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Harold Freeman

Named Professor

Ciba Professor of Textile Chemistry Emeritus

Textiles Complex NA


Prof. Freeman is a native North Carolinian, who completed high school, undergraduate training, and graduate school without leaving his beloved home state. Following the completion of the BS degree in chemistry from N.C. A&T State University, he was employed an organic chemist for 9.5 years at Burroughs-Wellcome Company. It was during this employment that he completed MS and PhD degrees in organic chemistry. He joined N.C. State University as Associate Professor of textile chemistry in 1982 and was promoted to professor in 1989. Two years later he was chosen the first Ciba-Geigy Professor of Dyestuff Chemistry.Prof. Freeman holds memberships in the American Chemical Society (Organic and Environmental Chemistry Divisions), Sigma Xi, The Genotoxicity and Environmental Mutagen Society, American Association of Textile Chemists and Colorists (AATCC), and American Association for the Advancement of Science. He received the J. William Weaver award and the Olney Medal from AATCC in 1992 and 2004, respectively. Prof. Freeman currently serves as a member of the editorial boards for Colourage and Coloration Technology and Guest Editor for Materials Journal. He is author or co-author of over 200 scientific publications in a variety of journals and books.Prof. Freeman and his wife, Ruby, share a weekly small group ministry at a local church and enjoy family life with their two adult sons and two grandchildren.


Prof. Harold S. Freeman Conducts Research on Organic Dyes and Pigments

Our 31 years of research in this area has involved 3 principal types of studies: 1) the design of dyes having high photostability on hydrophobic fibers; 2) the environmental chemistry of synthetic dyes and pigments; and 3) the analytical chemistry of synthetic dyes. Most recently, we have conducted research pertaining to the design of dyes for use in Photodynamic Therapy (PDT) and Dye Sensitized Solar Cells (DSSCs).

  1. Dyes having high photostability on hydrophobic fibersThe need for photostable (lightfast) dyes for hydrophobic fibers, especially polyester, stems from their use in automobile interiors, where stability to prolonged and repeated exposures to sunlight in combination with heat and humidity is paramount. Our research in this area began in 1985, with funding from a consortium of companies in the supply chain leading to fabric and carpet for automobile interiors and, subsequently, from NSF to characterize the contribution of heat and humidity to the dye fading process (cf. Fig 1). At the heart of this work was to determine the mechanisms of fading associated with prototype synthetic dyes used in this area of technology and to use the resulting information to design dyes immune to the observed mechanisms. This research led to a family of lightfast disperse dyes containing a built-in photostabilizer (e.g. 1-2). In this regard, it was found that the nature and location of the built-in stabilizer played a key role in the viability of the dyes obtained.

    Dyed PET films before (left) and after (right) sunlight exposure

    Fig. 1. Dyed PET films before (left) and after (right) sunlight exposure.

    Chemical structure

    In closely related studies, we are investigating the influence of the host fiber on the photodegradation of adsorbed dyes and preliminary results indicate that the photostability of dyes on polyester is adversely influenced by the host fiber unless a photostabilizer is present. This also suggests that stabilization of the excited polymer molecules is critical to the life of the adsorbed dye.

  2. Environmental chemistry of synthetic dyes and pigmentsSynthetic dyes, especially azo dyes, have come under increased scrutiny by regulatory agencies because certain precursors used in their manufacture were shown to pose a risk to human health and the environment. This led to the need to understand the relationships between azo dye structures and their genotoxic and ecotoxic potential. Our work in this area started in 1984 with funding from IBM, whose corporate interest was to generate results that could be used as a basis for knowing which dyes to avoid in commercial products, such as ink-jet printers, but our group saw an opportunity to use the same results to design safe alternatives to important dyes being eliminated from commerce because of their potential to undergo metabolism to produce carcinogenic arylamines such as benzidine (cf. 3, Fig. 2). This idea enabled the design of non-genotoxic aromatic amine precursors (e.g. 4-6) for azo dye and pigment synthesis and the use of the derivative colorants for textile and non-textile coloration.
    Metabolic cleavage of an azo dye to the corresponding arylamines

    Fig. 2. Metabolic cleavage of an azo dye to the corresponding arylamines.

    Chemical Structure

    Funding from the National Textile Center and Clariant Chemicals has permitted the design of metal complexed dyes for polyamide and protein fibers that would be devoid of the toxicity concerns associated with certain effluents from dye manufacture and textile dyeing operations. The main goal was to protect ecosystems associated with either drinking water or aquatic life (plants and animals). While the presence of chromium (Cr) and cobalt (Co) ions in textile dyes was deemed critical to producing photostable dyes for carpet fibers, the presence of free Cr and Co ions in ecosystems is undesirable. Our research in this area has produced environmental friendly iron (Fe) complexed azo and formazan dyes that maintain the desirable technical properties of the Cr- and Co-based prototypes. It was also found that the formation of low-spin rather than high-spin complexes is the key to overcoming the typically dull colors associated with Fe complexes (cf. Fig. 3).

    Optimized geometries for low-spin (left) vs. high-spin (right) Fe complexed formazan dyes

    Fig. 3. Optimized geometries for low-spin (left) vs. high-spin (right) Fe complexed formazan dyes.

  3. The analytical chemistry of synthetic dyesOur research in this area has been dedicated to the development of methods for purifying synthetic dyes for structure confirmation and toxicological studies. A variety of chromatographic, crystallographic, and spectrometric methods were developed and published for use by the color chemistry community (cf. Fig. 4). These methods also proved useful for characterizing complex mixtures and for correlating dye structure with choice of techniques to employ.
    Mass spectrometry and x-ray results from synthetic dye analyses
    Mass spectrometry and x-ray results from synthetic dye analyses

    Fig. 4. Mass spectrometry and x-ray results from synthetic dye analyses.

  4. Dyes for use in photodynamic therapy (PDT)An opportunity to merge our long-standing interest in synthetic dyes with an initial career interest in pharmaceuticals was the inspiration for current research pertaining to the design and synthesis of dye sensitizers for photodynamic therapy (PDT). PDT is a type of photochemotherapy for various types of cancers and requires the presence of light, a sensitizer, and molecular oxygen for treatments. During PDT, a sensitizer is administered intravenously, intraperitoneally, or topically, and selectively localizes in a tumor due to physiological differences between the tumor and healthy tissue. Localization into cancer cells and achieving a maximum tumor-to-normal cell concentration ratio can take 3 to 96 hours, depending on the photosensitizer and tumor. Following localization, fluorescence from the sensitizer can be used to diagnose and detect the tumor. Irradiation at a wavelength specific to the photosensitizer produces singlet oxygen, which reacts with and destroys the tumor. Suitable sensitizers are mainly porphyrinoid compounds, phthalocyanines, and related structures. Our research focuses on the design of novel dyes having high singlet oxygen generating efficiency and high selectivity for tumors. Porphyrin and formazan systems containing appendages that facilitate tumor uptake are currently under investigation (e.g. 7-8).
    Chemical structure
  5. Dyes for use in dye sensitized solar cells (DSSCs)Over the past 10 years, many metal-free organic dye sensitizers have been developed for application in DSSCs, with the typically structure based on a push-pull system (i.e. donor-spacer-acceptor system). Specifically, double bond based spacers have been frequently employed to give red-shifted absorption spectra aimed at high solar energy capture. However, widely employed C=C double bonds as spacers can limit DSSC efficiency, resulting in adverse effects such as self-quenching of generated electrons arising from cis-trans isomerization or dye aggregation. While the photovoltaic performance of a furan-based sensitizer has often been investigated with regard to recombination kinetics, fewer studies involving other heterocyclic ring systems as a spacer are reported. Hence, our contributions in this arena have involved 1) the synthesis of novel metal-free sensitizers by systematic variation of the spacer unit (cf. Fig. 5) and 2) determination of intrinsic factors affecting photovoltaic performance through use of the resultant dyes in DSSCs.Based on current-potential curves, current density increased in the order DP-TZ < DP-P < DP-F < DP-B < DP-T The highest plateau of quantum efficiency from IPCE spectra was obtained from DP-B, indicating a relationship between decreased (or increased) aggregation behavior of dyes on a TiO2 surface and higher (or lower) electron transfer yield. The dependence of open-circuit voltage on electron lifetime was evident, resulting in enhanced Voc in the order of devices based on DP-TZ< DP-F < DP-T < DP-B < DP-P. The lower polarizabilities of the molecules contributed to increased lifetimes but this benefit was weakened when efficient surface blocking was reduced, resulting in an unexpected drop in open-circuit voltage for DP-F. The DSSC device based N-methyl pyrrole (DP-P) showed good kinetic properties, resulting in high Voc and making the pyrrole unit a logical spacer for further molecular design studies towards high efficiency DSSCs. Given the similar maximum quantum efficiency (from IPCE data) of the device based on DP-P compared to DP-T, an enhanced absorption spectral shift would give high current densities needed for large solar energy capture. It should be added that molecular engineering of sensitizers having an N-methyl pyrrole unit should be careful to reduce the dihedral angle between spacers and neighboring group. Such experiments should be augmented by molecular modeling studies designed to examine the behavior of dye sensitizers on TiO2 in the presence of additives.
    Target molecular structures based on different spacers in a D-π-A system

    Fig. 5. Target molecular structures based on different spacers in a D-π-A system.


  • American Association of Textile Chemists and Colorists
  • American Chemical Society; National Technical Association
  • Society of Dyers and Colorists
  • Sigma Xi
  • Genotoxicity and Environmental Mutagenicity Society
  • American Association for the Advancement of Science


  • PCC 301
  • PCC 302
  • PCC 304
  • PCC 420
  • TC 720
  • TC 721

Background Papers

  • Alexandra B. Ormond and Harold S. Freeman, “Dye Sensitizers for Photodynamic Therapy”, Materials, 6(3), 817-840 (2013).
  • Alexandra B. Ormond and Harold S. Freeman, “Effects of Substituents on the Photophysical Properties of Symmetrical Porphyrins”, Dyes and Pigments, 96 (2), 440-448 (2013).
  • Francine I. Vacchi, Anjaina F. Albuquerque, Josiane A. Vendemiatti, Daniel A. Morales, Alexandra B. Ormond, Harold S. Freeman, Guilherme J. Zocolo, Maria V.B. Zanoni, Gisela Umbuzeiro, “Chlorine disinfection of dye wastewater: Implications for a commercial azo dye mixture”, Science of the Total Environment, 442, 302-309 (2013).
  • Harold S. Freeman, “Aromatic Amines: Use in Azo Dye Chemistry”, in Arylamine Induced Carcinogenesis, Frontiers in Bioscience, 18, 145-164, 2013.
  • Bo Hyung Kim and Harold S. Freeman, “Structure-Photovoltaic Performance Relationships for DSSC Sensitizers Having Heterocyclic and Benzene Spacers”, J. Mater. Chem, 22(38) 20403-20409 (2012).
  • Bo Hyung Kim and Harold S. Freeman, Effects of Bis-carbazole based D-p-A Sensitizers on Solar Energy Capture in DSSCs, Photochem. Photobiol. Sci., 2013, 12 (3), 421-431.
  • Harold S. Freeman, “Studies towards the Design of Lightfast Dyes for Polyester”, Proceedings of the AATCC International Conference and Exhibition, Charlotte, NC, March 22-24, 2012, 10pp.
  • Liang He, Harold S. Freeman, Lihua Lu, Shufen Zhang, “Spectroscopic study of anthraquinone dye/amphiphile systems in binary aqueous / organic solvent mixtures”, Dyes and Pigments, 91, 389-395 (2011).


  • Kiarash Arangdad (PhD)
  • Chengyang Lu (MS)
  • Yixin Liu (MS)
  • Nahid Mehraban (PhD)
  • Syed Zaidy (PhD)
  • Yi Ding (PhD)
  • Jasmine Park (PhD)
  • Tuane Santos (PhD)
  • Rui Su (PhD)
  • Tova Williams (PhD)

Graduate Projects

  • Weathering of Copolyester Films
  • Effects of Pre-treatments in PET Discoloration
  • Synthesis and Characterization of Reactive Dye Dimers
  • Design, Synthesis, and Encapsulation of PDT Sensitizers
  • Synthesis of Dyes for Atmospheric Plasma Application
  • Digital Printing: Color Gamunt Analysis Using Dyes Vs. Pigments
  • The Contribution of Heat, Moisture, and UV Light to Co-Polymer Weathering
  • Synthesis and Toxicological Properties of Natural Dyes
  • Novel DSSC Dyes: Design and Synthesis
  • Characterization of Hair Fiber Coloration using Experimental and Modeling Studies


Ph.D. Organic Chemistry North Carolina State University 1981

M.S. Organic Chemistry North Carolina State University 1978

B.S. Chemistry North Carolina A&T State University 1972

Area(s) of Expertise

Dyeing and Finishing
Textile Chemistry


View all publications 


Date: 06/01/19 - 2/28/23
Amount: $406,913.00
Funding Agencies: Academy of Finland

This project pertains to the characterization of colorants isolated from fungi and other plant media as potential alternatives to environmentally unfriendly synthetic dyes. Part 1 of our study seeks to verify that the resulting biocolourants are non-ecotoxic and non-mutagenic. Although from a natural origin, the biocolourants are new compounds that need to be examined for potential adverse effects on human health and aquatic biota. Part 2 seeks to establish viable methods for the application and evaluation of biocolourants on textile substrates. Specifically, the focus this aspect of our work involves dyeing and printing of textiles and determination of their fastness properties. Non-traditional applications (e.g. paints, coatings, and solar cells) for the new biocolourants will also be pursued.

Date: 09/01/18 - 8/14/20
Amount: $65,059.00
Funding Agencies: Everlight Chemical Industrial Corporation

Reactive dye-based printing currently offers one of the largest color gamuts of the various colorants available for digital printing and the dye is relatively stable in the print head. It provides excellent print quality and is used for a wide variety of printed home furnishings and apparel products. Reactive dyes form covalent bonds with cellulose under alkaline conditions; however, there is a significant drawback that is often ignored: a high dye utilization (fixation) percentage is hard to achieve. Although the cost of reactive dyes is relatively low when compared to other digital print colorants, particularly pigments, a significant percentage of reactive dye is wasted during the printing, fixation and wash-off process. In order to decrease costs and increase sustainability, this issue must be addressed. To decrease waste and costs associated with wasted dyestuff, the student will investigate the mechanism of low percentage fixation for reactive dye digital printing on cotton fabrics. A two year budget includes the student’s annual stipend or salary, tuition and health insurance.

Date: 11/30/-1 - 12/31/17
Amount: $277,776.00
Funding Agencies: Lubrizol Corporation

The thrust of this 1-year project is to examine processes and mechanisms leading to improvements in the wet and dry crock fastness on cotton, while maintaining the color gamut. In this regard, fundamental studies in ink/substrate interactions will be undertaken using instruments in the NCSU Surface Science Laboratory. These studies will involve the 1) comparison of Lubrizol (LZ) Gen 1/Gen2 and rotary screen pigment inks on cotton and 2) evaluation of LZ binder design, ink formulation and pretreatment using SPECS XPS, TOF-SIMS, and FIB-SEM methods.

Date: 02/15/17 - 9/15/17
Amount: $37,145.00
Funding Agencies: Leo Lens Technologies

The proposed investigation pertains to the development and validation of test methods for 1) assessing the molecular weight distribution of Sponsor's oligomer and 2) identifying and quantifying residual monomers isolated from the resultant lenses through solvent extraction.

Date: 08/15/14 - 5/15/17
Amount: $639,111.00
Funding Agencies: Walmart Inc.

Digitally printed fabrics for outdoor furnishings coupled with an efficient cut and sew fabrication process offer a game changing strategy for the domestic textile complex. Specifically, the objective of this project is to make significant portions of the outdoor furniture soft goods production in the USA competitive with overseas production. This will be accomplished by implementing new technologies in both fabric printing and cut/sew operations to enable a) the cost-effective domestic production required for success in servicing Walmart; b) new product innovations not feasible using current production technologies in this category, and c) a flexible and responsive supply chain capable of quick response to customer market trends.

Date: 11/30/-1 - 3/31/17
Amount: $55,635.00
Funding Agencies: Atex Technologies, Inc.

The proposed investigation pertains to the design, synthesis and evaluation of color additives for PE fibers. Target colors include yellow and green and must be suitable for SCF-CO2 application.

Date: 01/01/15 - 12/31/16
Amount: $98,676.00
Funding Agencies: Cotton, Inc.

This project is part of an investigation involving the modification of commercial dyes for cotton to give higher substantivity, thus making them more readily exhaustible. In part 1 of this investigation, the target dyes belong to the reactive dye family and proof of concept will be provided from their application to cotton. The focus of the present study is the conversion of commercial dyes having two reactive groups to the corresponding dimeric forms by reacting the former dyes with suitable dyebath additives. It is expected that the target dyes offer the potential to increase color strength on cotton and reduce salt levels required for dyebath exhaustion.

Date: 09/08/14 - 4/15/16
Amount: $49,991.00
Funding Agencies: Lubrizol Corporation

The objective of this investigation is to characterize the Sponsor's pre-treatment process by 1) performing an assessment and comparative analysis of the interaction between the pre-treatment and various commercially available inks on textiles and 2)characterizing the color shift that sometimes occurs with dark colored textiles following pre-treatment application.

Date: 11/30/-1 - 12/31/15
Amount: $76,696.00
Funding Agencies: Cotton, Inc.

This project is part of an investigation involving the modification of commercial dyes for cotton to give higher substantivity, thus making them more readily exhaustible. In part 2 of this investigation, the target dyes belong to the vat dye family and proof of concept will be provided from their application to cotton. The focus of the present study is the conversion of commercial indigo dye to dimeric forms by reacting the base structure with suitable reaction intermediates. The approach to be used involves standard reactions such as nitration, reduction, chlorosulfonation, and arylation, with indigo itself, along with indigo carmine used for the proposed modification.

Date: 10/06/14 - 9/15/15
Amount: $46,522.00
Funding Agencies: Hanesbrands, Inc.

This project is a continuation of studies pertaining to the synthesis and evaluation of a viable alternative to CHPTAC for forming cationized cotton. Having found that the novel compound CHPDMAP mitigates the unwanted odor associated with CHPTAC treated fabric, while facilitating reactive dye application on cotton, we now seek to optimize the structure required for efficient CHPDMAP bonding to cotton. This work will lead to a method for synthesizing CHPDMAP that can be scaled for plant trials.

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