY analyses show that, compared to poly(4-hydroxystyrene) (PHS), a polymer-based reference resist, aZnMIm emits more primary and secondary electrons but generates fewer slow electrons relative to its primary electron emission; its total electron yield is similar to that of poly(methyl methacrylate) (PMMA) resists. When exposed to EUV, aZnMIm predominantly outgasses H2, as determined by RGA. TOF-SIMS measurements demonstrate that high dose EUV exposure only partially fragments the 2-methylimidazole (2MIm) organic linkers, unlike high dose electron beam exposure, which is known to completely degrade them. Additionally, aZnMIm resists show promise for potential beyond-EUV lithography (BEUVL) due to the presence of Zn, which provides higher sensitivity at 6.7 nm compared to other metal ions, like Sn, that are currently used in the best-performing EUV metal-organic resists. TEY measurements demonstrate that aZnMIm emits nearly twice as many electrons as PHS at 6.7 nm. The BEUV TEY of aZnMIm also surpasses that of PMMA, poly(pentafluorostyrene), and poly(4-iodostyrene), with the latter two being known for their high EUV TEYs. This work provides new insights into zeolitic imidazolate framework (ZIF)-based EUV and BEUV resists and highlights their potential for both wet and dry development.

  PublisherOA PDFDOI

• <i>(Invited) </i>scalable and Environmentally Friendly Flexible Mxene-Tetrahedrites Thermoelectrics for Next Generation Wearable Devices

  ECS Meeting Abstracts · 2025-07-11

  article

  Traditional thermoelectric generators (TEGs) for harvesting low waste heat energy in room-temperature environments face scalability challenges due to high-temperature, long-duration curing processes and the use of rare-earth and toxic chalcogenides like Bismuth Telluride. Additive manufacturing has been investigated as a more time-, energy- and cost-efficient method that offers greater flexibility than traditional manufacturing techniques. Additionally, tetrahedrites are promising thermoelectric materials (TE) in high-temperature applications because they are non-toxic and earth-abundant. Herein, this work demonstrates the fabrication of scalable and sustainable Cu 12 Sb 4 S 13 (CAS) based composite films and flexible TEG devices ( f -TEGs) with 2D MXene nanosheets using a low-thermal budget additive manufacturing approach for room temperature applications. 2D MXene nanosheets introduced energy-barrier scattering and nanoscale features to effectively increase the room-temperature ZT to 0.22, 10% higher than bulk CAS, by decoupling electrical conductivity, Seebeck coefficient, and thermal conductivity. CAS and 2D MXenes were found to be environmentally safe through a bacterial viability study. The process is used to create a 5-leg f -TEG device producing a power of 5.3 µW and a power density of 140 at a ∆T of 25 K, this work demonstrates that combining scalable and sustainable materials and methods is an effective strategy for high-performance room-temperature f -TEGs. Furthermore, a study evaluated the effects of Chitosan-CAS and Chitosan-CAS-MXene inks on the gram-negative bacterium Shewanella Oneidensis MR-1, demonstrating that both CAS and MXene inks are environmentally safe. The low thermal budget manufacturing method, earth abundance, environmental safety, and nontoxicity combination demonstrate the sustainability of the methods and materials used to manufacture high-performance chitosan-CAS-MXene composites and f-TEGs for low-waste heat applications. Similarly, the additive manufacturing technique facilitates the costeffective scalability of these f-TEGs. For the first time, this study demonstrates the ability of CAS to effectively transform low waste heat energy into useable energy by combining a chitosan-CAS composite-based TE material coupled with 2D MXene nanosheets within f-TEG devices. Therefore, naturally available tetrahedrites present unique advantages, allowing for the widespread adoption of safe TEG in wearable and health monitoring devices. The f-TEG 5.3 mW power output at a temperature difference of 25 K closely matches the average power requirements of wearable monitoring sensors and devices. In future work, we aim to utilize the scalability of our low-cost and energy-efficient manufacturing technique to print and connect more TE legs in series, demonstrating tetrahedrite's potential to harness low-waste body heat as a self sufficient power source for wearable monitoring devices

  PublisherDOI